Q674B1034-Honeywell Q674B1034 Heat-Off-Cool Auto-On Thermostat Subbase - Industrial Stores
T874 Multistage Thermostats and Q674 Subbases APPLICATION These thermostats and subbases provide low voltage control of multistage heating and cooling systems, including heat pump systems. PRODUCT DATA FEATURES · T874 Thermostat has silent, dust-free mercury switches operated by coiled bimetal elements. · Heat anticipator(s) are adjustable or fixed cooling anticipator(s) are fixed. · Individual heat and cool levers and scales (most models) for temperature setting located on top of thermostat case. · Cover thermometer on most T874 Multistage Thermostat models. · Locking cover and locking lever screws available for T874 Multistage Thermostats. · VersaguardTM Thermostat Guard or custom key lock thermostat guards available for T874 Multistage Thermostats. · T874 Thermostat requires a Q674 Subbase. · Q674 Subbase provides system and fan switching, wiring terminals and mounting base for T874 Multistage Thermostat. · Adapter plate available for mounting Q674 on wall or horizontal outlet box. · Light-emitting diodes (LEDs) located on subbase for easy reference. · Up to three stages each of heating and cooling control possible. · Models with setpoint restrictions and locking cover with no thermometer available for Department of Defense (DoD) and other special applications. · Outdoor reset used on some models to improve thermal performance. Contents Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Ordering Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Checkout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Understanding Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Cross Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Wiring Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 ® U.S. Registered Trademark Copyright © 2001 Honeywell · All Rights Reserved 60- 2485- 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SPECIFICATIONS IMPORTANT The specifications given in this publication do not include normal manufacturing tolerances. Therefore, this unit may not exactly match the listed specifications. This product is tested and calibrated under closely controlled conditions, and some minor differences in performance can be expected if those conditions are changed. Super Tradeline®/Tradeline® Models SUPER TRADELINE controls offer features not available on TRADELINE or standard models, and are designed to replace a wide range of Honeywell and competitive controls. TRADELINE models are selected and packaged to provide ease of stocking, ease of handling, and maximum replacement value. Specifications of SUPER TRADELINE and TRADELINE controls are the same as those of standard models except as noted below. Super Tradeline Models T874 THERMOSTAT T874D Thermostat. Provides two stages of heating and two stages of cooling. Use with Q674A-F Subbases. Y594D (T874D/Q674E/TG504A) Thermostat/Subbase/key lock cover package. Provides two stages of heating and two stages of cooling. Includes a key lock cover for setpoint protection. Y594G (T874G/Q674F) Thermostat/Subbase package for heat pump. Provides two stages of heating and one stage of cooling. Automatic changeover in heat or cool mode. Available in beige or Premier White® color. Y594R (T874R/Q674L) Thermostat/Subbase package for heat pump. Provides two stages of heating and one stage of cooling. Manual changeover in heat or cool mode. Available in beige or Premier White® color. SUPER TRADELINE FEATURES: · SUPER TRADELINE package with cross reference label and special instruction sheet. · SUPER TRADELINE model supplied with locking lever and locking cover accessories. · Includes adjustable temperature locking stops. · T874D replaces T874A-F TRADELINE or standard models. Tradeline Models T874 THERMOSTAT · T874 TRADELINE models provide staged heat and/or cool operation. See Table 1. Table 1. Heating and Cooling Stages. Models Heating Stages Cooling Stages ABCDE F 1 1 2 2--2 1 2 1 2 2-- · T874A-F are standard models. TRADELINE FEATURES: · TRADELINE package with cross reference label and special instruction sheet. · T874A,C model available with factory stops for DoD applications. · T874A,C model available with adjustable temperature locking stops. Q674 SUBBASE Q674 switching subbases provide system and fan switching. See Table 2. Q674 A B C D E F G J L Table 2. System and Fan Switching. System Heat-Auto-Cool Heat-Off-Cool Off-Auto None Off-Heat-Auto-Cool Em. Ht.-Off-Heat-Auto-Cool Off-Auto Em. Ht.-Auto-Off Em. Ht.-Heat-Off-Cool Fan Auto-On Auto-On Auto-On None Auto-On Auto-On None Auto-On Auto-On TRADELINE FEATURE: · TRADELINE package with cross reference label and special instruction sheet. · Q674A-E,G are standard (non-heat pump) models. Q674F,J,L are heat pump models. ORDERING INFORMATION When purchasing replacement and modernization products from your TRADELINE® wholesaler or distributor, refer to the TRADELINE® Catalog or price sheets for complete ordering number. If you have additional questions, need further information, or would like to comment on our products or services, please write or phone: 1. Your local Home and Building Control Sales Office (check white pages of your phone directory). 2. Home and Building Control Customer Relations Honeywell, 1885 Douglas Drive North Minneapolis, Minnesota 55422-4386 (800) 328-5111 In Canada--Honeywell Limited/Honeywell Limitée, 35 Dynamic Drive, Scarborough, Ontario M1V 4Z9. International Sales and Service Offices in all principal cities of the world. Manufacturing in Australia, Canada, Finland, France, Germany, Japan, Mexico, Netherlands, Spain, Taiwan, United Kingdom, U.S.A. 60-2485--8 2 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Standard Models T874 THERMOSTATS Models: See Table 3. Electrical Rating: 24 to 30 Vac. Switching: Coiled bimetal elements operate mercury switches. Temperature Adjustment: Heating and cooling setting levers, with separate scales located on top of thermostat base. Common lever for heating and cooling on T874R; one cooling lever on T874E,V; and one heating lever on T874F,Q. Dimensions: See Fig. 1. Temperature: Scale Range: 42° to 88°F (6° to 31°C) standard; optional ranges available. THERMOSTAT MOUNTED ON SUBBASE FRONT 5-5/8 (143) SIDE 3/8 (10) Thermometer Range: 42° to 88°F (6 to 31°C) Changeover Differential: 4°F (2°C) minimum between heating and cooling (5°F [3°C] on T874W). Levers can be set apart for greater separation. Interstage Differential: Standard Models: Mechanical differential is 1°F (0.6°C) between heating or cooling stages; operating differential is approximately 1.9°F (1°C) between stages in heating or cooling. Special Models: See Table 3. Finish: Beige or Premier White® finish. Mounting Means: T874 Multistage Thermostat mounts on Q674 Subbase. Subbase mounts horizontally on wall or outlet box. Mounts on vertical outlet box with optional 193121A Adapter Plate Assembly. SUBBASE 3-9/32 (83) HEAT 50 60 70 80 50 60 70 80 50 60 70 80 COOL 1-1/2 (38) 3-1/2 (89) 3-7/16 (87) FAN AUTO ON OFF EM. HT. HEAT AUTO COOL FAN AUTO ON OFF EM. HT. HEAT AUTO COOL 1-7/8 (48) 2-3/16 (56) 5-1/8 (130) M5849 Fig. 1. T874 Thermostat and Q674 Subbase dimensions in in. (mm). Optional Specifications (T874 Only): Temperature scale ranges are 40° to 75°F (4° to 24°C) heat- ing and 75° to 90°F (24° to 32°C) cooling with stop; 44° to 68°F (7° to 20°C) heating, 80° to 86°F (27° to 30°C) cooling; 6° to 29°C (43° to 85°F) Celsius scale; 3° to 22°C (38° to 72°F) and 26° to 32°C (78° to 90°F) cooling with stop. Nonadjustable factory-added stop limits heating setpoint to 72°F (22°C) maximum and cooling setpoint to 78°F (26°C) minimum. OEM customer personalization. Locking cover and locking lever (see Thermostat Accessories). Thermostat cover without thermometer. Adjustable locking temperature stops. Voltage heat anticipation for first or second stage heat or both. See Table 3. Fast cycling on heating stage(s) for electric heat applications. C815A Outdoor Thermistor for improved performance on specified models. Thermostat Accessories: Locking Cover and Locking Lever Assembly: Part no. 194559R with thermometer; 194559S without thermometer. See Fig. 2. Includes cover, screws, and Allen wrench for locking cover. The screws must be used to assure proper operation. Adjustable Lever Stop: Part no. 4074ECK; includes lever stop and screws. Universal VersaguardTM Thermostat Guard: Includes wallplate, ring base, guard cover, tumbler lock, two keys and optional Honeywell logo insert. Double-wall construction provides extra measure of tamper-resistance. Tamperresistant lock; key cannot be removed without being in locked position. Vents in guard base allow airflow for optimum thermostat performance. See form 68-0104 for more information. -- TG511A1000: Clear cover. -- TG511B1008: Opaque cover. -- TG511D1004: Painted steel (off-white) cover. See Fig. 2. 3 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Key Lock Cover: Part no. TG504A replaces existing T874 cover. Mounts on T874 base and covers thermostat settling levers and subbase switches. Includes LED window and two keys. Should not be used with 193121A Adapter Plate. -- TG504A1025: Blank face, internal thermometer. -- TG504A1033: External thermometer. See Fig. 2. 194559R Locking Cover with Thermometer Allen Wrench TG504A1033 Key Lock Cover with External Thermometer TG511D1004 Includes Painted Steel Cover, Opaque Base and Wallplate Fig. 2. T874 Thermostat accessories. Table 3. T874 Thermostat Specifications. Anticipation System Stages Heating (Adj) Cooling (Fixed) Models and Options Replaces Applications Heat Cool Other Stage 1 Stage 2 Stage 1 Stage 2 T874A--Standard and TRADELINE®. T872A Standard 1 1 -- 0.1-1.2A -- 0-1.5A -- -- 72°F/78°F (22°C/26°C)setpoint stops with locking cover. -- Adjustable anticipator set 0.4A. -- Adjustable locking temperature stops (TRADELINE®). -- 72°F/78°F (22°C/26°C) setpoint stops with locking cover, no thermometer (for DoDa). T874B--Standard and TRADELINE. T872B Standard 1 2 -- 0.1-1.2A -- 0-1.2A 0-1.0A T874C--Standard and TRADELINE. T872C Standard 2 1 -- 0.1-1.2A 0.1-1.2A 0-1.5A -- -- 72°F/78°F (22°C/26°C)set stops with locking cover, no thermometer (for DoDa). -- 12°F (7°C) differential between H1 and H2 stages (T874C1125). -- Fast cycling. 0.120.6A 0.120.6A T874D--Standard and SUPER TRADELINE®. -- Adjustable locking temperature stops (SUPER TRADELINE). T872D Standard 2 2 -- 0.1-1.2A 0.1-1.2A 0-1.2A 0-1.0A T874E--Standard and TRADELINE. T872E 2-Stage Cool -- 2 -- -- -- 0-1.2A 0-1.0A T874F--Standard and TRADELINE. T872F 2-Stage Heat 2 -- -- 0.1-1.2A 0.1-1.2A -- -- -- Locking cover. a Department of Defense. b Changeover stage operates with heating. c Fixed voltage type anticipation. d Changeover stage operates with heating; a secondary changeover is provided in cooling switch. e Provides night setback used with standard T874 and timer-operated remote switching. f Manual changeover stage--use Q674B,L subbase. g Changeover stage operates with cooling.Q674 Subbases 60-2485--8 4 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES -- Fast cycling. Electric Heat T874G--Heat pump, cool changeover, with fast cycling. -- Fixed anticipator for H2. -- Fast cycling. T872G Heat Pump or 2 Standard 1 1b T874H--Use with Q674C. T872H Heat Pump or 1 Standard 1 1b T874J--Heat pump. None Heat Pump 2 1 2d T874K--Heat pump. None Heat Pump 2 1 1b T874L--Heat pump. None Heat Pump 2 1 -- T874N--Heat pump, heat changeover. T872N Heat Pump 2 1 1b T874P--Heat pump. None Heat Pump 2 1 -- T874Q--Night setback heating. T872Q Standard 1e -- -- T874R--Heat pump. T872R Heat Pumpf 2 1-- T874S--Two-speed compressor heat None Heat Pump 2 pump. 2 1g T874V--Standard. None Standard -- 1 -- T874W--Heat pump and standard. -- Night setback heating. T872W Heat Pump or 3 Standard 2-- a Department of Defense. b Changeover stage operates with heating. c Fixed voltage type anticipation. d Changeover stage operates with heating; a secondary changeover is provided in cooling switch. e Provides night setback used with standard T874 and timer-operated remote switching. f Manual changeover stage--use Q674B,L subbase. g Changeover stage operates with cooling.Q674 Subbases 0.120.6A 0.120.6A 0-1.0Ac 0.1-1.2A 0-1.0A 0-1.0Ac 0.1-1.5A 0.120.6A -- 0-1.0A 0-1.0Ae 0-1.5Ac 0-1.0Ac 0.1-1.2A 0-1.5Ac 0-1.5A 0.1-1.2A 0.1-1.2A 0-1.5A 0.1-1.2A 0.1-1.2A 0-1.0A 0.1-1.2A 0.1-1.2A 0-1.5A 0.1-1.2A -- -- 0-1.5Ac 0.1-1.2A 0-1.5A 0-1.2Ac 0-1.2Ac 0-1.2A -- -- 0-1.5A 0-1.2Ab 0-1.2Ac,d 0-1.2A -- -- -- -- -- -- -- -- -- 0-1.0A -- 0-1.0A Models: See Table 4. Electrical Ratings: Switch Contacts: 2.5A at 30 Vac (7.5A inrush). LED Lights (Optional): 30 Vac. Switches: Two slide switches (one switch on Q674G and K; no switches on Q674D) operated by levers. Switch position is shown on scaleplate. Mounting: Designed to mount horizontally on an outlet box or the wall. Adapter plate assembly available for mounting on a vertical outlet box (see Subbase Accessory). Finish: Dark brown or gray. Dimensions in in. (mm): 3-1/2 (89)height; 5-5/8 (143) width; 5/16 (8) depth. See Fig. 1. Table 4. Q674 Subbase Specifications. Models and Options Q674A--Standard and TRADELINE®. -- Indicator LEDs. Q674B--Standard and TRADELINE. -- Provision for fan relay operation from external fan switch (isolate G terminal). -- Indicator LEDs. Q674C--Standard and TRADELINE. -- Indicator LEDs. Q674D--Standard and TRADELINE. -- For use when subbase switching is not required. Replaces Q672A Application Standard Switch Positions System Fan HEAT-AUTO-COOL AUTO-ON Q672B Q672C Q672D Standard Heat Pump Standard Heat Pump Standard HEAT-OFF-COOL OVERRIDE-HEATOFF-COOL OFF-AUTO OVERRIDE-AUTOOFF None AUTO-ON AUTO-ON AUTO-ON AUTO-ON None 5 Use With T874A-D T874A-D T874G,H,L,R T874P T874A-H,W T874K,L,N T874P T874A-F 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Q674E--Standard and TRADELINE. Q674F--Two LED models. -- EM.HT. light. -- Provision for AUTO fan operation in EM.HT. Q674G--O and B terminals. Q674J--Provision for AUTO fan operation in EM.HT. -- Provision for outdoor thermistor. Q674K--Standard. Q672E Q672F Q672G Q672J Q672K Q674L--Provision for AUTO fan operation in EM.HT. -- Indicator LEDs. Q672L Q674N--Standard. Q672N Q674P--Standard. Q672P Q674Q--Standard. None Q674R--Standard. -- International symbols. Q674S--Indicator LED. None None Standard Heat Pump Standard Heat Pump Standard Heat Pump Evaporative Cooler Heat Pump Fan Coil Fan Coil Standard OFF-HEAT-AUTO- AUTO-ON COOL OFF-EM.HT.-HEAT- AUTO-ON AUTO-COOL OFF-COOL-AUTO- AUTO-ON HEAT-EM.HT. OFF-AUTO None EM.HT.-AUTO-OFF AUTO-ON EM.HT.-ON-OFF AUTO-ON SUPL.HT.-ON-OFF AUTO-ON OFF-HEAT-AUTOCOOL None OFF-WOOD-WOOD/ OIL-OIL None EM.HT.-HEAT-OFF- AUTO-ON COOL SUPL.HT.-HEATOFF-COOL AUTO-ON EVAP-COOL-OFF- AUTO-ON HEAT SUPL.HT.-HEATCOOL AUTO-ON HEAT-OFF-COOL LO-MED-HION OFF-COOL LO-HICONT. HEAT-COOL None T874A-D T874C,D,G,N,S T874A-F T874A,D,G,J T874F T874R,W T874C T874G T874A T874V T874C Optional Specifications (Q674 Only): Models available with up to four LEDs; for example, LEDs can show EM. HT, AUX. HT, SERVICE, CHECK, FILTER, and LOCKOUT. See Fig. 3. System switching marked HEAT-OFF/RESET-COOL for systems requiring impedance relay reset. Available on Q674B only. G terminal isolated on heating to provide fan relay operation from external low voltage fan switch (Q674B only). Auto fan operation on both heat and cool. L terminal is used for system monitoring devices. Common R terminal for heating/cooling. Changeover in cool or heat mode for heat pumps. Auto fan in EM.HT. for heat pumps. Subbase Accessory: 193121A Adapter Plate Assembly for mounting on vertical outlet box. Assembly includes adapter ring and cover plate. Use to cover wall marks from replaced thermostat. T874 Thermostat with One Setpoint Lever T874 Thermostat with Separate Heating and Cooling Levers Fig. 3. Heating, cooling levers and system LED indicators. Q674 Subbase with Four LEDs 60-2485--8 6 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES MERCURY NOTICE This control contains mercury in a sealed tube. Do not place control in the trash at the end of its useful life. If this control is replacing a control that contains mercury in a sealed tube, do not place your old control in the trash. Contact your local waste management authority for instructions regarding recycling and the proper disposal of this control, or of an old control containing mercury in a sealed tube. If you have questions, call the Honeywell Customer Response Center at 1-800-468-1502. INSTALLATION When Installing this Product... 1. Read these instructions carefully. Failure to follow them could damage the product or cause a hazardous condition. 2. Check the ratings given on the product to make sure the product is suitable for your application. 3. Installer must be a trained, experienced service technician. 4. After installation is complete, check out product operation as provided in these instructions. CAUTION Hazardous Voltage. Can damage heating/cooling system. 1. Disconnect power supply before beginning instal- lation to prevent electrical shock or equipment damage. 2. Do not short across coil terminals on relay. This can burn out thermostat heat anticipator. 3. To prevent interference with the thermostat linkage, keep wire length to a minimum and run wires as close as possible to the subbase. 4. Do not overtighten thermostat captive mounting screws because damage to subbase threads can result. IMPORTANT An incorrectly leveled thermostat will cause the temperature control to deviate from setpoint. It is not a calibration problem. Location Install the thermostat about 5 ft (1.5m) above the floor in an area with good air circulation at average temperature. Do not mount the thermostat where it can be affected by: -- drafts or dead spots behind doors, in corners or under cabinets. -- hot or cold air from ducts. -- radiant heat from the sun, fireplace, or appliances. -- concealed pipes and chimneys. -- unheated (uncooled) areas such as an outside wall behind the thermostat. Mount Subbase The subbase can be mounted on a vertical outlet box, horizontal outlet box or directly on the wall. 1. If the subbase is mounted on a vertical outlet box, order Honeywell part no. 193121A Adapter Assembly. See Fig. 4. The assembly includes an adapter ring, two screws and a cover plate to cover marks on the wall. Install the ring and cover plate on the vertical outlet box. NOTE: For a wall installation, hold subbase in position and mark holes for anchors. See Fig. 5. Wall anchors must be obtained from local hardware store. Be careful that the wires do not fall back into the wall opening. Set aside subbase. Drill four 3/16 in. (4.8 mm) holes and gently tap anchors into the holes until flush with the wall. 2. Pull wires through the cover plate (if used) and subbase cable opening. See Fig. 6. 3. Secure the cover plate (if used) and subbase with the screws provided. Do not fully tighten the subbase screws. Level the subbase using a spirit level, see Fig. 7, and firmly tighten subbase mounting screws. The subbase mounting holes provide for minor out-of-level adjustments. VERTICAL OUTLET BOX 1 MOUNTING SCREWS (2) ADAPTER RING 2 COVER PLATE 2 1 HORIZONTAL OUTLET BOX THERMOSTAT SUBBASE SUBBASE MOUNTING SCREWS (2) HEAT 80 70 60 50 COOL 80 70 60 50 THERMOSTAT COVER CAPTIVE MOUNTING SCREWS (2) 80 70 60 50 1 NOT INCLUDED WITH UNIT. 2 ACCESSORY PART AVAILABLE (193121A). M6009 Fig. 4. Installing Q674 Subbase on outlet box. 7 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES WALL WIRES THROUGH WALL OPENING WALL ANCHORS (2) MOUNTING HOLES M926 SUBBASE MOUNTING SCREWS (2) Fig. 5. Installing Q674 Subbase on wall. SPIRIT LEVEL WIRING TERMINAL THERMOSTAT CABLE OPENING All wiring must comply with local electrical codes and ordinances. IMPORTANT Use 18 gauge, solid-conductor wire whenever possible. If using 18 gauge stranded wire, no more than 10 wires can be used. Do not use larger than 18 gauge wire. Follow equipment manufacturer wiring instructions when available. To wire subbase, proceed as follows: 1. Connect the system wires to the subbase as shown in the applicable diagram. A letter code is located near each terminal for identification. Typical terminal designation and wiring connections are listed in Table 5. The terminal barrier permits straight or wraparound wiring connection. See Fig. 7. The subbase can require one or more jumpers that may or may not be factory-supplied. See Fig. 8 and the wiring diagrams for specific terminals to be jumpered. FOR STRAIGHT INSERTION STRIP 5/16 IN. (8 MM) FOR WRAPAROUND STRIP 7/16 IN. (11 MM) POST FOR MOUNTING MOUNTING HOLES (4) THERMOSTAT (2) TO SPRING FINGER CONTACTS ON THE THERMOSTAT (UP TO 12) M927 Fig. 6. Subbase components and leveling procedure. Wire Subbase Disconnect power supply before beginning installation to prevent electrical shock or equipment damage. BARRIER SUBBASE TERMINAL SCREW M928 Fig. 7. Barrier configuration. CAUTION Equipment Damage Hazard. Never install more than one wire per terminal unless using factory-supplied jumper with spade terminal. 2. Firmly tighten each terminal screw. 3. Fit wires as close as possible to the subbase. Push excess wire back into the hole. 4. Plug hole with nonflammable insulation to prevent drafts from affecting the thermostat. 60-2485--8 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES JUMPER WIRE (SUPPLIED WITH SOME MODELS) 1 1 1 TWO ADJACENT TERMINALS SHOWN JUMPERED ARE FOR EXAMPLE ONLY. COMPARE WIRING DIAGRAM AND SUBBASE TO IDENTIFY TERMINALS TO BE JUMPERED. M5899 Fig. 8. Jumper adjacent terminals for special system hookup using stripped wire 3/4 in. (19 mm). For nonadjacent terminals and using jumper wire supplied with subbase. Table 5. Terminal Designationsa Standard Terminal Designation B E G L O R RC RH W1 W2 W3 Y1 Y2 Y3 X T Alternate Designations or Customer Specials K F R V H1, R3 H2, Y, R4 C1, M C2 X1,X2,C A L, C, H P O A, A1, A2, Z, C, L Typical Connection Heating damper motor; changeover valve Emergency heat relay Fan relay coil System monitor Cooling damper motor; changeover valve Power connection to transformer (internally connected for heating and cooling) Power connection to cooling transformer Power connection to heating transformer Stage 1 heating control Stage 2 heating control Stage 3 heating controlb Stage 1 cooling control Stage 2 cooling control Stage 3 cooling control Clogged filter switch or common connection Outdoor thermistor HSII control panel Defrost Momentary circuit, changeover LEDs a Other terminal designations can be used that are not listed on this table. Refer to the hookup drawing and internal schematic for exact connections. b W3 controls the auxiliary heat like W2, and allows adding additional stages of auxiliary heat with outdoor thermostats while maintaining the proper second stage anticipation. 9 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 5. Terminal Designationsa Standard Terminal Designation Alternate Designations or Customer Specials Typical Connection T External temperature readout, T relay R1, R2 LO and HI speed fan relays RS Cooling contactor Y M Compressor contactor a Other terminal designations can be used that are not listed on this table. Refer to the hookup drawing and internal schematic for exact connections. b W3 controls the auxiliary heat like W2, and allows adding additional stages of auxiliary heat with outdoor thermostats while maintaining the proper second stage anticipation. Outdoor Disconnect The National Electrical Code requires the installation of a disconnect switch within sight of the outdoor unit of an air conditioner or heat pump. The switch is for the safety of any technician working on the unit. The technician can assure that the unit remains unpowered. Install and Adjust Stop Brackets The stop brackets should be installed only if there is a need to restrict the adjustable range of the heating and cooling temperature setpoint levers. If adjustable lever stops are desired, order 4074ECK Envelope Assembly, which contains two adjustable lever stop brackets, one brass insert, one mounting screw and two locking screws with insulated heads. When installed, the stop brackets limit the movement of the T874 HEAT and COOL levers. TO INSTALL: 1. Remove the thermostat cover by pulling the bottom edge of the cover upward until it snaps free of the mounting slots. 2. Turn to the back of the T874 Thermostat. Locate the hole for the brass insert in the plastic base below the LED window. 3. Push the brass insert into the hole with finger. 4. Turn to the front of the T874 Thermostat. 5. Place the two stop brackets in position with the tabs in the slot between the HEAT and COOL levers. See Fig. 9. HEAT LEVER HOLES FOR INSULATED LOCKING LEVER SCREWS COOL LEVER HOLE WITH BRASS INSERT BRACKET TABS ADJUSTABLE LOCKING LEVERS ADJUSTABLE LEVER STOP BRACKETS BRACKET SLOTS MOUNTING SCREW NONADJUSTABLE STOPS WITH LOCKING LEVER SCREWS 75°F (24°C) MAX. HEAT 75°F (24°C) MIN. COOL ADJUSTABLE STOPS NONADJUSTABLE D.O.D. STOPS 72°F (22°C) MAX. HEAT 78°F (26°C) MIN. COOL Fig. 9. Range limiting and lever locking methods. M7626 6. Insert the mounting screw into the two slots in the stop brackets and attach to the brass insert. Tighten the screw to pull the brass insert into the back of the ther- mostat. 7. Loosen the mounting screw enough to free the stop brackets for adjustment. 60-2485--8 10 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES 8. Move the HEAT and COOL levers to the maximum temperature desired. 9. Slide the stop brackets until one rests against the HEAT lever and the other against the COOL lever. 10. Firmly tighten the mounting screw. 11. If the HEAT and COOL levers are to be locked in place at a specific temperature, use the two insulated head screws supplied instead of the two adjustable lever stop brackets. ALLEN RETAINING SCREWS (2) CAUTION Equipment Damage Hazard. Do not use standard screws that provide metal-tometal contact with the stop brackets. Short circuit and potential equipment damage can result. Mount Thermostat 1. Remove the thermostat cover by pulling the bottom edge of the cover away from the base until it snaps free of the cover clip. NOTE: The cover is hinged at the top and must be removed by pulling up at the bottom. 2. Carefully remove and discard the polystyrene packing insert that protects the mercury switches during shipment. 3. If LED indication (EM.HT., CHECK, etc.) is to be used with the Q674 Subbase, install the preprinted insert under the thermostat setpoint scale. To install, push both thermostat setpoint levers to the far ends of the thermostat. Use index finger to gently pull out the plastic setpoint scale about 1/4 in. (6 mm). Position the desired preprinted insert in the space above the LED lights. Reposition setpoint levers. 4. Turn over the thermostat base and note the spring fingers that engage the subbase contacts. Make sure the spring fingers are not bent flat, preventing proper electrical contact with the subbase. 5. Set the heat anticipator indicator(s) to the respective current setting of each stage. See Set The Heat Anticipator section. 6. If the thermostat provides optional locking cover assembly, start the Allen locking screws in the cover with the wrench provided. See Fig. 10. 7. Note the two tabs along the top inside edge of the thermostat base. The tabs fit into corresponding slots on top of the subbase. Mount the thermostat on the subbase. 8. Align the two captive mounting screws in the thermostat base with the posts on the subbase. Tighten both screws. Do not overtighten screws or damage to subbase posts can result. M956 Fig. 10. Installation of locking cover assembly. SETTINGS CAUTION Equipment Damage Hazard. On systems using a gas valve, never apply a jumper across the valve coil terminals, even temporarily. This can burn out thermostat heat anticipator(s). Set the Heat Anticipator Move the indicator to match the primary control current draw. When using a T874 Thermostat with two stages of heating, set each heat anticipator to match its respective primary control current draw. If you cannot find the current rating on the primary control, or if further adjustment is necessary, see NOTE and use the following procedure to determine the current draw of each stage. The current draw of each heating stage must be measured with the thermostat removed and power on to the heating system. 1. Connect an ac ammeter of appropriate range between the heating terminals of the subbase: a. Stage 1--between W1 and RH or R; b. Stage 2--between W2 and RH or R c. Stage 3--between W3 and RH or R. 2. Move the system switch to HEAT or AUTO. 3. After one minute, read the ammeter and record the reading: a. Stage 1--__________A; b. Stage 2--__________A; c. Stage 3--__________A. NOTE: If equipment cycles too fast, set the indicator to a higher current rating, but not more than one-half division at a time, and recheck the cycle rate. Most conventional two-stage heating equipment is designed to operate at three cycles per hour per stage, and one-stage heating equipment at six cycles per hour, at 50 percent load conditions. When using the T874 Thermostat in heat pump systems, set the heat anticipator at 140 percent of the actual primary control current draw to reduce the cycling rate. See Fig. 11. 11 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Most heat pump systems should cycle 2-1/2 to 3 times per hour. 4. Hang the upper edge of the thermostat cover on top of the thermostat base and swing the cover downward until it engages with the cover clip. STAGE ONE ANTICIPATOR HEATING CONTROL .12 .15 .2 .3 1.2.8.6.5 .4 .12 .10 1.2.8.6 .4 .3 .15 .2 STAGE TWO ANTICIPATOR HEATING CONTROL MOVE INDICATOR TO MATCH CURRENT RATING OF PRIMARY CONTROL M5069 Fig. 11. Adjustable heat anticipator scales. Temperature Setting Move the heating and cooling levers to the desired comfort positions. See Fig. 12. On some models with two stages of heating or cooling, the same lever controls both stages. The minimum differential between heating and cooling setpoints is 4°F (2°C) (5°F [3°C]) on T874W. If model has optional screws to lock temperature control levers, loosen these screws before making temperature adjustment; tighten the screws when levers are set at desired position. STAGE 1 HEATING STAGE 3 HEATING HEATING LEVER COOLING LEVER STAGE 1 COOLING HEAT--heating system is automatically controlled by the thermostat. Cooling system is off. AUTO--thermostat automatically changes between heating and cooling system operation, depending on the indoor temperature. COOL--cooling system is automatically controlled by the thermostat. Heating system is off. EM.HT.--emergency heat relay is automatically controlled by the thermostat. Cooling system is off. Compressor is de-energized. SUPL.HT.--supplemental heat relay is energized. Cooling system is off. Compressor is de-energized. WOOD--heating system is operating with only the woodburning stage. OIL--heating system is operating with only the oil-burning stage. WOOD/OIL--wood and oil stages operate sequentially; first the WOOD stage operates, then the OIL stage operates if the WOOD stage cannot handle the load. EVAP--controls cooling system by water evaporation; see equipment instructions for further information. OVERRIDE--night setback is disabled. ON--heating system is controlled by the thermostat. EM. HT. or SUPL. HT. relay is not energized. FAN SWITCH positions control fan operation as follows: ON or CONT.--fan operates continuously. AUTO--fan operates as controlled by the thermostat in heat pump systems or conventional cooling mode; fan operates as controlled by the plenum switch in conventional heating mode. LO--fan operates constantly at low speed. MED--fan operates constantly at medium speed. HI--fan operates constantly at high speed. To move the subbase switches to the desired control positions, use thumb and index finger to slide the lever. The lever must stop over desired function indicator position for proper circuit operation. Spring return momentary position switching feature is available on selected subbase models. On these models, the fan switch is positioned to the right of the system switch. By moving the fan switch to the far right and releasing it, the ON position circuit makes. The lever springs back on release. This position is not marked on the subbase. STAGE 2 HEATING STAGE 2 COOLING CAPTIVE MOUNTING SCREWS (2) M7625 Fig. 12. Internal view of T874W (three stages of heating, two stages of cooling). Subbase Setting The subbase switching positions control the system operation as described below. SYSTEM SWITCH (see subbase for positions): OFF--both the heating and cooling systems are off. If the fan switch is at the AUTO position, the cooling fan is also off. Setting the Adjustable Differential The adjustable interstage differential feature, on a selected T874D model only, can be identified by the scale and tension screw near the heating and cooling mercury switches. See Fig. 13. On this model, the number of degrees between the making of the first and second stage mercury bulbs is adjustable. This feature is especially useful if the first stage controls the comfort temperature, and the second stage controls the energy savings temperature. Timers, such as the S6005, for insertion between the first and second stage control points must be ordered separately. Each mark on the scale represents 1°F (0.6°C) The differential is factory set at 2°F (1°C) the differential can be set as high as 12°F (7°C) To set the adjustable interstage differential, loosen the tension screw. See Fig. 13. Slide the adjustable scale to align with the number of degrees desired between stages. Use the lower edge of the tension screw bracket as a guide for alignment. In heating, slide the lever wider apart for a larger differential, or closer together for a 60-2485--8 12 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES smaller differential. In cooling, slide the lever closer together for a larger differential, or wider apart for a smaller differential. While supporting the scale with hand, tighten the tension screw. IMPORTANT Support the scale with hand while tightening tension screw. See Fig. 13. Failure to do so can result in twisting and damaging bimetal coil. TENSION SCREW HEATING SETPOINT LEVER HEAT 50 60 70 80 FIRST STAGE SWITCH .2 1.5 SCALE HEATING TENSION SCREW ALIGN LOWER EDGE WITH SCALE NOTCH 10°F SCALE 1 1.2 .8 .6 .4 .3 SECOND STAGE (ADJUSTABLE) SWITCH SLIDE LEVER WIDER APART FOR LARGER DIFFERENTIAL CAUTION Equipment Damage Hazard. When the thermostat is used to control a two-stage heating or cooling system, the second stage mercury bulb must never make before the first stage bulb, or severe equipment damage could result. To prevent this problem, provide at least 2°F (1°C) differential between stage-one and stage-two make points. Example: in heating, if stage-one makes at 70°F (21°C) stage-two should make at 68°F (20°C) or lower. Verify the Adjustment Heating Start with the heating setpoint lever all the way to the left. Slowly move the lever to the right, just until the first stage bulb makes (mercury rolls to the right side of the bulb). Note the setting on the temperature scale. Slowly move the lever to the right until the second stage bulb makes. Note the setting on the temperature scale. The difference between the two temperatures is the interstage differential, which should match the number set on the scale with the tension screw. Cooling Start with the cooling setpoint lever all the way to the right. Slowly move the lever to the left, just until the first stage bulb makes (mercury rolls to the left side of the bulb). Note the setting on the temperature scale. Slowly move the lever to the left until the second stage bulb makes. Note the setting on the temperature scale. The difference between the two temperatures is the interstage differential, which should match the number set on the scale with the tension screw. CHECKOUT COOLING TENSION SCREW ALIGN LOWER EDGE WITH SCALE NOTCH 4°F SCALE 1 SLIDE LEVER CLOSER TOGETHER FOR LARGER DIFFERENTIAL 1 EACH MARK ON THE SCALE REPRESENTS 1°F (0.6°C). M937 Fig. 13. Set adjustable interstage differential. Heating Move the system switch on the Q674 Subbase to HEAT or AUTO. Move the heat lever on the T874 about 10°F (6°C) above room temperature. See Fig. 12. Heating system should start and the fan should run after a short delay. Move the heat lever about 10°F (6°C) below room temperature. The heating equipment should shut off, and the fan should run for a short time, then shut off. In heat pump applications, sometimes time delays are involved before the compressor and auxiliary heat are activated. This is due to a minimum-off timer, which prevents the compressor from restarting for five minutes from when the thermostat last turned off the compressor, or from when the system first received power. Cooling CAUTION Equipment Damage Hazard. Do not operate cooling if outdoor temperature is below 50°F (10°C). Refer to manufacturer recommendations. 13 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Move the system switch on the Q674 Subbase to COOL or AUTO. Move the cool setting lever on the T874 Multistage Thermostat about 10°F (6°C) below room temperature. See Fig. 12. The cooling equipment and fan should start. If the system has two stages of cooling, both stages should start. Move the cool lever about 10°F (6°C) above room temperature. The cooling equipment and fan should stop. Fan Move the system switch to COOL, OFF, or AUTO. If necessary, position both temperature setting levers so that the heating and cooling equipment are off. Move the fan switch to ON or CONT. The fan should run continuously. When the fan switch is in AUTO, LO, MED, or HI position, fan operation is controlled by the heating or cooling system. Outdoor Reset Thermistor (Where Applicable) If the system is supplied with a thermistor, it must be used; if not used, thermostat performance deviates radically from proper operation. The proper thermistor operation must be verified to ensure the correct operation of the thermostat. Check thermistor operations as follows: 1. Disconnect the T wire on the subbase. 2. Use an ohmmeter to measure resistance between the T wire and the A subbase terminal. 3. Take outdoor temperature at thermistor location and find the correct thermistor resistance on the Fig. 14 chart. 4. If the resistance measured in step 2 and the calculated resistance in step 3 vary by more than 15 percent, the thermistor requires replacement. Contact Honeywell or installing dealer for replacement packaged outdoor thermistor, part no. C815A1005. THERMISTOR RESISTANCE (ohms) 4600 4400 4200 4000 3800 3600 3400 3200 3000 2800 2600 2400 2200 2000 1800 1600 1400 1200 1000 800 600 400 200 0 -20 C815A THERMISTOR RESISTANCE R = 400 ohms ± 10% AT 77°F (25°C) 0 20 40 60 80 100 120 140 TEMPERATURE OF THERMISTOR (°F) M1590A Fig. 14. Thermistor resistance chart. CALIBRATION Thermostat T874 Thermostats are accurately calibrated at the factory. They do not have provision for field calibration. Thermometer The thermometer in your thermostat has been accurately calibrated at the factory. The thermometer should only need adjustment if it has been dropped or shifted due to mishandling. If the setpoint lever and the thermometer reading do not agree, use the following procedure: 1. Remove the thermostat cover by pulling up from the bottom edge of the cover away from the base until it snaps free of the cover clip. 2. Set the thermostat cover on a table near an accurate thermometer. 3. Allow ten minutes for cover thermometer to sense area temperature; compare the readings. Be careful not to touch thermometer or breathe on it. 4. If the readings are the same, replace cover and put the system into operation. 5. If the readings are different, insert a small screwdriver in the thermometer slot and turn it until the thermometers have the same reading. See Fig. 15. 6. Replace thermostat cover and put the system into operation. M5070 Fig. 15. Thermometer calibration. UNDERSTANDING CIRCUITS To understand wiring diagrams, it is important to know what all the symbols mean and how to trace the path of the circuits from the transformer. See Fig. 16 through 25. Circuit descriptions and terminology are defined as follows: For standard heating-cooling circuits: Auto changeover--refers to the presence of an AUTO position in the system switching (EX: Q674E with OFFHEAT-AUTO-COOL switching). The thermostat automatically changes between heat and cool modes as indoor temperature changes. Manual changeover--requires a system switch movement to change mode (EX: Q674B with HEAT-OFF-COOL switching). T874D Multistage Thermostats with 2 heat or 2 cool switches are shown on most standard circuits. Most standard or TRADELINE® subbases (Q674A-E,G) can be used with T874A-F standard or TRADELINE 60-2485--8 14 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES thermostats. The schematics can be field-modified as required (EX: if T874C is being used, eliminate second stage of heat). For heat pump circuits: Cool changeover valve--operates on cooling. The reversing valve or relay is activated either by moving the system switch to COOL (manual changeover) or by a mercury switch that makes on a temperature rise (auto changeover). Heat changeover valve--operates on heating. The reversing valve or relay is activated either by moving the system switch to HEAT (manual changeover) or by a mercury switch that makes on a temperature fall (auto changeover). System monitor relay--optional equipment on some heat pumps includes an R4222P1065 or equivalent. This system monitor relay detects a malfunction in the compressor and indicates the malfunction by activating the EMERGENCY HEAT LED on the Q674 Switching Subbase. The system monitor relay is usually wired into the L terminal on the Q674. Each mercury switch is identified by function: H1--Stage 1 Heating. H2--Stage 2 Heating. H3--Stage 3 Heating. C1--Stage 1 Cooling. C2--Stage 2 Cooling. C3--Stage 3 Cooling. C/O--Changeover (heat pumps). Each anticipator is identified and each switch affected is named (EX: H1 anticipator, C1 anticipator). All T874 Multistage Thermostats use mercury switches. Each schematic indicates switch operation by being drawn in the open position with an arrow indicating operation with a temperature RISE or FALL. One circuit has been selected that is typical of various models used with heat pumps. This circuit has been traced to illustrate the functions performed by these control systems. Tracing Method: 1. Always begin at the system transformer or R terminal. You may want to draw the switch contacts in each switch position to aid in tracing. Colored pencils are helpful when only one copy of the circuit is available. See Fig. 16 for a description of the hookup symbols and Fig. 17 through 25 for typical hookups. 2. Completely trace only one circuit at a time (for example: heat or cool). 3. Connections are indicated by small dots at the point of intersection. If there is no dot, there is no connection. 4. The left portion of the circuit (the thermostat) contains the mercury switches. The heat switches make on a temperature fall, and the cool switches make on a tem- perature rise. Fixed anticipation is represented by a zigzag line and adjustable anticipation is a zigzag with an arrow. The resistance of the fixed anticipator is so large it limits current so that a system relay cannot be pulled in from a circuit path going through the fixed anticipator. The relay can be pulled in through an adjustable anticipator because its resistance is generally 0 to 5 ohms. 5. The center portion (the subbase) contains the switches. The fan switch is above the system switch. The small circles on the switch represent the maximum possible contacts available on the Q674 Subbase. The larger circles represent the switch positions available on this particular Q674, with the solid circle representing where it is actually switched on the diagram. NOTE: Solid circles are not interconnected electrically. At the right, the relays and contactors are shown, attached to the proper terminals. The terminals are represented by large circles with terminal designations in capital letters. See Table 3 for the meaning of each lettered terminal. Sometimes power for a fixed anticipator is brought through an off system relay like the changeover relay shown in Fig. 20. This current is kept low by the high resistance of the fixed anticipator so that relay does not pull in. KEY TO HOOKUP SYMBOLS TRANSFORMER (24 VAC SECONDARY) RELAY OR CONTACTOR COIL RELAY/CONTACTOR CONTACTS B TERMINAL LED MERCURY SWITCH FIXED ANTICIPATOR HIGH RESISTANCE (TYPICALLY 5 KILOHMS) ADJUSTABLE ANTICIPATOR LOW RESISTANCE (TYPICALLY 0 TO 5 OHMS) ODT OUTDOOR THERMOSTAT EHR EMERGENCY HEAT RELAY RTD TIME DELAY RELAY RD DEFROST RELAY CHP PRESSURE SWITCH LACO LOW AMBIENT CUTOFF M5848 Fig. 16. Key to hookup symbols. 15 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT FALL H1/C1 ANTICIPATOR 2 SUBBASE SYSTEM COMPONENTS (HOT) L1 L2 1 R ODT 1 H1 C1 3 4 H2 ANTICIPATOR 5 H2 6 FALL FAN SWITCH AUTO ON SYSTEM SWITCH EM. HT. HEAT OFF COOL W3 W2 AUX. HT. LED (GREEN) 2 X EM. HT. LED (RED) L G O E Y B 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 AUXILIARY HEAT LED AVAILABLE ON SOME MODELS. RTD 1 EHR 1 ODT 2 EHR 2 RTD 2 RTD 3 RTD 1 SYSTEM MONITOR RD FAN RELAY COOL CHANGEOVER VALVE EM. HT. RELAY LACO CHP COMPRESSOR CONTACTOR M5072A Fig. 17. Internal schematic and typical hookup of a T874R Thermostat and Q674L Subbase in a heat pump application. The thermostat provides two-stage heating and one-stage cooling manual changeover operates on cooling. 60-2485--8 16 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT FALL H1 C1 H1/C1 ANTICIPATOR 2 3 H2 FALL 4 H2 ANTICIPATOR 5 6 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. SUBBASE FAN SWITCH AUTO ON SYSTEM COMPONENTS L1 R (HOT) ODT 1 L2 1 RTD 1 W3 EHR 1 RTD 2 ODT 2 SYSTEM SWITCH EM. HT. HEAT OFF COOL W2 AUX. HT. LED (GREEN) X EM. HT. LED (RED) L RTD 1 SYSTEM MONITOR G O E EHR 2 RTD 3 RD FAN RELAY CHANGEOVER VALVE EM. HT. RELAY LACO Y B COMPRESSOR CONTACTOR CHP M5840 Fig. 18. Tracing the changeover relay circuit. THERMOSTAT FALL H1/ C1 ANTICIPATOR 2 H1 C1 3 4 H2 ANTICIPATOR 5 H2 6 FALL 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. SUBBASE FAN SWITCH AUTO ON SYSTEM SWITCH EM. HT. HEAT OFF COOL SYSTEM COMPONENTS R RTD 1 W3 ODT 1 EHR 1 L1 (HOT) L2 1 RTD 2 ODT 2 W2 AUX. HT. LED (GREEN) X EM. HT. LED (RED) L RTD 1 SYSTEM MONITOR G O E LACO Y B EHR 2 RTD 3 RD FAN RELAY CHANGEOVER VALVE EM. HT. RELAY COMPRESSOR CONTACTOR CHP M5841 Fig. 19. Tracing the heat 1 and anticipation circuit. 17 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT H1/ C1 ANTICIPATOR FALL 2 H1 C1 3 4 H2 ANTICIPATOR 5 H2 6 FALL 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. SUBBASE SYSTEM COMPONENTS FAN SWITCH AUTO ON SYSTEM SWITCH EM. HT. HEAT OFF COOL R RTD 1 W3 ODT 1 EHR 1 ODT 2 L1 (HOT) L2 1 RTD 2 W2 AUX. HT. LED (GREEN) X EM. HT. LED (RED) L RTD 1 SYSTEM MONITOR G O E EHR 2 RTD 3 RD FAN RELAY CHANGEOVER VALVE EM. HT. RELAY LACO Y B COMPRESSOR CONTACTOR CHP M5842 Fig. 20. Tracing the heat 1 anticipation circuit. THERMOSTAT FALL H1/C1 ANTICIPATOR 2 H1 C1 3 4 H2 ANTICIPATOR 5 H2 6 FALL 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. SUBBASE FAN SWITCH AUTO ON SYSTEM SWITCH EM. HT. HEAT OFF COOL SYSTEM COMPONENTS L1 R (HOT) ODT 1 L2 1 RTD 1 W3 EHR 1 RTD 2 ODT 2 W2 AUX. HT. LED (GREEN) X EM. HT. LED (RED) L RTD 1 SYSTEM MONITOR G O E EHR 2 RTD 3 RD FAN RELAY CHANGEOVER VALVE EM. HT. RELAY LACO Y B COMPRESSOR CONTACTOR CHP M5843 Fig. 21. Tracing the heat 2, anticipation and AUX. HT. LED circuit. 60-2485--8 18 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT FALL H1/C1 ANTICIPATOR 2 H1 C1 3 4 H2 ANTICIPATOR 5 H2 6 FALL 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. SUBBASE FAN SWITCH AUTO ON SYSTEM SWITCH EM. HT. HEAT OFF COOL SYSTEM COMPONENTS R RTD 1 ODT 1 EHR 1 L1 (HOT) L2 1 RTD 2 W3 ODT 2 W2 AUX. HT. LED (GREEN) X EM. HT. LED (RED) L RTD 1 SYSTEM MONITOR G O E LACO Y B EHR 2 RTD 3 RD FAN RELAY CHANGEOVER VALVE EM. HT. RELAY COMPRESSOR CONTACTOR CHP M5844 Fig. 22. Tracing the emergency heat and EM. HT. LED circuit. THERMOSTAT FALL H1/C1 ANTICIPATOR 2 H1 C1 3 4 H2 ANTICIPATOR 5 H2 6 FALL 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. SUBBASE FAN SWITCH AUTO SYSTEM COMPONENTS R RTD 1 W3 ODT 1 EHR 1 L1 (HOT) L2 1 RTD 2 ODT 2 ON SYSTEM SWITCH EM. HT. HEAT OFF COOL W2 AUX. HT. LED (GREEN) X EM. HT. LED (RED) L RTD 1 SYSTEM MONITOR G O E LACO Y B EHR 2 RTD 3 RD FAN RELAY CHANGEOVER VALVE EM. HT. RELAY COMPRESSOR CONTACTOR CHP M5845 Fig. 23. Tracing the cooling circuit. 19 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT FALL H1/C1 ANTICIPATOR 2 H1 C1 3 4 H2 ANTICIPATOR 5 H2 6 FALL 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. THERMOSTAT FALL H1/C1 ANTICIPATOR 2 H1 C1 3 4 H2 ANTICIPATOR 5 H2 6 FALL 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. SUBBASE FAN SWITCH AUTO ON SYSTEM COMPONENTS R RTD 1 ODT 1 EHR 1 L1 (HOT) L2 1 RTD 2 W3 ODT 2 SYSTEM SWITCH EM. HT. HEAT OFF COOL W2 AUX. HT. LED (GREEN) X EM. HT. LED (RED) L RTD 1 SYSTEM MONITOR G O E EHR 2 RTD 3 RD FAN RELAY CHANGEOVER VALVE EM. HT. RELAY LACO Y B COMPRESSOR CONTACTOR CHP M5846 Fig. 24. Tracing the auto fan circuit. SUBBASE FAN SWITCH AUTO ON SYSTEM SWITCH EM. HT. HEAT OFF COOL SYSTEM COMPONENTS R RTD 1 W3 ODT 1 EHR 1 ODT 2 L1 (HOT) L2 1 RTD 2 W2 AUX. HT. LED (GREEN) X EM. HT. LED (RED) L RTD 1 SYSTEM MONITOR G O E EHR 2 RTD 3 RD FAN RELAY CHANGEOVER VALVE EM. HT. RELAY LACO Y B COMPRESSOR CONTACTOR CHP M5847 Fig. 25. Tracing the fan on circuit. 60-2485--8 20 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES OPERATION Heat Anticipation/Cool Anticipation When controlling a heating unit with a thermostat, the temperature does not remain exactly at the thermostat setpoint, but varies within a certain temperature range. Heat anticipation is added to the thermostat to reduce this range. The anticipator is a small resistive heater in the thermostat that heats when the system is on (heat mode) or off (cool mode). The heat produced by the anticipator raises the internal bimetal temperature slightly faster than the surrounding room temperature. The thermostat anticipates the need to shut off the heating system sooner than it would if affected by room temperature only. There are two types of heat anticipation, adjustable and fixed. Adjustable anticipation is also called current anticipation. See Fig. 26. The heater is in series with the mercury switch and heating primary. The pointer is adjusted to match the current draw of the primary control, and the correct amount of heat is added for proper cycle rates. L1 L2 (HOT) H1 ANTICIPATOR H1 FALL STAGE 1 HEAT RELAY M5823 Fig. 26. Adjustable anticipation heater in series with load. Fixed anticipation is also called voltage anticipation. See Fig. 27. The heater is in parallel with the primary control and is not affected by the current draw of the primary. It establishes the proper cycle rate for any application. L1 L2 (HOT) FALL STAGE 1 HEAT RELAY H1 ANTICIPATOR H1 M5824 Fig. 27. Fixed anticipation heater in parallel with load. Heat anticipators add heat during the call for heat. Cooling anticipators are activated while the air conditioner is off. See Fig. 28. This heater makes the thermostat think it is warmer than it really is, and brings it on sooner than the bimetal alone would. L1 L2 (HOT) RISE C1 STAGE 1 COOL RELAY C1 ANTICIPATOR M5825 Fig. 28. Internal cooling anticipation schematic. Interstage Differential The mercury switch of each stage of heat makes at a slightly different temperature; that is, the mercury makes the contacts of the first stage bulb at one temperature, and the second stage bulb at another temperature. The difference between these two temperatures is the interstage differential. Interstage differential is the difference between the two make points when the bulbs are controlled by the heating of the bimetal and the action of the heat anticipator. The interstage differential is 1.9°F (1°C) between the stages of heating or the stages of cooling for most models. Mechanical differential is the difference between the make and break points of each switch. The mechanical differential for the T874 is 1°F (0.6°C) between the stages of heating or between the stages of cooling for most models. Droop The addition of anticipator heat to the bimetal causes a control factor called droop. As the weather grows colder, the heating appliance must operate longer and more frequently. More heat must be added to the bimetal. The bimetal now thinks it is warmer than it really is, and actual room temperature is controlled at a lower temperature than the setpoint indicates. At 100 percent heat load, this droop can be significant. The C815A Outdoor Reset Thermistor is used in heat pump systems to minimize droop. Without some method of countering this situation, the occupant could notice the temperature offset. Outdoor Reset Some T874/Q674 models are intended for use with the C815A Outdoor Thermistor. The outdoor thermistor provides significantly improved thermostat performance when compared to conventional multistage thermostats. The C815A is usually located in the heat pump condensing unit outdoors. 21 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES CAUTION Equipment Damage Hazard. Due to calibration techniques used for T874 Thermostats with outdoor reset, the C815A Thermistor must be wired into the system at all times. Failure to do so will result in serious degradation of performance. Service and Replacement of C815A Outdoor Thermistor To check and verify thermistor operation, perform the following steps: 1. Disconnect wire from T terminal on subbase. 2. Measure resistance with ohmmeter across the T sub- base wire and X subbase terminal. 3. Take outdoor temperature measurement at thermistor location and find correct thermistor resistance on the chart in Fig. 29. 4. Compare resistance on the chart with measured resistance. Replace C815A if resistance varies more than 15 percent. Contact installing dealer for packaged replacement outdoor thermistor. THERMISTOR RESISTANCE (ohms) 4600 4400 4200 4000 3800 3600 3400 3200 3000 2800 2600 2400 2200 2000 1800 1600 1400 1200 1000 800 600 400 200 0 -20 C815A THERMISTOR RESISTANCE R = 400 ohms ± 10% AT 77°F (25°C) 0 20 40 60 80 100 120 140 TEMPERATURE OF THERMISTOR (°F) M1590A Fig. 29. Thermistor resistance chart. Features Two of the features of the T874/Q674 include LED indicators and restricted setpoint. LED Indicators The light-emitting diodes (LED) indicators on the subbase light on command when something specific happens in the system. See Fig. 30. Up to four different LEDs are available. The thermostat has a clear lens window for viewing each LED. On TRADELINE models, a small insert is used so the LED function desired can be selected. This must be done during installation. A blank insert is factory-installed in some T874 models. To remove it, push both temperature setting levers to the far ends of the thermostat. Use index fingernail to gently pull out the scaleplate a fraction of an inch. Turn thermostat upside-down, and the blank insert falls out. A strip of four inserts is included with TRADELINE T874. Drop a strip into the recessed area behind the scaleplate so selected LEDs show. Make sure insert is completely seated in recessed area. Let scaleplate pop back; then set levers to desired position. · FILTER LED lights when the filter is clogged and needs replacement. · CHECK LED lights when something needs to be checked or done to maintain efficient operation of system. See heating system instructions for CHECK LED meaning. · EM. HT. LED lights when the emergency heat is operating. · SUPL. HT. LED lights when the supplemental heat is operating. · LOCKOUT LED lights when the system is shut down and needs maintenance. · AUXILIARY HEAT LED lights when the auxiliary heat is operating. · SERVICE or MALFUNCTION LED can have several meanings. Consult heating system instructions. LEDs cannot be replaced or added in the field. LEDS 80 EM. AUX HEAT FILTER SERV. HEAT 50 60 70 80 COOL M5830 Fig. 30. T874/Q674 LED location. Restricted Setpoint (DoD) The Department of Defense (DoD) models are equipped with a restricted setpoint feature for fuel efficiency. Fixed stops are factory-set so setpoint levers cannot be set above 72°F (22°C) on heating, or below 78°F (26°C) on cooling. Applications The T874/Q674 can be applied to standard residential systems for automatic or manual changeover, to commercial rooftop applications, or to heat pump applications. Changeover on Standard Residential Systems In a standard residential heating-cooling circuit, changeover between heating and cooling can be done either automatically or manually. Automatic changeover is done by an AUTO position on the subbase system switch. See Fig. 31. When the switch is in the AUTO position, the thermostat automatically changes between heat and cool modes, depending on the indoor temperature. 60-2485--8 22 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES When enthalpy is low enough, the thermostat and a sensor tell the economizer damper to open to let in cool air from the outside. When enthalpy is high, the thermostat and sensor tell the damper to close. No more outside air comes in, so the air conditioner is used instead. OFF EM. HT. HEAT AUTO COOL M5828 Fig. 31. System switching for automatic changeover. Automatic changeover is frequently used in areas where there are large temperature differences in 24 hours. Some uses for the automatic changeover feature are in the southern states (cool in the morning and hot in the afternoon) and in commercial applications. Manual changeover requires a system switch movement to change the mode. See Fig. 32. Most manual changeover switches consist of HEAT-OFF-COOL choices. For heating, switch to HEAT. For cooling, switch to COOL. It is not automatic. Manual changeover is often used in areas where the temperature is relatively stable between day and night. OFF EM. HT. HEAT COOL M5829 Fig. 32. System switching for manual changeover. Commercial Rooftop Application The T874 can be used as part of a commercial rooftop application to run mechanical cooling. An economizer is often used as part of a rooftop application to save on air conditioning. See Fig. 33. OUTDOOR AIR H205 OR H705 ENTHALPY CONTROL RETURN AIR DISCHARGE AIR SENSOR DOWNSTREAM FROM THE EVAPORATOR COIL M5827A Fig. 33. Typical commercial rooftop economizer application. Enthalpy is the temperature and humidity of the air. A more accurate analysis of the suitability for free cooling can be made by monitoring the enthalpy. Heat Pump Application A heat pump system operates much like an air conditioner. However, the heat pump is capable of moving heat in two directions; from inside the home to outdoors for cooling, or from outdoors to inside for heating. The heat pump can be controlled by separate relay/contactor components, which are energized or de-energized by the T874. Changeover between heating and cooling for heat pump circuits can be accomplished either manually or automatically. Manual changeover control requires a system switch movement to change the mode. The reversing valve is activated by moving the system switch to COOL for cooling or to HEAT for heating operation. Automatic changeover is accomplished by one of the mercury bulb switches in the thermostat. On a system with automatic changeover on cooling, the changeover valve is energized by a mercury switch that makes on a temperature rise. On heating, the changeover valve is energized by a mercury switch that makes on a temperature fall. A description of the methods used to control heat pumps follows. Space Temperature Sensing Low Voltage Controls Control systems for heat pumps usually utilize low voltage control circuits. The variety of control functions required and the relative complexity require a versatile and economical method of control. There are several interlocks and indication functions that would be more difficult and expensive to wire in line voltage circuits. Low voltage controls have the precision and flexibility needed. The thermostat used is a low voltage device that has good temperature sensitivity and several manual and automatic switching capabilities. Two-Stage Thermostat In most installations, the heat pump itself requires auxiliary heat, usually in the form of electric strip heaters, to carry the building heating load at design conditions. Since the heat pump is usually more efficient, the control strategy is to run the heat pump whenever possible and the auxiliary heat only when necessary--during very cold weather or if the heat pump fails. Usually the auxiliary heat is used only below the balance point (temperature at which the heat pump cannot handle heating load by itself). A two-stage thermostat makes this possible. The two stages make sequentially as the temperature drops. There is a degree or two between stages so that the second stage (the 23 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES one controlling the auxiliary heat) makes only when the heat pump alone cannot handle the load. That is how the strategy of using the most economical heat first is implemented. Cycling Rate Normally, thermostat anticipation is set to cycle a fossil fuel furnace about five or six times an hour (at 50 percent load). This provides a reasonable balance between comfort, stability and economy. A heat pump, being a mechanical refrigeration system, should be cycled at a rate of 2-1/2 to 3 times an hour. With a T874, this is accomplished by setting the anticipator at the total current draw of the controlled device (the contactor and possibly the changeover relay or valve). Most likely, the compressor operates from the first stage of the thermostat. The second stage normally controls the auxiliary heaters. This heat anticipator can be set for the current draw of the electric heat primary, and produces good control. Voltage Anticipation Although not a specific requirement for heat pumps, several models of the T874 have voltage heat anticipation instead of current anticipation. With voltage anticipation, the amount of heat added to the thermostat is constant no matter which load is connected to it. The anticipator realizes a constant voltage and produces a constant amount of heat during the ON cycle. This allows the cycling rate to be designed into the thermostat. The heat pump manufacturer is assured of correct performance independent of later thermostat adjustments. Outdoor Reset Outdoor reset, which a C815A Outdoor Thermistor makes possible, is sometimes applied in heat pump systems to help minimize the effect of the differential between stages. It takes 2°F (1.1°C) change in temperature to bring on the second stage and full heating. Added to a certain amount of droop under high loads, there can be a large offset between the setpoint and room temperature. Without some method to counteract this situation, the temperature offset from the setpoint could be as much as 6°F (3.3°C) under high load conditions. It is not likely that the occupants accept this variation without making frequent thermostat setting changes. Outdoor reset has the effect of raising the setpoint at cold outdoor temperatures. Then, even with a few degrees droop, the space temperature stays near the desired setting. This is done by calibrating the thermostat high by 5°F (3°C)-- the amount of expected offset. This offset compensates for differential and droop at high load factors so the thermostat switches at the setpoint. At warm temperatures, heat is added to the thermostat to compensate for this offset; at cold temperatures, the extra heat is automatically removed. The effect is the same as raising the setpoint as the outdoor temperature goes down. This is particularly important on the 3-stage T874. The additional stage means that more droop is introduced when the system is in operation. That is the reason the TRADELINE T874W is sold in a package with the outdoor sensor and the correct subbase. Outdoor Reset--How it Works The heater in the thermostat is connected in series with a thermistor sensor that measures outdoor temperature. See Fig. 34. In warm weather, the thermistor has very low resistance, permitting a large current flow in the heater, which generates a relatively large amount of heat in the thermostat. In cold weather, the outdoor sensor has high resistance, which results in low current flow and little or no heat being added to the thermostat. This raises the control point, overcoming the effects of droop and interstage differential. L1 L2 (HOT) RESET HEATER C815A OUTDOOR THERMISTOR SENSOR M5826 Fig. 34. Location of thermistor. Changeover Changeover between heating and cooing can be accomplished either automatically or manually, depending on the application. Changeover can occur in heating or cooling. The changeover valve is energized as long as the subbase function switch is in the appropriate position when manual changeover is used. If a system manually changes over on cooling, the valve energizes whenever the subbase switch is in the cooling mode. One of the mercury bulb switches is used for control when the thermostat has automatic changeover. When the automatic changeover is in cooling, the changeover valve is energized when the first stage cooling switch makes. The second stage switch turns on the compressor. It is more common with new equipment to find that changeover occurs with cooling; that is, the changeover valve is energized to produce cooling. Whether automatic or manual changeover is used and whether the reversing valve is energized with cooling or with heating, a heat pump system can be controlled by the appropriate T874 Multistage Thermostat. 60-2485--8 24 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Low Temperature Lockouts Some manufacturers of heat pumps have previously controlled their units so the compressor was locked out below a specified outdoor temperature. This was done because of the stress placed on the compressor by the very cold temperatures, and the fact that efficiency drops off at low temperatures. Other manufacturers say that although efficiency is low at cold temperatures, the problem of starting the cold compressor is the most critical point. It is more important to keep the compressor running than to shut it off and try to restart it when the temperature warms up to +10°F (-12°C). Also the crankcase heater, which can run only when the compressor is off, compensates for the lower compressor efficiency. So, it is equitable to let the heat pump run even with a coefficient of performance (COP) slightly less than one, rather than to turn it off and have to run the crankcase heater. NOTE: To determine the COP of a heat pump, use the following formula: COP = Btu Out/Btu we pay for or Btuh Capacity Unit Wattage x 3.413 Btu/Watt Another factor favoring this control strategy is that newer heat pump designs maintain a level of efficiency even at outdoor temperatures well below zero. Some brands do not reach 1.0 COP until -25°F (-32°C). Virtually all manufacturers now let the heat pump run continuously rather than lock it out at cold temperatures. Heat Pumps with Dual Compressors Staging residential sized heat pumps is a requirement that developed from the need to make heat pumps as efficient as possible. One of the methods used to improve overall seasonal efficiency is to reduce the amount of time the machine is operating in a transitional mode. Transitional mode is starting and stopping in addition to recovering from defrost. Under light loads, when the heat pump is cycling on and off, this can be a significant amount of time and can result in a significant efficiency reduction. Capacity control is one way to reduce the cycling rate and improve the efficiency. Additional capacity control methods used on other refrigeration systems (unloading, multiple compressors) are not as likely to be seen on residential heat pumps. With a single-stage heat pump, the compressor is normally controlled by the first stage and the auxiliary heat by the second stage. The T874G, N and R Thermostats are used for this purpose. With a two-stage compressor, the two thermostat switches control the individual compressor stages. Auxiliary heat is controlled along with the compressor stage-two, by the thermostat second stage. It comes on with the compressor high speed if an outdoor thermostat--wired in series with it-- is made. See Fig. 35. THERMOSTAT HEAT 2 HEAT 1 COMP. STAGE 1 OUTDOOR THERMOSTAT COMP. STAGE 2 AUXILIARY HEAT M5838 Fig. 35. Two-stage heat pump with two-stage thermostat. The outdoor thermostat is set at the balance point with both heat pump stages running. So if the heat pump can control the heating load down to +20°F (-7°C), the auxiliary heat comes on with the second stage of the compressor. In effect, this control strategy changes the heat input of the second stage, depending on the amount of heat needed. Additional stages of auxiliary heat can be added with or without the control of more outdoor thermostats, See Auxiliary Heat section. Another way to control a two stage heat pump is with a threestage thermostat. The T874W is designed for this application as well as others. See Fig. 36. The advantage of this system is that no auxiliary heat is used until there is an actual demand from the controlled space. THERMOSTAT HEAT 3 HEAT 2 HEAT 1 COMP. STAGE 1 COMP. STAGE 2 AUXILIARY HEAT M5837 Fig. 36. Two-stage heat pump with three-stage thermostat. Two speed Heat Pump One way to control capacity is to use a two-speed compressor. The compressor runs at low speed for stage-one heating and cooling. The compressor runs at the low speed instead of cycling the heat pump on and off under some light load conditions. The high speed is stage-two cooling. The compressor runs on high speed when loads increase so the low speed can no longer handle the cooling load. This reduces cycling rate and improves capacity. 25 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Defrost Control In some regions, during half or more of the heating season, the outdoor coil operates below 32°F (0°C) Frost or ice builds up on the outdoor coil of a heat pump similarly to the frost buildup in a household refrigerator. Eventually, this accumulation of ice interferes with efficient heat transfer from the outdoor air to the coil and refrigerant. Defrosting is occasionally required to remove this ice, and restore the heat pump ability to absorb heat from the air. Defrosting A heat pump defrosts its outdoor coil by temporarily switching to the cooling mode, which causes hot gas from the compressor to be directed to the outdoor coil instead of to the indoor coil so the heat pump is taking heat from the home to warm up the outdoor coil. Defrosting is the greatest detriment to heat pump efficiency. Defrost Control Functions Besides changing over to the cooling mode, defrosting requires several more control initiated actions that follow. OUTDOOR FAN When defrosting has begun, it is standard practice to turn off the outdoor fan to speed up the melting process. A separate defrost relay is required to control that fan. See Fig. 37. Other contacts can be needed on the defrost relay to power the changeover valve or power part of the auxiliary heat. CONTACTOR COMPRESSOR MOTOR CONTROLLED BY OUTDOOR DEFROST RELAY FAN MOTOR M5839 Fig. 37. Outdoor fan with defrost control. AUXILIARY HEAT DURING DEFROST Most pump manufacturers bring on some auxiliary heat during defrost, although this is not a universal practice. Some rely on the second stage of the thermostat to call for auxiliary heat as needed. Since the heat pump is operating in the cooling mode to defrost, it is delivering cold air to the living space. Auxiliary heat is used to offset this cooling. It requires another normally open contact on the defrost relay. See Fig. 38. L1 L2 (HOT) TRANSFORMER THERMOSTAT HEAT 2 HEAT 1 DEFROST RELAY CONTACT AUXILIARY HEAT RELAY M5835 Fig. 38. Auxiliary heat with defrost control. WHEN TO DEFROST Timely defrosting is an essential component of effective heat pump operation. Failure to defrost often enough permits too much ice to accumulate on the coil. At the very least, this hurts efficiency; at worst, it results in compressor damage. Insufficient defrosting is a condition the heat pump manufacturer wants very much to avoid. A 50 percent reduction in outdoor airflow is the maximum that would be tolerated. So the designer of a heat pump would select a control point that puts the system into defrost when airflow through the outdoor coil approaches half its normal level. Restricted airflow causes a greater load on the compressor; the outdoor coil runs colder, suction pressure is lower and the motor runs hotter. At the other end of the scale, defrosting too often hurts the overall energy efficiency of the system. Consider that in terms of heating the building, defrosting is a big loss. Not only does the system stop heating, but it actually moves heat out of the building. If electric strip heat is used, it is a further waste because its COP is 1.0 and not the 2.0 or more COP realized if the heat is provided by the heat pump. So, concern for equipment safety suggests fairly frequent defrosting while economy of operation argues for fewer defrost cycles. Since the equipment manufacturer chooses, the balance is usually tipped in favor of more frequent defrosting to avoid the possibility of damaging the compressor. Auxiliary Heat Except in warm climates, all air-to-air heat pump installations require auxiliary heat capability. Electric resistance heaters can provide this auxiliary heat. The electric heaters (sometimes called strip heaters) usually are supplied in 5 kW units or strips (about 17,000 Btu). The indoor unit of the heat pump is designed to accommodate various electric heat units so it can be used in variously sized buildings in different parts of the country. Two-Stage Thermostat The most common heat pump control strategy is for the thermostat first stage to switch the compressor and the second stage to switch the auxiliary heat. See Fig. 39. 60-2485--8 26 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT HEAT 2 HEAT 1 COMPRESSOR CONTRACTOR CONTROLS AT 65°F (18°C) AUXILIARY HEAT RELAY CONTROLS AT 63°F (17°C) M5836 Fig. 39. Auxiliary heat in two-stage thermostat. This method keeps the auxiliary heat off until the heating load is large enough to demand 100 percent heat pump operation. That demand is measured by the thermostat and is the actual heat requirement of the space. The two-stage thermostat requires about a 2°F (1.1°C) room temperature drop to bring on the second stage. Stage or Time Modulated Control There are two different ways to control auxiliary heat, staged or time modulated control. Outdoor thermostats are used to switch additional increments of electric heat into the thermostat circuit as the outdoor temperature gets lower. All increments of auxiliary heat are still controlled by stage-two of the thermostat but only if the outdoor temperature requires the additional capacity. See Fig. 40. THERMOSTAT HEAT 2 HEAT 1 COMPRESSOR CONTACTOR 20°F (-7°C) OUTDOOR THERMOSTATS 5°F (-15°C) AUXILIARY HEAT RELAY 1 AUXILIARY HEAT RELAY 2 AUXILIARY HEAT RELAY 3 M5834 Fig. 40. Outdoor thermostats for auxiliary heat. The rationale for this system is that it very closely matches the system capacity to the heating load of the building. By calculating the heat loss of a building, the installing contractor can pick the theoretical outdoor temperature at which to permit each additional unit of electric heat to be operated by the second stage of the room thermostat. The disadvantage of this system is that it can require several outdoor thermostats. Also, since the unit is operating most often at nearly full capacity, the thermostat is on longer which results in more droop, with a little more offset from the thermostat setpoint. In addition, the capacity is tied to theoretical load, based on heat loss calculations. Normally this is very close to the actual load, but there are times where the second stage is switched on too soon (no harm done) or too late (the building gets cold). The T874 Thermostat produces time modulated control, which is the on time of the thermostat changing during each cycle as the load changes. The on time of the heating system is directly proportional to the heating load of the building. As an example of the quality of time modulated control, consider the typical gas furnace. It can have a capacity of 100,000 Btu (293 kW), which is controlled On-Off. The output is 100,000 Btu (293 kW) or nothing. A quality thermostat controls so closely that the occupants rarely detect changes in room temperature. The same is true with 50,000 or 60,000 Btu (146.5 or 178.8 kW) of heat pump auxiliary electric heat. The T874 can provide the same high quality control. This scheme also eliminates the need for outdoor thermostats and thus offers the manufacturer an opportunity to reduce unit cost. One disadvantage is that a thermostat jiggler can be demanding more kW of strip heat when chilly. The method any particular manufacturer selects depends on which arguments it finds persuasive and the opinions of its distributors and dealers. Three-Stage Thermostat A definite improvement in quality of control and economy can be achieved with a three-stage thermostat (T874W), which is especially true with heat pumps using dual compressors. Three-stage control permits both the heat pump and the auxiliary heat to be tied directly to the demand of the controlled space. With a two-stage compressor, maximum (100 percent) heat pump operation is required before auxiliary heat is brought on. Emergency Heat Some provision is generally required to back up the compressor in the event of a failure during the heating season. In fact, it is quite common to find that local building codes or electric utilities require that a specified percent of the building heating requirements be available from emergency heat--a source other than the heat pump compressor. Almost universally, the source is electric resistance heaters. Typically, the requirement is for 70 or 80 percent of the building heating needs. Switching to Emergency Heat Conventional heat pump control (thermostat logic) usually includes a manual subbase switch to bring on the emergency heat. In one control strategy, the emergency heat relay is turned on by the EM.HT. selector switch on the thermostat subbase. The compressor is prevented from running. The electric heaters are cycled as they normally would be by the second stage of 27 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES the thermostat. A set of contacts on the emergency heat relay is used to bypass each outdoor thermostat so that all electric heat is under immediate thermostat stage-two control. So the emergency heat relay simply bypasses the outdoor thermostats. See Fig. 41. In the second method, the emergency heat relay is cycled directly by the thermostat mercury bulb. In this hookup, the relay is controlled by the thermostat first stage. The emergency heat relay energizes all of the auxiliary heat relays on a call for heat. See Fig. 42. So the emergency heat is controlled by the first stage of the thermostat. The emergency heat relay energizes all of the electric strip heaters so the heat and the indoor fan come on together as soon as the first stage calls for heat. With the first method, the fan remains on (being controlled by the first stage of the thermostat) and the electric heaters cycle on and off with the second stage. In either case, a subbase indicator light is turned on whenever the function switch is in the emergency heat (EM.HT.) position. THERMOSTAT FUNCTION SWITCH HEAT 2 HEAT 1 COMPRESSOR OUTDOOR THERMOSTAT AUXILIARY HEAT RELAY 1 AUXILIARY HEAT RELAY 2 EMERGENCY HEAT RELAY CONTACT EMERGENCY HEAT RELAY M5833 Fig. 41. Emergency heat relay that bypasses the outdoor thermostats. THERMOSTAT FUNCTION SWITCH HEAT 2 HEAT 1 24 V EMERGENCY HEAT RELAY CONTACT COMPRESSOR AUXILIARY HEAT RELAY EMERGENCY HEAT RELAY M5832 Fig. 42. Emergency heat relay that energizes all of the auxiliary heat relays on a call for heat. Crankcase Heat In any mechanical refrigeration system, refrigerant tends to migrate to the coldest part of the equipment and condense there. In a heat pump, this coldest spot could be the compressor because it is usually outdoors. In addition, the oil in the compressor crankcase is capable of absorbing a high concentration of refrigerant. On compressor startup, there are two risks: (1) the liquid refrigerant, which is noncompressible, can be drawn into the cylinder, and (2) considerable oil can be entrained in the refrigerant and swept out of the crankcase through the changeover valve and dispersed in the piping and coils. So the migration of refrigerant to the crankcase is undesirable because it can interfere with system lubrication and because the liquid refrigerant must be kept from going through the compressor. Adding a crankcase heater creates enough temperature differential to prevent this migration because the compressor is no longer the coldest part of the system so refrigerant does not migrate to it. Compressor Fault Relay Another very simple method of detecting a compressor failure has been developed. It uses the voltage developed across the capacitor in a permanent split capacitor compressor motor. The principle involved is that virtually all serious problems reduce the voltage across the motor capacitor. By carefully selecting the correct coil voltage, the normally closed relay does not pull in unless the proper voltage builds up across the capacitor, which brings on the SERVICE LED. See Fig. 43. Here is how it works: · On a call for cooling, the thermostat makes R to Y, the contactor coil is powered, and the compressor motor turns on. · At the same time, the indicator light is energized. · As the motor gets up to speed--about one second, the fault relay sees enough voltage to pull in. Its normally closed contact opens and the indicator light goes out. · Anything that prevents the motor from running prevents the fault relay from pulling in. COMPRESSOR MOTOR FAULT RELAY L1 RUN R C L3 CAP. START S Y R L X RISE LED L2 L1 (HOT) CONTACTOR THERMOSTATSUBBASE M5831 Fig. 43. Compressor fault relay schematic. 60-2485--8 28 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES CROSS REFERENCE The following section lists the current T874 Trade replacements for T872 and T874 Multistage Thermostats. It also lists the Q674 Trade replacements for Q672 and Q674 Subbases. All thermostats listed carry the Honeywell logo unless otherwise noted. When using the Cross Reference Charts, refer to the following instructions: 1. Locate and identify the existing thermostat and subbase model. 2. Refer to the Model Number column to find the model that matches the existing thermostat and subbase. 3. The Description column identifies certain characteristics of the existing device. 4. The Trade Replacement column identifies the correct replacement device. 5. The Remarks column lists any characteristics or adjustments to be made on the Trade replacement model. 6. The Fig. No. column lists the wiring hookup used for the specific model number. The wiring diagrams follow the Cross Reference section. 7. Refer to the circuit illustration that corresponds with the appropriate number. This figure illustrates the internal electric circuit for the desired model number. Table 6. T872-T874 Thermostat Cross Reference. Model Number Description T874 Trade Replacementa Remarks T872A 1-stage heat, 1-stage cool A1006 Standard OEM T874A1036 A1014 72-78°F (22-26°C) stop; locking cover; no thermometer T874A1010 Use T874A1176 for Dept. of Defense (DoD) application. A1022 Heat anticipator set at 0.45A T874A1036 A1030 0.4A heat anticipator setting T874A1036 A1048 TRADELINE T874A1036 A1055 AAF logo; locking cover T874A1036 A1063 Climatrol logo T874A1036 A1071 Lennox logo; 0.5A heat anticipator setting T874A1036 A1089 Melco logo T874A1036 A1097 Westinghouse logo T874A1036 A1105 Amana logo; 1.2A heat anticipator setting T874A1036 A1113 Trane logo T874A1036 A1121 Airtemp (Chrysler) logo T874A1036 A1139 Singer logo; no. 02005384 T874A1036 A1147 American Standard logo T874A1036 A1154 Carrier logo and color; no. HH07AT074 T874A1036 A1162 General Electric logo; no. AY28X097 T874A1036 A1170 Sears logo; no. 4291441 T874A1036 A1188 Command-Aire logo T874A1036 A1196 Singer logo; Celsius scale; no. 02005521 T874A1036 A1204 Carteret logo T874A1036 A1212 General Electric; no. AY28X114; 72-78°F (22-26°C) stop T874A1010 Use T874A1176 for Dept. of Defense (DoD) application. A1220 Singer logo; no. 050240-01 T874A1036 A1238 Celsius scale T874A1036 A1246 TRADELINE; locking cover and adjustable locking T874A1150 lever stops A1253 Trane Comfort Corp T874A1036 A1261 TRADELINE; 72-78°F (22-26°C) stop; locking cover; no thermometer; meets DoD specs T874A1176 a When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase. 29 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 6. T872-T874 Thermostat Cross Reference. Model Number A1279 A1287 A1295 A1303 A1311 A1329 A1337 A1345 A1352 A1360 A1378 T872B B1005 B1013 B1021 B1039 B1047 B1054 B1062 B1070 B1088 B1096 B1104 B1112 B1120 B1138 B1146 B1153 T872C C1004 C1012 C1020 C1038 C1046 C1053 C1061 C1079 C1087 C1095 Description T874 Trade Replacementa General Electric logo; no. AY28X114A; 75°F stop; T874A1010 locking cover; no thermometer. General Electric; no. AY28X097A; fan current T874A1036/ shunt for auto fan in heating; heat anticipator set at Q674B1018 0.4A. Lennox; Celsius scale T874A1036 Lennox logo; no. 64A0601; meets DoD specs T874A1176 Envirotron special; Celsius scale T874A1010 Carrier logo; Celsius scale; no. HH07AT074C T874A1036 Square D; no. HCD-3; heat anticipator set at 0.2A T874A1036 TRADELINE; Celsius scale T874A1010 Heat anticipator set 1.2A T874A1036 Friedrich logo; heat anticipator set at 0.2A T874A1036 Wesco logo; heat anticipator set at 0.8A T874A1036 1-stage heat, 2-stage cool Standard OEM T874B1019 0.4A heat anticipator setting T874B1019 TRADELINE T874B1019 Westinghouse logo T874B1019 American Standard logo T874B1019 Climatrol logo T874B1019 Carrier logo T874B1019 Trane logo T874B1019 Fedders logo T874B1019 Climatrol logo T874B1019 Carteret logo T874B1019 Singer logo; no. 050240-03 T874B1019 Celsius scale T874B1019 Singer logo; no. 02005711; locking cover and lever. T874B1019 Lennox logo; no. P-8-8895 T874B1019 Lennox logo; Celsius scale T874B1019 2-stage heat, 1-stage cool Standard OEM T874C1018 Heat anticipator set at 0.4A T874C1018 72-78°F (22-26°C) stop; locking cover; no T874C1141 thermometer; 42-88°F (6-31°C) setpoint range. TRADELINE T874C1018 American Standard logo T874C1018 Friedrich logo T874C1018 Lennox logo; no. P-8-8896 T874C1018 Westinghouse logo; stage 1 heat anticipator set at T874C1018 0.75A; stage 2 anticipator set at 1.2A Fast cycle performance on both heat stages; anticipator range 0.12-0.6A T874C1018 Payne logo; no. 0.1-0.175 T874C1018 Remarks Use T874A1176 for Dept. of Defense (DoD) application. Set thermostat stage 1 heat anticipator for total of fan and stage 1 primary control current draw. Use T874C1141 for Dept. of Defense (DoD) application. Adjust anticipator faster for correct performance. a When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase. 60-2485--8 30 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 6. T872-T874 Thermostat Cross Reference. Model Number Description T874 Trade Replacementa Remarks C1103 Amana logo; anticipator set at 1.2A T874C1018 C1111 Airtemp (Chrysler) logo T874C1018 C1129 Day and Night logo; no. 0.1-0.174 T874C1018 C1137 Fast cycle performance on both heat stages T874C1018 Adjust anticipator faster for correct performance. C1145 Rheem logo T874C1018 C1152 Ruud logo T874C1018 C1160 Climatrol logo T874C1018 C1178 Wesco logo T874C1018 C1186 Sears logo T874C1018 C1194 First Co. logo T874C1018 C1202 Carrier logo T874C1018 C1210 Carrier logo; Celsius scale T874C1018 C1228 0.4A heat anticipator setting T874C1018 C1236 Carrier logo; no. HH07AT070 T874C1018 C1244 Fraser-Johnson logo T874C1018 C1251 Trane logo T874C1018 C1269 Fedders logo T874C1018 C1277 Climatrol special T874C1018 C1285 Autogas logo T874C1018 C1293 Fedders logo T874C1018 C1301 Climatrol logo T874C1018 C1319 Command-Aire logo T874C1018 C1327 Melco logo; lock cover and levers T874C1018 C1335 Singer logo (Carteret) T874C1018 C1343 Singer logo; no. 050240-04 T874C1018 C1350 Celsius scale T874C1018 C1368 12°F (67°C) differential between heat 1 and heat 2 T874C1125 C1376 AAF logo; locking cover; 72-78°F (22-26°C) stop T874C1018 C1384 Servel logo T874C1018 C1392 TRADELINE; fast cycle performance on both heat T874C1018 stages. Adjust anticipator faster for correct performance. C1400 72-78°F (22-26°C) stop; locking cover; no thermometer; meets DoD specs T874C1141 C1418 Solaron logo T874C1018 C1426 Lennox logo; no. 42C04; four LEDs None C1434 Carrier logo; no. HH07AT070C; Celsius scale T874C1018 C1442 Goettl logo T874C1018 C1459 Goettl logo; used with Q672N1001, N1019 None C1467 Lennox logo; Celsius scale T874C1018 C1475 Tappan logo; no. 080-13708-37 T874C1018 C1483 Fasco logo; no. 1230-8161 T874C1018 C1491 Lennox logo; no. 64A0501; locking cover; no thermometer; meets DoD specs T874C1141 a When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase. 31 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 6. T872-T874 Thermostat Cross Reference. Model Number Description T874 Trade Replacementa Remarks C1509 Fedders logo; used with Q672L1102 Y594R1425 Wiring differences (old=new): C=X, K=E; remove Y-W1 jumper. C1517 Climatrol logo; used with Q672L1102 Y594R1425 Wiring differences (old=new): C=X, K=E; remove Y-W1 jumper. C1525 Square D logo; no. HCD-2 T874C1018 C1533 Airtemp logo T874C1018 C1541 Airtemp logo; used with Q672L1102 Y594R1425 Wiring differences (old=new): C=X, K=E; remove Y-W1 jumper. C1566 TRADELINE; Celsius scale T874C1018 Replacement has °F scaleplate. C1574 Whalen special; used with Q672B1269 None C1582 Lennox; meets DoD None C1590 Singer; 8°F (4.4°C) differential between stage 1 and stage 2 T874C1125 Replacement has 2°F (1° C) differential between H1 and H2. C1608 Singer logo; no. 02005784 8°F (4.4°C) differential T874C1125 between stage 1 and stage 2 Replacement has 2°F (1°C) differential between H1 and H2. C1616 Celsius scale; stop set at 23°C None Add 4074ECK adjustable stop. C1624 Heat Wave logo; no. 0360-116 T874C1018 C1632 York logo; heat anticipator set at 0.2A T874C1018 C1640 Heat anticipator set at 0.4A T874C1018 C1665 Wesco logo; heat anticipator set at 0.8A T874C1018 C1673 Wards logo; used with Q672B1285, B1293 Gas systems: T874C1018/ Q674B1034 Electric systems: Adjust anticipator faster for correct T874C1018/ performance. Q674B1075 C1681 Lechauffage Urbain logo; Celsius scale T874C1018 C1699 Duotherm logo; used with Q672E1068 or Q672F1000 T874C1018 See subbase description for replacement information. C1707 Sigler logo; used with Q672N1027 None C1715 Westinghouse logo T874C1018 T872D 2-stage heat, 2-stage cool D1003 Standard OEM T874D1165 D1011 TRADELINE T874D1165 D1029 Westinghouse logo T874D1165 D1037 Climatrol logo T874D1165 D1045 Lennox logo; no. P-8-8897; used with Q672E1191. T874D1165 D1052 York logo T874D1165 D1060 Singer logo; no. 02005385 T874D1165 D1078 Rheem logo T874D1165 D1086 Rudd logo T874D1165 D1094 York logo; locking cover T874D1165 D1102 American Standard logo T874D1165 D1110 ITT logo T874D1165 D1128 Carrier logo T874D1165 D1136 No anticipator on stage 1 cool; used with Q672C1029 T874D1165 a When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase. 60-2485--8 32 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 6. T872-T874 Thermostat Cross Reference. Model Number Description T874 Trade Replacementa Remarks D1144 Carrier logo; no. HH07AT072 T874D1165 D1151 General Electric logo; no. AY28X098; 0.4 heat anticipator setting T874D1165 D1169 Airtemp (Chrysler) logo; used with Q672E1118 T874D1165/ Q674E1049 Wiring differences (old=new): A=W1; set H1 anticipator to 1.2A. D1177 Trane logo T874D1165 D1185 Dunham-Bush logo T874D1165 D1193 Fedders logo T874D1165 D1201 Climatrol logo T874D1165 D1219 Command-Aire logo T874D1165 D1227 Singer logo; no. 02005522; Celsius scale T874D1165 D1235 Singer logo; (Carteret) T874D1165 D1243 Friedrich logo T874D1165 D1250 Singer logo; no. 050240-02 T874D1165 D1268 Airtemp logo T874D1165 D1276 Celsius scale T874D1165 D1284 Solaron T874D1165 D1292 Tokyo Carrier logo; no. HH07AT072C; Celsius scale T874D1165 D1300 SUPER TRADELINE T874D1165 D1318 General Electric logo; no. AY28X098A; fan current T874D1165/ shunt for auto fan in heating. Q674B1075 D1326 General Electric logo; locking cover 72-78°F (22-26°C) stop; fan current shunt for auto fan in heating. T874D1165 D1334 Lennox logo; Celsius scale T874D1165 D1342 Tappan logo; no. 080-13708-32 T874D1165 D1359 Singer logo; no. 02005740; Celsius scale; 6.6°C T874D1165 differential between H1 and H2. Only 2°F (1°C) differential between H1 and H2. D1367 Friedrich logo; no. 600-580-23 T874D1165 D1375 Singer logo; no. 02005713; Celsius scale; controls None 2 separate heat/cool circuits; used with Q674G1017 D1383 TRADELINE; Celsius scale T874D1165 D1391 Singer logo; no. 02005712; controls two separate None heat/cool circuits; used with Q674G1017 D1409 12°F (7°C) differential between H1 and H2 T874D1165 D1417 Fedders logo T874D1165 D1425 Climatrol logo T874D1165 D1433 Singer logo; no. 02005785; 8°F (4.4°C) differential T874D1165 between H1 and H2 D1441 American Air Filter T874D1165 D1474 Carrier; no. HH07AT072-03; Celsius scale T874D1165 T872E 2-stage cool E1002 Standard OEM T874E1016 E1010 TRADELINE T874E1016 E1028 Westinghouse logo T874E1016 a When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase. 33 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 6. T872-T874 Thermostat Cross Reference. Model Number E1036 E1044 E1051 E1069 E1077 E1085 E1093 E1101 E1119 E1127 E1135 E1143 E1150 E1168 T872F F1001 F1019 F1027 F1035 F1043 F1050 F1068 F1076 F1084 F1092 F1100 F1118 F1126 F1134 F1159 F1167 F1175 T872G G1000 G1018 Description T874 Trade Replacementa American Standard logo T874E1016 York logo; locking cover T874E1016 ITT logo T874E1016 Climatrol logo T874E1016 Airtemp (Chrysler) logo T874E1016 Lennox logo T874E1016 Trane logo T874E1016 Dunham-Bush logo T874E1016 Fedders logo T874E1016 Climatrol logo T874E1016 General Electric logo; no. AY28X108 T874E1016 Lennox logo; Celsius scale T874E1016 Celsius scale T874E1016 Airtemp logo T874E1016 2-stage heat Standard OEM T874F1015 TRADELINE T874F1015 Lennox logo; fast cycle heat anticipator T874C1018 Luxaire logo; fast cycle performance on both heat T874C1018 stages. York logo; locking cover; used with M839. T874C1018 Raehco logo T874F1015 Fast cycle performance on both heat stages. T874C1018 Wesco logo T874F1015 Lennox logo T874F1015 Auto Gas logo T874F1015 Celsius scale T874F1015 Lennox logo; Celsius scale T874F1015 Stages 1 and 2 heat electrically isolated; used with None Q672D1002 Square D logo; HCD-4 T874F1015 Wesco logo; heat anticipator set at 0.8A T874F1015 York logo T874F1015 Oneida Heater logo; no. 30A0287-01; used with T874F1015/ Q672K1012. Q674K1026 Heat pump models; 2-stage heat, 1-stage cool, 1-stage changeover. Fast cycle performance stage 2 heat; fixed Y594G1252 anticipator stage 1 heat and cool; changeover with cooling; used with Q672F1018. Adjustable anticipator stage 2 heat; fixed Y594G1393 anticipator stage 1 heat and cool; changeover with cooling; used with Q672E1027. Remarks M839 draws 0.72A; set adjustable heat anticipator to setting of 0.9A for proper cycle rate. Wiring differences (old=new): W=W2, X1=X. Wiring differences (old=new): Y1=O, Y2=Y. a When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase. 60-2485--8 34 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 6. T872-T874 Thermostat Cross Reference. Model Number Description T874 Trade Replacementa Remarks G1026 Lennox logo; fast cycle performance; stage 2 heat; None fixed anticipator stage 1 heat and cool; changeover with cooling; used with Q672E1019, F1067. See subbase description for replacement information. G1034 Westinghouse logo; adjustable anticipator stage 2 Y594G1252 heat; fixed anticipator stage 1 heat and cool; changeover with cooling; used with Q672F1091, F1141, F1257 or Q672J1013, J1062. Wiring differences (old=new): W=W2. G1042 York logo; fixed anticipator on all stages heat and Y594G1567 cool; changeover with cooling; used with Q672J1021. G1059 TRADELINE; no anticipator stage 2 heat; fixed Y594G1161 anticipator stage 1 heat and cool; changeover with cooling; used with Q672J1039 outdoor reset. Designed for use on General Electric heat pumps. G1067 Lennox logo; no. P-8-11222; fast cycle performance; stage 2 heat; fixed anticipator stage 1 heat and cool; changeover with cooling; used with Q672E1142, F1083. See subbase description for replacement information. G1075 Carrier logo; adjustable anticipator stage 2 heat; fixed anticipator stage 1 heat and cool; changeover with cooling; used with Q672J1054, L1052. See subbase description for replacement information. G1083 Adjustable anticipator stage 2 heat; fixed Y594G1252 anticipator stage 1 heat and cool; changeover with cooling; includes shunt to bypass stage 2 anticipator with auxiliary heat relays; used with Q672F1158. G1091 Lennox logo; same as T872G1026 except meets DoD specs. See subbase description for replacement information. G1109 Tappan logo; no. 080-13708-52; adjustable Y594G1252 anticipator stage 1 heat and cool; changeover with cooling; used with Q672F1117. Wiring differences (old=new): C=X. G1117 Changeover; used with Q672F1125. Y594G1252 Wiring differences (old=new): C=X. G1125 Lennox logo; no. 63A0401; Celsius scale; isolated None auxiliary heat power circuit; fast cycle anticipator stage 2 heat. G1133 Rheem logo; no. RXMT-B71; adjustable anticipator stage 2 heat; fixed anticipator stage 1 heat and cool; changeover with cooling; includes shunt to bypass stage 2 anticipator with auxiliary heat relays; used with Q672F1158, F1232. Y594G1252 G1141 Ruud logo; adjustable anticipator stage 2 heat; Y594G1252 fixed anticipator stage 1 heat and cool; changeover with cooling; includes shunt to bypass stage 2 anticipator with auxiliary heat relays; used with Q672F1158. G1158 Carrier logo; same as T872G1075. Except DoD styling. See subbase description for replacement information. G1166 BDP used with Q672F1125. Y594G1252 Wiring differences (old=new): C=X. G1174 BDP used with Q672F1125. Y594G1252 Wiring differences (old=new): C=X. G1182 Carrier; no. HH07AT071C; Celsius scale; used with Q672L1052, J1054. See subbase description for replacement information. G1190 Tappan; no. B13708-57; used with Q672L1078 for None 8 and 10 ton heat pumps with 2 compressors. a When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase. 35 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 6. T872-T874 Thermostat Cross Reference. Model Number Description T874 Trade Replacementa Remarks G1208 Marvair logo; special for Crispaire; used with Q672F1166, F1323. Y594G1393 G1216 Janitrol logo; no. 26G05; stage 2 heat anticipator Y594G1252 set at 1.2A; used with Q672F1117. Wiring differences (old=new): C=X. G1224 TRADELINE; adjustable anticipator stage 2 heat; Y594G1419 fixed anticipator stage 1 heat and cool; changeover in cool; used with Q672F1208. G1232 Heat Wave (Southwest Mfg.) logo; stage 2 heat anticipator set at 1.2A; used with Q672F1224. G1240 Lennox; fast cycle anticipator stage 2 heat; used None with Q672F1240. G1257 Carrier logo; no. HH07AT073; used with Q672L1169 (HH93AZ071). None G1265 Addison logo; used with Q672F1265. Y594G1252 Wiring differences (old=new): C=X. G1273 Carrier logo; (DoD model); 68°F (20°C) maximum heating; 78°F (26°C) minimum cooling; used with Q672L1052, J1054 See subbase description for replacement information. G1281 Wesco logo; used with Q672F1265. Y594G1252 Wiring differences (old=new): C=X. G1299 York logo; meets DoD specs; used with Q672L1177. Y594G1567 G1307 Carrier; no. 38EQ1900; Celsius; used with Q672J1054, L1052. See subbase description for replacement information. G1315 Luxaire special; stage 2 heat anticipator set to 1.2A; used with Q672F1281. Y594G1252 G1323 Lennox special; used with Q672L1201 and C815A1013. None G1331 York; used with Q672J1021. Y594G1567 Wiring differences (old=new): X=X1, L=X2, W=E; Y1-W1 and Y2W2 jumpers required. G1356 Westinghouse; used with Q672L1219. T874D1165/ Q674F1022 Wiring differences (old=new): X=X1, L=X2, W=E; Y1-W1 and Y2W2 jumpers required. G1364 York; used with Q672D1077. None G1372 Tappan/Janitrol logo; no. B-13708-521; used with Q672F1117. Y594G1252 Wiring differences (old=new): C=X. G1398 York logo; no. 025-21454C; used with Q672J1021. Y594G1567 T872H Heat pump model; 1 stage heat, 1 stage cool, 1 stage changeover. H1009 Command-Aire logo; fixed anticipator stage 1 heat Y594H1012 and cool; changeover with cooling; used with Q672C1086. H1017 Friedrich logo. Y594H1012 H1025 Friedrich logo; Celsius. Y594H1012 T872M 1 stage heat, 1 stage cool with stage 2 heat factory set at 60°F (16°C). M1003 Standard OEM; used with Q672D and external switching means. T874C1125 T874C1125 has 12°F (6.7°C) differential between stage 1 and stage 2 heat. T872N Heat pump model; 2-stage heat, 1-stage cool plus changeover, changeover in heat mode. N1002 None a When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase. 60-2485--8 36 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 6. T872-T874 Thermostat Cross Reference. Model Number Description T874 Trade Replacementa Remarks N1010 Williamson logo; adjustable anticipator stage 1 and T874N1016/ 2 heat; fixed anticipator stage 1 cool; used with Q674F1220 Q672F1133 or F1315. N1028 TRADELINE heat mode changeover; used with T874N1016 Q672F1216. N1036 Bard; used with Q672F1299. T874N1016/ Q674F1220 N1044 Thermotron logo; 1st stage changeover heat mode; used with Q672F1299. T874N1016/ Q674F1220 T872Q 1-stage heat; used with another T872 for heating setback. Q1009 Standard OEM T874C1125 Q1017 York logo T874C1125 Replacement only good for 1-stage heat and 1-stage cool applications. Q1025 ITT logo None Q1033 Lennox logo; no. P-8-8899. None Q1041 Lennox logo; no. 63A6401. None T872R Heat pump model; 2-stage heat, 1-stage cool, manual changeover. R1008 Fixed anticipator stage 1 heat and cool; no Y594R1425 anticipator stage 2 heat; changeover with cooling; used with Q672B1046. Wiring differences (old=new): W=W2; W1-Y1 jumper required. R1016 Addison same as T872R1008; used with Q672B1103. Y594R1425 Wiring differences (old=new): W=W2; W1-Y1 jumper required. R1024 Lennox logo; fast cycle stage 2 heat; fixed anticipator stage 1 heat and cool; changeover with cooling; used with Q672B1160 and Q672L1003. See subbase description for replacement information. R1032 York logo; fixed anticipator stage 1 and 2 heat and Y594R1664 stage 1 cool; changeover with cooling; used with Q672L1011. R1040 Lennox logo; fast cycle stage 2 heat; fixed anticipator stage 1 heat and cool; isolated stage 2 heat switch; changeover with cooling; used with Q672B1202 no. P-8-11221, Q672L1029 See subbase description for replacement information. R1057 TRADELINE; fixed anticipator stage 1 heat and Y594R1763 cool; no anticipator stage 2 heat; changeover on cooling; used with Q672L1037; outdoor reset. Designed for use on General Electric heat pumps. Wiring differences (old=new): A=T. R1065 Adjustable anticipator stage 2 heat; fixed Y594R1243 anticipator stage 1 heat and cool; changeover on cooling; used with Q672L1045. R1073 Lennox logo; no. 63A0301; Celsius scale; separate auxiliary heat power circuit; fast cycle stage 2 heat antic. None R1081 Ruud logo; same circuit as T872R1065; used with Y594R1243 Q672L1045, L1136. R1099 Dunham Bush special; used with Q672L1060, L1383. Y594R1243 R1107 Rheem; no. RXMT-B70; used with Q672L1045, Y594R1243 L1136. R1115 Friedrich logo; fixed anticipator; used with Q672B1244, L1086. See subbase description for replacement information. a When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase. 37 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 6. T872-T874 Thermostat Cross Reference. Model Number R1123 R1131 R1149 R1156 R1164 R1172 R1180 R1198 R1206 R1214 R1222 R1230 R1255 R1271 R1297 R1305 R1321 R1339 T872S S1005 T872T T1004 T872W W1019 W1027 W1035 Description T874 Trade Replacementa York logo; no. 025-21453C; Celsius scale. Y594R1664 Lennox logo; separate auxiliary heat power circuit; None fast cycle stage 2 heat anticipator; outdoor reset; used with Q672L1144, C815A1013. Westinghouse logo; adjustable stage 2 heat anticipator; cooling changeover; fixed anticipator stage 1 heat and cool; used with Q672L1110, L1128, L1151. Y594R1243 Marvair logo; used with Q672L1094, L1250. Y594R1243 Bard; used with Q672L1185. Heil Quaker; used with Q672L1193. Y594R1243 Y594R1243 York; Celsius; used with Q672L1011. TRADELINE; used with Q672L1227 For use with W89; used with Q672L1235. Intertherm logo; used with Q672L1276. Y594R1664 Y594R1243 None Y594R1300 York logo; used with C815A1039; adjustable anticipator stage-2 heat; used with Q672L1284 Y594R1672 Amana logo; no. C62397-1; used with Q672L1300, W89. None Singer logo; used with Q672L1326 and W89. None Westinghouse logo; used with Q672L1375 and W89. Y594R1664 York; Celsius scale; used with Q672L1011. None Used with Q672L1235 and W89. None Duotherm logo; used with Q672L1409, and W89. None Williamson; used with Q672L1391. Y594R1243 Heat pump model; 2-stage heat plus changeover, 1-stage cool. Westinghouse logo; adjustable anticipator stage 1 T874C1018/ and 2 heat; fixed anticipator stage 1 heat; Q674C1058 changeover with heating: used with Q672C1045 1-heat stage, 1-vent and 2-cool stages. Trane logo; used with Q672B1129. None 3-heat stages, 2-cool stages, manual changeover Lennox logo; no. 52C7501; used with Q672L1342 None and C815A1013. Westinghouse logo; used with Q672L1268 and C815A1021. None TRADELINE; used with C815A1043 and Q672B1251. Y594W1014 Remarks Wiring differences (old=new): W=W2. Replacement has auto fan in Emergency Heat mode. Wiring differences (old=new): B=X, W=W2. Wiring differences (old=new): W1=B, Z=L, K=E. Wiring differences (old=new): V=RC-RH, F=G, C=Y1, Z=B, H2=W2; W1-Y1 jumper required. a When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase. 60-2485--8 38 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 7. Q672-Q674 Subbase Cross Reference. Model Number Description Q674 Trade Replacementa Remarks Q672A System: HEAT-AUTO-COOL, Fan: AUTO-ON A1005 Standard OEM Q674A1019 A1013 TRADELINE Q674A1019 A1021 RC-RH jumper Q674A1019 RC-RH jumper required. A1039 RC-RH jumper; Chek Lite Q674A1019 RC-RH jumper required. Q672B System: HEAT-OFF-COOL, Fan: AUTO-ON B1004 Standard OEM Q674B1034 B1012 Isolated G terminal. Q674B1018 B1020 System: HEAT-OFF-RESET-COOL Q674B1034 Used system off as reset position. B1038 TRADELINE Q674B1034 B1046 Heat pump circuit; used with T872R1008. Y594R1425 Wiring differences (old=new): W1=Y1, W=W2. B1053 RC-RH jumper Q674B1034 RC-RH jumper required. B1061 Chek Lite Q674B1034 B1079 Auto fan operation in heat and cool. Q674B1075 B1087 Carrier no. HH93AZ078; RC-RH jumper. Q674B1075 B1095 Carrier no. HH93AZ084; RC-RH jumper. Q674B1034 B1103 Addison; heat pump circuit; used with T872R1016. Y594R1425 Wiring differences (old=new): W=W2; W1-Y1 jumper required. B1111 Carrier no. HH93AZ080; isolated G terminal. Q674B1018 B1129 Trane special circuit; used with T872T1004. None B1137 RC-RH jumper; isolated G terminal. Q674B1018 RC-RH jumper required. B1145 Fedders special Q674B1034 RC-RH jumper required. B1152 Fedders special; auto fan operation in heat and cool. Q674B1075 B1160 Lennox; heat pump circuit; used with T872R1024; includes compressor lockout in EM. HT. Y594R1243 Wiring differences (old=new): V-VR=R, M=Y, Y=W2, F=G, R=O. B1178 General Electric no. AY28X107; auto fan operation in heat and cool. Q674B1075 B1186 Trane; isolated G terminal; Filter LED. Q674B1018 B1194 General Electric no. AY28X124; auto fan operation in heat and cool. Q674B1075 Set T874 stage-1 anticipator for combined load of heat relay and fan relay. B1202 Lennox no. P-8-11223; heat pump circuit; used Y594R1243 with T872R1040. Wiring differences (old=new): V-VR=R, M=Y, Y=W2, F=G, R=O. B1210 None B1228 General Electric no. BAY28X137; isolated G terminal. Q674B1018 B1236 Carrier no. HH-93AZ079; RC-RH jumper; LOCKOUT LED indicates compressor lockout switch activated. Q674B1034 RC-RH jumper; LED cannot be provided in TRADELINE model. B1244 Friedrich; heat mode changeover; used with T872R1115. T874C1018/ Q674B1034 Wiring differences (old=new): C=no connection; RC-RH and W1-Y1 jumpers required. B1251 Used with T872W1035 and C815A1043. Y594W1014 a When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and subbase. 39 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 7. Q672-Q674 Subbase Cross Reference. Model Number Description Q674 Trade Replacementa Remarks B1269 Whalen; Hi-Lo fan switch; constant fan in heat None and cool system switch positions; used with T872C1574. B1277 Square D no. HCB-5. Q674B1034 B1285 Wards; RC-RH and F-W3 jumpers; used with T872C1673. Gas Furnace: T874C1018/ Q674B1034 Electric Furnace: T874C1018/ Q674B1075 Adjust anticipator faster for correct performance. B1293 Lennox no. 41C96; used with T872C1673. Same as Q672B1285 Q672C System: OFF-AUTO, Fan: AUTO-ON C1003 Standard OEM Q674C1058 C1011 Westinghouse; RC-RH jumper. Q674C1058 RC-RH jumper required. C1029 W1-Y2 jumper; for heat pump; used with T872D1136. Q674E1049 Replacement has heat/cool system switching. C1037 Chrysler Airtemp; System: COOL-OFF-AUTO. Q674C1058 C1045 Westinghouse; heat pump; used with T872S1005. T874C1018/ Q674C1058 Wiring differences (old=new): V=RC-RH, F=G, C=Y1, Z=B, H2=W2; W1-Y1 jumper required. C1052 Isolated stage 2 heat circuit for dc electric heat Recontrol relay. Use T874G1246/Q674F1212 which adds HEAT-COOL-EM.HT. system switch. C1060 Fedders special. Q674C1058 C1078 General Electric no. AY28X109. Q674C1058 C1086 Command-Aire; heat pump; used with T872H1009. Y594H1012 C1102 TRADELINE Q674C1058 Q672D System: None. Fan: None. D1002 Standard OEM; used with T872F1126. Q674D1040 D1010 Lennox special. None D1028 Carrier; RC-RH jumper. None D1036 Carrier no. HH93AZ070; RC-RH jumper. Q674D1040 RC-RH jumper required. D1044 General Electric no. AY-28X100. None D1069 Square D no. HCB-4. None D1077 York; used with T872G1364. None D1085 TRADELINE Q674D1040 Q672E System: OFF-HEAT-AUTO-COOL Fan: AUTO-ON E1001 Standard OEM Q674E1049 E1019 Lennox no. P-8-8892; heat pump; cool mode T874D1165/ changeover; used with T872G1026. Q674B1075 E1027 Heat pump circuit; W1-Y2 jumper; cool mode Y594G1393 changeover; used with T872G1018. Wiring differences (old=new): Y1=O, Y2=Y. E1035 Heat pump circuit; W1-Y2 jumper; cool mode Y594G1393 changeover. Wiring differences (old=new): Y1=O, Y2=Y. E1043 Heat pump circuit; heat mode changeover. Q674E1049 Wiring differences (old=new): W1=B, W2=W1; W1-Y1 jumper. a When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and subbase. 60-2485--8 40 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 7. Q672-Q674 Subbase Cross Reference. Model Number Description Q674 Trade Replacementa Remarks E1050 TRADELINE Q674E1049 E1068 RC-RH jumper; used with T872C1699. Q674E1049 RC-RH jumper required. E1076 RC-RH internal jumper; EM. HT. LED. Q674E1049 RC-RH jumper required. E1084 Carrier no. HH93AZ076; RC-RH jumper. Q674E1049 RC-RH jumper required. E1092 Carrier no. HH93AZ082; RC-RH jumper; B terminal; isolated G terminal. Q674E1049 E1100 General Electric no. AY28X099. Q674E1049 E1118 Airtemp; heat pump; used with T872D1169. T874D1165/ Q674E1049 Wiring differences (old=new): A=W1; set H1 anticipator to 1.2A. E1126 Common R terminal. Q674E1049 RC-RH jumper required. E1134 ITT Nesbitt; RC-RH jumper; O and B terminals; Q674E1049 isolated G terminal. E1142 Lennox no. P-8-11224; heat pump; Y594G1252 V-VR jumper; cool mode changeover; used with T872G1067. Wiring differences (old=new): V-VR=R, Y=W2, R=O, M=Y, F=G. E1159 Carrier no. HH93AZ077; RC-RH jumper; LOCKOUT LED indicates activation of compressor lockout switch. Q674E1049 RC-RH jumper required; no LED in TRADELINE model. E1167 Square D no. HCB-2; Chek Lite. Q674E1049 E1183 Square D no. HCB-3. Q674E1049 E1191 Lennox; HIGH and LOW LEDs; used with T872D1045. Q674E1049 No LEDs on replacement. Q672F System: EM. HT.-HEAT-AUTO-COOL-OFF Fan: AUTO-ON. F1000 With EM. HT. LED; used with T872C1699. Q674F1022 Remove W3-X2 jumper to E-X2. F1018 Heat pump; heat mode changeover; Chek Lite; Y594G1252 used with T872G1000. Wiring differences (old=new): W=W2, X1=X. F1026 Chek Lite; W2-X2 jumper. Q674F1022 F1034 Airtemp; EM. HT. LED; RC-RH and X2-E jumpers. Q674F1022 If RC-RH jumper removed on Q672F1034, Q674F1022 does not replace. F1042 W2-X2 jumper; Chek Lite. Q674F1022 F1059 Carrier no. HH93AZ074; EM. HT. LED. Q674F1022 Remove W2-X2 jumper to E-X2; X terminal same as C. F1067 Lennox; heat pump; cool mode changeover; EM. HT. LED; used with T872G1026. None F1075 Heat pump circuit; EM. HT. LED; 2 terminal; RC- None RH jumper. F1083 Lennox no. P-8-11225; heat pump; None V-VR jumper; cool mode changeover; EM. HT. LED; used with T872G1067. F1091 Westinghouse; heat pump; EM. HT. LED; cool mode changeover; compressor lockout in EM. HT.; used with T872G1034. Y594G1252 Wiring differences (old=new): W=W2. F1109 Airtemp no. 3778567ACC; R-X2 jumper; EM. HT. LED. Q674F1022 R-X2 jumper required. F1117 Tappan no. 080-13708-53; heat pump; EM. HT. LED; cool mode changeover; compressor lockout and auto fan in EM. HT.; used with T872G1109, G1216, G1372. Y594G1252 Wiring differences (old=new): C=X. a When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and subbase. 41 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 7. Q672-Q674 Subbase Cross Reference. Model Number Description Q674 Trade Replacementa Remarks F1125 BDP no. 3442DP90; used with T872G1117, G1166, G1174. Y594G1252 Wiring differences (old=new): C=X. F1133 Williamson; heat pump; EM. HT. LED; heat mode changeover; compressor lockout in EM. HT.; used with T872N1010. T874N1016/ Q674F1220 F1141 Westinghouse; EM. HT. LED; auto fan in EM. HT.; used with T872G1034. Y594G1252 Wiring differences (old=new): W=W2. F1158 Rheem Ruud; heat pump; EM. HT. LED; cool Y594G1252 mode changeover; compressor lockout in EM. HT.; used with T872G1083, G1133, G1141; auto fan in EM. HT. F1166 Crispaire; EM. HT. LED; used with T872G1208. Y594G1252 F1174 Carrier no. HH93AZ081; EM. HT. LED. Q674F1022 F1182 Square D no. HCB-1; Chek Lite; R-X2 jumper; Q674F1022 System: Aux. Heat replaces EM. HT. R-X2 jumper; add monitor switch between X1 and low side of power. F1190 EM. HT. LED; X2-E and RC-RH jumpers. None F1208 TRADELINE; cool mode changeover; EM. HT. Y594G1419 LED; used with T872G1224. F1216 TRADELINE; heat mode changeover; EM. HT. T874N1016/ LED; used with T872N1028. Q674F1220 F1224 Heatwave (Southwest Mfg.); compressor lockout in EM. HT.; EM. HT. LED; used with T872G1232. Y594G1252 F1232 Rheem; cool mode changeover; EM. HT. and AUX. HEAT LEDs; compressor lockout in EM. HT.; used with T872G1133. Y594G1252 F1240 Lennox; cool mode changeover; EM. HT. and None SERVICE LEDs; used with T872G1240. F1257 Westinghouse; cool mode changeover; EM. HT. and AUX. HEAT LEDs; auto fan in EM. HT; used with T872G1034. Y594G1252 Wiring differences (old=new): W=W2. F1265 Wesco Addison; Chek and EM. HT. LEDs; used Y594G1252 with T872G1281, G1265. Wiring differences (old=new): C=X. F1273 Southwest special; no. 0361-136; W2-X2 jumper. None F1281 Luxaire special; used with T872G1315. Y594G1252 F1299 Bard special; used with T872N1036, N1044. T874N1016/ Q674F1220 F1315 Williamson special; used with T872N1010. T874N1016/ Q674F1220 F1323 Crispaire special; used with T872G1208. Y594G1252 Q672G System: OFF-AUTO. Fan: None. G1009 Standard OEM Q674G1070 G1017 Singer; O-B jumper; used with T872D1375. Q674G1070 G1025 Includes O and B terminals. Q674G1070 G1033 General Electric no. AY28X102. Q674G1070 G1041 Singer no. 02005649; French wording; O-B jumper. Q674G1070 Less French wording. G1066 SLI-Mammoth; heat pump; heat mode changeover. Q674G1070 Connect fan (G) wire to Y1 terminal; B-O and RC-RH jumpers. a When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and subbase. 60-2485--8 42 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 7. Q672-Q674 Subbase Cross Reference. Model Number G1074 G1082 G1090 Q672H H1008 Q672J J1005 J1013 J1021 J1039 J1047 J1054 J1062 Q672K K1004 K1012 Q672L L1003 L1011 L1029 L1037 L1045 Description Q674 Trade Replacementa Singer no. 02005754; X1 and X2 terminals for field-added indicator lights; used with T872D1375. None Singer no. 02005792; X1 and X2 terminals for field-added indicator lights; used with T872D1375. None TRADELINE; B and O terminals. Q674G1070 System: OFF-ON Fan: NIGHT INT.-DAY CONT. Used with T872. None System: EM. HT.-AUTO-OFF Fan: AUTO-ON. With EM. HT. LED; used with T872C or D. None Westinghouse; heat pump; EM. HT. LED; cool mode changeover; compressor lockout in EM. HT.; used with T872G1034. Y594G1252 York; heat pump; EM. HT. LED; cool mode Y594G1567 changeover; compressor lockout and auto fan in EM. HT.; E-W jumper; used with T872G1042, G1331, G1398. Heat pump; EM. HT. and AUX. HEAT LEDs; Y594G1161 cool mode changeover; compressor lockout and auto fan in EM. HT.; used with T872G1059. Singer no. 02005699; heat pump; EM. HT. LED; Q674F1022 heat mode changeover. Carrier no. HH93AZ073A; heat pump; EM. HT. LED; cool mode changeover; compressor lockout in EM. HT.; used with T872G1075, G1182, G1307. Y594G1252 Westinghouse; EM. HT. and AUX. HEAT LEDs; Y594G1252 used with T872G1034. System: OFF-HEAT-AUTO-COOL. Fan: None. Carrier no. HH93AZ072. Q674E1049 Oneida Heater no. 30A0288-01; System: OFF- T874F1155/ WOOD-WOOD/OIL-OIL; used with T872F1175. Q674K1026 System: EM. HT.-HEAT-OFF-COOL. Fan: ON-AUTO. Lennox; heat pump; EM. HT. LED; cool mode Y594R1425 changeover; used with T872R1024. York; heat pump; EM. HT. LED; cool mode Y594R1664 changeover; compressor lockout and auto fan in EM. HT.; used with T872R1032, R1180, R1297. Lennox no. P-8-11226; heat pump; EM. HT. LED; V-VR jumper; cool mode changeover; compressor lockout in EM. HT.; used with T872R1040. Y594R1425 Heat pump; EM. HT. and AUX. HT. LEDs; cool Y594R1763 mode changeover; compressor lockout and auto fan in EM. HT.; used with T872R1057. Rheem; heat pump; EM. HT. LED; cool mode changeover; compressor lockout in EM. HT.; auto fan in EM. HT; used with T872R1065, R1081, R1107. Y594R1243 Remarks Designed for use on General Electric heat pumps. Wiring differences (old=new): C=X. Wiring differences (old=new): W=W2. Fan switch does not function. Wiring differences (old=new): V-VR=R, M=Y, Y=W2, F=G, R=O. Wiring differences (old=new): A=T; designed for used on General Electric heat pumps. a When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and subbase. 43 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 7. Q672-Q674 Subbase Cross Reference. Model Number Description Q674 Trade Replacementa Remarks L1052 Carrier no. HH93AZ075; heat pump; EM. HT. LED; cool mode changeover; compressor lockout in EM. HT.; used with T872G1075, G1182, G1273, G1307. Y594R1615 Wiring differences (old=new): C=X. L1060 Dunham Bush; EM. HT. LED; used with T872R1099. Y594R1243 L1078 Tappan no. B13708-58; heat pump; EM. HT. LED; cool mode changeover; compressor lockout in EM. HT.; EM. HT. relay provides fan operation in EM. HT.; used with T872G1190. None L1086 Friedrich; heat mode changeover; EM. HT. LED; Y594R1243 used T872R1115 with L terminal. Wiring differences (old=new): X2=E, C=X. L1094 Crispaire; W2-H jumper; EM. HT. LED; used with T872R1065, R1156. Y594R1243 Replacement has auto fan in Emergency Heat mode. L1102 Fedders; heat mode changeover; EM. HT. LED; Y594R1425 used with T872C1509, C1517, C1541. Wiring differences (old=new): K=E, C=X; remove Y-W1 jumper. L1110 Westinghouse; EM. HT. LED; used with T872R1149. Y594R1243 Wiring differences (old=new): W=W2. L1128 Westinghouse; EM. HT. LED; used with T872R1149. Y594R1243 Wiring differences (old=new): W=W2. L1136 Rheem no. 41-20796-07; cool mode Y594R1243 changeover; EM. HT. and AUX. HT. LEDs; used with T872R1081, T872R1107. L1144 Lennox; V-VR jumper; EM. HT. and SERVICE LEDs; isolated stage 2 heat; used with T872R1131, C815A1013. None L1151 Westinghouse; AUX. HT. and EM. HT. LEDs; Y594R1243 used with T872R1149. Wiring differences (old=new): W=W2. L1169 Carrier no. HH93AZ071; EM. HT. LED; used with T872G1257 (HH07AT073). None L1177 York; DoD; EM. HT. LED; used with T872G1299. Y594G1567 L1185 Bard; used with T872R1164. Y594R1243 L1193 Heil Quaker no. NAXA001TS01; used with T872R1172. Y594R1243 Wiring differences (old=new): B=X, W=W2. L1201 Lennox special; no. 1485701; used with T872G1323. None L1219 Westinghouse special; used with T872G1356. T874D1165/ Q674F1022 Wiring differences (old=new): X=X1, L=X2, W=E; Y1-W1 and Y2-W2 jumpers required. L1227 Heat pump; used with T872R1198. Y594R1243 L1235 Intertherm; used with T872R1206, R1305. None L1250 Crispaire special; used with T872R1156 and C815A1021. Y594R1243 L1268 Westinghouse special; used with T872W1027 None and C815A1021. L1276 Intertherm special; used with T872R1214. Y594R1300 Wiring differences (old=new): W1=B, Z=L, K=E. L1284 York special; used with T872R1222. Y594R1672 L1300 Amana special; no. C62345-1; used with T872R1230. None L1326 Singer; used with T872R1255. None a When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and subbase. 60-2485--8 44 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 7. Q672-Q674 Subbase Cross Reference. Model Number L1342 L1375 L1383 L1391 L1409 Q672N N1001 N1019 N1027 Q672P P1009 Description Q674 Trade Replacementa Lennox no. 52C7601; used with T872W1019 None and C815A1013. Westinghouse; used with T872R1271, W89. None Dunham Bush; used with T872R1099. Y594R1243 Williamson; used with T872R1339. Y594R1243 Duotherm special; used with T872R1321, W89. None System: OFF-HEAT-COOL-EVAP. Goettl; heat pump; heat mode changeover; evaporative cooler circuit; Fan: AUTO-ON; System: AUTO; used with T872C1459. None Goettl; heat pump; heat mode changeover; None evaporative cooler circuit; W1-Y1 jumper; used with T872C1459. Siegler special; used with T872C1707. None System: EM. HT.-HEAT-COOL. Carrier special; no. HH93AZ069; used with T872G1075 (HH07AT071). Y594R1243 Remarks Replacement has OFF system switch position a When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and subbase. 45 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Number T874A A1002 A1010 A1028 A1036 A1044 A1051 A1069 A1077 A1085 A1093 A1101 A1119 A1127 A1135 A1143 A1150 A1168 A1176 A1184 A1192 Fig. No. Description 1-stage heat, 1-stage cool. 44, 65 Honeywell logo; Standard OEM; used with Q674B1331. 44 Honeywell logo; includes Allen wrench and screws to lock cover; non-adjustable range stops set at 72°F (max. heat) and 78°F (min. cool) (22-26°C); field adjustable locking levers. 44 Honeywell logo; heat anticipator factory set at 0.4A. 44 Honeywell logo; TRADELINE® model; includes Allen wrench and screws to lock cover; field adjustable locking levers. 44 Obsolete. AAF/Snyder General logo; part no. 4ELN3006C; °F/°C scaleplate. 44 Lennox logo; part no. 12F9901; °F/°C scaleplate; heat anticipator set at 0.45A. 44 Obsolete. Westinghouse logo; used with Q674A-E,G. 46, 82 Obsolete. Amana Air Conditioning logo; part no. D68535-1; heat anticipator factory set at 1.2A; used with Q674B1075, E1056; used in Y594A1001, A1019. 44, 46, Obsolete. Trane logo; part no. 13510451; used with 55, 66 Q674B1018, B1075, D1008. 44 Obsolete. McQuay logo; part no. 02005935; °F/°C scaleplate. 51, 53 Carrier logo; part no. HH07AT174; used with Q674B. 82 Obsolete. Sears logo; part no. 541. 91441/49. 9144; °F/ °C scaleplate; used with Q674E1007; used in Y594A1068. 44 Obsolete. Climate Control logo; part no. 02005936; °C scaleplate. 44 Fedders multi-logo; part no. THTX-110-WCHA, 88-58-00500-001. 44 Honeywell logo; °C scaleplate. 44 Honeywell logo; TRADELINE model; includes Allen wrench and screws to lock cover; field adjustable locking levers (68°F max. heat, 78°F min. cool). 44 Obsolete. Trane Comfort Corps logo. 44 Honeywell logo; meets DoD specs; includes Allen wrench and screws to lock cover; no thermometer; nonadjustable range stops set at 72°F (max. heat) and 78°F (min. cool) (22-26°C); field adjustable locking levers. 51, 53 Trane logo; part no. BAY28X182; °F/°C scaleplate; automatic fan in heating and cooling modes; heat anticipator set at 0.4A; used with Q674B1141, E1080. 44 Obsolete. Lennox logo; part no. 13F0001; °C scaleplate; heat anticipator factory set at .458A. Trade Model Replacement T874A1036 T874A1010 Remarks T874A1036 T874A1036 T874A1036 T874A1036 T874A1036 T874A1036 Replacement has °F scaleplate. Replacement has °F scaleplate. T874A1036 T874A1036 Replacement has °F/°C scaleplate. Y594C1421 or When using the T874C1036, T874A1036a set stage 1 heat anticipator for total current draw of fan and stage 1 heat primary. T874A1036 Replacement has °F scaleplate. T874A1036 T874A1036 Replacement has °F scaleplate. T874A1036 T874A1150 Replacement has °F scaleplate. T874A1036 T874A1176 T874A1036a T874A1036 When used with Q674E1080, set stage 1 heat anticipator for total current draw of fan and stage 1 heat primary; replacement has °F scaleplate. Replacement has °F scaleplate. aBoth the thermostat and subbase must be replaced. 60-2485--8 46 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Number A1200 Fig. No. Description 51, 53 Obsolete. Carrier logo; part no. HH07AT164; °C scaleplate; includes Allen wrench and screws to lock cover; used with Q674B. A1226 A1234 A1242 A1259 A1267 A1275 A1283 44 Honeywell logo; Honeywell Canada TRADELINE model; °C scaleplate; includes Allen wrench and screws to lock cover. 44 Obsolete. Friedrich Climate Master logo; heat anticipator factory set 1.2A. 44 Obsolete. Friedrich Climate Master logo. 44 Obsolete. Wesco logo; heat anticipator set at 0.8A. 59 Obsolete. McQuay logo; used with Q674Q1004. 44 Obsolete. Lennox logo; part no. 13F0101; meets DoD specifications. 75 McQuay Air Conditioning logo; part no. 03005047; used with Q674C1132 and thermistor to display outdoor temperature. A1291 A1309 A1317 A1325 64 No logo; three-speed fan; one setpoint lever for heat and cool setpoints; used with Q674Q1012; used in Y594A1126. 44 Obsolete. Arcoaire Air Conditioning and Heating logo; part no. AO2076; includes Allen wrench and screws to lock cover. 44 Obsolete. McQuay logo; part no. 60685301; no scaleplate; used with Q674A-E,G. 75 Obsolete. McQuay logo; part no. 60685401; no scaleplate; used with Q674C1306 and outdoor thermistor to display outdoor temperature. A1341 A1358 A1366 44 Obsolete. Trane logo; part no. THT-0577; meets DoD specifications. 44 York-Miraco logo. 51, 53 Obsolete. BDP Multi-logo; part no. HH07AT182. A1374 44 American Standard logo; part no. ASYSTAT610; heat anticipator factory set at 0.4A. A1390 44 Obsolete. Climate Control logo; part no. 654958804; °F/ °C scaleplate. A1416 44 Obsolete. Reznor logo; part no. 654758803; °F/°C scaleplate. A1424 214 Obsolete. Carrier Olympia Series Split System logo; part no. HH07AT194; used with Q674B1455 (HH93AZ208). A1440 91 Obsolete. Simplex System 2000 logo; heat anticipator factory set at 1.2A; used with Q674G1005; used in Y594A. A1465 212 Honeywell Trol-A-TempTM logo; Premier White® color; heat anticipator factory set at 0.10A; used with Q674E1379. aBoth the thermostat and subbase must be replaced. Trade Model Replacement T874A1036a T874A1036 T874A1036 T874A1036 T874A1036 T874A1036 T874A1176 T874A1036 T874A1036/ Q674B1075a T874A1036 T874A1036 T874A1036 T874A1176 T874A1036 T874A1036a T874A1036a T874A1036 T874A1036 See OEM for replacement. T874A1036 None Remarks Set stage 1 heat anticipator for total current draw of fan and stage 1 heat primary; replacement has °F scaleplate. Replacement has °F scaleplate. Replacement does not have ability to display external temperature or momentary system switch position. Replacement has two levers and 1 speed fan. Replacement does not have ability to display external temperature or momentary system switch position. Set stage 1 heat anticipator for total current draw of fan and stage 1 heat primary. Replacement has °F scaleplate. Replacement has °F scaleplate. See Trol-A-Temp for replacement. 47 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Number A1481 A1507 A1523 A1549 A1556 A1572 A1580 A1598 A1614 A1622 T874B B1001 B1019 B1027 B1035 B1043 Fig. No. Description 44 Obsolete. Honeywell logo; Carrier part no. HH621602; includes locking cover and non-adjustable range stops set at 72°F (max. heat) and 78°F (min. cool). 44 Obsolete. Climate-Tel logo; includes Allen wrench and screws to lock cover and non-adjustable range stops set at 72°F (max. heat) and 78°F (min. cool). 224, Obsolete. AAF/Snyder General logo; part no. 225 066804404; °F/°C scaleplate; no cooling anticipation; used with Q674E1312, C1298. 224, Obsolete. McQuay logo; part no. 066816601; no cooling 225 anticipation; used with Q674E1312, C1298. 51, 53 Carrier logo; part no. HH07AT164-W; °C scaleplate; Premier White® color; includes Allen wrench and screws to lock cover; used with Q674B. 224, Obsolete. McQuay logo; part no. 066816611; Premier 225 White® color; °F/°C scaleplate; no cooling anticipation. 91 California Economizer logo; Premier White® color; heat anticipator factory set at 1.2A. 224, McQuay logo; part no. 073319001; Premier White® 225 color; °F/°C scaleplate; includes Allen wrench, screws to lock cover and AAF insert. 44 Honeywell logo; TRADELINE® model; °C scaleplate; Premier White® color; includes Allen wrench and screws to lock cover; used with Q674B. 44 Obsolete. York logo; part no. 2TH04703224A; includes Allen wrench and screws to lock cover and nonadjustable range stops set at 72°F (max. heat) and 78°F (min. cool). 1-stage heat, 2-stage cool. 44 Obsolete. Honeywell logo. 44 Honeywell logo; TRADELINE model; includes Allen wrench and screws to lock cover. 44 Obsolete. Westinghouse logo. 44, 46 Obsolete. Trane logo; used with Q674B1018, B1075; used in Y594B1026, B1034. 44 Obsolete. Honeywell logo; °C scaleplate. B1050 44 Lennox logo; part no. 13F0201; °F/°C scaleplate. B1068 44 Honeywell logo; Honeywell Canada TRADELINE model; °C scaleplate; includes Allen wrench and screws to lock cover. B1076 88 Obsolete. Lennox Power Saver Two-Speed logo; part no. 91C7401; °F/°C scaleplate; used with Q674E1155. B1084 44 Obsolete. Lennox Two-Speed logo; part no. 13F0301; °C scaleplate. B1092 44 Obsolete. Honeywell logo; Heil Quaker part no. HQ521389HW. B1100 88 Obsolete. Janitrol logo; part no. CHTS36-60; °F/°C scaleplate; used with Q674E1338; used in Y594B1042. B1118 44 Honeywell logo; °C scaleplate; used with Q674A-E, G. aBoth the thermostat and subbase must be replaced. Trade Model Replacement T874A1036 Remarks T874A1176 See OEM for replacement. See OEM for replacement. T874A1036a See OEM for replacement. T874A1036 Replacement has °F scaleplate; replacement is beige. See OEM for replacement. T874A1036 T874A1010 Replacement has °F scaleplate; replacement is beige. T874B1019 T874B1019 T874B1019 T874B1019 T874B1019 T874B1019 T874B1019 Replacement has °F scaleplate. Replacement has °F scaleplate. Replacement has °F scaleplate. T874B1019 T874B1019 T874B1019 Replacement has °F scaleplate. Replacement has °F scaleplate. T874B1019 T874B1019 Replacement has °F scaleplate. Replacement has °F scaleplate. 60-2485--8 48 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Number B1134 Fig. No. Description 222 Obsolete. Carrier Synergy 2000 logo; part no. HH07AT199; °C scaleplate; used with Q674E1395 (HH93AZ209). T874C C1000 C1018 C1026 C1034 2-stage heat, 1-stage cool. 44, 76 Honeywell logo; used with Q674B1075, C1181; used in Y594C1058. 60, 61, Honeywell logo; TRADELINE model; includes Allen 81, 92 wrench and screws to lock cover; used with Q674C1074. 44 Obsolete. AAF logo; °C scaleplate; includes Allen wrench and screws to lock cover; non-adjustable range stops set at 23°C (max. heat and min. cool) (73°F). 44 Lennox logo; part no. 13F0401; °F/°C scaleplate. C1042 C1059 C1067 C1075 44 Obsolete. Westinghouse logo; H1 anticipator factory set at.75A; H2 anticipator factory set at 1.2A; used with Q674A-E,G. 44, 142 Obsolete. Amana Air Conditioning logo; part no. D68535-2; H1 anticipator factory set at 1.2A; used with Q674E1056, Q674B1059, Q674F1022; used in Y594C1009, Y594C1017, Y594C1256, Y594C1330. 44 Obsolete. Sears logo; part no. 42. 9297; °F/°C scaleplate. 51, 53 Carrier logo; part no. HH07AT170; used with Q674B1166. C1083 C1117 44 Obsolete. Trane logo; used with Q674E1007; used in Y594C1082. 44 Honeywell logo; °C scaleplate. C1125 C1133 C1141 C1158 C1166 60, 61, Obsolete. Honeywell logo; 12°F (6.7°C) differential 92 between stage 1 heat and stage 2 heat; used with Q674G1047. 96 Obsolete. AAF/Snyder General logo; part no. 4ELN7546; no H1 heat anticipation; used with Q674AG,N and Q674C1173. 44 Obsolete. Honeywell logo; meets DoD specs; includes Allen wrench and screws to lock cover; no thermometer; non-adjustable range stops set at 72°F (max. heat) and 78°F (min. cool) (22-26°C); field adjustable locking levers. 44 Obsolete. Solaron special. 51, 53 Obsolete. Carrier logo; part no. HH07AT160; °C scaleplate; includes Allen wrench and screws to lock cover; used with Q674B. C1174 C1182 C1190 44 Obsolete. Goettl logo. 60 Obsolete. Goettl logo; H1 anticipator factory set at 0.8A; used with Q674N1015. 44 Obsolete. Lennox logo; part no. 13F0501; °C scaleplate. aBoth the thermostat and subbase must be replaced. Trade Model Replacement Remarks T874B1019/ Q674E1049a Wiring differences (old=new): W1=W; RC-RH jumper required; replacement has no LEDs. T874C1018 T874C1018 T874C1018 Replacement has °F scaleplate. T874C1018 T874C1018 Replacement has °F scaleplate. T874C1018 T874C1018 Replacement has °F scaleplate. Y594C1421 or When using the T874C1018, T874C1018a set stage 1 heat anticipator for total current draw of fan and stage 1 heat primary. T874C1018 T874C1018 Replacement has °F scaleplate. T8611M2025 T874C1018 Must have H1 anticipator set to maximum value. T874C1141 T874C1018 T874C1018a T874C1018 T874C1018 Replacement has °F scaleplate; set stage 1 heat anticipator for total current draw of fan and stage 1 heat primary. T874C1018 Replacement has °F scaleplate. 49 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Number C1216 C1224 C1240 C1257 C1265 Fig. No. Description 44 Obsolete. Fasco part no. 1230-8197. 105 Obsolete. Square D logo. 44 Honeywell logo; Honeywell Canada TRADELINE model; °C scaleplate; includes Allen wrench and screws to lock cover. 44 Obsolete. Singer part no. 0200-5931; 8°F (4.4°C) differential between H1 and H2 heat. 44 Obsolete. Singer special; °C scaleplate; 5°C (8°F) differential between H1 and H2 heat. C1273 C1281 C1307 C1315 C1323 44 Honeywell logo; °C scaleplate; includes Allen wrench and screws to lock cover; non-adjustable range stops factory set at 23°C (max. heat and min. cool) (73°F). 44 Obsolete. Heat Wave special. 44 Obsolete. Friedrich Climate Master logo. 44 Obsolete. Wesco logo; heat anticipator factory set at 0.8A. 44 Obsolete. Le Chauffage Urbain special; °C scaleplate. C1331 C1349 C1372 82, 141 Obsolete. Duotherm logo; used with Q674E or Q674F. 61 Obsolete. Sigler logo; used with Q674N1023. 52 Obsolete. Honeywell logo; used with Q674B1190. C1398 C1406 C1414 C1422 C1430 C1448 105 Obsolete. Fedders logo; °F/°C scaleplate; used with Q674L1090. 105 Obsolete. Climatrol logo; °F/°C scaleplate; used with Q674L1090. 105 Obsolete. Airtemp logo; °F/°C scaleplate; used with Q674L1090. 187 Obsolete. Honeywell logo; used with Q674B1208. 49 Obsolete. Lennox Zone Master Two-Speed logo; part no. 25F7201; used with Q674B1224. 110, Obsolete. Lennox logo; part no. 24F5101; meets DoD 190 specifications; requires outdoor reset; used with Q674L1165, L1355. C1455 C1463 127 Obsolete. Williamson logo; used with Q674L1322. 82 Obsolete. AAF logo; °C scaleplate. C1471 56 Obsolete. Mammoth logo; part no. 71120102; used with Q674B1257; used in Y594C1314. aBoth the thermostat and subbase must be replaced. Trade Model Replacement Remarks T874C1018 T874C1018 T874C1018 Replacement has °F scaleplate. T874C1125 T874C1125 T874C1018 Replacement has 12°F differential between H1 and H2 heat. Replacement has 12°F differential between H1 and H2 heat; replacement has °F scaleplate. Replacement has °F scaleplate. T874C1018 T874C1018 T874C1018 T874C1018 T874C1018 T874C1018 T874C1018/ Q674B1034 T874C1018/ Q674B1075 Y594R1425a Y594R1425a Y594R1425a None T874C1018 Replacement has °F scaleplate. For systems requiring automatic fan in cooling mode only. For systems requiring automatic fan in heating and cooling. Wiring differences (old=new): K=E, C=X; replacement has °F scaleplate. Wiring differences (old=new): K=E, C=X; replacement has °F scaleplate. Wiring differences (old=new): K=E, C=X; replacement has °F scaleplate. Y594R1763a Y594R1243a T874C1018 T874C1018 Wiring differences (new=old): R=V-VR, Y=M, G=F, B-X, W=Y, T=A, O=R, X2=E; Emergency Heat becomes stage 1 heat source. Replacement has °F scaleplate. 60-2485--8 50 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Number C1489 C1497 C1513 C1562 C1570 C1638 C1653 C1661 Fig. No. Description 121 Obsolete. Honeywell logo; non-adjustable range stops set at 75°F (max. heat and min. cool) (24°C); used with Q674L1157. 121 Obsolete. Honeywell logo; meets DoD specifications; used with Q674L1157. 44 Obsolete. Borg-Warner multi-logo; part no. 6TH11703124A. 44 Obsolete. Honeywell logo; Heil Quaker part no. HQ712001HW. 45 Obsolete. Williamson logo; used with Q674B1000; used in Y594C1280. 121 Obsolete. Honeywell logo; meets DoD specifications; includes Allen wrench and screws to lock cover; no thermometer; non-adjustable range stops set at 72°F (max. heat) and 78°F (min. cool) (22-26°C); field adjustable locking levers; used with Q674L1561; used in Y594C1322. 70 Obsolete. Fiberglas Canada; °C scaleplate; no H1, H2, or C1 anticipation; used with Q674S1000; used in Y594C1348. 99 Obsolete. McQuay logo; part no. 61202401; °F/°C scaleplate; includes momentary system switch position with spring release; used with Q674C1363. C1695 45 Obsolete. Miller logo; used with Q674B1000; used in Y594C1355. C1703 45 Obsolete. Intertherm logo; used with Q674B1000; used in Y594C1363. C1737 44 Obsolete. Honeywell logo; Carrier part no. HH621603. C1745 44 Obsolete. AAF/Snyder General logo; part no. 4ELN7919. C1752 219 Obsolete. McQuay/Snyder General logo; part no. 061202402; 12°F offset between H1 and H2; °F/°C scaleplate; no C1 anticipation; used with Q674C1363. C1760 44 Bard logo. C1778 219 Obsolete. AAF/Snyder General logo; part no. 066804405; 12°F offset between H1 and H2; °F/°C scaleplate; no C1 anticipation; used with Q674C1363. C1794 53 Obsolete. Carrier logo; Canada; part no. HH07AT160-W; Premier White® color; °C scaleplate; includes locking cover. C1802 246 Obsolete. California Economizer logo; °F/°C scaleplate; used with Q674G1005; used in Y594C1371. C1810 237 Obsolete. Honeywell logo; TRADELINE model; Premier White® color; used with Q674B1547; used in Y594C1389. C1844 238 Energy Night logo; used with Q674F1592; used in Y594C1413. C1851 60 Obsolete. Whalen logo. C1869 219 McQuay logo; part no. 0073318801 Premier White® color; °F/°C scaleplate. aBoth the thermostat and subbase must be replaced. Trade Model Replacement Y594C1322a Y594C1322a T874C1018 T874C1018 T874C1018 Y594C1322a Remarks See OEM for replacement. T874C1125/ Q674B1075a T874C1018 Replacement has HEAT-OFFCOOL system switching; no momentary system switch position; no LEDs. T874C1018 T874C1018 T874C1018 T8611M2025 T874C1018 See OEM for replacement. T874C1018 T874C1018 Set stage 1 heat anticipator for total current draw of fan and stage 1 heat primary. Y594C1389 Y594R1425 T874C1018 See OEM for replacement. Jumper E-W2; system switch: EM.HT.-HEAT-OFF-COOL. 51 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Fig. Number No. Description Trade Model Replacement Remarks C1877 53 Obsolete. Honeywell logo; TRADELINE model; used with Q674B1554; used in Y594C1421. Y594D1347 Jumper RC-RH; system switch: OFF-HEAT-AUTOCOOL T874D 2-stage heat, 2-stage cool. D1009 166, 82 Obsolete. Honeywell logo; used with Q674F1337, E1007; used in Y594D1222, D1339. T874D1165 D1017 44, 88 Obsolete. Honeywell logo; TRADELINE model; includes Allen wrench and screws to lock cover; used with Q674A-G and Q674E1155. T874D1165 D1025 44 Obsolete. Westinghouse logo; H1 anticipator factory set T874D1165 at 0.75A; H2 anticipator factory set at 1.2A. D1033 44 Lennox logo; part no. 13F0601; °F/°C scaleplate. T874D1165 Replacement has °F scaleplate. D1041 53 York logo; part no. 2TH04701524A; used with Q674B1125. T874D1165 D1058 44 Obsolete. Shiger special. T874D1165 D1066 44 Obsolete. ITT logo. T874D1165 D1074 51, 53, Carrier logo; part no. HH07AT172; used with 146 Q674F1030 (HH93AZ174), F1063 (HH93AZ181) or Q674B. T874D1165a Set H1 anticipator for current draw of fan and stage 1 heat primary. D1082 44, 46, Trane logo; used with Q674B1018, C1009, B1075, 48, 72 B1133; used in Y594D1024, D1040. T874D1165 D1090 44 Obsolete. Dunham-Bush logo. T874D1165 D1108 44 Obsolete. Westinghouse logo. T874D1165 D1116 76, 89, Obsolete. Comfortmaker logo; part no. 1505-682; °F/°C T874D1165 Replacement has °F 94 scaleplate; used with Q674C1116, E1197, G1104. scaleplate. D1124 44 Obsolete. Airtemp special. T874D1165 D1132 44 Honeywell logo; °C scaleplate. T874D1165 Replacement has °F scaleplate. D1140 44 Obsolete. Solaron special. T874D1165 Replacement has °F scaleplate. D1157 51, 53, Carrier logo; part no. HH07AT172; °C scaleplate; used 146 with Q674B or Q674F1030, F1063. T874D1165a Replacement has °F scaleplate; set H1 anticipator for current draw of fan and stage 1 heat primary. D1165 82 Honeywell logo; SUPER TRADELINE® model; includes T874D1165 Allen wrench and screws to lock cover, field-adjustable range stops, field-adjustable locking levers. D1173 51, 53 Trane logo; part no. BAY28X183; heat anticipator factory set at 0.4A. T874D1165a Set H1 anticipator for current draw of fan and stage 1 heat primary. D1181 51, 53 Obsolete. General Electric logo; locking cover includes Allen wrench and screws to lock cover and range stops set at 72°F (max. heat) and 78°F (min. cool). T874D1165a Set H1 anticipator for current draw of fan and stage 1 heat primary. D1199 44 Obsolete. Lennox logo; part no. 13F0701; °C scaleplate. T874D1165 Replacement has °F scaleplate. D1207 114 Obsolete. Lennox logo; part no. 24F5201; used with Q674L1199 and C815A1013 or Q674L1389. T8611M2025 Wiring differences (old=new): (programmable) V-VR=R, Y=W3, X=C, R=O, M=Y, M2=Y2-W2, F=G; jumper Y2-W2; no outdoor reset needed; use only one system transformer. aBoth the thermostat and subbase must be replaced. 60-2485--8 52 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Number D1215 D1223 D1231 Fig. No. Description 44 Obsolete. Friedrich Climate Master logo; part no. AT5415; °F/°C scaleplate. 44 Honeywell logo; Honeywell Canada TRADELINE model; Celsius scale. 44 Obsolete. Honeywell logo; 12°F (7°C) differential between H1 and H2. D1249 D1256 D1264 D1272 44 Obsolete. Fedders special. 44 Obsolete. Climatrol special. 107 Obsolete. Carrier Heat Pump System Control logo; part no. HH07AT173; used with Q674L1116 (HH93AZ171). 51, 53 Obsolete. Carrier logo; part no. HH07AT162-03; °C scaleplate; used with Q674B. D1280 D1298 D1306 D1314 44 Obsolete. Command-Aire logo. 90, 232 Obsolete. Singer special; °C scaleplate; controls two separate heat/cool circuits; used with Q674D or Q674G1054, G1062. 90, 186 Obsolete. Trane special; part no. 02005949; controls two separate heat/cool circuits; used with Q674G1013. 44 Obsolete. McQuay logo; part no. 02005941; 12°F (6.6°C) differential between H1 and H2. D1322 D1330 46 Obsolete. Amana logo; part no. D68535-03; used with Q674B1075; used in Y594D1149. 44 Obsolete. Trane logo; part no. 13080242; °C scaleplate. D1355 D1363 44 Obsolete. Climate Control special; part no. 02005942; °C scaleplate; 6°C (11°F) differential between H1 and H2. 44 Obsolete. McQuay logo; part no. 02005943; 12°F (6.6°C) differential between H1 and H2; 6°F (3.3°C) differential between C1 and C2. D1405 44 Obsolete. Trane logo; part no. 02005952; 12°F (6.6°C) differential between H1 and H2; 6°F (3.3°C) differential between C1 and C2. D1413 44 Obsolete. Trane logo; part no. 02005956; 12°F (6.6°C) differential between H1 and H2. D1421 D1439 D1447 D1454 44 Obsolete. Climate Control special; part no. 02005938; °C scaleplate. 90 McQuay logo; part no. 02005935; used with Q674G1096. 90 Obsolete. Climate Control special; part no. 02005940; °C scaleplate; used with Q674G1096. 51, 53 Obsolete. Carrier logo. D1462 80 Obsolete. Fedders multi-logo; part no. THTX-220-A0HB, 88-58-00550-001; used with Q674E1205. aBoth the thermostat and subbase must be replaced. Trade Model Replacement Remarks T874D1165 Replacement has °F scaleplate. T874D1165 Replacement has °F scaleplate. T874D1165 Replacement has 2°F differential between H1 and H2. T874D1165 T874D1165 See OEM for replacement. T874D1165a Replacement thermostat has °F scaleplate; set H1 anticipator for current draw of fan and stage 1 heat primary. T874D1165 See OEM for replacement. See OEM for replacement. T874D1165 T874D1165 Replacement has °F scaleplate; 2°F differential between H1 and H2. T874D1165 T874D1165 T874D1165 T874D1165 T874D1165 T874D1165 T874D1165 Replacement has °F scaleplate. Replacement has 2°F differential between H1 and H2. Replacement has 2°F differential between H1 and H2; 2°F differential between C1 and C2. Replacement has 2°F differential between H1 and H2; 2°F differential between C1 and C2. Replacement has 2°F differential between H1 and H2. Replacement has °F scaleplate. T874D1165 T874D1165a T874D1165 Replacement has °F scaleplate. Set H1 anticipator for current draw of fan and stage 1 heat primary. 53 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Number D1470 D1488 D1496 D1504 D1512 D1520 D1538 D1553 Fig. No. Description 44 Obsolete. York logo; part no. 2TH04701624A; includes Allen wrench and screws to lock cover; °C scaleplate. 44 Obsolete. Risco special. 44 Obsolete. Borg Warner multi-logo; part no. 6TH04701524A; includes Allen wrench and screws to lock cover. 82 York logo; part no. 025-23321-000; °C scaleplate; used with Q674E1007; used in Y594D1180. 44 Honeywell logo; Heil Quaker part no. HQ712002HW. 44 Obsolete. Bard logo; adjustable lever stops set 68°F (max. heat) and 78°F (min. cool). 44 Obsolete. McQuay logo; part no. 02005937. 44 Obsolete. Climate Control special; part no. 02005944; °C scaleplate; 6°C differential between H1 and H2; 3°C differential between C1 and C2. D1561 D1587 D1595 44 Obsolete. General Electric logo; used with Q674 A-G. 44 Obsolete. Stiles Four Seasons logo. 139 Obsolete. Nepco logo; used with Q674F1394. D1603 D1611 D1629 D1678 44 Obsolete. Arcoaire logo. 44 Obsolete. No logo; Friedrich part no. AT5411; °F/°C scaleplate. 82 Obsolete. Reznor logo; °F/°C scaleplate; used with Q674E1007; used in Y594D1248. 44 Obsolete. Honeywell logo; Saudi Oger special; °C scaleplate; one setpoint lever; used with Q674A-K. D1686 98 Obsolete. McQuay logo; part no. 60685501; 8°F (4.4°C) differential between H1 and H2; 6°F (3.3°C) differential between C1 and C2; used with Q674E1312. D1694 202 Obsolete. McQuay logo; part no. 60685201; used with Q674G1120. D1702 44 Obsolete. McQuay logo; part no. 60685101. D1710 44 Trane logo. D1728 44 York-Miraco logo. D1744 44 American Standard logo; heat anticipator factory set at 0.4A. D1751 44 Obsolete. Goettl logo; part no. 372080; range stops set at 68°F (max. heating) and 78°F (min. cooling). D1769 82 Obsolete. Arcoaire logo; part no. 1506753; °F/°C scaleplate; used with Q674E1346; used in Y594D1297. D1777 44 Obsolete. Climate Control logo; part no. 65495806; °F/ °C scaleplate. D1785 82 Obsolete. Comfortmaker logo; part no. 1505753; °F/°C scaleplate; used with Q674E1346; used in Y594D1305. D1793 44 Obsolete. McQuay logo; part no. 65495805; °F/°C scaleplate. aBoth the thermostat and subbase must be replaced. Trade Model Replacement Remarks T874D1165 Replacement has °F scaleplate. T874D1165 T874D1165 T874D1165 T874D1165 T874D1165 Replacement has °F scaleplate. T874D1165 T874D1165 T874D1165 T874D1165 T874D1165/ Q674B1018a T874D1165 T874D1165 T874D1165 T874D1165 T874D1165 See OEM for replacement. T874D1165 T874D1165 T874D1165 T874D1165 Replacement has 2°F differential between H1 and H2; 2°F differential between C1 and C2; replacement has °F scaleplate. Replacement has HEAT-OFFCOOL system switching; no LEDs. Replacement has °F scaleplate. Replacement has °F scaleplate. Replacement has °F scaleplate; separate heating and cooling setpoint levers. Replacement has 2°F differential between H1 and H2; 2°F differential between C1 and C2. T874D1165 T874D1165 T874D1165 T874D1165 T874D1165 Replacement has °F scaleplate. Replacement has °F scaleplate. Replacement has °F scaleplate. Replacement has °F scaleplate. 60-2485--8 54 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Number D1801 D1819 Fig. No. Description 45, 208 Trol-A-Temp by Honeywell logo; H1 and H2 anticipators set at 0.10A; used with Q674B1463, D1115. 44 Marv Air Com Stat logo; part no. 50059; adjustable interstage between H1 and H2 and between C1 and C2; includes Allen wrench and screws to lock cover; field adjustable range stops; °F/°C scaleplate. D1827 D1843 D1850 D1868 D1876 D1892 D1918 D1926 D1934 D1942 D1959 D1967 D1975 D1983 D1991 45, 208 Trol-A-Temp by Honeywell logo; Premier White® color; H1 and H2 heat anticipators set at 0.10A; used with Q674B1471, D1123. 45 Obsolete. Janitrol logo; Goodman part no. CHT 90-120; used with Q674B1000; used in Y594D1321. 44 Honeywell logo; Carrier part no. HH621606. 44 Bard logo; part no. 8405-031; H1 and H2 heat anticipators factory set at 0.25A; 5°F interstage differential between H1 and H2 and between C1 and C2; includes Allen wrench and screws to lock cover; field adjustable range stops. 44 Obsolete. AAF/Snyder General logo; part no. 4ELN6981A; °F/°C scaleplate. 44 Obsolete. Climate-Tel logo. 224, Obsolete. AAF/Snyder General logo; °F/°C scaleplate; 225 no cooling anticipation; used with Q674E1312, C1298; 66804407. 226 Obsolete. AAF/Snyder General logo; °F/°C scaleplate; no cooling anticipation; used with Q674G1120; 66804406. 44 Bard logo. 82 Honeywell logo; TRADELINE model; used with Q674E1403; used in Y594D1347; designed to replace York part no. 2TH04701024. 44 Rheem part no. 41-21444-01. 44 Obsolete. Desert Aire logo. 224, Obsolete. McQuay part no. 066816603; °F/°C 225 scaleplate; no cooling anticipation. 226 Obsolete. McQuay part no. 066816602; °F/°C scaleplate; no cooling anticipation; used with Q674G1120. 51, 53 Carrier logo; Premier White® color; °C scaleplate. D2007 44 Ultra-Zone logo. D2023 44 Honeywell logo; TRADELINE model; Premier White® color; °C scaleplate; includes locking cover; used with Q674A-K. D2031 82 Obsolete. Honeywell logo; no cover; used with Q674E1049 and TG504A1025; used in Y594D1354. D2049 45, 72, Obsolete. Carrier Heat Pump System Control logo; part 55, 66, no. HH07AT236; °F/°C scaleplate; used with Q674B-D, 184 Q674G; used in Y594D. aBoth the thermostat and subbase must be replaced. Trade Model Replacement None T874D1165 None Remarks See Trol-A-Temp for replacement. Replacement has a 2°F fixed interstage differential between H1 and H2 and between C1 and C2; replacement has °F scaleplate. See Trol-A-Temp. T874D1165 T874D1165 T874D1165 Replacement has 2°F fixed interstage differential between H1 and H2 and between C1 and C2. T874D1165 T874D1165 See OEM for replacement. Replacement has °F scaleplate. See OEM for replacement. T874D1165 Y594D1347a T874D1165 T874D1165 See OEM for replacement. See OEM for replacement. T874D1165a T874D1165 T874D1165 Set H1 anticipator for total current draw of fan and stage 1 primary; replacement has °F scaleplate. Replacement has °F scaleplate and is beige. T874D1165 or Y594D1354 T874D1165 Replacement has °F scaleplate. 55 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Fig. Number No. Description Trade Model Replacement Remarks D2056 44 Obsolete. ComStat logo; part no. 50056; °F/°C scaleplate; adjustable interstage on both heating and cooling; includes locking cover and field-adjustable locking levers. T874D1165 Replacement has °F scaleplate and 2°F fixed differential in heating and cooling. D2064 53 Obsolete. Carrier Weathermaker; part no. HH07AT209; stage 1 and 2 heat anticipator factory set 0.1A; taupe color; used with Q674E1445; used in Y594D1412. T874D1165 Set stage 1 heat anticipator for total current draw of fan and stage 1 heat primary. Replacement is beige. D2072 53 Obsolete. Carrier Zone Perfect; part no. HH07AT208; T874D1165 Set stage 1 heat anticipator for taupe color; used with Q674E1445; used in Y594D1420. total current draw of fan and stage 1 heat primary. Replacement is beige. D2080 139 Obsolete. Hydroheat logo. T874D1165/ Replacement system switch: Q674B1018a HEAT-OFF-COOL; no LEDs. D2098 44 Obsolete. Honeywell logo; °F scaleplate; one setpoint lever; used with Q674D1008; used in Y594D1438. T874D1165 Replacement has °F scaleplate and two setpoint levers D2106 44 Obsolete. Honeywell logo; °C scaleplate; one setpoint lever; used with Q674D1008; used in Y594D1446. T874D1165 Replacement has °F scaleplate and two setpoint levers. D2114 44 Obsolete. Bard logo; °C scaleplate. T874D1165 Replacement has °F scaleplate. D2122 224, Obsolete. McQuay 225 T874D2023 Replacement has °C scaleplate. T874D1165 Replacement has °F scaleplate. D2130 226 Obsolete. McQuay See OEM for replacement. D2148 44 Obsolete. Dry Aire Systems logo; °F/°C scaleplate. T874D1165 D2155 139 Hydroheat logo; Premier White® color; °F/°C scaleplate; T874D1165/ Replacement system switch: used with Q674F1634. Q674B1018a HEAT-OFF-COOL; no LEDs. D2163 208 Obsolete. Amana logo; part no. P1217501F; °F/°C scaleplate. T874D1165 D2171 44 Obsolete. Amana logo; part no. P1217701F; °F/°C scaleplate. T874D1942 D2189 44 Armstrong logo; part no. 01142A024; °F/°C scaleplate; includes Air Ease insert. T874D1165 D2197 44 Liebert logo; part no. 138968P3; °F/°C scaleplate; interstage differential between H1 and H2 and between C1 and C2; includes Allen wrench and screws to lock cover; field-adjustable locking levers. T874D1165 D2205 44 Aaon logo; Premier White® color; °F/°C scaleplate. T874D1165 T874E 0-stage heat, 2-stage cool. E1008 44 Obsolete. Honeywell logo. T874E1016 E1016 44 Honeywell logo; TRADELINE model; includes Allen wrench and screws to lock cover; field-adjustable locking levers. T874E1016 E1024 44 Obsolete. Westinghouse logo. T874E1016 E1032 44 Lennox logo; part no. 13F0901; °F/°C scaleplate. T874E1016 Replacement has °F scaleplate. E1040 72 Obsolete. Trane logo; used with Q674C1009; used in Y594E1015. T874E1016 aBoth the thermostat and subbase must be replaced. 60-2485--8 56 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Number E1081 Fig. No. Description 44 Trane logo; part no. BAY28X186; °F/°C scaleplate. E1099 44 Obsolete. Lennox logo; part no. 13F1001; °C scaleplate. E1107 44 Honeywell logo; °C scaleplate. E1123 E1149 E1156 E1164 E1206 E1230 T874F F1007 F1015 F1023 F1031 F1049 44 Obsolete. Amana logo; part no. D68535-4. 44 Obsolete. York logo; part no. 2TH04701724A. 44 Obsolete. Borg Warner multi-logo; part no. 6TH04701724A. 44 Obsolete. E. A. Juffali & Bros. logo. 44 Obsolete. Trane logo. 44 Obsolete. Climar logo. 2-stage heat, 0-stage cool. 44 Honeywell logo. 44 Honeywell logo; TRADELINE model; includes Allen wrench and screws to lock cover; field-adjustable locking levers. 44 Obsolete. Lennox logo; part no. 13F1101. 44 Obsolete. Honeywell logo; °C scaleplate; used with 40003440-001 wallplate; used in Y594F1022. 44 Obsolete. Lennox logo; °C scaleplate. F1056 F1072 F1098 F1106 F1114 F1122 F1130 F1148 F1155 T874G G1006 55, Obsolete. Honeywell logo; stages 1 and 2 heat 66 electrically isolated; used with Q674D1008. 44 Obsolete. Wesco logo; heat anticipator factory set at 0.8A. 189 Obsolete. Lennox logo; used with Q674D1008 to control an M839. 95 Obsolete. Oneida logo; part no. 30A0287-02; used with Q674K1018 on combination wood and oil applications. 44 Honeywell logo; Honeywell Canada TRADELINE model; °C scaleplate; includes Allen wrench and screws to lock cover; field-adjustable locking levers. 62 Obsolete. Honeywell logo; two heat setpoint levers; used with Q674B1307. 72, 91 Obsolete. Reznor logo; °F/°C scaleplate; used with Q674C, D, or G; used with Q674C1009, G1005; used in Y594F1048. 44 Obsolete. Trane logo; part no. THT 0584. 95 Honeywell logo; used with Q674K1026 on combination wood and oil applications. Heat pump models; 2-stage heat, 1-stage cool; 1stage changeover. 84, 155 Obsolete. Honeywell logo; used with Q674E1015. aBoth the thermostat and subbase must be replaced. Trade Model Replacement T874E1016 T874E1016 T874E1016 T874E1016 T874E1016 T874E1016 Remarks Replacement has °F scaleplate. Replacement has °F scaleplate. Replacement has °F scaleplate. T874E1016 T874E1016 T874E1016 T874F1015 T874F1015 T874F1015 T874F1015 T874F1015 None Replacement has °F scaleplate. Replacement has °F scaleplate. T874F1015 T874F1015 T874F1155 Set H1 and H2 anticipators to lowest settings. T874F1015 Replacement has °F scaleplate. T874F1015/ Q674D1040 T874F1015 Replacement has no LED. Replacement has °F scaleplate. T874F1015 T874F1155 Y594G1252a Wiring differences (old=new): R=O, M=Y, F=G, V=R, Y=W2; E-W2 jumper required. 57 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Number G1014 G1022 G1048 Fig. No. Description 86, 150 Obsolete. Lennox logo; part no. 24F5801; °F/°C scaleplate; H2 anticipator factory set at 0.25A for fast cycle performance; changeover in cooling mode; independent heating and cooling circuits; used with Q674E1148, F1113. 86, 150 Obsolete. Lennox logo; part no. 24F5701; °F/°C scaleplate; H2 anticipator factory set at 0.25A for fast cycle performance; changeover in cooling mode; independent heating and cooling circuits; used with Q674E1148, F1113. 153, Obsolete. Westinghouse logo; H2 anticipator factory set 159 at 1.2A; used with Q674F1121, J1019. G1055 G1071 G1089 G1097 G1105 G1113 G1121 G1139 G1147 G1154 161 Carrier Heat Pump System Control logo; part no. HH07AT171; H2 anticipator factory set at 0.8A; changeover in cooling mode; used with Q674J1035 (HH93AZ173). 50, 103, Obsolete. Carrier Heat Pump System Control logo; 126, meets DoD specifications; H2 anticipator factory set at 183 0.8A; used with Q674P1005 (HH93AZ169), L1041 (HH93AZ175), B1158, or J1050. 154 Obsolete. Marvair logo; special for Crispaire; H2 anticipator factory set at 1.2A; used with Q674F1204; used in Y594G1153. 155 Obsolete. Honeywell logo; Rheem part no. ZXMT-B79; used with Q674F1238 (41-20797-14). 153 Obsolete. Heat Wave (Southwest Mfg.) logo; H2 anticipator factory set at 1.2A; used with Q674F1170. 103 Obsolete. Carrier Heat Pump System Control logo; meets DoD specifications; H2 anticipator factory set at 0.8A; used with Q674L1041. 103 Obsolete. Carrier Heat Pump System Control logo; part no. HH07AT161; °C scaleplate; H2 anticipator factory set at 0.8A; includes Allen wrench and screws to lock cover. 143, Obsolete. Honeywell logo; used with Q674B1240, 234 C1108. 148 Obsolete. Honeywell logo; changeover in cooling mode; used with Q674F1139. 84, 139 Obsolete. Lennox logo; used with Q674E1015, F1105. G1162 155 Obsolete. Lennox logo; meets DoD specifications; used with Q674F. G1170 160 Obsolete. York logo; part no. 2TH11702424A; H2 anticipator is fixed; used with Q674J1027; used in Y594G1013. G1188 147 Obsolete. Honeywell logo; Keeprite/Westinghouse special; H2 anticipator factory set 1.2A; °C scaleplate; changeover in cooling mode; used with Q674F1295. G1196 160 Obsolete. York logo; °C scaleplate; changeover in cooling mode; used with Q674J1027; used in Y594G1138. aBoth the thermostat and subbase must be replaced. Trade Model Replacement Remarks Y594G1252a Wiring differences (old=new): R=O, M=Y, F=G, Y=W2, V-VR=R (must use single transformer). Y594G1252a Wiring differences (old=new): R=O, M=Y, F=G, Y=W2, V-VR=R (must use single transformer). Y594G1252a None Wiring differences when replacing T874G/Q674J1019 (old=new): W=W2. See subbase description for replacement information. Y594G1419 Wiring differences (old=new): C=X; jumper Y1-W1. Y594G1393a Wiring differences (old=new): A=L. Y594G1252a Y594G1252a Y594G1419a Wiring differences (old=new): C=X; jumper Y1 -W1. Y594G1419a Wiring differences (old=new): C=X; jumper Y1-W1. None Y594G1252a Y594G1252a Y594G1419a See subbase description for replacement information. Wiring differences (old=new): C=X. See subbase description for replacement information. W1-Y1 jumper required. Y594G1567a Y594G1252a Wiring differences (old=new): S=L. Y594G1567a 60-2485--8 58 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Fig. Number No. Description Trade Model Replacement Remarks G1204 162 Honeywell logo; designed for use on Trane heat pumps; Y594G1161a Designed for use on Trane no H2 anticipation; changeover in cooling mode; used heat pumps. with Q674J1043 and C815A1005; used in Y594G1161. G1212 155 Obsolete. Honeywell logo; H2 anticipator factory set at 0.2A; changeover in cooling mode; includes shunt to bypass H2 anticipator with W3 heat relays; used with Q674F1238. Y594G1252a G1220 235 Obsolete. Rheem logo; part no. RXMT-C71; changeover Y594G1252a in cooling mode; used with Q674F1238. G1238 155 Obsolete. Ruud logo; part no. UXMT-C71; changeover in cooling mode; used with Q674F1238. Y594G1252a G1246 Obsolete. Honeywell logo; changeover in cooling mode. 155 Used with Q674F1212; used in Y594G1195, G1252, G1369. Y594G1252a 170 Used with Q674F1410; used in Y594G1393. Y594G1393a G1261 58, 157 Obsolete. Borg-Warner; used with Q674D1032, F1253. None See subbase description for replacement information. G1279 58, 157 Obsolete. Bryant logo; used with Q674D1032, F1253. None See subbase description for replacement information. G1287 58, 157 Obsolete. Wesco logo; used with Q674D1032, F1253. None See subbase description for replacement information. G1295 58 Obsolete. York logo; part no. 2TH11702724A; used with T874D1165/ Wiring differences (old=new): Q674D1032. Q674D1040 Y=Y2, O=Y1, W=W2; jumper W1-Y2. G1345 160 Obsolete. York logo; part no. 2TH11702624A; °C scaleplate; used with Q674J1027. Y594G1575a G1352 73 Obsolete. Command-Aire logo; 12°F differential between H1 and H2 for night setback; used with Q674C1066. Y594H1012a Wiring differences (old=new): Y1=O, Y2=Y, L=R, R=none; RL jumper required; no night setback. T8600D1004 Wiring differences (old=new): (programmable) Y1=O, Y2=Y, L=RH; RC-RH jumper required; includes night setback. G1378 79 Obsolete. Mammoth logo; H2 anticipator factory set at Y594H1012a Wiring differences (old=new): 0.8A; 12°F differential between H1 and H2 for night R1=none, R2=L; R-L jumper setback; °F/°C scaleplate; used with Q674C1124; used required; no night setback. in Y594G1294. T8090A1007/ Includes night setback; W-Y Q682A1038a jumper required. (programmable) G1402 129 Obsolete. York part no. 2TH11702824A; meets DoD specifications; used with Q674L1363. Y594R1425a Wiring differences (old=new): W=W2, X=E, B=X; jumper Y-W1. G1410 155 Obsolete. Borg-Warner multi-logo; part no. 6TH11703024A; used with Q674F1311. T874G1246a or Y594G1252a G1428 160 Obsolete. Borg-Warner multi-logo; part no. 6TH11702424A; used with Q674J1027; used in Y594G1229. Y594G1567a G1436 58 Obsolete. Borg-Warner multi-logo; part no. 6TH11702724A. T874D1165/ Wiring differences (old=new): Q674D1040 Y=Y2, O=Y1, W=W2; jumper W1-Y2. aBoth the thermostat and subbase must be replaced. 59 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Fig. Number No. Description Trade Model Replacement Remarks G1444 160 Obsolete. ROCA logo; °C scaleplate; used with Q674J1027. Y594G1567a Replacement has °F scaleplate. G1451 155 Obsolete. BDP multi-logo; part no. HH641502; used with T874G1246a or Q674F1212; used in Y594G1245. V594G1252a G1469 194 Obsolete. No logo; Addison special; used with Q674F1345; used in Y594G1344. Y594G1252a Wiring differences (old=new): Y1=O, C=X, W1=Y1, X=L. G1485 163 Obsolete. AAF logo; part no. 4ELN-7839; °F/°C Y594G1393a No night setback or scaleplate; 10°F differential between H1 and H2 for night momentary reset switch. setback and momentary RESET system switch position; T8611G1004 Includes night setback; no used with Q674C1199. (programmable) momentary reset switch. G1493 167 Obsolete. Honeywell logo; Rheem part no. 41-20797-18; Y594G1526a used with Q674F1360. G1501 195 Obsolete. Coleman logo; part no. 3600-375; changeover Y594G1252a Wiring differences (old=new): in cooling mode; used with Q674F1378. L1=L; changeover in cooling only. G1535 163 Obsolete. AAF/Snyder General logo; 4ELN7839 °F/°C Y594G1393a No night setback or scaleplate; 10°F differential between H1 and H2 for night momentary reset switch. setback and momentary RESET system switch position; used with Q674C1199. T8611G1004 Includes night setback. (programmable) G1543 194 Obsolete. Addison logo; Weather King part no. 8403197; used with Q674F1345; used in Y594G1328. Y594G1252a Wiring differences (old=new): Y1=O, C=X, W1=Y, X=L. G1568 160 Obsolete. Luxaire logo; part no. 026-00068-000; °C Y594G1367a Replacement has °F scaleplate; used with Q674J1126; used in Y594G1351. scaleplate. G1576 169 Obsolete. Coleman logo; part no. 3600-373; changeover Y594G1633a in heating and cooling mode; used with Q674F1402; used in Y594G1377. G1584 73 Obsolete. No logo; Friedrich part no. AT5784; 8°F (4.4°C) differential between H1 and H2; used with Q674C1223. Y594H1012a Wiring differences (old=new): Y1=O, Y2=Y, L=R, R=none; L-R jumper required; no night setback. T8611G1004 Includes night setback. (programmable) G1592 155 Obsolete. Arcoaire logo; used with Q674F1212; used in T874G1246a or Y594G1385. Y594G1252a G1600 199 Obsolete. Honeywell logo; meets DoD specifications; used with Q674F1428; used in Y594G1401. Y594G1419a Wiring differences (old=new): jumper W1-Y1. G1618 73 Obsolete. Honeywell logo; 12°F differential between H1 Y594H1012a Wiring differences (old=new): and H2 for night setback; used with Q674C1256. Y1=O, Y2=Y, L=R, R=none; L-R jumper required; no night setback. T8600C1162 Wiring differences (old=new): (programmable) L=R, W=O; W-Y jumper required; includes night setback. G1626 167 Honeywell logo; used with Q674F1436; used in Y594G1526. None G1642 227 Honeywell logo; TRADELINE model; meets DoD specifications; used with Q674F1444; used in Y594G1419. Y594G1419a aBoth the thermostat and subbase must be replaced. 60-2485--8 60 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Fig. Number No. Description Trade Model Replacement Remarks G1659 177 Obsolete. Mammoth logo; 0.8A maximum current Y594H1012a Wiring differences (old=new): through B or O terminal; 12°F differential between H1 R2=L, R1=none; L-R jumper and H2 for night setback; used with Q674C1330; used in required; no night setback. Y594G1427. T8611G1004 Includes night setback. (programmable) G1675 174 Obsolete. American Standard logo; part no. ASYSTAT650; used with Q674J1142; used in Y594G1443. Y594G1161a G1691 176 Obsolete. Command Aire logo; part no. P1013-0060; 12°F (6.6°C) differential between H1 and H2 for night setback; used with Q674C1389, C1397. Y594H1012a Wiring differences (old=new): Y1=O, Y2=Y, R=none; L-R jumper required; no night setback. T8611G1004 Includes night setback. (programmable) G1717 175 Obsolete. Carrier Heat Pump System Control logo; part no. HH07AT102N; used with Q674J1167; used in Y507J1201. Y594G1252a Wiring differences (old=new): C=X, D=L; replacement has AUX. HEAT and EM. HEAT LEDs. G1741 227 Honeywell logo; TRADELINE model; includes factory set range stops at 68°F (max. heat) and 78°F (min. cool); Premier White® color; used with Q674F1477; used in Y594G1476. Y594G1476a G1758 211 Trol-A-Temp by Honeywell logo; Premier White® color; changeover is provided by Trol-A-Temp zone panel; used with Q674F1485; used in Y594G1492. None See Trol-A-Temp for replacement. G1774 216 Obsolete. Comfortmaker logo; part no. 1505756; used with Q674J1175; used in Y594G1500. Y594G1252a Wiring differences (old=new): E=W2, W1=W3, X=E, C=X. G1782 216 Obsolete. Arcoaire logo; part no. 1506756; used with Q674J1175; used in Y594G1518. Y594G1252a Wiring differences (old=new): E=W2, W1=W3, X=E, C=X. G1790 161 Obsolete. Carrier logo; Premier White® color; °C scaleplate; includes Allen wrench and screws to lock cover; used with Q674J1191. Y594G1252a Wiring differences (old=new): C=X; replacement has °F scaleplate. G1816 163 Climate Master logo; part no. AT5716; °F/°C scaleplate; Y594G1393a No momentary reset switch. 10°F differential between H1 and H2 and momentary RESET system switch position. G1824 227 Honeywell logo; Australian TRADELINE model; Premier Y594G1476a White® color; °C scaleplate; used with Q674F1477; used in Y594G1534. G1832 231 Obsolete. Intertherm logo; used with Q674F1519; used in Y594G1542. Y594G1252a Replacement has auto changeover in cooling mode only. G1840 231 Obsolete. Miller logo; used with Q674F1519; used in Y594G1559. Y594G1252a Replacement has auto changeover in cooling mode only. G1857 229 Obsolete. Lennox logo; °C scaleplate; Premier White® color; used with Q674F1535; used in Y594G1583. Y594G1161a Wiring differences (old=new): E=X2, C=B, L=F. G1865 160 Honeywell logo; TRADELINE model; designed to Y594G1567a replace Y594G1013 (York part no. 2TH11702424), Y594G1229 (York part no. 6TH11702424), and York part no. 2TH117704124); used with Q674J1209; used in Y594G1567. aBoth the thermostat and subbase must be replaced. 61 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Fig. Number No. Description Trade Model Replacement Remarks G1873 160 Obsolete. Honeywell logo; TRADELINE model; Premier Y594G1567a Replacement is beige. White® color; designed to replace Y594G1013 (York part no. 2TH11702424), Y594G1229 (York part no. 6TH11702424), and York part no. 2TH117704124); used with Q674J1225; used in Y594G1575. G1881 167 Rheem; part no. 41-20797-18. Y594G1526a G1899 169 Obsolete. Amana; part no. 10574101; used with Q674F1550; used in Y594G1591. Y594G1633a G1915 155 Econar logo; used with Q674F1212; used in Y594G1609. Y594G1252a 170 Used with Q674F1410. Y594G1393a G1923 176 Trane logo; part no. X13510599010; H2 make 12°F below H1 make. Y594H1012a Wiring differences (old=new): Y1=O, Y2=Y, R=none; L-R jumper required; no night setback. T8611G1004 Includes night setback. (programmable) G1931 155, Obsolete. Honeywell logo; Premier White® color; °C 170 scaleplate; used with Q674F1568. None See subbase description for replacement information. G1949 73 Obsolete. Carrier Heat Pump System Control logo; part Y594H1012a Wiring differences (old=new): no. HH07AT204; °F/°C scaleplate; H2 make 8°F below Y1=O, Y2=Y, L=R, R=none; R- H1 make; used in Y594. L jumper required; no night setback. T8600D1004 Wiring differences (old=new): (programmable) Y1=O, Y2=Y, L=RH; RC-RH jumper required; includes night setback. G1956 30, 103, Obsolete. Carrier logo; Canada; Premier White® color; 126, °C scaleplate; includes locking cover. 183 Y594G1476 Replacement has °F scaleplate. G1964 160 York logo; Canada; Premier White® color; °C scaleplate; Y594G1575a Replacement has °F used in Y594G1625. scaleplate. G1972 169 Honeywell logo; TRADELINE model; used with Q674F1584; used in Y594G1633. Y594G1633a G1980 169 Obsolete. Amana logo; part no. 10574103; used with Q674F1600; used in Y594G1641. Y594G1633a Wiring differences (old=new): W3=W2. G1998 155 Obsolete. Tempstar logo (Inter-City Products); used in Y594G1658; used with Q674F1212. Y594G1252a G2004 103 Honeywell logo; TRADELINE model; used with Q674L; Y594G1666 used in Y594G. 161 Used with Q674J1274; used in Y594G1674. Y594G1674 G2046 155, WaterFurnace logo; part no. TA21H03; Premier White® 170 color; °F/°C scaleplate; used with Q674F1667; used in Y594G1716. Y594G1716 T874H Heat pump model; 1-stage heat, 1-stage cool, 1-stage changeover in cool. H1005 74 Obsolete. Command Aire logo; used with Q674C1041. Y594H1012a Wiring differences (old=new): Y1=O, Y2=Y; L-R jumper required. H1013 74 Obsolete. Friedrich part no. AT5813; °C scaleplate; used Y594H1012a Wiring differences (old=new): with Q674C1041. Y1=O, Y2=Y; L-R jumper required; replacement has °F scaleplate. aBoth the thermostat and subbase must be replaced. 60-2485--8 62 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Number H1021 Fig. No. Description 74 Obsolete. Friedrich Climate Master logo; part no. AT5821; °F/°C scaleplate; used with Q674C1041. H1039 H1054 79 Obsolete. Mammoth logo; °F/°C scaleplate; used with Q674C1124; used in Y594H1004. 74 Obsolete. No logo; Friedrich part no. AT5854; used with Q674C1041. H1062 H1070 H1088 H1096 H1112 164 Honeywell logo; used with Q674C1249; used in Y594H1012. 172, Obsolete. Carrier Heat Pump System Control logo; part 173 no. HH07AT166; °C scaleplate; used with Q674B1406 (HH93AZ200) or Q674C1322 (HH93AZ199). 172, Obsolete. Carrier Heat Pump System Control logo; part 173 no. HH07AT167; used with Q674B1406 (HH93AZ200) or Q674C1322 (HH93AZ199). 177 Obsolete. Mammoth Water Source Heat Pump logo; °F/ °C scaleplate; changeover stage 0.8A maximum; used B or O terminal; used with Q674C1330. 74 No logo; Friedrich part no. AT5812; used with Q674C1355. H1120 H1138 205 Obsolete. Command Aire logo; part no. P1013-0055; used with Q674C1389, C1397. 221 Obsolete. Climate Master logo; part no. AT5838; used with Q674C1470. H1146 205 Trane logo; part no. X13510598010. H1153 173 Obsolete. Carrier Heat Pump System Control logo; part no. HH07AT167; °F/°C scaleplate; used with Q674C1322; used in Y594H1053. H1161 74 Obsolete. Carrier Heat Pump System Control logo; part no. HH07AT203; °F/°C scaleplate; used with Q674C1496; used in Y594H1038. T874J Heat pump model. 2-stage heat, 1-stage cool. J1002 124, Obsolete. Carrier Heat Pump System Control logo; part 144, no. HH07AT175; used with Q674J1068 (HH93AZ183), 206, Q674J1159 (HH93AZ196), Q674L1074 (HH93AZ186), 207 Q674L1637 (HH93AZ195). J1010 124, Obsolete. BDP multi logo; part no. 34427DP124/P272171 2471; used with Q674J1084, L1371. J1028 124, Obsolete. Carrier Heat Pump System Control logo; part 144, no. HH07AT165; °C scaleplate; used with Q674J1068 206, (HH93AZ183), Q674J1159 (HH93AZ196), Q674L1074 207 (HH93AZ186), Q674L1637 (HH93AZ195). J1036 124, Obsolete. Miller logo; part no. 9132230; used with 171 Q674J1217. J1044 124, Obsolete. Intertherm logo; part no. 9132240; used with 171 Q674J1217. J1051 124, Obsolete. Carrier logo; part no. HH07AT165-W; Premier 144 White® color; °C scaleplate. aBoth the thermostat and subbase must be replaced. Trade Model Replacement Y594H1012a Y594H1012a Y594H1012a Y594H1012a None None Y594H1012a Y594H1012a Y594H1012a Y594H1012a Y594H1012a None Y594H1012a None None None T8511G1021 T8511G1021 None Remarks Wiring differences (old=new): Y1=O, Y2=Y; L-R jumper required; replacement has °F scaleplate. Wiring differences (old=new): R1=R, R2=L. Wiring differences (old=new): Y1=O, Y2=Y; L-R jumper required. See subbase description for replacement information. See subbase description for replacement information. Wiring differences (old=new): R1=R, R2=L; L-R jumper required. Wiring differences (old=new): Y1=O, Y2=Y; L-R jumper required. Wiring differences (old=new): Y1=O, Y2=Y. Wiring differences (old=new): Y1=O, Y2=Y; replacement has MALFUNCTION LED only. Wiring differences (old=new): Y1=O, Y2=Y. See subbase description for replacement information. Wiring differences (old=new): Y1=O, Y2=Y; L-R jumper required. See subbase description for replacement information. See subbase description for replacement information. See subbase description for replacement information. See subbase description for replacement information. 63 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Fig. Number No. Description Trade Model Replacement Remarks J1069 124, Obsolete. Honeywell logo; TRADELINE model; used 144, with Q674J1282; used in Y594J1019. 206, 207 T8511G1021 J1077 124, Obsolete. Nordyne logo; part no. 9148300; °F/°C 171 scaleplate. T8511G1021 T874K Heat pump model; 2-stage heat, 1-stage cool, automatic changeover in heat. K1001 77 Obsolete. LSI Mammoth logo; used with Q674C1090. Y594G1419a Wiring differences (old=new): RH-RC=R, W1=B, W3=W2, W2=W1; remove Y1-W1 jumper. K1019 181 Obsolete. McQuay/Snyder General logo; part no. Y594G1252a Wiring differences (old=new): 60687301; °F/°C scaleplate; H1 anticipator set at 0.83A; C=X, W=B, A=L; jumper 8°F interstage differential between H1 and H2 for night E-W2; no night setback. setback; used with Q674C1280. T8611G1004 Wiring differences (old=new): (programmable) C=X, W=B, A=X2; jumper X2- R; remove external time clock; includes night setback. K1027 181 Obsolete. AAF/Snyder General logo; part no. Y594G1252a Wiring differences (old=new): 066804403; °F/°C scaleplate; H1 anticipator set at C=X, W=B, A=L; jumper 0.83A; 8°F interstage differential between H1 and H2 for E-W2; no night setback. night setback; used with Q674C1280. T8611G1004 Wiring differences (old=new): (programmable) C=X, W=B, A=X2; jumper X2-R; remove external time clock; includes night setback. T874L Heat pump model; 2-stage heat, 1-stage cool, changeover in cool. L1000 198 Obsolete. Carrier logo; part no. HH07AT176; used with Y594G1419a E-W2 jumper required. Q674E1270 (HH93AZ189). L1018 138, Obsolete. Carrier Multiplex System logo; part no. 165 HH07AT178; used with Q674B1356 (HH93AZ192) or Q674C1264 (HH93AZ193). See OEM for replacement. L1026 198 Obsolete. Honeywell logo; BDP part no. P272-2786; used with Q674E1304. Y594G1419a E-W2 jumper required. L1034 203 Obsolete. McQuay logo; part no. 60687201; °F/°C Y594G1419a Wiring differences (old=new): scaleplate; H1 anticipator factory set at 0.83A; used with Y=Y1, W=B, A=X1; remove Q674C1280. Y1-W1 jumper. L1059 215, Obsolete. Carrier logo; part no. HH07AT192; used with 213 Q674B1448 (HH93A2202) or Q674C1413 (HH93AZ204). See OEM for replacement. L1067 203 Obsolete. AAF/Snyder General logo; part no. 066804402; H1 anticipator factory set at 0.83A; used with Q674C1280. Y594G1419a Wiring differences (old=new): Y=Y1, W=B, A=X1; remove Y1-W1 jumper. L1075 203 Obsolete. McQuay logo; part no. 073318601; Premier White® color; °F/°C scaleplate; includes AAF insert. See OEM for replacement. T874N Heat pump model; 2-stage heat; 1-stage cool plus changeover; changeover in heat mode. N1008 178 Obsolete. Williamson logo; used with Q674F1196; used T874N1016 in Y594N1007. N1016 178 Honeywell Heat Pump Thermostat logo; used with Q674F1220. T874N1016 N1024 179, Bard logo; H1 and C1 anticipation fixed; used with 217 Q674F1261. None See subbase description for replacement information. aBoth the thermostat and subbase must be replaced. 60-2485--8 64 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Fig. Number No. Description Trade Model Replacement Remarks N1040 179 Obsolete. Honeywell logo; H1 and C1 anticipation fixed; used with Q674F1261; used in Y594N1015. None N1057 178 Obsolete. Intertherm logo; part no. 9111882; used with Q674F1220; used in Y594N1023. T874N1016 N1065 178 Obsolete. Miller logo; Nordyne part no. 9122240; used with Q674F1220; used in Y594N1031. T874N1016 T874P Heat pump model; 2-stage heat, 1-stage cool, automatic changeover in cool. P1006 57, 78 Obsolete. McQuay logo; part no. 860-442725B-00; 8°F (4.4°C) interstage differential between H1 and H2; used with Q674B1273, C1140. None See subbase description for replacement information. P1014 78 Obsolete. Friedrich/Climate Master logo; °F/°C T8600D2028 Wiring differences (old=new): scaleplate; 8°F (4.4°C) differential between H1 and H2 (programmable) L=R, W=O; W-Y jumper for night setback; used with Q674C1207. required; includes night setback. P1022 97 Obsolete. Friedrich/Climate Master logo; part no. AT5922; °F/°C scaleplate; 8°F (4.4°C) differential between H1 and H2 for night setback; used with Q674C1215. None See subbase description for replacement information. P1030 97 Obsolete. No logo; Friedrich part no. AT5930; 8°F (4.4°C) differential between H1 and H2 for night setback; used with Q674C1215. None See subbase description for replacement information. P1055 68, 97 Obsolete. Carrier Heat Pump System Control logo; part no. HH07AT205; °F/°C scaleplate; heat interstage differential 8°F (4.4°C). None See subbase description for replacement information. T874Q 1-stage heat; used with another T874 for night setback. Q1005 44 Honeywell logo. T874A1036 Q1013 44 Obsolete. Lennox logo; part no. 13F1201; °F/°C scaleplate. T874A1036 Replacement has °F scaleplate. Q1021 44 Obsolete. Lennox logo; part no. 13F1301; °C scaleplate. T874A1036 Replacement has °F scaleplate. T874R Heat pump model; 2-stage heat, 1-stage cool, manual changeover. R1004 47 Obsolete. Honeywell logo; used with Q674B1042; used Y594R1243a Wiring differences (old=new): in Y594R1029. W1=W2. R1012 47 Obsolete. Honeywell logo; Addison heat pump; used with Q674B1109. Y594R1243a Wiring differences (old=new): W1=W2. R1020 102 Obsolete. Lennox logo; part no. 24F5401; °F/°C Y594R1243a Wiring differences (old=new): scaleplate; H1 and C1 anticipators are fixed; auxiliary M=Y, F=G, V-VR=R, Y=W2, heat circuit powered by separate transformer; used with R=O; replacement has °F Q674L1025. scaleplate. R1038 102 Obsolete. Lennox logo; °C scaleplate; H1 and C1 anticipators are fixed; auxiliary heat circuit powered by separate transformer; used with Q674L1025. Y594R1243a Wiring differences (old=new): M=Y, F=G, V-VR=R, Y=W2, R=O; replacement has °F scaleplate. R1046 120, Obsolete. York logo; part no. 2TH11702224A; H2 101 anticipator is fixed; used with Q674L1272 in Y594R1011 or with Q674L1094. Y594R1664a R1053 109 Obsolete. Honeywell logo; H2 anticipator is fixed; used Y594R1763a Designed for use on Trane with Q674L1140; used in Y594R1136. heat pumps. R1061 104 Obsolete. Honeywell logo; H2 anticipator is field adjustable; changeover in cooling; used with Q674L1082. Y594R1243a Replacement has auto fan in Emergency Heat mode. aBoth the thermostat and subbase must be replaced. 65 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Number R1079 R1087 R1095 R1103 R1111 R1129 R1137 R1145 R1152 R1160 R1178 R1186 R1194 R1202 R1210 R1228 R1236 R1244 R1251 R1269 R1285 R1301 Fig. Trade Model No. Description Replacement Remarks 123 Obsolete. Ruud logo; part no. UXMT-C70; used with Q674L1157. Y594R1243a 120 Obsolete. Honeywell logo; Special for Dunham Bush; use with Q674L. Y594R1664a 123 Obsolete. Rheem logo; part no. RXMT-C70; used with Q674L1157. T874R1152/ Y594R1243a 104 Obsolete. Westinghouse logo; used with Q674L. Y594R1243a 116, Obsolete. Marvair logo; H2 anticipator factory set at 104 1.2A; used with Q674L1215, L1082; used in Y594R1128. Y594R1243a Replacement has auto fan in Emergency Heat mode. 113 Bard logo; used with Q674L1181. Y594R1243a Wiring differences (old=new): X1=X. 108, Obsolete. Honeywell logo; Heil Quaker part no. 125 HQ711597HW; used with Q674L1132; used in Y594R1110. Y594R1292a 120 Obsolete. York logo; °C scaleplate; H2 anticipator is fixed; used with Q674L1272; used in Y594R1102. Y594R1664a 115 Honeywell logo; used with Q674L1207, L1033; used in Y594R1243a Y594R1243. 182 Obsolete. Honeywell Advanced Heat Pump System logo; used with Q674L1298 and W89. None 110, Obsolete. Lennox logo; part no. 24F5601; °F/°C 111 scaleplate; auxiliary heat circuit powered by separate transformer; fast cycle stage H2 anticipator; requires outdoor reset and independent circuits; used with Q674L1165, L1355. Y594R1763a Wiring differences (old=new): V-VR=R, M=Y, F=G, X=B, Y=W, A=T, R=O, E=X2. 182 Obsolete. Honeywell Advanced Heat Pump System logo; used with Q674L1231 and W89. None 115 Obsolete. Amana logo; used with Q674L1249 and W89. Y594R1243a 201 Obsolete. Intertherm logo; part no. 9111871; used with Q674L1264 or Q674L1595; used in Y594R1185. Y594R1672a Wiring differences (old=new): W2=W, Z=no connection, K=X, W=G, W1=H, X=B. 101 Obsolete. Roca logo; °C scaleplate; used with Q674L1017. Y594R1243a Wiring differences (old=new): W=W2, X=L, B=X. 120 Obsolete. York logo; part no. 2TH11702524A; °C scaleplate; used with Q674L1272 and C815A1005; used in Y594R1144. Y594R1672a 115 Obsolete. Williamson logo; includes Allen wrench and screws to lock cover; used with Q674L1348. T874R1152 115 Obsolete. Westinghouse logo; used with Q674L1314 and W89. T874R1152/ Y594R1243a 120 Obsolete. York logo; part no. 2TH11702324A; H2 anticipator is fixed; used with Q674L1272 and C815A1039. Y594R1672a 122 Obsolete. Fedders multi logo; part no. THTX-120-HEHB 88-58-00540-001; used with Q674L1066; used in Y594R1037. Y594R1615a Wiring differences (old=new): K=E, C=X, W1=B, Z=L. 123 Obsolete. Honeywell logo; Rheem part no. 41-20796-15; Y594R1243a used with Q674L1157. 113 Obsolete. Comfortmaker logo; part no. 1505-714; used Y594R1243a Wiring differences (old=new): with Q674L1181; used in Y594R1417. X1=X. aBoth the thermostat and subbase must be replaced. 60-2485--8 66 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Number R1319 R1327 R1335 R1343 R1350 R1368 R1376 R1384 R1392 R1400 R1426 R1434 R1442 R1459 R1467 R1475 R1483 R1491 R1509 R1517 R1525 R1541 R1558 R1566 Fig. Trade Model No. Description Replacement Remarks 191 Obsolete. Carrier part no. 42QH400083; used with Q674B1281 on two speed fan applications. See OEM for replacement. 120 Obsolete. Borg-Warner multi-logo; part no. 6TH11702224A; used with Q674L1272; used in Y594R1193. Y594R1672a 106 Obsolete. BDP multi-logo; part no. HH641501; H2 Y594R1243a anticipator factory set 1.2A; used with Q674L1405; used in Y594R1201. 133 Obsolete. Fedders multi-logo; part no. THTX-120-HEHC 88-58-0056-001; used with Q674L1413; used in Y594R1219. Y594R1425a Wiring differences (old=new): K=E, C=X1, Z=L; remove Y1-W1 jumper. 113 Obsolete. Honeywell logo; used with Q674L1181. Y594R1243a Wiring differences (old=new): X1=X. 125 Obsolete. Coleman logo; part no. 3600-368; used with Q674L1421; used in Y594R1235. Y594R1797a 115 Honeywell logo; °C scaleplate; used with Q674L1207. T874R1152 131, Obsolete. Carrier Heat Pump System Control logo; part 135 no. HH07AQ170; used with Q674L (HH93AZ187), Q674L (HH93AZ197), or Q674L (HH93AZ198). Y594G1243a Wiring differences (old=new): C=X. 128 Obsolete. Williamson logo; used with Q674L1447; used Y594R1425a Wiring differences (old=new): in Y594R1250. A=L. 113 Obsolete. LSI part no. 104710001; used with Q674L1181, L1462. See subbase description for replacement information. 136 Obsolete. Trane Weathertron Heat Pump logo; part no. BAYSTAT339 (WY28X0112); °F/°C scaleplate; used with Q674L1496; used in Y594R1284. Y594R1763a 134 Ruud logo; part no. 41-20796-32; used with Q674L1504; Y594R1300a used in Y594R1649. 134 Rheem logo; part no. 41-20796-28; used with Q674L1504; used in Y594R1631. Y594R1300a 134 Obsolete. Honeywell logo; Rheem part no. 41-20796-25; Y594R1300a used with Q674L1504. 108 Honeywell logo; used with Q674L1512; used in Y594R1292. Y594R1292a 123 Honeywell logo; scale range 42°F to 88°F; used with Q674L1520; used in Y594R1300. Y594R1300a 130 Obsolete. Comfortmaker logo; °F/°C scaleplate; used Y594R1763a Wiring differences (old=new): with Q674L1538 and C815A1005; used in Y594R1318. W1=W, E=X2, X=F, C=B. 137 Obsolete. Honeywell logo; TRADELINE model; used with Q674L1553; used in Y594R1326. Y594R1615a 47 Obsolete. Slant/Fin logo; used with Q674B1042; used in Y594R1243a Wiring differences (old=new): Y594R1334. W1=W2. 130 Obsolete. Arcoaire logo; part no. 150671; used with Q674L1538 and C815A1005; used in Y594R1342. Y594R1763a Wiring differences (old=new): W1=W, E=X2, X=F, C=B. 113 Obsolete. Arcoaire logo; used with Q674L1181; used in Y594R1243a Wiring differences (old=new): Y594R1359. X1=X. 67 Obsolete. Goettl logo; part no. 372071; used with Q674B1349. Y594R1300a 134 Obsolete. Universal Parts logo; part no. 41-20796-45; used with Q674L1504; used in Y594R1623. Y594R1300a 130 Obsolete. Honeywell logo; used with Q674L1538 and C815A1005; used in Y594R1375. Y594R1763a Wiring differences (old=new): W1=W, E=X2, X=F, C=B. aBoth the thermostat and subbase must be replaced. 67 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Number R1574 R1582 R1590 Fig. No. Description 132 Obsolete. Comfortmaker logo; part no. 1505739; used with Q674L1538; used in Y594R1383. 132 Obsolete. Arcoaire logo; part no. 150739; used with Q674L1538; used in Y594R1391. 115 Obsolete. Refac logo; used with Q674L1207. R1608 119 Obsolete. Honeywell logo; Intertherm heat pump; used with Q674L1264; used in Y594R1409. R1616 R1624 168 Honeywell logo; SUPER TRADELINE® model; used with Q674L1587; used in Y594R1425. 200 Obsolete. Honeywell logo; used with Q674L1595; used in Y594R1433. R1632 R1640 R1657 R1673 R1699 134 Obsolete. Honeywell logo; used with Q674L1603. 115 Obsolete. Hitecsa logo; °C scaleplate; H2 anticipator factory set at 1.2A; used with Q674L1207. 136 Obsolete. American Standard logo; part no. ASYSTAT651; requires outdoor reset; used with Q674L1611; used in Y594R1441. 108 Heil logo; part no. 1060321, HAXB004TW01; used with Q674L1132; used in Y594R1466. 119 Obsolete. Miller logo; used with Q674L1264; used in Y594R1482. R1707 R1715 R1723 R1731 R1749 R1814 R1822 R1830 R1855 209 Trol-A-Temp by Honeywell logo; Premier White® color; used with Q674L1678; used in Y594R1490. 209 Trol-A-Temp by Honeywell logo; used with Q674L1186; used in Y594R1508. 218 Obsolete. No logo; Snyder General part no. 654958B07; °F/°C scaleplate; used with Q674L1702 and C815A1005; used in Y594R1516. 108 Obsolete. Inter-City Products logo; part no. HQ11477909HW; used with Q674L1132; used in Y594R1524. 108 Tempstar logo; part no. 1060322, TAXB004TW01; used with Q674L1132; used in Y594R1532. 108 Obsolete. Honeywell logo; Keeprite part no. THPC; °C scaleplate; used with Q674L1132; used in Y594R1607. 230 Honeywell logo; TRADELINE model; used with Q674L1710; used in Y594R1615. 134 Obsolete. Addison logo; WeatherKing part no. 4120796-61; used with Q674L1504; used in Y594R1656. 228 Obsolete. Lennox logo; Premier White® color; °C scaleplate; outdoor reset required (use C815A1005); used with Q674L1728; used in Y594R1714. R1871 120 Honeywell logo; designed to replace Y594R1011 (York part no. 2TH11702224); used with Q674L1736; used in Y594R1664. aBoth the thermostat and subbase must be replaced. Trade Model Replacement Remarks Y594R1243a Wiring differences (old=new): C=X, X=L, W=W2. Y594R1243a Wiring differences (old=new): C=X, X=L, W=W2. T874R1152/ Replacement has °F Y594R1243a scaleplate. Y594R1763a Wiring differences (old=new): W2=W, X=B, Z=F, K=X2, W1=O. Y594R1425a Y594R1243a Y594R1243a Y594R1243a Y594R1763a Wiring differences (old=new): X=B, Z=F, W2=W, K=X2, W1=O. Replacement has °F scaleplate. Y594R1292a Y594R1763a None None Y594R1672a Wiring differences (old=new): W2=W, X=B, Z=F, K=X2, W1=O. See Trol-A-Temp for replacement. See Trol-A-Temp for replacement. Wiring differences (old=new): W1=W, X=X2, C=B. Y594R1292a Y594R1292a Y594R1292a Y594R1615a Replacement has °F scaleplate. Y594R1300a Y594R1763a Y594R1664a Wiring differences (old=new): Y1=Y, L=F, W1=W, E=X2, C=B; replacement has °F scaleplate. 60-2485--8 68 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Fig. Number No. Description Trade Model Replacement Remarks R1889 120 Honeywell logo; designed to replace Y594R1151 (York part no. 2TH11702324), Y594R1193 (York part no. 6TH11702224), and York part no. 2TH11704024; used with Q674L1736 and C815A1054; used in Y594R1672. Y594R1672a R1897 230 Honeywell logo; Premier White® color; used with Q674L1751; used in Y594R1680. Y594R1680a R1905 120 Obsolete. Honeywell logo; Premier White® color; designed to replace Y594R1151 (York part no. 2TH11702324), Y594R1193 (York part no. 6TH11702224), and York part no. 2TH11704024; used with Q674L1777 and C815A1054; used in Y594R1698. Y594R1672a Replacement is beige. R1913 120 Obsolete. Honeywell logo; Premier White® color; designed to replace Y594R1011 (York part no. 2TH11702224); used with Q674L1777; used in Y594R1706. Y594R1664a Replacement is beige. R1921 115 Obsolete. Econar logo; used with Q674L1207; used in Y594R1722. Y594R1243a R1939 197 American Standard logo (Trane); part no. ASYSTAT651A; includes outdoor reset; used with Q7674L1801; used in Y594R1748. Y594R1763a R1947 168 Obsolete. Inter-City Products logo; part no. HQ1149406HW; used with Q674L1819; used in Y594R1755. Y594R1425a R1954 197 Honeywell logo; TRADELINE model; includes outdoor reset; used with Q674L1827; used in Y594R1763. Y594R1763a Direct replacement for Y594R1748 (T874R1939/ Q674L1801) American Standard logo (ASYSTAT 651A) and Y594R1136 (T874R1053/Q674L1140). R1962 115 Obsolete. Consolidated Industries logo; part no. Y594R1680a Includes CHECK LED. 9036100; Premier White® color; used with Q674L1843; used in Y594R1771. R1970 120 York logo; Canada; Premier White® color; °C scaleplate; Y594R1672a Replacement has °F used in Y594R1789; used with C815A1039. scaleplate. R1988 125 Honeywell logo; TRADELINE model; used with Q674L1868; used in Y594R1797. Y594R1797 Direct replacement for Y594R1235 (T874R1368/ Q674L1421) Evcon/Coleman part no. 3600-368. R2002 245 Obsolete. Amana Air Conditioning logo; part no. 10574102; used in Y594R1805. Y594R1797 Wiring differences (old=new): C/X=X. R2010 245 Obsolete. Amana Air Conditioning logo; part no. 10574104. Y594R1797 Wiring differences (old=new): C/X=X, W3=W2. R2028 209 Obsolete. York logo; part no. 2TH11703424A; used with Y594R1797 Q674L1918 in Y594R1821. R2036 134 Ruud logo; °C scaleplate; used with Q674L1504. See OEM for replacement. T874S 2-stage heat, 3-stage cool. S1001 223 Obsolete. Carrier Synergy 2000 Heat Pump System Control logo; used with Q674F1501. T8611M2025 Includes night setback. (programmable) or see OEM for direct replacement. T874V 1-stage cool. V1008 69 Obsolete. No logo; Carrier part no. HH07AT177; used with Q674R1003. T874A1036 aBoth the thermostat and subbase must be replaced. 69 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Fig. Number No. Description Trade Model Replacement Remarks T874W 3-stage heat, 2-stage cool, manual changeover. W1007 118 Obsolete. Honeywell logo; Westinghouse special; used T8611M2025 Includes night setback. with Q674L1256. (programmable) W1015 54 Honeywell logo; used with Q674B1216 and C815A1005; T874W1015 used in Y594W1014. W1023 233 Obsolete. Lennox Advanced Heat Pump System logo; used with Q674L1280 and W89. T874W1015 W1031 140 Obsolete. No logo; Rheem part no. 41-20797-20; used T8611M2025 Includes night setback. with Q674L1546 and C815A1005; used in Y594W1022. (programmable) W1049 100 Obsolete. McQuay logo; part no. 61202501; 12°F interstage differential between H2 and H3 for night setback; used with Q674C1363. T8611M2025 Includes night setback. (programmable) W1056 220 Obsolete. McQuay/Snyder General logo; part no. See OEM for 1202501; 12°F differential between H2 and H3 for night replacement. setback; used with Q674C1363 (61202502). W1064 220 Obsolete. AAF/Snyder General logo; part no. 066804408; 12°F differential between H2 and H3 for night setback; used with Q674C1363 (66804408). See OEM for replacement. W1072 140 Obsolete. Honeywell logo (Inter-City Products); used in T8611M2025 Includes night setback. Y594W1030. (programmable) W1080 220 McQuay logo; part no. 073318901; Premier White® color; 12°F differential between H2 and H3 for night setback. None W1106 247 Obsolete. Addison logo; part no. 843-277; °F/°C scaleplate; used with Q674L1934 in Y594W1055. T8611M2025 T874Y Heat pump model; 2-stage heat, 2-stage cool, heat or cool auto changeover. Y1005 210 Obsolete. Mammoth Water Source Heat Pump logo; used with Q674E1353; used in Y594Y1004. See OEM for replacement. Y1013 248 Obsolete. WaterFurnace logo; part no. TA21H03; Premier White® color; °F/°C scaleplate; used with Q674F1675 (32003081). See OEM for replacement. aBoth the thermostat and subbase must be replaced. 60-2485--8 70 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9. Q674 Subbase Cross Reference. Model Fig. Number No. Description Q674 Trade Replacement Remarks Q674A System: HEAT-AUTO-COOL; Fan: AUTO-ON A1001 71 Standard OEM. Q674A1019 A1019 71 TRADELINE® model; used with T874A-D. Q674A1019 A1035 71 Obsolete. Trane part no. BAS-0435; used with T874A-D. Q674A1019 A1043 71 Honeywell logo; TRADELINE model; Q674A1019 A1050 71 Obsolete. Standard OEM. Q674A1043 Q674B System: HEAT-OFF-COOL; Fan: AUTO-ON B1000 45 Standard OEM; used with T874C1570, C1695, C1703, Q674B1034 D1843; used in Y594C1363. B1018 44 Standard OEM; used with T874B1035, D1082; used in Q674B1018 Y594B1026, D1016. B1026 45 Obsolete. System: HEAT-OFF-RESET-COOL. Q674B1034 B1034 45 TRADELINE Q674B1034 B1042 47 Obsolete. Used with T874R1004, R1509; used in Y594R1029, R1334. Y594R1243a Wiring differences (old=new): W1=W2. B1059 45 Obsolete. Factory installed RC-RH jumper; used with T874C1059; used in Y594C1256. Q674B1034 Field wire RC-RH. B1075 46 Auto fan in heating and cooling mode; used with T874B1035, C1000, D1082; used in Y594D1040. Q674B1075 B1083 51 Obsolete. Carrier part no. HH93AZ178; factory installed RC-RH jumper. Q674B1075a One system transformer only. B1091 45 Obsolete. Carrier part no. HH93AZ184; factory installed RC-RH jumper. Q674B1034 B1109 47 Obsolete. Addison heat pump; used with T874R1012. Y594R1243a Wiring differences (old=new): W1=W2. B1117 44 Obsolete. Carrier part no. HH93AZ180; factory installed RC-RH jumper. Q674B1018a B1125 53 Obsolete. York part no. 2TB04700324A; used with T874D1041. Q674B1075a Jumper RC-RH; replacement has no LOCKOUT LED. B1133 48 Obsolete. Includes FILTER LED; used with T874D1082; used in Y594D1156. Q674B1018 B1141 51 Trane part no. BAY28X185; automatic fan operation in heat and cool mode. Q674B1075 Set T874 H1 anticipator for combined load of heat relay and fan relay. B1158 50 Obsolete. Used with T874G1071. T874C1018/ W1-Y1 and RH-RC jumpers Q674B1018a required. B1166 249 Carrier part no. HH93AZ179; factory installed RC-RH jumper; LOCKOUT LED; used with T874C1075 (HH07AT170). Y594C1421 or Replacement only requires Q674B1075a one transformer and has no LOCKOUT LED. B1190 52 Obsolete. Wards special; factory installed RH-RC and Gas Furnace: F-W3 jumpers; used with T874C1372. Q674B1034 Electric Furnace: Q674B1075 B1208 187 Obsolete. Used with T874C1422. None B1216 54 Used with T874W1015 and C815A1005; used in Y594W1014. Q674B1216 B1224 49 Obsolete. Lennox part no. 25F7301; four LEDs; used with T874C1430. Q674B1034 Replacement has no LEDs. a Both the thermostat and subbase must be replaced. 71 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9. Q674 Subbase Cross Reference. Model Number B1240 B1257 B1273 B1281 B1299 B1307 B1315 B1331 B1349 B1356 B1372 B1380 B1398 B1406 B1414 B1448 B1455 B1463 B1471 B1513 B1521 B1539 B1547 Fig. Q674 Trade No. Description Replacement Remarks 234 Obsolete. Northrup heat pump; AUX HEAT LED; used with T874G1139. Y594G1252a Wiring differences (old=new): Y1=Y2, W1=W2; EM HT system switch position is not operational. 56 Obsolete. LSI-Mammoth; RESET LED; automatic fan operation in heat and cool modes; used with T874C1471; used in Y594C1314. Q674B1075 Replacement has no LED. 57 Obsolete. McQuay part no. 860-442727B-00; System: T874A1036/ Wiring differences (old=new): OVERRIDE-HEAT-OFF-COOL; used with T874P1006. Q674B1075a Y=Y1, L=R, W=O; jumper Y1W1; no night setback. T8600D2028 Wiring differences (old=new): (programmable) L=R, W=O; W-Y jumper required; night setback. 191 Obsolete. Carrier no. 42QH400103; System: HEATOFF-COOL; Fan: LOW-HI-CONT; international symbols on switches; used with T874R1319. See OEM for replacement. 46 Obsolete. Heil Quaker part no. HQ521714HW. Q674B1075 62 Obsolete. Includes two LEDs; used with T874F1122. T874F1015/ Replacement has no LEDs. Q674D1040a 68 Obsolete. Friedrich part no. AQ5215; OVERRIDE and T8600D2028 Wiring differences (old=new): SERVICE LEDs; used with T874P1022, P1030. (programmable) L=R, W=O; W-Y jumper required; set dual fuel switch to electric heat; night setback. 65 Obsolete. Includes two LEDs; used with T874A1002. Q674B1034 Replacement has no LEDs. 67 Obsolete. Goettl part no. 372072; used with T874R1541. Y594R1300a 138 Obsolete. Carrier part no. HH93AZ192; used with T874L1018 (HH07AT178). See OEM for replacement. 44 Obsolete. Trane part no. BAS-0427; used with T874A-D. Q674B1018 46 Obsolete. Trane part no. BAS-0426; used with T874A-D. Q674B1075 48 Obsolete. Trane part no. BAS-0431; FILTER LED; used Q674B1034 Replacement has no LEDs. with T874A-D. 172 Obsolete. Carrier part no. HH93AZ200; FAULT and CHECK FILTER LEDs; used with T874H1070 (HH07AT166), T874H1088 (HH07AT167) or T874H1153 (HH07AT167); used in Y594H1046. T874A1150/ Wiring differences (old=new): Q674B1075a Y=Y1; jumper W1-Y1; replacement has no LEDs. 51 American Standard (Trane) part no. ASYSTAT1617. Q674B1075 215 Obsolete. Carrier part no. HH93A2202; Fan: Lo-MedHigh-On; used with T874L1059. See OEM for replacement. 214 Obsolete. Carrier part no. HH93AZ208; Fan: Lo-Med- See OEM for High-On; used with T874A1424 (HH07AT194). replacement. 45 Trol-A-Temp; used with T874D1801. None See Trol-A-Temp. 45 Trol-A-Temp; used with T874D1827. None See Trol-A-Temp. 53 Obsolete. TRADELINE; exact replacement for Q674B1125 (York part no. 2TB04700324). Q674B1075 Jumper RC-RH; replacement has no LOCKOUT LED. 53 Obsolete. Carrier Canada part no. HH93AZ179-W; gray color; includes LOCKOUT LED and removable jumpers between RC and RH terminals. Q674B1075 Jumper RC-RH; replacement has no LOCKOUT LED; beige color. 45 Obsolete. Carrier part no. HH93AZ139; used with T874D2049; used in Y594D1370. Q674B1034 237 Obsolete. TRADELINE; gray color; used with T874C1810; used in Y594C1389. Y594C1389 a Both the thermostat and subbase must be replaced. 60-2485--8 72 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9. Q674 Subbase Cross Reference. Model Fig. Number No. Description Q674 Trade Replacement Remarks B1554 82 Obsolete. TRADELINE; includes LOCKOUT LED and removable jumpers between RC and RH terminals; used with T874C1877; used in Y594C1421. Y594D1347 Jumper RH-RC; system switch: Off-HEAT-AUTOCOOL. B1562 45 Obsolete. Amana logo; part no. P1217701F; removable jumpers between RC and RH terminals. Q674B1034 B1570 45 Obsolete. Armstrong logo; part no. 03299A18. Q674B1034 Replacement is beige. B1588 45 Obsolete. Standard OEM. Q674B1034 Replacement is beige. Q674C System: OFF-AUTO; Fan: AUTO-ON C1009 72 Standard OEM; used with T874D1082; used in Y594D1024. Q674C1058 C1017 Obsolete. Includes factory-installed RC-RH jumper; used with T874A,F,Q. Q674C1058 C1033 72 Trane part no. BAY28X187. Q674C1058 C1041 74 Obsolete. Command Aire heat pump; used with T874H1005, H1054. Y594H1012a Wiring differences (old=new): Y1=O, Y2=Y; W-Y jumper required. C1058 72 TRADELINE Q674C1058 C1066 73 Obsolete. Command Aire heat pump; used with T874G1352. Y594H1012a Wiring differences (old=new): Y1=O, Y2=Y, L=R, R=none; RL jumper required; no night setback. T8600D2028 Wiring differences (old=new): (programmable) Y1=O, Y2=Y, L=R; W-Y jumper required; night setback. C1074 81 Obsolete. Used with T874C1018. Q674C1058 Jumper W2-Y1 and RH-RC. C1090 77 Obsolete. LSI-Mammoth heat pump; used with T874K1001. Y594R1419a Wiring differences (old=new): RH-RC=R, W1=B, W3=W2, W2=W1; remove Y1-W1 jumper. C1108 143 Obsolete. Northrup special; AUX HEAT LED; used with Y594R1243a Wiring differences (old=new): T874G1139. Y1=Y, W1=W2, C=X. C1116 76 Obsolete. McQuay part no. 02005959; two LEDs; used Q674C1058 Replacement has no LEDs. with T874D1116. C1124 79 Obsolete. LSI-Mammoth heat pump; RESET LED; used with T874G-H; used in Y594G-H. Y594G1294 T8600D2028 C1132 75 Obsolete. McQuay part no. 03005049; spring return momentary system switch position; used with T874A1283. See OEM for replacement. C1140 78 Obsolete. McQuay no. 860-442728B-00; System: OVERRIDE-AUTO-OFF; used with T874P1006. T8600D2028 Wiring differences (old=new): (programmable) L=R, W=O; W-Y jumper required; night setback. C1157 72 Obsolete. York part no. 2TB04700124A. Q674C1058 C1165 192 Obsolete. McQuay part no. 03005050; spring return momentary system switch position. See OEM for replacement. C1173 96 Obsolete. American Air Filter part no. 4ELN-8787; used Q674C1058 Replacement has no LEDs. with T874C1133. C1181 76 Obsolete. California heat pump; used with T874C1000. Q674C1058 C1199 163 Obsolete. American Air Filter part no. 4ELN-8788; two LEDs; spring return momentary system switch position; used with T874G1485, G1535. T8600D2028 No momentary reset switch. a Both the thermostat and subbase must be replaced. 73 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9. Q674 Subbase Cross Reference. Model Fig. Number No. Description Q674 Trade Replacement Remarks C1207 78 Obsolete. Friedrich; System: OVERRIDE-AUTO-OFF; T8600D2028 Wiring differences (old=new): used with T874P1014. (programmable) L=R, W=O; W-Y jumper required; night setback. C1215 97 Obsolete. Friedrich part no. AQ5315; System: OVERRIDE-AUTO-OFF; OVERRIDE and SERVICE LEDs; used with T874P1022, P1030. T8600D2028 Wiring differences (old=new): (programmable) L=R, W=O; W-Y jumper required; night setback. C1223 73 Obsolete. Friedrich part no. AQ5323; used on systems requiring night setback contacts; used with T874G1584. Y594H1012a Wiring differences (old=new): Y1=O, Y2=Y, L=R, R=none; RL jumper required; no night setback. T8600D2028 Wiring differences (old=new): (programmable) L=R, W=O; W-Y jumper required; night setback. C1249 164 Includes MALFUNCTION LED; used with T874H1062; Y594H1012a used in Y594H1012. C1256 73 Obsolete. Used with T874G1618. Y594H1012a Wiring differences (old=new): Y1=O, Y2=Y, L=R, R=none; RL jumper required; no night setback. T8600D2028 Wiring differences (old=new): (programmable) L=R, W=O; W-Y jumper required; night setback. C1264 165 Obsolete. Carrier part no. HH93AZ193; used with T874L1018 (HH07AT178). See OEM for replacement. C1280 181, Obsolete. McQuay heat pump; part no. 60687401; 203 COMP FAULT LED; used with T874K1019, L1034. T8600D2028 See thermostat description for replacement information. C1298 76, Obsolete. McQuay part no. 60684801; SERVICE LED; See OEM for 225 used with T874A1523, A1549, D1918. replacement. C1306 75 Obsolete. McQuay part no. 60685001; SERVICE LED; See OEM for spring return momentary system switch position; used replacement. with T874A1325. C1314 72 Obsolete. Trane part no. BAS-0429; used with T874A-F. Q674C1058 C1322 173 Obsolete. Carrier part no. HH93AZ199; FAULT and CK FILTER LEDs; used with T874H1070 (HH07AT166), T874H1088 (HH07AT167) or T874H1153 (HH07AT167); used in Y594H1053. Y594H1012a Wiring differences (old=new): 2=X. C1330 177 Obsolete. LSI-Mammoth part no. 71115201; RESET LED; used on systems with night setback contacts; used with T874G1659, H1096; used in Y594G1427, H1020. Y594H1012a Wiring differences (old=new): R1=R; R2=L. C1355 74 Friedrich part no. AQ355; SERVICE LED; used with T874H1112. Y594H1012a Wiring differences (old=new): Y1=O, Y2=Y; L-R jumper required. C1363 99 Obsolete. McQuay part no. 61202601; SERVICE LED; T874C1125/ Replacement has HEAT-OFF- auto fan in heat and cool mode; used with T874C. Q674B1075a COOL. 219 Obsolete. Used with T874C. See OEM for replacement. 220 Obsolete. Used with T874W. See OEM for replacement. 100 Obsolete. Used with T874W. T8611M2025 Includes night setback. (programmable) C1371 72 American Standard part no. ASYSTAT616. Q674C1058 a Both the thermostat and subbase must be replaced. 60-2485--8 74 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9. Q674 Subbase Cross Reference. Model Fig. Number No. Description Q674 Trade Replacement Remarks C1389 205, Obsolete. Command Aire part no. P1099-0021; two 176 LEDs; used with T874G-H. None See thermostat description for replacement information. C1397 205, Obsolete. Command Aire part no. P1099-0023; used 171 with T874G-H. None See thermostat description for replacement information. C1413 213 Obsolete. Carrier part no. HH93AZ204; Fan: Lo-MedHigh-On; used with T874L1059. See OEM for replacement. C1439 217 Obsolete. Bard part no. 8404-016; used with T874N1024. See OEM for replacement. C1454 163 Obsolete. Climate Master part no. AQ5354; two LEDs; Y594G1393a No momentary reset switch. spring return momentary system switch position. C1462 25 Climate Master Special. Q674C1058 Replacement has no LEDs. C1470 221 Obsolete. Climate Master part no. RQ5370; used with T874H1138. Y594H1012a Wiring differences (old=new): Y1=O, Y2=Y; replacement has MALFUNCTION LED only. C1496 74 Obsolete. Carrier part no. HH93AZ213; includes SERVICE LED; used with T874H1161; used in Y594H1038. Y594H1012a Wiring differences (old=new): Y1=O, Y2=Y; L-R jumper required. C1504 83 Obsolete. Carrier part no. HH93AZ214; used in Y594. Y594H1012a Wiring differences (old=new): Y1=O, Y2=Y, L=R, R=none; RL jumper required; no night setback. T8600D2028 Wiring differences (old=new): (programmable) Y1=O, Y2=Y, L=R; W-Y jumper required; night setback. C1512 97 Obsolete. Carrier part no. HH93AZ216; System: Override-Auto-Off; includes two LEDs; used in Y594. T8600D2028 Wiring differences (old=new): (programmable) L=R, W=O; W-Y jumper required; night setback. C1520 72 Obsolete. Carrier part no. HH93AZ210; used with T874D2049; used in Y594D1388. Q674C1058 C1538 163 Climate Master part no. AQ5354; System: Off-AutoOverride; includes two LEDs and momentary spring position. Y594G1393 No momentary reset switch. C1546 76, Obsolete. McQuay part no. 060684802; gray color; 225 includes one LED. Q674C1058 Replacement has no LEDs; beige color C1553 181, Obsolete. McQuay logo; part no. 073319901; includes Q674C1058 Replacement is beige. 203 one LED. C1561 76 McQuay logo; part no. 073319701; includes one LED. See OEM for replacement. C1579 99, McQuay logo; part no. 073320001; includes one LED. See OEM for 100 replacement. C1595 72 Obsolete. Standard OEM. Q674C1058 Q674D System: None; Fan: None D1008 55, 66 Obsolete. Used with T874D1082, F1056; used in Y594D1057. Q674D1040 D1016 55 Obsolete. Carrier part no. HH93AZ170; RC-RH jumper. Q674D1040 RC-RH jumper required. D1032 58 Obsolete. Borg-Warner; used with T874G. T874D1165/ Wiring differences (old=new): Q674D1040a Y=Y2, O=Y1, W=W2; jumper W1-Y2 required. D1040 55 TRADELINE Q674D1040 D1057 55, 66 Obsolete. York part no. 2TB04700424A. Q674D1040 a Both the thermostat and subbase must be replaced. 75 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9. Q674 Subbase Cross Reference. Model Number D1065 Fig. No. Description 63 Obsolete. Includes two LEDs; used with T874F1122. D1099 D1107 D1115 D1123 D1156 D1164 D1172 D1180 D1198 55, 66 Obsolete. Trane part no. BAS-0430; used with T874A-F. 55, 66 Obsolete. Snyder General part nos. 654958801/ 1520503/ 4ELN30070. 208 Trol-A-Temp; used with T874D1801. 208 Trol-A-Temp; gray color; used with T874D1827. 55 Obsolete. Gray color; includes removable jumper between RC and RH terminals. 66 Obsolete. Carrier part no. HH93AZ211; used in Y594D1440. 208 Obsolete. Amana logo; part no. P121501F; removable jumpers between RC and RH terminals. 55 Obsolete. York logo; part no. 2TH04703224A. 55, 66 Obsolete. Standard OEM. Q674E E1007 E1015 System: OFF-HEAT-AUTO-COOL; Fan: AUTO-ON 82 Used with T874D1504; used in Y594D1180. 84 Obsolete. Lennox heat pump; used with T874G1006, G1154. E1049 E1056 E1064 E1072 E1080 E1098 E1106 193 TRADELINE; used with T874D2031 and TG504A1025; used in Y594D1354. 82 Obsolete. Amana part no. D68535-7; used with T874C1059, C1331; used in Y594C1009. 83 Obsolete. RC-RH jumpered internally; EM HEAT LED. 82 Carrier part no. HH93AZ176; RC-RH jumpered internally. 82 Trane part no. BAY28X184. 85 Obsolete. Used with T874A-D. 185 Obsolete. ITT Nesbitt. E1114 E1122 E1148 87 Carrier part no. HH93AZ177; RC-RH jumper; LOCKOUT LED to indicate compressor lockout; used with HH07AT series thermostats. 83 Obsolete. Square D part no. 63600-002-10; CHECK LED. 86 Obsolete. Lennox heat pump; used with T874G1014, G1022. E1155 E1197 88 Obsolete. Lennox part no. 91C7501; HIGH and LOW LEDs; used with T874B1076, D1017. 89 Obsolete. McQuay part no. 02005961; two LEDs; used with T874D1116. E1205 80 Obsolete. Fedders special; SERVICE LED; used with T874D1462. E1213 82 York part no. 2TB04700224A. E1221 82 Heil Quaker part no. HQ712003HW. a Both the thermostat and subbase must be replaced. Q674 Trade Replacement T874F1015/ Q674D1040a Q674D1040 Q674F1040. Remarks Replacement has no LEDs. None None Q674D1040 See Trol-A-Temp. See Trol-A-Temp. Replacement is beige color. Q674D1040 Q674D1040 Q674D1040 T874D1165/ Q674D1040 Replacement is beige color. Q674E1049 Y594G1252a Q674E1049 Wiring differences (old=new): R=O, M=Y, F=G, V=R, Y=W2; E-W2 jumper required. Q674E1049 RC-RH jumper required. Q674E1049 Q674E1049 RC-RH jumper required. Q674E1049 Q674E1049 See OEM for replacement. Q674E1049 RC-RH jumper required. RC-RH jumper required; replacement has no LED. Q674E1049 Replacement has no LED. Y594G1252a Q674E1049 Wiring differences (old=new): R=O, M=Y, F=G, Y=W2, V-VR=R; must use single transformer. Replacement has no LEDs. Q674E1049 Q674E1049 Wiring differences (old=new): D=O; replacement has no LEDs. Replacement has no LEDs. Q674E1403 Q674E1049 60-2485--8 76 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9. Q674 Subbase Cross Reference. Model Number E1262 E1270 E1304 E1312 E1320 E1338 E1346 E1353 E1379 E1395 Fig. No. Description 82 Lennox part no. 13F1701. 198 Obsolete. Carrier part no. HH93AZ189; used with T874L1000 (HH07AT176). 82 Obsolete. BDP part no. P272-1887; used with T874L1026. 224 Obsolete. McQuay part no. 60684901; one LED; used with T874A1523, A1549, D1686, D1918. 82 Obsolete. Trane part no. BAS-0434. 88 Obsolete. Goodman part no. CHTS36-60; HIGH and LOW LEDs; used with T874B1100; used in Y594B1042. 82 Obsolete. Snyder General part nos. 1505753/1506753/ 654958B02; used with T874D1769; used in Y594D1297. 210 Obsolete. Mammoth; used with T874Y1005; used in Y594Y1004. 212 Trol-A-Temp by Honeywell; used with T874A1465. 222 Obsolete. Carrier part no. HH93AZ209; used with T874B1134 (HH07AT199). E1403 E1411 E1429 E1445 E1460 E1478 82 TRADELINE; designed to replace York 2TH04701024; used with T874D1942; used in Y594D1347. 82 Obsolete. Carrier Canada part no. HH93AZ176-W; gray color; removable jumper between RC and RH terminals. 87 Carrier Canada part no. HH93AZ177-W; gray color; includes LOCKOUT LED; removable jumper between RC and RH terminals. 82 Obsolete. Carrier part no. HH93AZ217-W; gray color; removable jumper between RC and RH terminals. 224 McQuay logo; part no. 073319801; includes one LED. 82 Obsolete. Armstrong logo; part no. 03299A19. E1486 82 Obsolete. Standard OEM. Q674F F1006 F1022 F1030 F1048 System: EM.HT.-HEAT-AUTO-COOL-OFF; Fan: AUTO-ON 141 Obsolete. Includes EM HEAT LED; used with T874C1331. 142 Includes LED and field selectable inserts; used with T874C1059; used in Y594C1017, C1330. 146 Carrier part no. HH93AZ174; SUPL HEAT LED; used with T874D1074 (HH07AT172). 149 Obsolete. Includes EM HEAT LED and auxiliary power terminal Z. F1063 146 Obsolete. Carrier part no. HH93AZ181; SUPL HEAT LED; used with T874D1074 (HH07AT172). F1071 142 Obsolete. Square D part no. 63600-002-11; CHECK LED. a Both the thermostat and subbase must be replaced. Q674 Trade Replacement Q674E1049 Y594G1419a Remarks E-W2 jumper required. Y594G1419a E-W2 jumper required. Q674E1049 Replacement has no LEDs. Q674E1049 Q674E1049 Replacement has no LEDs. Q674E1049 T8611M2025 None T874B1019/ Q674E1049a Y594D1347a See Trol-A-Temp. Wiring differences (old=new): W1 =W; RC-RH jumper required; replacement has no LEDs. Q674E1049 RC-RH jumper required. Replacement is beige color. Q674E1049 Q674E1049 RC-RH jumper required. Replacement has no LOCKOUT LED and is beige color. RC-RH jumper required. Replacement is beige color. Q674E1049 Q674E1049 RC-R jumper required. Replacement is beige color. RC-R jumper required. Replacement is beige color. Q674F1022 Jumper E-X2. Q674F1022 Q674F1022 Q674F1022 Q674F1022 Q674F1022 Wiring differences (old=new): C=X1, X=X2. Replacement does not include Z terminal and only requires one transformer. Wiring differences (old=new): C=X1, X=X2. 77 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9. Q674 Subbase Cross Reference. Model Number F1089 F1097 F1105 Fig. No. Description 152 Obsolete. Includes EM HEAT LED; X2-E and RC-RH jumpers. 142 Obsolete. Southwest special; W2-X2 jumper. 145 Obsolete. Lennox heat pump; EM HEAT LED; used with T874G1154. F1113 150 Obsolete. Lennox heat pump; part no. 24F6201; V-VR jumper; EM HEAT LED; changeover in cooling; used with T874G1014, G1022. F1121 153 Obsolete. Westinghouse heat pump; EM HEAT LED; used with T874G1048. F1139 148 Obsolete. Tappan heat pump; EM HEAT LED; auto fan in emergency heat mode; used with T874G1147. F1162 151 Obsolete. Crispaire heat pump; EM HEAT LED; used with T874G. F1170 153 Obsolete. Heatwave (Southwest Mfg.) heat pump; EM HT LED; used with T874G1105. F1188 153 Obsolete. Luxaire heat pump. F1196 178 Obsolete. Williamson; EM HEAT and SERVICE LEDs; used with T874N1008; used in Y594N1007. F1204 154 Obsolete. Special for Crispaire; EM HEAT and COMP FAULT LEDs; used with T874G1089; used in Y594G1153. F1212 155 Includes AUX HEAT and EM HEAT LEDs; used with T874G1246, G1451, G1592, G1915; used in Y594G1252. F1220 178 Used with T874N1016; used in Y594N. F1238 155 Obsolete. Rheem part no. 41-20797-14; AUX HEAT and EM HEAT LEDs; used with T874G1097, G1212, G1220, G1238. F1246 156 Obsolete. Westinghouse heat pump; EM HEAT and AUX HEAT LEDs; auto fan in emergency heat mode; changeover in cooling mode. F1253 157 Obsolete. Wesco/Addison heat pump; used with T874G1261, G1279, G1287. F1261 179 Includes two LEDs; used with T874N1024; used in Y594N. F1279 158 Obsolete. Westinghouse heat pump; two LEDs; used with T874G. F1295 147 Obsolete. Keeprite/Westinghouse heat pump; SERVICE, AUX HEAT and EM HEAT LEDs; used with T874G1188. F1311 155 York heat pump; AUX HEAT and EM HEAT LEDs; used with T874G1410. F1329 142 Obsolete. Heil Quaker part no. HQ712005HW; one LED and field selectable inserts. F1337 166 Obsolete. WeatherKing heat pump; two LEDs and field selectable inserts; used with T874D1009; used in Y594D1222. F1345 194 Obsolete. Addison heat pump; EM HEAT and CHECK LEDs; used with T874G; used in Y594G. a Both the thermostat and subbase must be replaced. Q674 Trade Replacement Q674F1022 Remarks Q674F1022 Y594G1252a Y59461252a Y594G1252a Wiring differences (old=new): V=R, Y=W2, F=G, X2=X, R=O, M=Y; L-E jumper required. Wiring differences (old=new): R=O, M=Y, F=G, Y=WC, V=VR=R; must use single transformer. Y594G1252a Y594G1393a Wiring differences (old=new): C=X. Y594G1252a Y594G1252a Q674F1220 Y594G1393a Wiring differences (old=new): A=L. Q674F1212 or Y594G1252a Q674F1220 Y594G1252a Y594G1252a Y594G1252a Y594G1419a Y594G1252a Y594G1252a Y594G1252a Wiring differences (old=new): Y1=O, C=X, W1=Y, X=L. Wiring differences (old=new): L=X2, Y=Y1. Wiring differences (old=new): L1=L. Wiring differences (old=new): S=L; replacement does not include A or T terminals. Q674F1022 Q674F1022 Y594G1252a Wiring differences (old=new): R=RC-RH; replacement has no LEDs. Wiring differences (old=new): Y1=O, C=X, W1=Y, X=L. 60-2485--8 78 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9. Q674 Subbase Cross Reference. Model Number F1360 F1378 F1394 F1402 F1410 F1428 F1436 F1444 F1451 F1477 F1485 F1501 F1519 F1535 F1543 F1550 F1568 F1584 F1592 F1600 F1634 F1667 Fig. Q674 Trade No. Description Replacement Remarks 167 Obsolete. Rheem part no. 41-20797-17; AUX HEAT and EM HEAT LEDs; used with T874G1493. Y594G1526a 195 Obsolete. Includes EM HEAT and AUX HEAT LEDs; used with T874G1501. Y594G1252a Wiring differences (old=new): L1=L; changeover in cooling only. 139 Obsolete. Nepco heat pump; HEAT PUMP and AUX HEAT LEDs; System: AUX HEAT-HEAT PUMP-2 STAGE HEAT-OFF-COOL; used with T874D1595. T874D1165/ Replacement has HEAT-OFFQ674B1018a COOL system switching and no LEDs. 169 Obsolete. Coleman heat pump; two LEDs; used with T874G1576; used in Y594G1377. Y594G1633a 170 Used with T874G1246, G1915; used in Y594G1393. Y594G1393a 199 Obsolete. Used with T874G1600; used in Y594G1401. Y594G1419a Wiring differences (old=new): jumper W1-Y1. 167 Includes AUX HEAT and EM HEAT LEDs; changeover in heating mode; used with T874G1626; used in Y594G1526. None 227 Includes AUX HEAT, EM HEAT and CHECK LEDs; used with T874G1642; used in Y594G1419. Y594G1419a 204 Obsolete. York part no. 2TB047700524A; one LED and Q674F1012 Wiring differences (old=new): field selectable inserts. X2=X; X1=B. 227 TRADELINE; gray color; used with T874G1741, G1824; used in Y594G1476, G1534. Y594G1476a 211 Trol-A-Temp by Honeywell; changeover is provided by Trol-A-Temp zone panel; used with T874G1758; used in Y594G1492. None See Trol-A-Temp. 223 Obsolete. Carrier two-speed compressor heat pump; T8611M2025 Includes night setback. used with T874S1001. (programmable) 231 Obsolete. Nordyne; used with T874G1832, G1840; used in Y594G1542, G1559. Y594G1252a Replacement has auto changeover in cooling mode only. 229 Obsolete. Lennox heat pump; gray color; used with T874G1857; used in Y594G1583. Y594G1161a Wiring differences (old=new): E=X2, C=B, L=F. 204 Obsolete. TRADELINE Q674F1022 Wiring differences (old=new): X2=X, X1=B. 243 Obsolete. Amana part no. 10573901; includes two LEDs; used with T874G1899; used in Y594G1591. Y594G1633 155 Obsolete. Gray color; includes two LEDs; used with only T874G1931. Y594G1476 Y1-W1 jumper required. 169 TRADELINE; includes two LEDs; used with T874G1972; used in Y594G1633. Direct replacement for Coleman/Evcon Y594G1377 (T874G1576/ Q674D1402); Coleman part no. 3600-373. Y594G1633a 238 Heat Controller; Fan: AUTO-ON; System: AUX HEATHEAT PUMP- 2 STAGE HEAT-OFF-COOL; includes two LEDs; used with T874C1844; used in Y594C1413. Y594R1425 E-W2 jumper required; system switch: EM.HT.-HEAT-OFFCOOL. 169 Obsolete. Amana part no. 10573903; includes two LEDs; used with T874G1980; used in Y594G1641. Y594G1633 Wiring differences (old=new); W3=W2. 139 Standard OEM; System: AUX HEAT-HEAT PUMP2 STG HEAT-OFF-COOL; includes two LEDs; used with T874D2155. Y594G1716 155 WaterFurnace logo; part no. TA21H03; System: OFFAUTO-HEAT-EM HT; includes two LEDs; used with T874G2046. Y594G1716 a Both the thermostat and subbase must be replaced. 79 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9. Q674 Subbase Cross Reference. Model Number F1675 Q674G G1005 G1013 Fig. No. Description 248 Obsolete. WaterFurnace logo; part no. TA21H03; includes four LEDs. System: OFF-AUTO; Fan: None 184 Obsolete. Used in Y594F1063. 186 Obsolete. Climate Control; used with T874D1298. G1021 G1047 G1054 G1062 91 Obsolete. Includes O and B terminals; used with T874A-F,Q or T874D1082; used in Y594D1032. 92 Obsolete. Used with T874C1018, C1125. 188 Obsolete. Singer part no. 0200-5963; used with T874D1298. 232 Obsolete. Singer; used with T874D1298. G1070 91 TRADELINE G1088 92 Obsolete. LSI-Mammoth part no. 71120201; used with T874C. G1096 90 Obsolete. Climate Control part no. 02005958; used with T874D1439, D1447. G1104 94 Obsolete. McQuay part no. 0200-5963; two LEDs; used with T874D1116. G1120 202, Obsolete. McQuay part no. 60684701; two SERVICE 226 LEDs; no fan switching; used with T874D1694, G1926. G1138 91 Obsolete. Trane part no. BAS-0433; used with T874A-F. G1153 184 Obsolete. Carrier part no. HH93AZ212; used in Y594D1396. G1161 184 Gray color. G1179 202 Obsolete. McQuay logo; part no. 073319601; includes two LEDs. Q674J System: EM.HT.-AUTO-OFF; Fan: AUTO-ON J1001 180 Obsolete. Singer heat pump part no. 02005964; EM HEAT LED; changeover heat mode. J1019 159 Obsolete. Westinghouse heat pump; EM HT LED; System: EM.HT.-ON-OFF; used with T874G1048. J1027 160 Obsolete. York part no. 025-22291; EM HEAT LED; auto fan in emergency heat mode; changeover in cool mode; used with T874G1170, G1196, G1428, G1345, G1444; used in Y594G1013, G1138, G1229. J1035 161 Carrier heat pump; part no. HH93AZ173; System: SUPL.HT.-ON-OFF; SUPL HEAT LED; used with T874G1055 (HH07AT171). J1043 162 TRADELINE heat pump model; designed for use on Trane heat pumps; AUX HT and EM HT LEDs; auto fan in emergency heat; changeover in cooling mode; used with T874G1204 and C815A1008; used in Y594G1161. J1050 183 Obsolete. Westinghouse heat pump; EM HEAT and AUX HEAT LEDs; used with T874G1071. J1068 144 Obsolete. Carrier heat pump; part no. HH93AZ183; used with T874J1002 (HH07AT175) or T874J1028 (HH07AT165). J1076 180 Obsolete. McQuay part no. 02005964; two LEDs; used with T874A,D. a Both the thermostat and subbase must be replaced. Q674 Trade Replacement See OEM for replacement. Q674G1070 See OEM for replacement. Q674G1070 T8611 See OEM for replacement. See OEM for replacement. Q674G1070 See OEM for replacement. See OEM for replacement. See OEM for replacement. See OEM for replacement. Q674G1070 Q674G1070 Q674G1070 Q674G1161 See OEM for replacement. Y594G1252a Y594G1567a Y594G1674a Q674J1043 or Y594G1161a Y594G1674a Y594J1019 Q674F1022 Remarks Replacement is beige color. Replacement has no LEDs. Wiring differences (old=new): W=W2. Designed for use on Trane heat pumps. Replacement has no LEDs. 60-2485--8 80 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9. Q674 Subbase Cross Reference. Model Number J1084 J1118 J1126 J1142 J1159 J1167 J1175 J1191 J1209 J1217 J1225 J1241 J1258 J1266 J1274 J1282 Q674K K1000 K1018 Fig. Q674 Trade No. Description Replacement Remarks 171 Obsolete. BDP heat pump; part no. 34427DP126, P272-1879; EM HEAT LED; used with T874J1010. Y594J1019 Wiring differences (old=new): W1=W2, F=L. 196 Obsolete. Carrier heat pump; part no. HH93AZ188; SUPL HEAT LED; System: SUPL.HT.-ON-OFF; used with T874G1055 (HH07AT171). Y594G1674 Wiring differences (old=new): C=X;Y1=W1; jumper required; no auto fan in emergency heat. 160 Obsolete. Luxaire no. 026-00068-000; EM HEAT LED; Y594G1567a used with T874G1568; used in Y594G1351. 174 Obsolete. American Standard part no. WY28X0250; AUX HEAT and EM HEAT LEDs; used with T874G1675; used in Y594G1443. Y594G1161a 206 Obsolete. Carrier heat pump; part no. HH93AZ196; used with T874J1002 (HH07AT175) or T874J1028 (HH07AT165). Y594J1019 175 Obsolete. Carrier heat pump; MANUAL, AUTO, HEAT PUMP and DEFROST LEDs; System: SUPL HEATON-OFF; used with T874G1717; used in Y507J1201. Y594G1252a Wiring differences (old=new): C=X, D=L; replacement has AUX HEAT and EM HEAT LEDs. 216 Obsolete. Snyder General part nos. 1505756, 1506756; CHECK, AUX HEAT and SYSTEM LEDs; used with T874G1774, G1782; used in Y594G1500, G1518. Y594G1252a Wiring differences (old=new): E=W2, W1=W3, X=E, C=X. 161 Obsolete. Carrier heat pump; gray color; used with T874G1790. Y594G1252a Wiring differences (old=new): C=X; replacement has °F scaleplate. 160 TRADELINE; designed to replace Y594G1013 (York part no. 2TH11702424), Y594G1229 (York part no. 6TH11702424) and York part no. 2TH11704124; used with T874G1865; used in Y594G1567. Y594G1567a 171 Obsolete. Nordyne part no. 9132250; used with T874J1036, J1044. Y594J1019 Wiring differences (old=new): F=L. 160 Obsolete. TRADELINE; gray color; designed to replace Y594G1013 (York part no. 2TH11702424), Y594G1229 (York part no. 6TH11702424) and York part no. 2TH11704124; used with T874G1873; used in Y594G1575. Y594G1567a Replacement is beige. 144 Obsolete. Carrier Canada part no. HH93AZ183-W; gray color; System: SUPL HT-ON-OFF; includes one LED. See OEM for replacement. 161 Obsolete. Carrier Canada part no. HH93AZ173-W; gray color; System: SUPL HT-ON-OFF; includes one LED. Y594G1674a Replacement is beige color. 160 York Canada; gray color; includes EM HT LED; used in Y594G1567a Y594G1625. 161 TRADELINE; System: SUPL HT-ON-OFF; includes Y594G1674 one LED; used with T874G2004; used in Y594G1674. 244 Obsolete. TRADELINE; System: SUPL HT-ON-OFF; includes SUPL HT LED; used with T874J1069; used in Y594J1019. (Recontrol) T8511G1021 System: OFF-HEAT-AUTO-COOL; Fan: None 93 Obsolete. Carrier part no. HH93AZ172; RC-RH jumper. Q674E1049 Fan switch is not operational. 95 Obsolete. Oneida Heater part no. 3040284-02; System: OFF-WOOD-WOOD/OIL-OIL; used with T874F1106. Q674K1026 a Both the thermostat and subbase must be replaced. 81 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9. Q674 Subbase Cross Reference. Model Number K1026 K1034 K1042 Q674L L1017 L1025 L1033 L1041 L1066 L1074 L1082 L1090 L1108 L1116 L1132 L1140 L1157 L1165 L1173 L1181 Fig. No. Description 95 System: OFF-WOOD-WOOD/ OIL-OIL; used with T874F1155. 93 Obsolete. Snyder General part no. 4ELN-7920. 93 Obsolete. Carrier part no. HH93AZ172-W; gray color; includes removable jumper between RC and RH terminals. System: EM.HT.-HEAT-OFF-COOL; Fan: ON-AUTO 101 Obsolete. York heat pump; EM HEAT LED; cooling mode changeover; compressor lockout; auto fan in EM.HT; used with T874R1046. 102 Obsolete. Lennox heat pump; part no. 24F6101; EM. HEAT LED; V-VR jumper; used with T874R1020, J1038. 115 Obsolete. Rheem heat pump; EM HEAT LED; used with T874R1152. 103 Obsolete. Carrier heat pump; part no. HH93AZ175; SUPL HEAT LED; used with T874G1055 (HH07AT171), G1071 (HH93AZ175), G1113. 122 Obsolete. Fedders heat pump; used with T874R1269; used in Y594R1037. 124 Obsolete. Carrier heat pump; part no. HH93AZ186; SUPL HT LED; used with T874J1002 (HH07AT175) or T874J1028 (HH07AT165). 104 Obsolete. Crispaire heat pump; W2-H jumper; EM HEAT LED; used with T874R1061, R1111. 105 Obsolete. Fedders heat pump; EM HEAT LED; changeover in heat mode; used with T874C1398, C1406, C1414. 106 Obsolete. Westinghouse; EM HEAT LED. 107 Obsolete. Carrier part no. HH93AZ171; SUPL HEAT LED; used with T874D1264 (HH07AT173). 108 Heil Quaker part no. HQ711598; used with T874R1137, R1673, R1731, R1749, R1814; used in Y594R1110, R1466, R1524, R1532, R1607. 109 Obsolete. Includes EM HEAT and AUX HEAT LEDs; used with T874R1053; used in Y594G1136. 115 Obsolete. Rheem part no. 41-20796-14; EM HEAT and AUX HEAT LEDs; used with T874R. 121 Obsolete. Used with T874C. 123 Obsolete. Used with T874R. 110 Obsolete. Lennox no. 24F5901; factory installed V-VR jumper; EM HEAT and SERVICE LEDs; stage 2 heat is isolated; used with T874C1448, R1178 and C815A1013. 112 Obsolete. Westinghouse; AUX HEAT and EM HEAT LEDs. 113 Used with T874R1129; used in Y594R. a Both the thermostat and subbase must be replaced. Q674 Trade Replacement Q674K1026 Remarks Q674E1049 Fan switch is not operational. Q674E1049 Fan switch is not operational. Y594R1243a Wiring differences (old=new): W=W2, X=L, B=X. Y594R1243a Y594R1243a Wiring differences (old=new): M=Y, F=G, V-VR=VR, Y=W2, R=O. Y594G1419 Wiring differences (old=new): C=X, jumper Y1=W1. Y594R1615a Y594J1001 Wiring differences (old=new): K=E, C=X, W1=B, Z=L. Y594R1243a Y594R1425a Replacement has auto fan in emergency heat mode. Wiring differences (old=new): K=E, C=X. Y594R1243a See OEM for replacement. Y594R1292a Y594R1763a Q674L1207a Designed for use on Trane heat pumps. Y594C1322a Y594R1243a Y594R1763a Wiring differences (old=new): V-VR=R, M=Y, F=G, X=B, Y=W, A=T, R=O, E=X2. Y594R1243a Y594R1243a Wiring differences (old=new): X1=X. 60-2485--8 82 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9. Q674 Subbase Cross Reference. Model Fig. Number No. Description Q674 Trade Replacement Remarks L1199 114 Obsolete. Lennox no. 24F6001; used with T874D1207 T8611M2025 Wiring differences (old=new): and C815A1013. (programmable) V-VR=R, Y=W3, X=C, R=O, M=Y, M2=Y2-W2, F=G; jumper Y2-W2; no outdoor reset needed; use only one system transformer. L1207 115 Used with T874R1152, R1590, R1640, R1921; used in Q674L1207 or Y594R1243, R1706. Y594R1243a L1215 116 Obsolete. Crispaire heat pump; used with T874R1111; used in Y594R1128. Y594R1243a Replacement has auto fan in emergency heat mode. Wiring differences (old=new): A=L; set anticipator to 1.2. L1223 117 Obsolete. Westinghouse special. See OEM for replacement. L1231 182 Obsolete. Used with T874R1186 and W89. None L1249 115 Obsolete. Used with T874R1194 and W89. Y594R1243a L1256 118 Obsolete. Westinghouse special; used with T874W1007. T8611M2025 Includes night setback. (programmable) L1264 119 Obsolete. Intertherm heat pump; EM HEAT and SERV Y594R1672a or Wiring differences (old=new): LEDs; used with T874R1202, R1608, R1699; used in Y594R1763a W2=W, X=B, Z=no Y594R1185, R1409, R1482. connection, K=X, W1=H. L1272 120 Obsolete. York part no. 025-22290; used with T874R1046, R1145; used in Y594R1011, R1102; used with T874R1228, R1251 R1327 and C815A1039; used in Y594R1144, R1151, R1193. Y594R1672a L1280 233 Obsolete. Lennox no. 52C7601; used with T874W1023 Y594W1014a and W89. L1298 182 Obsolete. Singer heat pump; used with T874R1160 and W89. See OEM for replacement. L1314 115 Obsolete. Westinghouse heat pump; used with T874R1244 and W89. Q674L1207 or Y594R1243a L1322 127 Obsolete. EM HEAT and AUX HEAT LEDs; used with T874C1455. Y594R1243a L1330 120 Obsolete. York heat pump; used with T874R. Y594R1664a Wiring differences (old=new): L=X, X=B. L1348 115 Obsolete. Williamson heat pump; used with T874R1236. Q674L1207 L1355 111, Obsolete. Lennox part no. 31F3201; V-VR jumper; 190 used with T874C1448, R1178 and C815A1015. Y594R1763a Wiring differences (old=new): V-VR=R, M=Y, F=G, X=B, Y=W, A=T, R=O, E=X2. L1363 129 Obsolete. York heat pump; EM HEAT LED; used with T874G1402. Y594R1425a Wiring differences (old=new): W=W2, X=E, B=X; jumper YW1. L1371 124 Obsolete. BDP heat pump; part no. 34427DP125, P272-1878; EM HEAT LED; used with T874J1010. Y594J1001 Wiring differences (old=new): W1=W2, F=L. L1389 114 Obsolete. Lennox part no. 41F6501; V-VR jumper; used with T874D1207. T8611M2025 Wiring differences (old=new): (programmable) V-VR=R, Y=W3, X=C, R=O, M=Y, M2=Y2-W2, F=G; jumper Y2-W2; no outdoor reset needed; use only one system transformer. L1397 103 Obsolete. Carrier part no. HH93AZ185A; SUPL HEAT Y594G1393a Wiring differences (old=new): LED. C=X. a Both the thermostat and subbase must be replaced. 83 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9. Q674 Subbase Cross Reference. Model Fig. Number No. Description Q674 Trade Replacement Remarks L1405 106 Obsolete. BDP heat pump; part no. HH641501; used with T874R1335; used in Y594R1201. Y594R1243a L1413 133 Obsolete. Fedders heat pump; used with T874R1343; used in Y594R1219. Y594R1425a Wiring differences (old=new): K=E, C=X, Z=L; remove W1-Y jumper. L1421 125 Obsolete. Coleman heat pump; used with T874R1368; Y594R1797a used in Y594R1235. L1439 131 Obsolete. Carrier part no. HH93AZ187; SUPL HEAT LED; System: SUPL HT-HEAT- COOL; used with T874R1384 (HH07AQ170). Q674L1207 or Wiring differences (old=new): Y594G1393a C=X. L1447 128 Obsolete. Williamson heat pump; three LEDs; used with T874R1392; used in Y594R1250. Y594R1425a Wiring differences (old=new): A=L. L1454 131 Obsolete. Carrier part no. HH93AZ197; SUPL HEAT LED; used with T874R1384 (HH07AQ170). Y594R1393a Wiring differences (old=new): C=X. L1462 113 Obsolete. LSI heat pump; part no. 104710002; used with T874R1400. Y594R1243a Wiring differences (old=new): X1=X. L1496 136 Obsolete. Trane heat pump; used with T874R1426; used in Y594R1284. Y594R1763a L1504 134 Rheem part no. 41-20796-24; used with T874R1442, R1434, R1459; used in Y594R1631, R1649, R1854. Y594R1300a L1512 108 Includes two LEDs; used with T874R1467; used in Y594R1292. Y594R1292a L1520 123 Includes EM HEAT and AUX HEAT LEDs; used with T874R1475; used in Y594R1300. Y594R1300a L1538 130 Obsolete. Snyder General heat pump; used with T874R1483, R1517, R1566 and C815A1005; used in Y594R1318, R1342, R1375. Y594R1763a Wiring differences (old=new): C=B, W1=W, E=X2, X=F. 132 Obsolete. Used with T874R1574, R1582; used in Y594R1383, R1391. Y594R1243a Wiring differences (old=new): C=X, X=L, W=W2. L1546 140 Obsolete. Rheem part no. 41-20797-21; three LEDs; used with T874W1031 and C815A1005; used in Y594W1022. T8611M2025 Includes night setback. (programmable) L1553 137 Obsolete. Includes three LEDs; used with T874R1491; Y594R1615a used in Y594R1326. L1561 121 Obsolete. Used with T874C1638; used in Y594C1322. Y594C1322a Use Y594C1322 when T874C is used. 123 Obsolete. Used with T874R. Y594R1243a Use Y594R1243 when T874R is used. L1579 135 Obsolete. Carrier heat pump; part no. HH93AZ198; SUPL HEAT LED; used with T874R1384 (HH07AQ170). Y594R1243a Wiring differences (old=new): C=X. L1587 168 Used with T874R1616; used in Y594R1425. Y594R1425a L1595 200, Obsolete. Miller heat pump; used with T874R1624 or Y594R1243a or 201 T874R1202; used in Y594R1433. Y594R1763a L1603 134 Obsolete. Used with T874R1632. Y594R1243a L1611 136 Obsolete. American Standard heat pump; part no. WY28X235; used with T874R1657; used in Y594R1441. Y594R1763a L1637 207 Obsolete. Carrier heat pump; part no. HH93AZ195; used with T874J1002 (HH07AT175) or T874J1010 (HH07AT165). Y594J1001a a Both the thermostat and subbase must be replaced. 60-2485--8 84 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9. Q674 Subbase Cross Reference. Model Fig. Number No. Description Q674 Trade Replacement Remarks L1678 209 Trol-A-Temp by Honeywell; gray color; used with T874R1707; used in Y594R1490. None See Trol-A-Temp. L1686 209 Trol-A-Temp by Honeywell; used with T874R1715; used in Y594R1508. None See Trol-A-Temp. L1702 132 Obsolete. Snyder General heat pump; part no. 654958B07; used with T874R1723 and C815A1005; used in Y594R1516. Y594R1672a Wiring differences (old=new): C=B, W1=W, X=X2. L1710 230 Used with T874R1822; used in Y594R1615. Y594R1615a L1728 228 Obsolete. Lennox; gray color; used with T874R1855; used in Y594R1714. Y594R1763a Wiring differences (old=new): Y1=Y, L=F, W1=W, E=X2, C=B. L1736 120 Designed to replace Y594R1011 (York part no. 2TH11702224); used with T874R1871; used in Y594R1664. Y594R1664a Designed to replace Y594R1151 (York part no. 2TH11702324), Y594R1193 (York part no. 6TH11702224) and York part no. 2TH11704024; used with T874R1889 and C815A1054; used in Y594R1672. Y594R1672a L1751 230 Gray color; used with T874R1897, used in Y594R1680. Y594R1680a L1769 124 Obsolete. Nordyne part no. 9132260; used with T874J. See OEM for replacement. L1777 120 Obsolete. Gray color; designed to replace Y594R1151 (York part no. 2TH11702324), Y594R1193 (York part no. 6TH11702224) and York part no. 2TH11704024; used with T874R1905 and C815A1059; used in Y594R1698. Y594R1672a Replacement is beige. Designed to replace Y594R1011 (York part no. 2TH11702224); used with T874R1913; used in Y594R1706. Y594R1664a Replacement is beige. L1785 103 Obsolete. Carrier part no. HH93AZ175-W; Canada; gray color; System: Supl Ht-Heat-Off-Cool; includes one LED. Y594G1476a Wiring differences (old=new): C=X; Y1-W1 jumper required. L1793 124 Obsolete. Carrier Canada part no. HH93AZ186-W; gray color; Fan: Auto-On; System: Supl Ht-Heat-OffCool; includes one LED. Y594J1019a L1801 197 American Standard (Trane) part no. THT1225; includes Y594R1763a two LEDs; used with T874R1939; used in Y594R1748. L1819 168 Obsolete. Inter-City Products part no. HQ1149407HW; includes three LEDs; used with T874R1947; used in Y594R1755. Y594R1425a L1827 197 TRADELINE; includes two LEDs; used with T874R1954; used in Y594R1763; direct replacement for Trane/American Standard Y594R1748 (T874R1939/Q674L1801) Trane part no. ASYSTAT 631A, Y594R1136 (T874R1053/Q674L1140). Y594R1763a L1835 140 Obsolete. Inter-City Products; includes three LEDs; used in Y594W1030. T8611M2025a Includes night setback. (programmable) L1843 115 Obsolete. Consolidated Industries part no. 9036100; gray color; includes two LEDs; used with T874R1962; used in Y594R1771. Y594R1680a Includes CHECK LED. L1850 120 York Canada; gray color; includes one LED; used with Y594R1672a T874R1970; used in Y594R1789. a Both the thermostat and subbase must be replaced. 85 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9. Q674 Subbase Cross Reference. Model Number L1868 L1876 L1884 L1892 L1900 L1918 L1934 Q674N N1015 N1023 Q674P P1005 Fig. No. Description 125 TRADELINE; includes two LEDs; used with T874R1988; used in Y594R1797; direct replacement for Evcon/Coleman Y594R1235 (T874R1368/ Q674L1421) Coleman part no. 3600-368. 245 Obsolete. Amana part no. 10573902; includes two LEDs; used with T874R2002; used in Y594R1805. 245 Obsolete. Amana part no. 10573904; includes two LEDs; used with T874R2010; used in Y594R1813. 103 Obsolete. TRADELINE; System: SUPL HT-HEATOFF-COOL; includes one LED; used with T874G2004; used in Y594G1666; direct replacement for Carrier Y507J1011 (T874G1055/Q674L1041) Carrier part no. HH07AT171/HH93AZ175. 241 Obsolete. TRADELINE; System: SUPL HT-HEATOFF-COOL; includes SUPL HT LED; used with T874J1069; used in Y594J1001; direct replacement for Carrier T874J1028/Q674J1068 (Carrier part no. HH07AT165/HH93AZ183), Carrier T874J1002/ Q674J1068 (Carrier part no. HH07AT175/ HH93AZ183). 125 Obsolete. York logo; part no. 2TH11703424A; includes two LEDs; used with T874R2028 in Y594R1821. 123 Obsolete. Addison logo; part no. 843-277; includes three LEDs; used with T874W1106 in Y594W1055. System: OFF-HEAT-COOL-EVAP; Fan: AUTO-ON 60 Obsolete. Goettl heat pump; changeover in heat mode; evaporative cooler circuit; used with T874C1182. 61 Obsolete. Sigler heat pump; evaporative cooler circuit; used with T874C1349. System: SUPL HT-HEAT-COOL; Fan: AUTO-ON 126 Obsolete. Carrier heat pump; part no. HH93AZ169; used with T874G1071 (HH07AT171). Q674Q Q1004 System: HEAT-OFF-COOL; Fan: LOW-MED-HI-ON 59 Obsolete. McQuay special; used with T874A1267. Q1012 Q674R R1003 Q674S S1000 Q674W W1006 64 Used with T874A1291. System: OFF-COOL; Fan: LO-HI-CONT 69 Obsolete. Carrier part no. HH93AZ190; international symbols on fan and switches; used with T874V1008 (HH07AT177). System: HEAT-COOL; Fan: None 70 Obsolete. Fiberglas; Canada; SERVICE LED; used with T874C1653; used in Y594C1348. System: OFF-ON; Fan: LO-MED-HI 240 Obsolete. Snyder General part no. 044271801. a Both the thermostat and subbase must be replaced. Q674 Trade Replacement Y594R1797a Remarks Y594R1797 Y594R1797 Y594G1674 Wiring differences (old=new): C/X=X. Wiring differences (old=new): C/X=X, W3=W2. Replacement has auto changeover. Y594J1019 Replacement has auto changeover. Y594R1797a T8611M2025 See OEM for replacement. See OEM for replacement. Y594G1419a Wiring differences (old=new): C=X; jumper Y1-W1; replacement has OFF-EM HTHEAT-AUTO-COOL system switching. See OEM for replacement. None See OEM for replacement. See OEM for replacement. See OEM for replacement. 60-2485--8 86 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 10. Y594 Cross Reference. Model Number Y594A A1001 A1019 A1035 A1043 A1050 A1068 A1126 A1159 Fig. No. Description 46 Obsolete. Amana part no. D68535-11; contains T874A1077, Q674B1075. 82 Obsolete. Amana part no. P68535-12; contains T874A1077, Q674E1056. 44 Obsolete. Trane part no. 268-0187-1; contains T874A1085, Q674B1018. 46 Obsolete. Trane part no. 268-0201-5; contains T874A1085, Q674B1075. 55, 66 Obsolete. Trane part no. 268-0201-3; contains T874A1085, Q674D1008. 82 Obsolete. Sears part no. 42-9144; contains T874A1119, Q674E1007. 64 Contains T874A1291, Q674Q1012. 91 Obsolete. Contains T874A1440, Q674G1005. A1167 A1175 A1191 Y594B B1026 B1034 B1042 Y594C C1009 C1017 C1058 184 California Economizer; Premier White® color; contains T874A1580 and Q674G1161. 55 Obsolete. York logo; part no. 2TH04703224; contains T874A1622, Q674D1180. 46 Obsolete. Amana logo: part no. P6853524R; contains T874A1002, Q674B1075. 44 Trane part no. BAYSTAT012; contains T874B1035, Q674B1018. 46 Obsolete. Trane part no. 163-552-1; contains T874B1035, Q674B1075. 88 Obsolete. Goodman part no. CHTS36-60; contains T874B1100, Q674E1338. 82 Obsolete. Amana part no. D68535-9; contains T874C1059, Q674E1056. 142 Obsolete. Amana part no. D68535-10; contains T874C1059, Q674F1022. 46 Obsolete. Contains T874C1000, Q674B1075. C1082 C1256 C1280 C1314 82 Obsolete. Trane part no. 166-162-1; contains T874C1083, Q674E1007. 45 Obsolete. Amana part no. D68535-16; contains T874C1059, Q674B1059. 45 Obsolete. Williamson; contains T874C1570, Q674B1000. 56 Obsolete. LSI; contains T874C1471, Q674B1257. C1322 121 Obsolete. Contains T874C1638, Q674L1561. C1330 142 Obsolete. Amana part no. D68535-21; contains T874C1059, Q674F1022. a Both the thermostat and subbase must be replaced. Trade Model Replacementa T874A1036/ Q674B1075 T874A1036/ Q674E1049 T874A1036/ Q674B1018 T874A1036/ Q674B1075 T874A1036/ Q674D1040 T874A1036/ Q674E1049 None T874A1150/ Q674G1070 T874A1036/ Q674G1070 T874A1010/ Q674D1040 T874A1036/ Q674B1075 T874B1019/ Q674B1018 T874B1019/ Q674B1075 T874B1019/ Q674E1049 T874C1018/ Q674E1049 T874C1018/ Q674F1022 T874C1018/ Q674B1075 T874C1018/ Q674E1049 T874C1018/ Q674B1034 T874C1018/ Q674B1034 T874C1018/ Q674B1018 Y594C1322 T874C1018/ Q674F1022 Remarks Replacement is beige color. No LEDs on replacement. Jumper RC-RH. Jumper RC-RH. Jumper RC-RH; no RESET LED on replacement. 87 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Model Number C1348 Table 10. Y594 Cross Reference. Fig. No. Description 70 Obsolete. Fiberglas; contains T874C1653, Q674S1000. Trade Model Replacementa T874C1000/ Q674B1075 C1355 C1363 45 Obsolete. Nordyne "Miller" part no. 9122250; contains T874C1695, Q674B1000. 45 Obsolete. Nordyne "Intertherm" part no. 911100001; contains T874C1703, Q674B1000. T874C1018/ Q674B1034 T874C1018/ Q674B1075 C1371 C1389 C1413 C1421 C1439 Y594D D1016 D1024 D1032 D1040 D1057 D1149 D1156 D1180 D1222 184 Obsolete. California Economizer; contains T874C1802 and Q674G1005. 237 Obsolete. TRADELINE; Premier White® color; contains T874C1810 and Q674B1547. 238 Heat Controller "Energy Night" logo; contains T874C1844 and Q674F1592. 249 Obsolete. TRADELINE; contains T874C1877 and Q674B1554. T874C1869 and Q674C1579. T874C1018/ Q674G1070 Y594C1389 Y594R1425 Y594D1347 None 44 Obsolete. Trane part no. 268-0201-2; contains T874D1082, Q674B1018. 72 Trane part no. BAYSTAT010; contains T874D1082, Q674C1009. 91 Obsolete. Trane part no. BAYSTAT011; contains T874D1082, Q674G1021. 46 Amana part no. P68535-19R; contains T874D1082, Q674B1075. 55, 66 Obsolete. Trane part no. BAYSTAT007; contains T874D1082, Q674D1008. 46 Obsolete. Amana part no. P68535-20C; contains T874D1322, Q674B1075. 48 Obsolete. Trane part no. BAYSTAT013; contains T874D1082, Q674B1133. 82 York part no. 025-23321-000; contains T874D1504, Q674E1007. 166 Obsolete. WeatherKing; contains T874D1009, Q674F1337. T874D1165/ Q674B1018 T874D1165/ Q674C1058 T874D1165/ Q674G1070 T874D1165/ Q674B1075 T874D1165/ Q674D1040 T874D1165/ Q674B1075 T874D1165/ Q674B1018 T874D1165/ Q674E1049 T874D1165/ Q674F1022 D1248 82 Obsolete. Reznor part no. 93437; contains T874D1629, Q674E1007. D1297 82 Obsolete. ArcoAire part no. 1506753; contains T874D1769, Q674E1346. D1305 82 Obsolete. Comfortmaker part no. 1505753; contains T874D1785, Q674E1346. D1321 45 Obsolete. Goodman part no. CHT 90-120; contains T874D1843, Q674B1000. D1339 82 Obsolete. Nordyne part no. 5471180; contains T874D1009, Q674E1007. a Both the thermostat and subbase must be replaced. T874D1165/ Q674E1049 T874D1165/ Q674E1049 T874D1165/ Q674E1049 T874D1165/ Q674B1034 T874D1165/ Q674E1049 Remarks Wiring differences (old=new): Y=Y1; jumper RC-RH and Y1W1; replacement has no SERVICE LED; replacement has fan switching and HEATOFF-COOL system switching. Wiring differences (old=new): Y=Y1; jumper RC-RH; Y1-W; replacement has no SERVICE LED. E-W2 jumper required; system: EM.HT.-Heat-Off-Cool. Replacement has auto changeover; jumper RH-RC. Replacement has no FILTER LED. Wiring differences (old=new): R=RH; jumper RC-RH; replacement has no EM.HT. or AUX. HT. LEDs. 60-2485--8 88 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Model Number D1347 D1354 D1370 D1388 D1396 D1404 D1412 D1420 D1438 D1446 Table 10. Y594 Cross Reference. Fig. No. Description 82 TRADELINE® contains T874D1942, Q674E1403. 82 SUPER TRADELINE® contains T874D2031 (no cover), Q674E1049, and TG504A with two keys. 45 Obsolete. Carrier part no. 50QE90022101; contains T874D2049 and Q674B1539. 72 Obsolete. Carrier part no. 50QE90023101; contains T874D2049 and Q674C1520. 184 Obsolete. Carrier part no. 50QE90025101; contains T874D2049 and Q674G1153. 55, 66 Obsolete. Carrier part no. 50QE90024101; contains T874D2049 and Q674D1164. 82 Obsolete. Carrier "Weathermaker" part no. HH07AT209; taupe color; contains T874D2064 and Q674E1445. 82 Obsolete. Carrier "Zone Perfect" part no. HH07AT208; taupe color; contains T874D2072 and Q674E1445. 55, 66 Obsolete. Contains T874D2098 and Q674D1008. 55, 66 Obsolete. Contains T874D2106 and Q674D1008. Trade Model Replacementa Y594D1347 Y594D1354 T874D1165/ Q674B1034 T874D1165/ Q674C1058 T874D1165/ Q674G1070 T874D1165/ Q674D1040 T874D1165/ Q674E1049 T874D1165/ Q674E1049 T874D1165/ Q674D1040 T874D1165/ Q674D1040 D1453 208 Obsolete. Amana logo; part no. P1217501F; contains T874D2163 and Q674D1172. D1461 45 Obsolete. Amana logo; part no. P1217701F; contains T874D2171 and Q674B1562. Y594E E1015 72 Obsolete. Trane part no. BAYSTAT015; contains T874E1040, Q674C1009. Y594F F1022 44 Obsolete. Contains T874F1031 and 40003440-001 wallplate with installed diode. F1048 72 Obsolete. Reznor part no. 93436; contains T874F1130, Q674C1009. F1063 91 Obsolete. Reznor part no. 93435; contains T874F1130, Q674G1005. Y594G G1013 160 Obsolete. York part no. 2TH11702424; contains T874G1170, Q674J1027. G1138 160 Obsolete. York part no. 025-22286; contains T874G1196, Q674J1027. G1153 154 Obsolete. Crispaire part no. HP10-51; contains T874G1089, Q674F1204. G1161 162 Contains T874G1204, Q674J1043. G1195 155 Obsolete. Heil Quaker part no. HQ521387HW; contains T874G1246, Q674F1212. G1229 160 Obsolete. York part no. 6TH11702424; contains T874G1428, Q674J1027. G1245 155 Obsolete. BDP part no. HH641502; contains T874G1451, Q674F1212. G1252 155 TRADELINE; contains T874G1246, Q674F1212. a Both the thermostat and subbase must be replaced. T874D1165/ Q674D1040 T874D1942/ Q674B1034 T874B1019/ Q674C1058 T874F1015 T874F1015/ Q674C1058 T874F1015/ Q674G1070 Y594G1567 Y594G1567 Y594G1252 Y594G1161 Y594G1252 Y594G1567 Y594G1252 Y594G1252 Remarks Replacement has °F scaleplate. Replacement has °F scaleplate. Replacement has °F scaleplate. Replacement has °F scaleplate. Replacement is beige color. Replacement is beige color. Replacement has 2 setpoint levers. Replacement has °F scaleplate and 2 setpoint levers. Wiring differences (old=new): A=L. 89 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Model Number G1294 G1328 G1344 G1351 G1369 G1377 G1385 G1393 G1419 G1427 G1443 G1476 G1492 Table 10. Y594 Cross Reference. Fig. Trade Model No. Description Replacementa 79 Obsolete. LSI; contains T874G1378, Q674C1124. See OEM for replacement. 194 Obsolete. Addison part no. 8403-197; contains T874G1543, Q674F1345. Y594G1252 194 Obsolete. Heat Controller part no. 7601-110B; contains T874G1469, Q674F1345. Y594G1252 160 Obsolete. Luxaire part no. 026-00068-000; contains T874G1568, Q674J1126. Y594G1567 155 Obsolete. Contains T874G1246, Q674F1212. Y594G1252 169 Obsolete. Coleman part no. 3600-373; contains T874G1576, Q674F1402. Y594G1633 155 Obsolete. ArcoAire; contains T874G1592, Q674F1212. Y594G1252 170 Obsolete. Contains T874R1393, Q674L1454. Y594G1393 227 TRADELINE; contains T874G1642, Q674F1444. Y594G1419 177 Obsolete. Mammoth part no. 73034101; contains T874G1659, Q674C1330. See OEM for replacement. 174 Obsolete. American Standard (Trane) part no. ASYSTAT650; contains T874G1675, Q674J1142. Y594G1161 227 TRADELINE; same as Y594G1419 except Premier White® color; contains T874G1741, Q674F1477. Y594G1476 211 Trol-A-Temp; contains T874G1758, Q674F1485. None G1500 216 Obsolete. Comfortmaker part no. 1505756; contains T874G1774, Q674J1175. G1518 216 Obsolete. ArcoAire part no. 1506756; contains T874G1782, Q674J1175. G1526 167 TRADELINE; contains T874G1626, Q674F1436. G1534 227 TRADELINE; °C; white; Australia; contains T874G1824, Q674F1477. G1542 231 Obsolete. Intertherm part no. 9129290; contains T874G1832, Q674F1519. G1559 231 Obsolete. Miller part no. 9129310; contains T874G1840, Q674F1519. G1567 160 TRADELINE; contains T874G1865, Q674J1209. G1575 160 Obsolete. TRADELINE; same as Y594G1567 except Premier White® color; contains T874G1873, Q674J1225; direct replacement for York 2TH11702424 (Y594G1013 contains T874G1170/ Q674J1027) and 6TH11702424 (Y594G1229 contains T874G1428/Q674J1027). G1583 229 Obsolete. Lennox Canada part no. 97E78; contains T874G1857, Q674F1535. G1591 243 Obsolete. Amana part no. 10636701; contains T874G1899 and Q674F1550. G1609 155 Obsolete. Econar; contains T874G1915 and Q674F1212. a Both the thermostat and subbase must be replaced. See OEM for replacement. See OEM for replacement. None None Y594G1252 Y594G1252 Y594G1567 Y594G1567 Y594G1161 Y594G1633 Y594G1252 Remarks H2 is night setback. Wiring differences (old=new): Y1=O, X=L, C=X. Wiring differences (old=new): Y1=O, X=L, C=X; W1=Y. H2 is night setback. See Trol-A-Temp for replacement. Cooling changeover only. Cooling changeover only. Replacement is beige. Wiring differences (old=new): E=X2, C=B, L=F. 60-2485--8 90 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 10. Y594 Cross Reference. Model Number G1617 G1625 G1633 G1641 G1658 G1666 G1674 G1716 Y594H H1004 H1012 H1020 H1038 H1046 H1053 Y594J J1001 Fig. Trade Model No. Description Replacementa Remarks 73 Obsolete. Carrier part no. 50QE90020101; contains T874G1949 and Q674C1504. Y594H1012a Wiring differences (old=new): Y1=O, Y2=Y, L=R, R=none; R-L jumper required; no night setback. T8600D2028 Wiring differences (old=new): (programmable) Y1=O, Y2=Y, L=R; W-Y jumper required; night setback. 160 York Canada part no. 2TH11702524; contains T874G1964 and Q674J1266. Y594G1567a Replacement has °F scaleplate. 169 TRADELINE; contains T874G1972 and Q674F1584; direct replacement for Y594G1377 (T874G1576/Q674F1402) Evcon/Coleman part no. 3600-373. Y594G1633a 169 Obsolete. Amana part no. 10636703; contains T874G1980 and Q674F1600. Y594G1633 Wiring differences (old=new): W3=W2. 155 Obsolete. Tempstar "Inter-City Products" part no. 1149910; contains T874G1998 and Q674F1212. Y594G1252 103 Obsolete. TRADELINE; manual changeover; contains T874G2004 and Q674L1892; direct replacement for Y507J1011 (T874G1055/ Q674L1041) Carrier part no. 99TZ90041106 (HH07AT171/HH93AZ1750). Y594G1674 Replacement has auto changeover. 161 TRADELINE; automatic changeover; contains T874G2004 and Q674J1274; direct replacement Y507J1003 (T874G1055/Q674J1035) Carrier part no. 99TZ90040106 (HH07AT171/HH93AZ173). Y594G1674 155 WaterFurnace logo; part no. TA21H03; contains T874G2046 and Q674F1667. Y594G1716 79 Obsolete. LSI part no. 73033901; contains T874H1039 and Q674C1124. 164 Contains T874H1062 and Q674C1249; replaces T874H1005/Q674C1041. 177 Obsolete. Mammoth part no. 71117101; contains T874H1096 and Q674C1330. 74 Obsolete. Carrier part no. 50QE90019101; contains T874H1161 and Q674C1496. 172 Obsolete. Carrier part no. 50QE90026101; contains T874H1153 and Q674B1406. 173 Obsolete. Carrier part no. 50QE90027101; contains T874H1153 and Q674C1322. T8600D2028 H2 is night setback. Y594H1012 Y594H1012 Y594H1012a T874A1130/ Q674B1075a Y594H1012a Wiring differences (old=new): R1=R, R2=L; use jumper provided. Wiring differences (old=new): X1=O, Y2=Y; L-R jumper required. Wiring differences (old=new): Y=Y1; W1-Y1 jumper required; replacement has no LEDs. Wiring differences (old=new): Z=X. 241 Obsolete. TRADELINE; manual changeover; contains T874J1069 and Q674L1900; direct replacement for T874J1002 or T874A1028 used with Q674L1074 or Q674L1637 (HH07AT175 or HH07AT165 used with HH93AZ186 or HH93AZ195). (Recontrol) T8511G1021 a Both the thermostat and subbase must be replaced. 91 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Model Number J1019 Y594N N1007 N1015 Table 10. Y594 Cross Reference. Fig. No. Description 244 Obsolete. TRADELINE; automatic changeover; contains T874J1069 and Q674J1282; direct replacement for T874J1002 or T874J1028 used with Q674J1068 or Q674J1159 (HH07AT175 or HH07AT165 used with HH93AZ183 or HH93AZ196). Trade Model Replacementa (Recontrol) T8511G1021 178 Obsolete. Williamson part no. 75-189; contains T874N1008 and Q674F1196. 179 Obsolete. Contains T874N1040 and Q674F1261. T874N1016/ Q674F1196 Y594G1419a N1023 N1031 Y594P P1005 178 Obsolete. Intertherm part no. 9111882; contains T874N1057 and Q674F1220. 178 Obsolete. Nordyne "Miller" part no. 9122240; contains T874N1065 and Q674F1220. T874N1016/ Q674F1220 T874N1016/ Q674F1220 97 Obsolete. Carrier part no. 50QE90021101; contains T8600D2028 T874P1055 and Q674C1512. Y594R R1011 R1029 R1037 R1102 R1110 R1128 R1136 R1151 R1185 120 Obsolete. York part no. 2TH11702224; contains T874R1046 and Q674L1272. 47 Obsolete. Bryant; contains T874R1004 and Q674B1042. 122 Obsolete. Fedders part no. 88-58-00540-001; contains T874R1269 and Q674L1066. 120 Obsolete. York part no. 025-22285-000; contains T874R1145 and Q674L1272. 108 Obsolete. Heil Quaker part no. HQ712004HW; contains T874R1137 and Q674L1132. 116 Obsolete. Crispaire part no. HP9-51; contains T874R1111 and Q674L1215. 109 Obsolete. Contains T874R1053 and Q674L1140. 120 Obsolete. York part no. 2TH11702324; contains T874R1251, Q674L1272 and C815A1039. 201 Obsolete. Intertherm part no. 9111871; contains T874R1202 and Q674L1264. Y594R1664 Y594R1243 Y594R1615 Y594R1664 Y594R1292 Y594R1243 Y594R1763 Y594R1672 Y594R1672 R1193 R1201 R1219 120 Obsolete. York part no. 6TH11702224; contains T874R1327 and Q674L1272. 106 Obsolete. BDP part no. HH641501; contains T874R1335 and Q674L1405. 133 Obsolete. Fedders part no. 88-58-00560-001; contains T874R1343 and Q674L1413. Y594R1664 Y594R1243 Y594R1425 R1235 125 Obsolete. Coleman part no. 3600-368; contains T874R1368 and Q674L1421. R1243 115 TRADELINE; contains T874R1152 and Q674L1207. R1250 128 Obsolete. Williamson part no. 75-191; contains T874R1392 and Q674L1447. R1284 136 Obsolete. Trane part no. BAYSTAT339; contains T874R1426 and Q674L1496. a Both the thermostat and subbase must be replaced. Y594R1797 Y594R1243 Y594R1425 Y594R1763 Remarks Wiring differences (old=new): L=X2, Y=Y1. Wiring differences (old=new): Y=Y1, W=O; Y1-W1 jumper required. Wiring differences (old=new): W1=W2. Wiring differences (old=new): K=E, C=X, W1=B, Z=L. Wiring differences (old=new): A=L. Wiring differences (old=new): W2=W, X=B, Z=no connection, K=X, W1=H. Wiring differences (old=new): K=E, C=X, Z=L; remove factory installed jumper. Wiring differences (old=new): A=L. 60-2485--8 92 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Model Number R1292 R1300 R1318 R1326 R1334 R1342 R1359 R1375 R1383 R1391 R1409 Table 10. Y594 Cross Reference. Fig. Trade Model No. Description Replacementa 108 Contains T874R1467 and Q674L1512; replaces Y594R1110 (T874R1137/Q674L1132). Y594R1292 123 Contains T874R1475 and Q674L1520. Y594R1300 130 Obsolete. Comfortmaker part no. 1505721; contains T874R1483, Q674L1538 and C815A1005. Y594R1763 137 Obsolete. SUPER TRADELINE; contains T874R1491 and Q674L1553. Y594R1615 47 Obsolete. Slant Fin; contains T874R1509 and Q674B1042. Y594R1243 130 Obsolete. ArcoAire part no. 1506721; contains T874R1517, Q674L1538 and C815A1005. Y594R1763 113 Obsolete. ArcoAire part no. A02074; contains T874R1525 and Q674L1181. Y594R1243 130 Obsolete. Contains T874R1566, Q674L1538 and C815A1005. Y594R1763 132 Obsolete. Comfortmaker part no. 1505739; contains T874R1574 and Q674L1538. Y594R1243 132 Obsolete. ArcoAire part no. 1506739; contains T874R1582 and Q674L1538. Y594R1243 119 Obsolete. Intertherm part no. 6244630; contains T874R1608 and Q674L1264. Y594R1763 R1417 R1425 R1433 113 Obsolete. Comfortmaker part no. 1505-735; contains T874R1301 and Q674L1181. 168 SUPER TRADELINE; contains T874R1616 and Q674L1587. 200 Obsolete. Miller part no. 9115900; contains T874R1624 and Q674L1595. Y594R1243 Y594R1425 Y594R1243 R1441 R1466 R1482 136 Obsolete. American Standard (Trane) part no. ASYSTAT651; contains T874R1657 and Q674L1611. 108 Heil Quaker part no. 1060321; model no. HAXB004TW01; contains T874R1673 and Q674L1132. 119 Obsolete. Nordyne "Miller" part no. 9122230; contains T874R1699 and Q674L1264. Y594R1763 Y594R1292 Y594R1763 R1490 209 Trol-A-Temp; contains T874R1707 and Q674L1678. None R1508 209 Trol-A-Temp; contains T874R1715 and Q674L1686. None R1516 132 Obsolete. Snyder General part no. 654958B07; contains T874R1723, Q674L1702 and C815A1005. R1524 108 Obsolete. Inter-City Products part no. HQ1147925HW; contains T874R1731 and Q674L1132. R1532 108 Heil Quaker part no. 1060322; model no. TAXB004TW01; contains T874R1749 and Q674L1132. R1607 108 Obsolete. Keeprite THPC; contains T874R1814 and Q674L1132. a Both the thermostat and subbase must be replaced. Y594R1763 Y594R1292 Y594R1292 Y594R1292 Remarks Wiring differences (old=new): W1=W, E=X2, X=F, C=B. Wiring differences (old=new): W1=W2. Wiring differences (old=new): W1=W, E=X2, X=F, C=B. Wiring differences (old=new): X1=X. Wiring differences (old=new): W1=W, E=X2, X=F, C=B. Wiring differences (old=new): W=W2, C=X, X=L. Wiring differences (old=new): W=W2, C=X, X=L. Wiring differences (old=new): W2=W, X=B, Z=F, K=X2, W1=O. Wiring differences (old=new): X1=X. Wiring differences (old=new): W2=W, X=B, Z=F, K=X2, W1=O. Wiring differences (old=new): W2=W, X=B, Z=F, K=X2, W1=O. See Trol-A-Temp for replacement. See Trol-A-Temp for replacement. Wiring differences (old=new): W1=W, C=B, X=X2. 93 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 10. Y594 Cross Reference. Model Fig. Number No. Description R1615 230 TRADELINE; contains T874R1822 and Q674L1710; replaces Y594R1326 (T874R1491/ Q674L1553). R1623 134 Obsolete. Rheem Universal Parts part no. 4120796-46; contains T874R1558 and Q674L1504. R1631 134 Rheem part no. 41-20796-29; contains T874R1442 and Q674L1504. R1649 134 Ruud part no. 41-20796-33; contains T874R1434 and Q674L1504. R1656 134 Obsolete. WeatherKing part no. 41-20796-64; contains T874R1830 and Q674L1504. R1664 120 TRADELINE; contains T874R1871 and Q674L1736; direct replacement for York 2TH11702224 (Y594R1011 contains T874R1046/ Q674L1272). R1672 120 TRADELINE; contains T874R1889, Q674L1736 and C815A1054; direct replacement for York 2TH11702324 (Y594R1151 contains T874R1251/ Q674L1272/C815A1039) and 6TH11702224 (Y594R1193 contains T874R1327/Q674L1272). R1680 230 TRADELINE; same as Y594R1615 except Premier White® color; contains T874R1897 and Q674L1751; direct replacement for Y594R1326 (T874R1491/Q674L1553). R1698 120 Obsolete. TRADELINE; Premier White® color; contains T874R1905, Q674L1777 and C815A1054. R1706 120 Obsolete. TRADELINE; same as Y594R1664 except Premier White® color; contains T874R1913 and Q674L1777; direct replacement for Y594R1011 (T874R1046/Q674L1272) York part no. 2TH11702224. R1714 228 Obsolete. Lennox part no. 97E79; Canada; Premier White® color; contains T874R1855 and Q674L1728. R1722 115 Obsolete. Econar; contains T874R1921 and Q674L1207. R1748 197 American Standard (Trane) part no. ASYSTAT651A; contains T874R1939 and Q674L1801. R1755 168 Obsolete. Inter-City Products part no. HQ1149376HW; contains T874R1947 and Q674L1819. R1763 197 TRADELINE: contains T874R1954 and Q674L1827; direct replacement for Y594R1136 (T874R1053/Q674L1140), Y594R1748 (T874R1939/Q674L1801) Trane part no. ASYSTAT651A, Y594R1441 (T874R1657/ Q674L1611) Trane part no. ASYSTAT651. R1771 115 Obsolete. Consolidated Industries part no. 9036100; contains T874R1962 and Q674L1843. R1789 120 York Canada part no. 2TH11701524; contains T874R1970 and Q674L1850. a Both the thermostat and subbase must be replaced. Trade Model Replacementa Y594R1615 Y594R1300 Y594R1300 Y594R1300 Y594R1300 Y594R1664 Y594R1672 Y594R1680 Y594R1672 Y594R1664 Y594R1763 Y594R1243a Y594R1763a Y594R1425a Y594R1763 Y594R1680a Y594R1672a Remarks Replacement is beige. Replacement is beige. Wiring differences (old=new): Y1=Y, L=F, W1=W, E=W2, C=B. Includes CHECK LED. Replacement has °F scaleplate. 60-2485--8 94 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 10. Y594 Cross Reference. Model Number R1797 R1805 R1813 R1821 R1839 R1854 Y594W W1014 W1022 W1030 W1055 Y594Y Y1004 Y1012 Fig. No. Description 125 TRADELINE; contains T874R1988 and Q674L1868; direct replacement for Y594R1235 (T874R1368/Q674L1421) Evcon/Coleman part no. 3600-368). 245 Obsolete. Amana part no. 10636702; contains T874R2002 and Q674L1876. 245 Obsolete. Amana part no. 10636704; contains T874R2010 and Q674L1884. 125 Obsolete. York logo; part no. 2TH11703424A; contains T874R2028 and Q674L1918. 134 Rudd logo; part no. 41-20796-48; contains T874R2036 and Q674L1504. 123 Obsolete. Rheem logo; part no. 41-20796-47; contains T874R1996 and Q674L1504. Trade Model Replacementa Y594R1797a Remarks Y594R1797 Y594R1797 Y594R1797 Wiring differences (old=new): C/X=X. Wiring differences (old=new): C/X=X, W3=W2. See OEM for replacement. Y594R1300 54 Contains T874W1015, Q674B1216 and C815A1005. Y594W1014 140 Obsolete. Rheem part no. 41-20797-19; contains T874W1031, Q674L1546 and C815A1005. T8611M2025. 68 Obsolete. Inter-City Products part no. 1072350; T8611M2025 Includes night setback. contains T874W1072, Q674L1835 and C815A1005 (programmable) Outdoor Thermistor. 247 Obsolete. Addison logo; part no. 843-277; contains T874W1106, Q674L1934 and C815A1005. T8611M2025 210 Obsolete. Mammoth part no. 71117301; contains T874Y1005 and Q674E1353. 248 Obsolete. WaterFurnace logo; part no. TA21H03; contains T874Y1013 and Q674F1675. See OEM for replacement. a Both the thermostat and subbase must be replaced. 95 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES WIRING DIAGRAMS THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 H1 FALL H1 ANTICIPATOR 4 FALL H2 6 H2 ANTICIPATOR 8 C1 RISE 9 FAN SWITCH AUTO ON SYSTEM SWITCH HEAT OFF COOL RISE 10 C1 ANTICIPATOR C2 ANTICIPATOR 11 C2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 JUMPER RH, RC FOR SINGLE TRANSFORMER. RH HEAT RELAY 1 W1 HEAT RELAY 2 W2 HEAT CHANGEOVER VALVE B 2 COOL CHANGEOVER VALVE O FAN RELAY G COMPRESSOR CONTACTOR 2 Y2 COMPRESSOR CONTACTOR 1 Y1 RC L1 (HOT) L2 1 NOTE: Model ing No. T874A T874B T874C T874D T874E T874D L2 L1 (HOT) 1 Heating Cool- Bulbs H1 H1 H1,H2 H1,H2 H1,H2 Bulbs C1 C1,C2 C1 C1,C2 C1,C2 M2903 Fig. 44. Schematic and hookup of T874A,B,C,D,E,F with Q674B. Used in standard applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 H1 FALL H1 ANTICIPATOR 4 FAN SWITCH AUTO ON RH L1 (HOT) 3 HEAT RELAY 1 L2 W1 1 HEAT RELAY 2 W2 HEAT CHANGEOVER VALVE B FALL H2 6 H2 ANTICIPATOR 8 C1 RISE 9 SYSTEM SWITCH HEAT OFF COOL X1 O COOL CHANGEOVER VALVE G 2 FAN RELAY Y2 10 C1 ANTICIPATOR COMPRESSOR CONTACTOR 2 RISE C2 ANTICIPATOR 11 C2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Y1 COMPRESSOR CONTACTOR 1 RC L2 L1 (HOT) 1 2 JUMPER RH, RC FOR SINGLE TRANSFORMER. 3 OPTIONAL LED ON SOME MODELS. M933C Fig. 45. Schematic and hookup of T874C,D with Q674B. Used in standard applications. 60-2485--8 96 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 H1 FALL H1 ANTICIPATOR 4 FAN SWITCH AUTO ON HEAT RELAY 1 W1 HEAT RELAY 2 W2 HEAT CHANGEOVER VALVE B FALL RISE RISE H2 6 H2 ANTICIPATOR 8 C1 9 SYSTEM SWITCH HEAT OFF COOL 10 C1 ANTICIPATOR C2 ANTICIPATOR 11 C2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. R O COOL CHANGEOVER VALVE G FAN RELAY Y2 COMPRESSOR CONTACTOR 2 Y1 COMPRESSOR CONTACTOR 1 Fig. 46. Schematic and hookup of T874A,B,D with Q674B. Used in standard applications. L1 (HOT) L2 1 M2904 . THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 C1 FALL 1 H1/C1 ANTICIPATOR 2 3 4 FAN SWITCH AUTO ON SYSTEM SWITCH O COOL CHANGEOVER VALVE G FAN RELAY R L1 (HOT) L2 1 FALL HEAT 5 OFF COOL H2 6 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. W1 AUX. HT. RELAY Y COMPRESSOR CONTACTOR M2906 Fig. 47. Schematic and hookup of T874R with Q674B. Used in heat pump applications. 97 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE 1 H1 FALL H1 ANTICIPATOR 4 H2 H2 6 FALL ANTICIPATOR 8 C1 RISE 9 RISE 10 C1 ANTICIPATOR C2 ANTICIPATOR 11 C2 FAN SWITCH AUTO ON SYSTEM SWITCH HEAT OFF COOL 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 CLOGGED FILTER, SERVICE SWITCH. SYSTEM COMPONENTS HEAT RELAY 1 W1 FAN RELAY G L1 (HOT) L2 1 EXTERNAL FAN SWITCH RC HEAT RELAY 2 W2 HEAT CHANGEOVER VALVE B RH 2 X1 FILTER LED (RED) O COOL CHANGEOVER VALVE Y1 COMPRESSOR CONTACTOR 1 Y2 COMPRESSOR CONTACTOR 2 L2 L1 (HOT) 1 M2905 Fig. 48. Schematic and hookup of T874D with Q674B. Used in standard applications. 60-2485--8 98 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H2 FALL H1 ANTICIPATOR 1 4 H2 ANTICIPATOR 6 FALL H1 8 C1 ANTICIPATOR 9 C1 10 RISE FAN SWITCH AUTO ON SYSTEM SWITCH HEAT OFF COOL HEAT LED (RED) HEAT RELAY 1 W1 BLOWER RELAY G R HEAT RELAY 2 W2 T COOL LED (YELLOW) COMPRESSOR CONTACTOR Y1 L1 (HOT) L2 1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. L LO SPEED LED (GREEN) C HI SPEED LED (GREEN H HSII CONTROL PANEL Fig. 49. Schematic and hookup of T874C with Q674B. Used in standard applications. L1 (HOT) L2 M5945 THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 H1 ANTICIPATOR O COOL CHANGEOVER VALVE H1 FALL 2 FAN SWITCH 4 AUTO ON Y COMPRESSOR CONTRACTOR FALL H2 H2 ANTICIPATOR 6 CO 8 SYSTEM SWITCH RISE C1 RISE 9 C1 ANTICIPATOR HEAT OFF COOL 10 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. G AUX. HT. RELAY W2 FAN RELAY L2 R L1 1 (HOT) M8000 Fig. 50. Schematic and hookup of T874G with Q674B. Used in heat pump applications. 99 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL H1 1 H1 ANTICIPATOR 3 4 FAN SWITCH AUTO ON W1 G RC 2 HEAT RELAY 1 FAN RELAY L1 (HOT) 1 L2 HEAT RELAY 2 6 FALL H2 H2 ANTICIPATOR C1 RISE RISE 8 9 C1 ANTICIPATOR 10 C2 ANTICIPATOR 11 SYSTEM SWITCH HEAT OFF COOL W2 B 3 RH O 3 Y1 Y2 HEAT CHANGEOVER VALVE COOL CHANGEOVER VALVE COMPRESSOR CONTACTOR 1 COMPRESSOR CONTACTOR 2 C2 1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 FIELD WIRE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER. 3 B, O TERMINALS ON SOME MODELS. L1 L2 (HOT) M5944 Fig. 51. Schematic and hookup of T874D with Q674B. Used in standard applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 FALL H1 ANTICIPATOR 1 4 5 FAN SWITCH AUTO ON W1 HEAT RELAY 1 G RC 3 W3 2 FAN RELAY L1 (HOT) L2 1 6 W2 H2 FALL H2 ANTICIPATOR F SYSTEM SWITCH RH HEAT B OFF 8 COOL C1 RISE 9 O C1 ANTICIPATOR Y1 10 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 OPTIONAL FIELD WIRE JUMPER. W3 AND F TO BE JUMPERED EXCEPT FOR TWO STAGE GAS APPLICATION. 3 FIELD WIRE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER. HEAT RELAY 2 COMPRESSOR CONTACTOR M5999 Fig. 52. Schematic and hookup of T874C with Q674B. Used in standard applications. 60-2485--8 100 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 H1 ANTICIPATOR FALL H1 4 FAN SWITCH AUTO ON HEAT RELAY 1 W1 HEAT RELAY 2 W2 FALL H2 6 H2 ANTICIPATOR 8 RISE C1 9 SYSTEM SWITCH HEAT OFF COOL RISE 10 C1 ANTICIPATOR C2 ANTICIPATOR 11 C2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. R G FAN RELAY Y2 COMPRESSOR CONTACTOR 2 Y1 COMPRESSOR CONTACTOR 1 Fig. 53. Schematic and hookup of T874D with Q674B. Used in standard applications. L1 (HOT) L2 1 M3202A THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL 1 H1 ANTICIPATOR H1 2 H2 ANTICIPATOR FALL 3 H3 4 H3 ANTICIPATOR 5 FALL H2 6 RESET HEATER RISE C1 8 C1 ANTICIPATOR FAN SWITCH AUTO ON SYSTEM SWITCH HEAT OFF COOL 1 R C815A THERMISTOR T L1 (HOT) L2 W1 HEAT RELAY 1 W2 HEAT RELAY 2 W3 HEAT RELAY 3 B HEAT CHANGEOVER VALVE G FAN RELAY RISE 10 C2 ANTICIPATOR 11 C2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. O COOL CHANGEOVER VALVE Y2 COMPRESSOR CONTACTOR 2 Y1 COMPRESSOR CONTACTOR 1 M3674 Fig. 54. Schematic and hookup of T874W with Q674B. Used in standard applications. 101 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 FALL 1 H1 ANTICIPATOR FALL 4 H2 ANTICIPATOR 3 5 6 H2 8 C1 RISE 9 C2 RISE C1 ANTICIPATOR 10 C2 ANTICIPATOR 11 NO FAN SWITCH NO SYSTEM SWITCH RH 3 B HEAT RELAY 1 W1 HEAT RELAY 2 W2 2 COMPRESSOR CONTACTOR 2 Y2 COMPRESSOR CONTACTOR 1 Y1 RC 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 JUMPER RC, RH FOR SINGLE TRANSFORMER. 3 B AND 5 TERMINALS AVAILABLE ON SOME MODELS. L1 (HOT) L2 1 L2 L1 (HOT) M3667A Fig. 55. Schematic and hookup of T874A,D,F with Q674D. Used in standard applications. SUBBASE SYSTEM COMPONENTS 1 FALL H1 H1 ANTICIPATOR 4 H2 ANTICIPATOR 6 FAN SWITCH AUTO ON X RESET LED (RED) G R RESET FAN RELAY AUX. HT. RELAY W2 H2 FALL 8 9 C1 ANTICIPATOR C1 RISE 10 11 SYSTEM SWITCH HEAT OFF COOL 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. B B RELAY O O RELAY Y2 COMPRESSOR CONTACTOR 1 Y1 Fig. 56. Schematic and hookup of T874C with Q674B. Used in standard applications. L1 (HOT) L2 1 M5975 60-2485--8 102 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL H2 1 2 H1 ANTICIPATOR 3 FAN SWITCH AUTO ON Y COMPRESSOR CONTACTOR G FAN RELAY R CLOSED-DAY B RELAY OPEN-NITE 1 B L 4 SYSTEM SWITCH 5 OVERRIDE 6 CO RISE H1 8 HEAT OFF COOL S JUMPER 2 P RISE 9 C1 ANTICIPATOR C1 10 COOL CHANGEOVER VALVE W T 1 POWERSUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 JUMPER HONEYWELL SUPPLIED, FIELD INSTALLED. M8004 L1 (HOT) L2 Fig. 57. Schematic and hookup of T874P with Q674B. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS 2 H1 ANTICIPATOR H1 FALL 3 Y NO FAN SWITCH ECONOMIZER PACKAGE 4 RH Y O O FALL H2 ANTICIPATOR 6 W W2 H2 8 NO SYSTEM SWITCH RISE 9 B C1 ANTICIPATOR CO 10 RC O C1 RISE CONTROL PANEL M3722 Fig. 58. Schematic and hookup of T874G with Q674D. Used in standard applications. 103 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR 1 SYSTEM SWITCH HEAT FALL H1 OFF 4 COOL 8 RISE C1 9 C1 ANTICIPATOR 10 LO MED HIGH ON FAN SWITCH W1 HEAT RELAY 1 B R G1 K1 RELAY G2 K2 RELAY O 1 L2 L1 (HOT) L2 L1 K1 K1 K2 K2 K2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Y1 COMPRESSOR CONTACTOR HI MED LO 3 SPEED FAN SCHEMATIC M3729 Fig. 59. Schematic and hookup of T874A with Q674Q. Used in fan coil applications. THERMOSTAT H1 ANTICIPATOR 1 FALL H1 4 SUBBASE FAN SWITCH AUTO ON SYSTEM COMPONENTS L1 (HOT) L2 1 W1 COOL RELAY CONTACT FAN RELAY G R FALL H2 6 H2 ANTICIPATOR 8 RISE 9 SYSTEM SWITCH EVAP COOL OFF HEAT C1 C1 ANTICIPATOR 10 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. ELEC. HT. RELAY W2 CHANGEOVER VALVE B COMPRESSOR CONTACTOR Y1 EVAPORATOR RELAY Y2 M2863 Fig. 60. Schematic and hookup of T874C with Q674N. Used in evaporative cooler applications. 60-2485--8 104 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL H1 1 H1 ANTICIPATOR 4 FALL H2 ANTICIPATOR 6 H2 RISE 8 C1 9 10 C1 ANTICIPATOR FAN SWITCH AUTO ON SYSTEM SWITCH EVAP. COOL OFF HEAT COMPRESSOR CONTACTOR Y1 FAN RELAY G R ELEC. HT. RELAY W2 EVAPORATOR RELAY Y2 CHANGEOVER RELAY O 1 L1 (HOT) L2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M2862 Fig. 61. Schematic and hookup of T874C with Q674N. Used in evaporative cooler applications. THERMOSTAT FALL H2 1 H2 ANTICIPATOR 4 FALL H1 8 9 H1 ANTICIPATOR 10 SUBBASE FAN SWITCH AUTO ON SYSTEM SWITCH HEAT OFF COOL YELLOW GREEN 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. SYSTEM COMPONENTS FAN RELAY G W2 AUX. HT. RELAY R C WOOD/COAL RELAY W1 COMPRESSOR CONTACTOR X2 EXTERNAL COOLING THERMOSTAT (SUCH AS T87 F) X1 Y R L2 L1 (HOT) 1 M3723A Fig. 62. Schematic and hookup of T874F with Q674B. Used in wood/coal applications. 105 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL H2 H2 ANTICIPATOR FALL H1 NO FAN SWITCH 1 4 NO SYSTEM SWITCH 8 YELLOW GREEN AUX. HT. RELAY W2 R C W1 1 HEAT/COOL SWITCH WOOD/COAL 9 RELAY H1 ANTICIPATOR 10 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M3725 L1 (HOT) L2 Fig. 63. Schematic and hookup of T874F with Q674D. Used in wood/coal applications. THERMOSTAT SUBBASE SYSTEM COMPONENT 1 H1 ANTICIPATOR H1 2 FALL 2 3 4 C1 5 ANTICIPATOR RISE C1 SYSTEM SWITCH HEAT OFF COOL FAN SWITCH LO MED HIGH ON W1 HEAT RELAY 1 B B RELAY R K1 RELAY G1 1 L1 (HOT) L2 L2 L1 G2 O RELAY O K2 RELAY K1 K1 K2 K2 K2 COMPRESSOR CONTACTOR Y1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 SINGLE SETPOINT LEVER AND BIMETAL. HI LO MED 3-SPEED FAN SCHEMATIC M8005 Fig. 64. Schematic and hookup of T874A with Q674Q. Used in fan coil applications. 60-2485--8 106 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 H1 ANTICIPATOR 4 FALL 6 H1 FAN AUTO SWITCH ON W1 NO. 1 HEAT RELAY W2 B HEAT DAMPER RH 8 9 RISE C1 10 C1 ANTICIPATOR 11 SYSTEM SWITCH HEAT OFF COOL RC COOL DAMPER O G FAN RELAY Y2 NO. 1 COMP. RELAY FILTER LED (RED) Y1 X1 SERVICE LED (YELLOW) X2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Fig. 65. Schematic and hookup of T874A with Q674B. Used in standard applications. L1 (HOT) L2 L1 (HOT) L2 1 M5976 THERMOSTAT H1 H2 1 H1 ANTICIPATOR 4 FALL 5 FALL 6 H2 ANTICIPATOR 8 9 10 SUBBASE NO FAN SWITCH NO SYSTEM SWITCH SYSTEM COMPONENTS HEAT RELAY 1 W1 HEAT RELAY 2 W2 RH L1 (HOT) L2 1 L1 RC (HOT) L2 1 Y2 11 Y1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M7011 Fig. 66. Schematic and hookup of T874A,D,F with Q674D. Used in standard applications. 107 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 H1 C1 FALL 2 H1/C1 ANTICIPATOR 3 4 5 FALL H2 6 FAN SWITCH AUTO ON SYSTEM SWITCH HEAT OFF X FAN RELAY G L1 R (HOT) 1 L2 HEAT CHANGEOVER VALVE B W2 AUX. HT. RELAY COOL COMPRESSOR CONTACTOR Y 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M5998 Fig. 67. Schematic and hookup of T874R with Q674B. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS H2 FALL RISE CO C1 1 3 H1 ANTICIPATOR 2 3 4 5 6 H1 8 RISE 9 C1 ANTICIPATOR 10 FAN SWITCH AUTO ON SYSTEM SWITCH OVERRIDE HEAT OFF COOL 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 JUMPER HONEYWELL SUPPLIED, FIELD INSTALLED. 3 H2 MAKE OFFEST 8° F BELOW H1 MAKE. OVERRIDE LED (RED) Y COMPRESSOR CONTACTOR G FAN RELAY C CLOSED-DAY OPEN-NITE R SERVICE LED (RED) B L X L2 L1 (HOT) 1 B RELAY S COMPRESSOR FAULT JUMPER 2 P COOL CHANGEOVER VALVE W T M101A Fig. 68. Schematic and hookup of T874P with Q674B. Used in heat pump applications. 60-2485--8 108 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT RISE 8 C1 FAN SWITCH LO AUTO HI CONT. SUBBASE SYSTEM SWITCH OFF COOL SYSTEM COMPONENTS Z RELAY Z G FAN RELAY R L1 (HOT) 1 L2 9 10 C1 ANTICIPATOR Y 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COOL RELAY M107A Fig. 69. Schematic and hookup of T874V with Q674R. Used in fan coil applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 H1 FALL 4 NO FAN SWITCH SERVICE LED (RED) S COMPRESSOR FAULT H2 FALL H1 FALL 6 W2 SYSTEM SWITCH 8 HEAT COOL R 9 Y 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. AUX. HT. RELAY COMPRESSOR CONTACTOR 1 L2 L1 (HOT) M1402A Fig. 70. Schematic and hookup of T874C with Q674S. Used in heat pump applications. 109 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 H1 ANTICIPATOR H1 FALL 4 FALL H2 6 H2 ANTICIPATOR 8 RISE C1 9 10 C1 ANTICIPATOR FAN SWITCH AUTO ON SYSTEM SWITCH HEAT AUTO COOL CHECK 3 RH HEAT RELAY 1 W1 HEAT RELAY 2 W2 X1 G 2 FAN RELAY Y2 COMPRESSOR CONTACTOR 2 RISE C2 ANTICIPATOR 11 C2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Y1 COMPRESSOR CONTACTOR 1 RC 2 JUMPER RH, RC FOR SINGLE TRANSFORMER. 3 OPTIONAL LED ON SOME MODELS. L1 (HOT) L2 1 L2 L1 (HOT) 1 M932B Fig. 71. Schematic and hookup of T874A-D with Q674A. Used in standard applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR 1 H1 FALL 4 6 FALL H2 ANTICIPATOR H2 8 RISE C1 9 C1 ANTICIPATOR 10 FAN SWITCH AUTO ON SYSTEM SWITCH OFF AUTO C2 ANTICIPATOR 11 C2 RISE 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 JUMPER TERMINALS RC-RH FOR SINGLE SYSTEM TRANSFORMER ONLY. 3 B,O TERMINALS ON SOME MODELS. RH 2 W1 HEAT RELAY 1 W2 HEAT RELAY 2 B 3 HEAT DAMPER O COOL DAMPER G FAN RELAY Y2 COMPRESSOR CONTACTOR 2 Y1 COMPRESSOR 2 CONTACTOR 1 RC L1 (HOT) L2 1 1 L2 L1 (HOT) M5122A Fig. 72. Schematic and hookup of T874D,E,F with Q674C. Used in standard applications. 60-2485--8 110 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL H ANTICIPATOR 2 H1 3 4 SETBACK FALL 6 FAN SWITCH AUTO ON Y1 REVERSING VALVE RELAY Y2 COMPRESSOR CONTACTOR G FAN RELAY RISE RISE 8 9 CO 10 C ANTICIPATOR C1 SYSTEM SWITCH OFF AUTO OPEN-NIGHT CLOSED-DAY R SETBACK RELAY L 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. L2 L1 1 (HOT) M7008 Fig. 73. Schematic and hookup of T874G with Q674C. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL H1 2 H1 ANTICIPATOR 3 4 FAN SWITCH AUTO ON Y1 COOL CHANGEOVER VALVE FAN RELAY G R 8 RISE CO 9 C1 ANTICIPATOR 10 SYSTEM SWITCH OFF AUTO RISE C1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 SERVICE LED ON SELECT MODELS. Y2 COMPRESSOR CONTACTOR B 1 O L1 L2 (HOT) 2 X SERVICE LED (YELLOW) COMPRESSOR FAULT C M3680A Fig. 74. Schematic and hookup of T874H with Q674C. Used in heat pump applications. 111 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR 1 SYSTEM SWITCH OFF AUTO FILTER LED (YELLOW) W1 3 X HEAT RELAY 4 H1 FALL 8 RISE C1 9 C1 ANTICIPATOR 10 11 THERMISTOR 12 FAN SWITCH AUTO ON 2 A SERVICE LED (RED) G R FAN RELAY O MOMENTARY CIRCUIT O Y COMPRESSOR CONTACTOR T EXTERNAL TEMP. READOUT T 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 MOMENTARY POSITION. SPRING RETURN TO "ON" UPON SWITCH RELEASE. 3 FILTER LED ON SELECT MODELS. M5731 Fig. 75. Schematic and hookup of T874A with Q674C. Used in standard applications. 1 L1 (HOT) L2 THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 H1 ANTICIPATOR H1 FALL 4 FAN SWITCH AUTO ON FALL H2 6 H2 ANTICIPATOR 8 C1 RISE 9 SYSTEM SWITCH OFF RISE C2 10 C1 ANTICIPATOR 11 AUTO C2 ANTICIPATOR 2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 3 FILTER LED (YEL) SERVICE LED (RED) 2 FOR T874C, DELETE C2. 3 FILTER LED ON SELECT MODELS. W1 HEAT RELAY 1 W2 HEAT CHANGEOVER VALVE B RH HEAT RELAY 2 L2 L1 1 (HOT) RC COOL CHANGEOVER VALVE O L1 (HOT) L2 1 G Y2 COMPRESSOR CONTACTOR 2 Y1 FAN RELAY COMPRESSOR CONTACTOR 1 X A M7025 Fig. 76. Schematic and hookup of T874A-D with Q674C. Used in standard applications. 60-2485--8 112 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS CO H2 H1 1 FALL 3 FALL 4 FALL 6 H1 ANTICIPATOR FAN SWITCH AUTO ON RISE C1 8 9 C1 ANTICIPATOR 10 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 JUMPER RH AND RC FOR SINGLE TRANSFORMER SYSTEM. SYSTEM SWITCH OFF AUTO RESET LED (RED) X1 FAN RELAY G RH L1 (HOT) 2 L2 1 HEAT CHANGEOVER VALVE W1 HEAT RELAY 2 W3 HEAT RELAY 1 W2 "B" RELAY B RC O COMPRESSOR CONTACTOR Y1 L1 (HOT) L2 1 "O" RELAY M4729 Fig. 77. Schematic and hookup of T874K with Q674C. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 H2 FALL 2 H1 ANTICIPATOR 3 4 FAN SWITCH AUTO ON 5 6 SYSTEM SWITCH CO H1 OVERRIDE RISE C1 RISE 8 9 C1 ANTICIPATOR 10 AUTO OFF 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 JUMPER HONEYWELL SUPPLIED, FIELD INSTALLED. Y COMPRESSOR CONTACTOR G FAN RELAY C R SETBACK CONTACT B HEAT CHANGEOVER VALVE L S JUMPER 2 P REVERSING VALVE W Fig. 78. Schematic and hookup of T874P with Q674C. Used in heat pump applications. L1 (HOT) L2 1 M7026 113 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT 1 H1 ANTICIPATOR H1 FALL 4 6 H2 FALL 3 8 9 CO RISE C1 ANTICIPATOR 10 SUBBASE FAN SWITCH AUTO ON SYSTEM SWITCH OFF AUTO RESET LED (RED) SYSTEM COMPONENTS RESET X G FAN RELAY R1 2 SETBACK CONTACT R2 COOL CHANGEOVER VALVE O COMPRESSOR CONTACTOR Y L1 (HOT) L2 1 C1 RISE 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 SETBACK CONTACT ON Q674C1124. 3 H2 ON T874G. M7027 Fig. 79. Schematic and hookup of T874G,H with Q674C. Used in standard applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL 1 H1 W1 HEAT RELAY 1 CONTACTOR COMPRESSOR 1 H1 ANTICIPATOR FAN SWITCH 4 AUTO ON Y1 G RC FAN RELAY H2 ANTICIPATOR 6 H2 FALL 8 RISE C1 9 C1 ANTICIPATOR 10 C2 ANTICIPATOR C2 11 SYSTEM OFF SWITCH HEAT AUTO COOL 2 W2 RH HEAT RELAY 2 C SERVICE LED (RED) Z COMPRESSOR FAULT COMPRESSOR CONTACTOR 2 Y2 RISE 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 OPTIONAL FIELDWIRE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER. M5997 Fig. 80. Schematic and hookup of T874D with Q674E. Used in standard applications. L1 (HOT) L2 1 60-2485--8 114 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL H1 1 CHANGEOVER RELAY W1 4 FALL H2 ANTICIPATOR 6 H2 8 RISE C1 9 FAN SWITCH AUTO ON SYSTEM SWITCH OFF C1 ANTICIPATOR 10 AUTO 1 POWER SUPPLY. PROVIDE DISCONECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. B FAN RELAY G R W2 COMPRESSOR CONTACTOR Y1 1 L1 L2 (HOT) M5981 Fig. 81. Schematic and hookup of T874C with Q674C. Used in heat pump applications. THERMOSTAT FALL H1 1 H1 ANTICIPATOR 4 H2 ANTICIPATOR SUBBASE FAN SWITCH AUTO ON SYSTEM COMPONENTS RH HEAT RELAY 1 W1 L1 (HOT) L2 1 2 HEAT RELAY 2 W2 FALL 6 H2 8 RISE C1 9 C1 ANTICIPATOR 10 C2 ANTICIPATOR 11 SYSTEM SWITCH OFF HEAT AUTO COOL 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION C2 AS REQUIRED. RISE 2 JUMPER RC, RH FOR SINGLE TRANSFORMER. 3 O AND B TERMINALS ON SELECTED MODELS. O 3 B FAN RELAY G COMPRESSOR CONTACTOR 2 Y2 COMPRESSOR CONTACTOR 1 Y1 RC L2 1 L1 (HOT) M934 Fig. 82. Schematic and hookup of T874A,C,D with Q674E. Used in standard applications. 115 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS L1 (HOT) 1 L2 H1 ANTICIPATOR 1 FALL H1 4 H2 ANTICIPATOR FALL H2 6 FAN SWITCH AUTO ON HEAT RELAY 1 W1 COMPRESSOR CONTACTOR 1 Y1 FAN RELAY G RC HEAT RELAY 2 W2 8 RISE RH C1 OFF 9 HEAT C1 ANTICIPATOR 10 AUTO COOL CHECK LED (RED) X1 Y2 COMPRESSOR CONTACTOR 2 C2 ANTICIPATOR 11 RISE C2 1 POWER SUPPLY. PROVIDE DISCONECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. L2 1 L1 (HOT) M5982 Fig. 83. Schematic and hookup of T874G with Q674C. Used in standard applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 H1 ANTICIPATOR 2 H1 FALL 4 FAN SWITCH AUTO ON H2 ANTICIPATOR 6 FALL H2 CO RISE 8 C1 ANTICIPATOR 9 SYSTEM SWITCH OFF HEAT RISE C1 AUTO 10 COOL 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. R COOL CHANGEOVER VALVE OUTDOOR FAN RELAY DEFROST SWITCH DEFROST RELAY M HIGH PRESSURE SWITCH COMPRESSOR CONTACTOR F DEFROST RELAY FAN RELAY V DEFROST AUX. HT. RELAY RELAY Y L2 1 L1 (HOT) M4666 Fig. 84. Schematic and hookup of T874G with Q674E. Used in heat pump applications. 60-2485--8 116 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 1 H1 ANTICIPATOR FALL 4 6 FALL H2 ANTICIPATOR H2 8 RISE C1 9 RISE C1 ANTICIPATOR 10 C2 ANTICIPATOR 11 FAN SWITCH AUTO ON SYSTEM SWITCH OFF HEAT AUTO COOL W1 COMPRESSOR CONTACTOR 1 Y1 G R HEAT RELAY 1 FAN RELAY L1 (HOT) L2 1 HEAT RELAY 2 W2 COMPRESSOR CONTACTOR 2 Y2 C2 1 POWER SUPPLY. PROVIDE DISCONECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M5983 Fig. 85. Schematic and hookup of T874A-D with Q674E. Used in standard applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR 1 2 FALL H1 3 FAN SWITCH AUTO ON 5 H2 FALL 6 H2 ANTICIPATOR RISE CO C1 8 SYSTEM SWITCH C1 ANTICIPATOR 9 OFF HEAT AUTO 10 COOL RISE 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. L1 (HOT) 1 L2 R COOL CHANGEOVER VALVE D. F. O. DEFROST SWITCH DEFROST RELAY M HIGH PRESSURE SWITCH F COMPRESSOR CONTACTOR FAN RELAY V DEFROST RELAY CONTACT Y DEFROST RELAY CONTACT VR AUX. HT. RELAY 1 L2 L1 M4667 (HOT) Fig. 86. Schematic and hookup of T874G with Q674E. Used in heat pump applications. 117 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 H1 FALL H1 ANTICIPATOR 4 H2 ANTICIPATOR FALL H2 6 RISE 8 C1 RISE C2 9 C1 ANTICIPATOR 10 C2 ANTICIPATOR 11 FAN SWITCH AUTO ON W1 HEAT RELAY 1 Y1 COMPRESSOR CONTACTOR 1 G FAN RELAY RC L1 (HOT) 1 L2 SYSTEM SWITCH W2 B 2 HEAT RELAY 2 OFF HEAT AUTO COOL RH X C LOCKOUT LED (RED) Y2 SYSTEM FAULT CONTACT L2 1 L1 (HOT) COMPRESSOR CONTACTOR 2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 FIELDWIRE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER. M4668 Fig. 87. Schematic and hookup of T874D with Q674E. Used in standard applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 FAN H1 SWITCH ANTICIPATOR H1 FALL AUTO 4 ON FALL H2 ANTICIPATOR 6 H2 RISE 8 C1 RISE C2 9 C1 ANTICIPATOR 10 C2 ANTICIPATOR 11 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. SYSTEM SWITCH OFF HEAT AUTO COOL W1 HEAT RELAY 1 G FAN RELAY RC 1 L1 (HOT) L2 W2 HEAT RELAY 2 RH X HIGH LED (RED) L2 1 L1 (HOT) Y2 LOW LED (GREEN) Y1 COMPRESSOR CONTACTOR 2 COMPRESSOR CONTACTOR 1 Fig. 88. Schematic and hookup of T874B,D with Q674E. Used in standard applications. M4669 60-2485--8 118 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 H1 ANTICIPATOR FALL H1 4 AUTO FAN SWITCH ON B HEAT RELAY 1 HEAT CHANGEOVER VALVE W1 COMPRESSOR CONTACTOR 1 Y1 FAN RELAY 6 G H2 ANTICIPATOR H2 FALL 8 C1 RISE 9 10 C1 ANTICIPATOR SYSTEM SWITCH OFF HEAT AUTO COOL FILTER LED (YEL) SERVICE LED (RED) RC HEAT RELAY 2 W2 RH X A L1 (HOT) L2 1 L1 (HOT) L2 1 COMPRESSOR CONTACTOR 2 11 Y2 C2 ANTICIPATOR C2 RISE COOL CHANGEOVER VALVE O 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M7023 Fig. 89. Schematic and hookup of T874D with Q674E. Used in standard applications. THERMOSTAT 1 H1 ANTICIPATOR SUBBASE FILTER LED (YEL) SERVICE LED (RED) H1 H2 FALL 4 5 6 FALL H2 ANTICIPATOR 7 8 C1 RISE 9 NO FAN SWITCH SYSTEM SWITCH OFF AUTO 10 C1 ANTICIPATOR 11 C2 ANTICIPATOR C2 RISE 12 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. FILTER LED (YEL) SERVICE LED (RED) SYSTEM COMPONENTS X2 A2 HEAT RELAY 1 W1 X1 A1 W2 T RELAY T HEAT RELAY 2 RC HEAT CHANGEOVER VALVE B RH COOL CHANGEOVER VALVE O Y2 COMPRESSOR CONTACTOR 1 Y1 L1 (HOT) L2 1 L1 (HOT) L2 1 COMPRESSOR CONTACTOR 2 M7022 Fig. 90. Schematic and hookup of T874D with Q674G. Used in standard applications. 119 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 H1 ANTICIPATOR FALL H1 4 FALL H2 6 H2 ANTICIPATOR 8 RISE C1 9 NO FAN SWITCH SYSTEM SWITCH OFF AUTO RISE 10 C1 ANTICIPATOR C2 ANTICIPATOR 11 C2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 JUMPER RH, RC FOR SINGLE TRANSFORMER. RH HEAT RELAY 1 W1 HEAT RELAY 2 W2 B HEAT DAMPER O 2 COOL DAMPER Y2 COMPRESSOR CONTACTOR 2 Y1 COMPRESSOR CONTACTOR 1 RC L1 (HOT) L2 1 L2 L1 (HOT) 1 M3201B Fig. 91. Schematic and hookup of T874A-F,Q with Q674G. Used in standard applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR 1 3 FALL H1 4 H2 ANTICIPATOR 6 FALL H2 8 C1 RISE 9 C1 ANTICIPATOR 10 NO FAN SWITCH SYSTEM SWITCH OFF AUTO W1 CHANGEOVER RELAY B W2 FAN RELAY G Y1 COMPRESSOR CONTACTOR R 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 1 L2 L1 (HOT) M6008A Fig. 92. Schematic and hookup of T874C with Q674G. Used in heat pump applications. 60-2485--8 120 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL H1 1 H1 ANTICIPATOR 4 6 NO FAN SWITCH HEAT FAN RELAY W1 HEAT RELAY W2 H2 H2 FALL ANTICIPATOR SYSTEM RH SWITCH 8 OFF RISE C1 HEAT AUTO Y1 9 COOL C1 ANTICIPATOR 10 RC C2 ANTICIPATOR RISE 11 Y2 C2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. L1 (HOT) L2 1 COMPRESSOR CONTACTOR 1 L1 (HOT) L2 1 COMPRESSOR CONTACTOR 2 M4664 Fig. 93. Schematic and hookup of T874D with Q674K. Used in standard applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 H1 ANTICIPATOR NO FAN SWITCH FALL H1 4 6 H2 ANTICIPATOR H2 FALL 8 C1 RISE 9 10 C1 ANTICIPATOR SYSTEM SWITCH OFF AUTO 11 C2 RISE C2 ANTICIPATOR 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. B HEAT CHANGEOVER VALVE W1 HEAT RELAY 2 W2 RH RC FILTER LED (YELLOW) HEAT RELAY 1 L2 1 L1 (HOT) L1 (HOT) L2 1 X A SERVICE LED (RED) Y1 COMPRESSOR CONTACTOR 2 Y2 COMPRESSOR CONTACTOR 1 COOL CHANGEOVER VALVE O "T" RELAY T M7013 Fig. 94. Schematic and hookup of T874D with Q674G. Used in standard applications. 121 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTATS SUBBASE SYSTEM COMPONENTS 1 FALL H1 ANTICIPATOR 2 H1 3 4 FALL 5 H2 H2 ANTICIPATOR 6 NO FAN SWITCH SYSTEM SWITCH OFF WOOD WOOD/OIL OIL L1 R (HOT) L2 1 W2 OIL LED (RED) X WOOD LED (GREEN) W1 OIL RELAY WOOD RELAY 1 POWER SUPPLY. PROVIDE DISCONECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M5984 Fig. 95. Schematic and hookup of T874F with Q674K. Used in wood/oil applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 FALL 1 FAN SWITCH AUTO ON 4 W1 NO. 1 HEAT RELAY W2 HEAT NO. 2 DAMPER HEAT RELAY B FALL H2 C1 RISE 6 H2 ANTICIPATOR 8 9 10 C1 ANTICIPATOR 11 SYSTEM SWITCH OFF AUTO 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. ON LED (YELLOW) SERVICE LED (RED) L2 RH L1 (HOT) 1 RC O FAN RELAY COOL DAMPER G NO. 1 COMPRESSOR Y2 CONTACTOR Y1 X L2 A L1 (HOT) C M104A Fig. 96. Schematic and hookup of T874C with Q674C. Used in standard applications. 60-2485--8 122 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL 1 3 H2 2 H1 ANTICIPATOR 3 4 5 RISE 6 CO H1 8 C1 RISE 9 FAN SWITCH AUTO ON SYSTEM SWITCH OVERRIDE AUTO OFF OVERRIDE LED (RED) Y COMPRESSOR CONTACTOR G C CLOSED-DAY OPEN-NITE FAN RELAY L2 R SERVICE LED (RED) B B RELAY L L1 (HOT) 1 X COMPRESSURE FAILURE S JUMPER 2 10 C1 ANTICIPATOR 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. P W COOL CHANGEOVER VALVE 2 JUMPER HONEYWELL SUPPLIED, FIELD INSTALLED. 3 H2 MAKE OFFEST 8° F BELOW H1 MAKE. M100A Fig. 97. Schematic and hookup of T874P with Q674C. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 H1 ANTICIPATOR H1 FALL 4 FALL H2 6 H2 ANTICIPATOR 8 C1 RISE RISE C2 9 10 C1 ANTICIPATOR 11 FAN SWITCH AUTO ON SYSTEM SWITCH OFF HEAT AUTO COOL SERVICE LED (RED) A W1 HEAT RELAY 1 W2 CHANGEOVER RELAY B RH SYSTEM MONITOR HEAT RELAY 2 L2 L1 1 (HOT) RC CHANGEOVER RELAY O L1 (HOT) L2 1 G Y2 COMPRESSOR CONTACTOR 2 Y1 FAN RELAY COMPRESSOR CONTACTOR 1 C2 ANTICIPATOR 2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 T874A IS SINGLE-STAGE (NO W2 OR Y2). M5106A Fig. 98. Schematic and hookup of T874D with Q674E. Used in standard applications. 123 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR 1 W1 HEAT RELAY 1 3 2 FALL 4 H1 OFF AUTO SYSTEM SWITCH HEAT RELAY 2 W2 5 W3 6 4 H2 ANTICIPATOR FALL H2 7 C1 RISE 3 8 9 C1 ANTICIPATOR 10 FAN SWITCH AUTO ON 2 5 THERMISTER 11 12 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 MOMENTARY POSITION. SPRING RETURN TO "ON" UPON SWITCH RELEASE. Y2 SERVICE LED (RED) A G FAN RELAY R MOMENTARY O CIRCUIT COMPRESSOR RELAY Y1 T EXTERNAL TEMP. T READOUT L2 L1 (HOT) 1 4 H3 OFFSET 12°F FROM H2 FOR NIGHT SETBACK. 5 THERMISTOR INTERNAL TO THERMOSTAT. M531 3 H1 AND C1 ARE DPST SWITCHES. Fig. 99. Schematic and hookup of T874C with Q674C. Used in standard applications. 60-2485--8 124 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR 1 3 2 FALL 4 H1 5 FALL H3 4 H2 ANTICIPATOR 6 H2 FALL 3 C1 RISE C2 ANTICIPATOR 7 8 9 C2 RISE 10 C2 ANTICIPATOR OFF AUTO FAN SWITCH AUTO ON 2 SYSTEM SWITCH W1 HEAT RELAY 1 SERVICE LED (RED) W2 HEAT RELAY 3 W3 HEAT RELAY 2 Y2 COMPRESSOR CONTACTOR 2 A G FAN RELAY R MOMENTARY O CIRCUIT COMPRESSOR RELAY Y1 L2 L1 (HOT) 1 5 THERMISTER 11 12 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 MOMENTARY POSITION. SPRING RETURN TO "ON" UPON SWITCH RELEASE. 3 H1 AND C1 ARE DPST SWITCHES. T EXTERNAL TEMP. T READOUT 4 H3 OFFSET 12°F FROM H2 FOR NIGHT SETBACK. 5 THERMISTOR INTERNAL TO THERMOSTAT. M532 Fig. 100. Schematic and hookup of T874W with Q674C. Used in standard applications. THERMOSTAT SUBBASE 2 H1/C1 H1 ANTICIPATOR C1 FALL 3 4 5 H2 FALL 6 H2 ANTICIPATOR 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. AUTO ON FAN SWITCH SYSTEM SWITCH EM. HT. HEAT OFF COOL SYSTEM COMPONENTS COOL CHANGEOVER VALVE O G FAN RELAY R W X EM. HT. LED (RED) B AUX. HT. RELAY L1 (HOT) L2 1 COMPRESSOR CONTACTOR M3718A Y Fig. 101. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 125 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE FALL 1 H1/C1 ANTICIPATOR 2 H1 C1 3 4 5 FALL H2 6 H2 ANTICIPATOR 7 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 FIELD WIRE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER. FAN SWITCH AUTO ON SYSTEM SWITCH EM. HT. HEAT OFF COOL SYSTEM COMPONENTS COMPRESSOR OVERLOAD CONTACTOR SWITCH HIGH INTERNAL PRESSURE THERMOSTAT SWITCH M F V Y 2 E EM. HT. LED (RED) X VR R FAN RELAY OUTDOOR THERMOSTAT SUPPL. ELEC. HT. RELAY EM. HT. RELAY CONTACT TIME DELAY FAN RELAY EM. HT. RELAY COOL CHANGEOVER VALVE L1 L2 (HOT) 1 L1 L2 1 (HOT) M4726 Fig. 102. Schematic and hookup of T874J,R with Q674L. Used in heat pump applications. 60-2485--8 126 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT 1 H1 ANTICIPATOR 2 H1 FALL 4 SUBBASE FAN SWITCH AUTO ON SYSTEM COMPONENTS COOL CHANGEOVER VALVE O 1 L1 (HOT) L2 G R FAN RELAY OUTDOOR THERMOSTAT W2 HEAT RELAY 1 FALL H2 6 H2 ANTICIPATOR RISE CO C1 RISE 8 9 C1 ANTICIPATOR 10 SYSTEM SWITCH SUPL. HT. HEAT OFF COOL E 2 L SUPL. HT. LED (RED) C Y HEAT RELAY HEAT RELAY 2 CONTACT 1 HEAT RELAY HEAT RELAY 3 CONTACT 2 COMPRESSOR FAULT COMPRESSOR CONTACTOR 1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS 2 N.O. SWITCH INSTALLER ADDED, TO LIGHT SUPL. HT. LED AND OVERLOAD PROTECTION AS REQUIRED. WHEN COMPRESSOR OPERATION IS NOT NORMAL. M4665 Fig. 103. Schematic and hookup of T874G with Q674L. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 C1 FALL 2 H1/C1 ANTICIPATOR 3 4 5 H2 ANTICIPATOR 6 FALL H2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 OPTIONAL FIELD WIRE JUMPER TO CYCLE AUXILIARY HEAT RELAY H1 INSTEAD OF H2 (FASTER RESPONSE). FAN SWITCH AUTO ON SYSTEM SWITCH EM. HT. HEAT OFF COOL E EM. HT. LED (RED) X B R W2 2 H Y G O EM. HT. RELAY "B" RELAY AUX. HT. RELAY COMPRESSOR CONTACTOR L1 (HOT) L2 1 YR COM G R8233B W ELEC. HT. RELAY O EH M4728 Fig. 104. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 127 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 H1 ANTICIPATOR 2 H1 FALL FAN SWITCH AUTO ON FAN RELAY G HEAT RELAY 2 W2 K 4 L 6 FALL H2 ANTICIPATOR H2 8 RISE C1 C1 ANTICIPATOR 10 SYSTEM SWITCH EM. HT. HEAT OFF COOL EM. HT. LED (RED) SYSTEM MONITOR SWITCH C R RHI Y W1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 1 EM. HT. RELAY IHRI COMPRESSOR CONTRACTOR HEAT RELAY 1 L1 L2 (HOT) M8384 Fig. 105. Schematic and hookup of T874C with Q674L. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL H1 C1 2 H1/C1 ANTICIPATOR 3 4 5 6 H2 FALL H2 ANTICIPATOR 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. FAN SWITCH AUTO ON SYSTEM SWITCH EM. HT. HEAT OFF COOL EM. HT. LED (RED) COOL CHANGEOVER VALVE O FAN RELAY G R L1 (HOT) L2 1 AUX. HT. RELAY W2 X Y EM. HT. RELAY E COMPRESSOR CONTACTOR M4724 Fig. 106. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 60-2485--8 128 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT H1 FALL 2 H1 ANTICIPATOR 3 4 H2 ANTICIPATOR 5 H2 FALL 8 C1 RISE C1 ANTICIPATOR 10 C2 ANTICIPATOR 11 C2 RISE SUBBASE FAN SWITCH AUTO ON SYSTEM COMPONENTS COOL CHANGEOVER VALVE O FAN RELAY G OUTDOOR THERMSTAT SUPPL. HT. RELAY SYSTEM SWITCH EM. HT. HEAT OFF COOL Y1 EM. HT. RELAY CONTACT COMPRESSOR CONTACTOR 2 E L EM. HT. LED (RED) C EM. HT. RELAY COMP. FAILURE L1 R (HOT) 1 L2 Y 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COMPRESSOR CONTACTOR 1 Fig. 107. Schematic and hookup of T874D with Q674L. Used in heat pump applications. M4727 THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 C1 FALL H1/C1 ANTICIPATOR 2 3 4 FALL 5 H2 6 H2 ANTICIPATOR 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. FAN SWITCH AUTO ON SYSTEM SWITCH EM. HT. HEAT OFF COOL R L1 (HOT) L2 1 FAN RELAY G AUX. HT. RELAY W AUX. HT. LED (YELLOW) B EM. HT. LED (RED) X COOL CHANGEOVER VALVE O COMPRESSOR CONTACTOR Y M4725 Fig. 108. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 129 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT 1 SUBBASE SYSTEM COMPONENTS AUX. HT. RELAY W H1 C1 FALL 2 H1/ C1 ANTICIPATOR 3 4 5 RESET HEATER FAN SWITCH AUTO ON AUX. HT. LED (GREEN) B EM. HT. LED (RED) F G COMPRESSOR FAILURE R FAN RELAY L1 (HOT) L2 1 H2 FALL 6 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. SYSTEM SWITCH EM. HT. HEAT OFF COOL X2 OUTDOOR THERMOSTAT T COOL CHANGEOVER VALVE OUTDOOR THERMISTOR O COMPRESSOR CONTACTOR Y M5071 Fig. 109. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 60-2485--8 130 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS RESET 1 H1 FALL 2 H1 ANTICIPATOR 3 4 5 H2 FALL 6 H2 ANTICIPATOR 7 C1 RISE 8 C1 ANTICIPATOR 10 FAN SWITCH AUTO ON SYSTEM SWITCH EM. HT. HEAT OFF COOL V 2 VR COMPRESSOR CONTACTOR L1 (HOT) L2 1 INTERNAL THERMOSTAT M FAN RELAY OVERLOAD SWITCH HI PRESSURE SWITCH F SERVICE SERVICE L LED (RED) OUTDOOR THERMOSTAT SUPL. ELEC. HT. RELAY S 3 Y EM. HT. RELAY CONTACT TIME DELAY FAN RELAY ELEC. HT. RELAY E EM. HT. LED (YELLOW) X C815A OUTDOOR THERMISTOR A COOL CHANGEOVER VALVE R 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 REMOVE FACTORY INSTALLED V-VR JUMPER WHEN CONNECTING A TWO TRANSFORMER SYSTEM. 3 REMOVE FACTORY-INSTALLED S-Y JUMPER TO DISABLE SERVICE LIGHT. Fig. 110. Schematic and hookup of T87C,R with Q674L. Used in heat pump applications. M2854 131 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT H1 C1 FALL 1 RESET HEATER 2 H1/ C1 ANTICIPATOR 3 4 5 SUBBASE FAN SWITCH AUTO ON SYSTEM COMPONENTS V 2 VR 1 L1 (HOT) L2 COMPRESSOR CONTACTOR INTERNAL THERMOSTAT M OVERLOAD SWITCH HIGH PRESSURE SWITCH F FAN RELAY SERVICE L SERVICE LED (RED) OUTDOOR THERMOSTAT EM. HT. RELAY 6 7 H2 FALL H2 ANTICIPATOR SYSTEM SWITCH EM. HT. HEAT OFF COOL Y E EM. HT. LED (YELLOW) X A R EM. HT. RELAY EM. HT. RELAY SUPPL. ELEC. HT. RELAY C815A OUTDOOR THERMISTOR COOL CHANGEOVER VALVE 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 REMOVE FACTORY INSTALLED V-VR JUMPER WHEN CONNECTING A TWO TRANSFORMER SYSTEM. M2851 Fig. 111. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 60-2485--8 132 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL H1 C1 2 H1/C1 ANTICIPATOR 3 4 5 H2 ANTICIPATOR 6 H2 FALL 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. FAN SWITCH AUTO ON SYSTEM SWITCH EM. HT. HEAT OFF COOL O G R COMPRESSOR FAILURE L1 COOL CHANGEOVER VALVE FAN RELAY L1 (HOT) L2 1 EM. HT. LED (RED) X AUX. HT. LED (GREEN) AUX. HT. RELAY W2 COMPRESSOR CONTACTOR Y EM. HT. RELAY E M8383 Fig. 112. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 133 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1/C1 ANTICIPATOR 1 2 H1 C1 3 FALL 4 H2 FALL 5 H2 ANTICIPATOR 6 7 FAN SWITCH AUTO ON SYSTEM SWITCH EM. HT. HEAT OFF COOL 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. R HEAT EM. HT. RELAY CONTRACTOR 3 L1 (HOT) L2 1 EM. HT. RELAY W3 OUTDOOR THERMOSTAT HEAT CONTRACTOR 2 DEFROST RELAY HEAT HIGH LIMIT W2 CONTRACTOR 1 SWITCH B CHECK LED (GREEN) L X2 X1 EM. HT. LED (RED) E G Y LOW AMBIENT CUTOFF O DEFROST RELAY REVERSING VALVE OPTIONAL COMP. FAILURE DEVICE EM. HT. RELAY FAN RELAY COMPRESSOR CONTACTOR HIGH PRESSURE SWITCH COOL CHANGEOVER VALVE M4720 Fig. 113. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 60-2485--8 134 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS RESET HEATER 1 H1 ANTICIPATOR 2 3 H1 FALL 4 5 H2 FALL 6 H2 ANTICIPATOR 7 RISE C1 8 C1 ANTICIPATOR 10 RISE C2 C2 ANTICIPATOR 11 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. FAN SWITCH AUTO ON M2 OUTDOOR THERMOSTAT M FAN RELAY F HIGH SPEED COMPRESSOR CONTACTOR LOW SPEED COMPRESSOR CONTACTOR V R 2 L L1 (HOT) L2 1 COOL CHANGEOVER SERVICE VALVE SYSTEM SWITCH EM. HT. HEAT OFF COOL X EM. HT. LED (YELLOW) E OUTDOOR THERMOSTAT VR SERVICE LED (RED) Y EM. HT. RELAY C815A OUTDOOR THERMISTOR A EM. HT. RELAY SUPPL. ELEC. HT. RELAY SUPPL. ELEC. HT. RELAY 2 REMOVE FACTORY INSTALLED V-VR JUMPER WHEN CONNECTING A TWO TRANSFORMER SYSTEM. M2853 Fig. 114. Schematic and hookup of T874D with Q674L. Used in heat pump applications. 135 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT FALL H1/C1 ANTICIPATOR 2 SUBBASE SYSTEM COMPONENTS (HOT) L1 L2 1 R ODT 1 H1 C1 3 4 H2 ANTICIPATOR 5 H2 6 FALL FAN SWITCH AUTO ON SYSTEM SWITCH EM. HT. HEAT OFF COOL W3 W2 AUX. HT. LED (GREEN) 2 X EM. HT. LED (RED) L G O E Y B 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 AUXILIARY HEAT LED AVAILABLE ON SOME MODELS. RTD 1 EHR 1 ODT 2 EHR 2 RTD 2 RTD 3 RTD 1 SYSTEM MONITOR RD FAN RELAY COOL CHANGEOVER VALVE EM. HT. RELAY LACO CHP COMPRESSOR CONTACTOR M5072A Fig. 115. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 60-2485--8 136 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 C1 FALL 2 H1/C1 ANTICIPATOR 3 4 5 H2 ANTICIPATOR 6 FAN SWITCH AUTO ON SYSTEM SWITCH E X EM. HT. LED (RED) B R W2 2 H EM. HT. RELAY AUX. HT. RELAY COMPRESSOR CONTACTOR H2 FALL 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 OPTIONAL FIELD WIRE JUMPER TO CYCLE AUXILIARY HEAT RELAY WITH H1 INSTEAD OF H2 (FASTER RESPONSE). EM. HT. HEAT OFF COOL A COMP. FAULT LED (YELLOW) Y G O L1 (HOT) L2 1 YR COM G R8233B W ELEC. HT. RELAY O EH M2857 Fig. 116. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 137 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 2 FALL H1 H1 ANTICIPATOR 3 4 FAN SWITCH AUTO ON R ENTHALPY CONTROL RELAY B HEAT RELAY CONTACT 1 G ECONOMIZER RELAY DEFROST RELAY L1 (HOT) L2 1 DEFROST SWITCH MOTOR 3 OUTDOOR FAN RELAY 1 H2 ANTICIPATOR 5 FALL H2 6 8 C1 RISE ENTHALPY CONTROL 2 ENTHALPY CONTROL RELAY 2 DEFROST SWITCH RELAY TM1 TM2 LOW AMBIENT THERMOSTAT 1 OUTDOOR FAN RELAY 2 1ST STAGE LOW PRESSURE LIMIT OUTDOOR FAN RELAY 3 1ST STAGE Y1 ENTHALPY SHORT CYCLE CONTROL MOTOR 1 CONTROL RELAY 1 TIME DELAY HEATER C1 ANTICIPATOR 10 TIME DELAY Y2 2ND STAGE SHORT CYCLE 2ND STAGE LOW CONTROL PRESSURE LIMIT MOTOR 2 C2 ANTICIPATOR 11 C2 RISE SYSTEM SWITCH EM. HT. HEAT OFF COOL W LED (GREEN) X L SERVICE LED (RED) SERVICE DEFROST RELAY OUTDOOR THERMOSTAT DEFROST RELAY HEAT RELAY 1 O 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COOL CHANGEOVER VALVE M7755 2 OPTIONAL ECONOMIZER HOOKUP (DOTTED LINES). Fig. 117. Schematic and hookup of T874D with Q674L. Used in heat pump applications. 60-2485--8 138 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 H1 FALL 2 H2 FALL H1 ANTICIPATOR H2 ANTICIPATOR 3 4 H3 ANTICIPATOR 5 FALL H3 6 8 C1 RISE 9 C1 ANTICIPATOR C2 ANTICIPATOR 10 C2 RISE FAN SWITCH AUTO ON SYSTEM SWITCH EM. HT. HEAT OFF COOL 11 RESET HEATER 12 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 OPTIONAL ECONOMIZER HOOKUP (DOTTED LINES). R ECONOMIZER RELAY B HEAT RELAY CONTACT 1 G ENTHALPY CONTROL 2 DEFROST RELAY L1 (HOT) L2 1 ECONOMIZER RELAY DEFROST SWITCH MOTOR 3 OUTDOOR FAN RELAY 1 DEFROST RELAY DEFROST SWITCH RELAY TM1 TM2 OUTDOOR THERMOSTAT 1 ECONOMIZER RELAY 2 OUTDOOR FAN RELAY 2 1ST STAGE LOW PRESSURE LIMIT OUTDOOR FAN RELAY 3 1ST STAGE Y1 ECONOMISER SHORT CYCLE CONTROL MOTOR 1 RELAY 1 TIME DELAY HEATER TIME DELAY RELAY Y2 2ND STAGE DEFROST RELAY 2ND STAGE LOW PRESSURE LIMIT SHORT CYCLE CONTROL MOTOR 2 W AUX. HEAT LED (GREEN) O DEFROST RELAY CONTACT AUXILIARY HEAT RELAY DEFROST RELAY CONTACT COOL CHANGEOVER VALVE X EM. HEAT LED (RED) E A C815 OUTDOOR THERMISTOR EMERGENCY HEAT RELAY M7756 Fig. 118. Schematic and hookup of T874W with Q674L. Used in heat pump applications. 139 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT RESET HEATER 1 SUBBASE SYSTEM COMPONENTS L1 L2 (HOT) 1 C815A OUTDOOR THERMISTOR T H2 ANTICIPATOR 2 3 FAN SWITCH AUTO ON W2 AUX. HT. RELAY G FAN RELAY R H1 C1 FALL 4 5 C1 ANTICIPATOR 6 11 SYSTEM SWITCH EM. HT. HEAT OFF COOL X SERVICE LED (YELLOW) Z SERVICE EM. HT. LED (RED) EM. HT. RELAY K COMPRESSOR CONTACTOR Y H2 12 W1 FALL H1 ANTICIPATOR 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. HEAT CHANGEOVER RELAY M5955 Fig. 119. Schematic and hookup of T874R with Q674L. Used in heat pump applications. THERMOSTAT SUBBASE 2 FALL H1/C1 H1 C1 ANTICIPATOR 3 4 5 FAN SWITCH AUTO ON FALL H2 6 H2 ANTICIPATOR SYSTEM SWITCH EM. HT. HEAT OFF EM. HT. LED (RED) COOL 11 RESET HEATER 12 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. SYSTEM COMPONENTS L1 L2 (HOT) FAN RELAY 1 G R AUX. HT. RELAY W H "H" RELAY B X EM. HT. RELAY T C815A1039 THERMISTOR O CHANGEOVER VALVE (COOL) Y COMPRESSOR CONTACTOR M3173B Fig. 120. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 60-2485--8 140 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT 2 H1 ANTICIPATOR 3 H1 FALL 4 5 H2 ANTICIPATOR 6 SUBBASE FAN SWITCH AUTO ON SYSTEM COMPONENTS R COMPRESSOR FAILURE ODT1 L1 (HOT) L2 1 EHR1 RTD2 L EM. HT. LED (RED) RTD1 X ODT2 EHR2 RTD3 H2 FALL 8 C1 ANTICIPATOR 10 C1 RISE SYSTEM SWITCH EM. HT. HEAT OFF COOL 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. AUX. HT. LED (GRN) W2 RD G O E LACO Y RTD1 FAN RELAY COOL CHANGEOVER VALVE EM. HT. RELAY COMPRESSOR CONTACTOR CHP HEAT CHANGEOVER VALVE B M7012 Fig. 121. Schematic and hookup of T874C with Q674L. Used in heat pump applications. 141 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 2 FALL H1 C1 H1/C1 ANTICIPATOR 3 FAN SWITCH AUTO ON FAN RELAY G L2 1 R L1 (HOT) W2 AUX. HT. RELAY 4 FALL H2 5 H2 ANTICIPATOR 6 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. SYSTEM SWITCH EM. HT. HEAT OFF COOL K L EM. HT. LED (YELLOW) C SERVICE LED (RED) Y W1 Z SERVICE EM. HT. RELAY CO COMPRESSOR CONTACTOR CHANGEOVER VALVE M8379 Fig. 122. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 60-2485--8 142 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 C1 FALL 2 H1/C1 ANTICIAPTOR 3 4 5 H2 FALL H2 ANTICIPATOR 6 FAN SWITCH AUTO ON 8 10 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 CONNECT CHANGEOVER RELAY TO B FOR HEAT CHANGEOVER, TO O FOR COOL CHANGEOVER. SYSTEM SWITCH EM. HT. HEAT OFF COOL RTD 1 ODT 1 EHR 1 ODT 2 RTD 2 L1 L2 (HOT) 1 EHR 2 RTD 3 R L EM. HT. LED (RED) X AUX. HT. LED (GREEN) W2 COMPRESSOR MONITOR RTD 1 G O E LACO Y B RD FAN RELAY 2 COOL CHANGEOVER VALVE EM. HT. RELAY CHP COMPRESSOR 2 CONTACTOR HEAT CHANGEOVER VALVE M1030A Fig. 123. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 143 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS L1 L2 (HOT) 1 FALL H1 FALL 2 3 H1 ANTICIPATOR 4 H2 ANTICIPATOR 5 FAN SWITCH AUTO ON R Y G 2 W2 EM. HT. OR SUPL. HT. LED (RED) COMPRESSOR CONTACTOR FAN RELAY HEAT RELAY 1 OUTDOOR THERMOSTAT H2 6 RISE CO 8 9 C1 ANTICIPATOR 10 RISE C1 CO 11 12 SYSTEM SWITCH EM. HT. OR SUPL. HT. HEAT OFF COOL L HEAT RELAY HEAT RELAY 2 2 CONTACT 1 C HEAT RELAY CONTACT 2 HEAT RELAY 3 E X "P" RELAY "X" RELAY P O COOL CHANGEOVER VALVE 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 ON MODELS INCLUDING EXTERNAL JUMPER, W2=W1 AND L=F. M8003 Fig. 124. Schematic and hookup of T874J with Q674L. Used in heat pump applications. 60-2485--8 144 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE 2 H1/C1 ANTICIPATOR 3 H1 FALL FALL C1 4 H2 ANTICIPATOR H2 6 FAN SWITCH AUTO ON SYSTEM SWITCH EM. HT. HEAT OFF COOL SYSTEM COMPONENTS R L EM. HT. LED (RED) 3 W3 AUX. HT. RELAY 2 X AUX. HT. LED (GRN) W2 AUX. HT. RELAY FAN RELAY G L1 (HOT) L2 1 COOL CHANGEOVER VALVE O E EM. HT. RELAY Y COMPRESSOR CONTACTOR B "B" RELAY 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 TERMINAL LABELED C/X ON SOME MODELS. 3 W3 TERMINAL AVAILABLE ON SOME MODELS ONLY. M3683A Fig. 125. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 145 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT 1 H1 ANTICIPATOR 2 H1 FALL 4 FALL 6 H2 H2 ANTICIPATOR 8 CO C1 ANTICIPATOR RISE 9 10 C1 RISE SUBBASE FAN SWITCH AUTO ON SYSTEM SWITCH SUPL. HT. HEAT COOL SYSTEM COMPONENTS COOL CHANGEOVER VALVE O L1 (HOT) L2 1 FAN RELAY G R OUTDOOR THERMOSTAT W2 HEAT RELAY 1 E 2 L SUPL. HT. LED (RED) C HEAT RELAY HEAT RELAY 2 CONTACT 1 HEAT RELAY HEAT RELAY 3 CONTACT 2 Y 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 N.O. SWITCH INSTALLER ADDED, TO LIGHT EM. HT. LED WHEN COMPRESSOR OPERATION IS NOT NORMAL. COMPRESSOR CONTACTOR 1 Fig. 126. Schematic and hookup of T874G with Q674P. Used in heat pump applications. M4722 THERMOSTAT SUBBASE FALL H1 2 H1 ANTICIPATOR 3 FALL 4 H2 ANTICIPATOR 5 H2 6 RISE 8 C1 10 C1 ANTICIPATOR 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. FAN SWITCH AUTO ON SYSTEM SWITCH EM. HT. HEAT OFF COOL SYSTEM COMPONENTS R RTD1 W3 ODT1 EHR1 L1 (HOT) L2 1 ODT2 RTD2 RTD1 W2 EHR2 RTD3 AUX.HT. LED (GREEN) X EM. HT. COMPRESSOR LED (RED) FAILURE RD L G FAN RELAY O EM. HT. COOL CHANGEOVER RELAY VALVE E COMPRESSOR LACO CONTACTOR CHP Y B M5652A Fig. 127. Schematic and hookup of T874C with Q674L. Used in heat pump applications. 60-2485--8 146 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT FALL H1/C1 ANTICIPATOR 2 H1 C1 3 FALL 4 H2 ANTICIPATOR 5 H2 6 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. SUBBASE FAN SWITCH AUTO ON SYSTEM SWITCH EM. HT. HEAT OFF COOL R A SERVICE LED (RED) W3 SYSTEM COMPONENTS RD RTD1 ODT1 EHR1 L1 (HOT) L2 1 ODT2 RTD2 RTD1 W2 EHR2 RTD3 AUX. HT. LED (GREEN) X EM. HT. LED SYSTEM (YELLOW) MONITOR RD L FAN RELAY G O COOL CHANGEOVER EM. HT. RELAY VALVE E COMPRESSOR LACO CONTACTOR CHP Y B M5653A Fig. 128. Schematic and hookup of T874R with Q674L. Used in heat pump applications. THERMOSTAT H1 FALL 2 H1 ANTICIPATOR 3 SUBBASE FAN AUTO SWITCH ON SYSTEM COMPONENTS FAN RELAY G L1 R (HOT) 1 L2 4 H2 ANTICIPATOR FALL 6 H2 RISE SYSTEM SWITCH EM. HT. HEAT OFF W EM. HT. RELAY X B EM. HT. LED (RED) AUX. HT. RELAY COOL CO 8 COOL CHANGEOVER VALVE RISE C1 9 O C1 ANTICIPATOR 10 Y COMPRESSOR CONTACTOR 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M102A Fig. 129. Schematic and hookup of T874G with Q674L. Used in heat pump applications. 147 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 2 H1 C1 FALL H1/C1 ANTICIPATOR 3 4 5 H2 FALL 6 H2 ANTICIPATOR 11 FAN SWITCH AUTO ON SYSTEM SWITCH EM. HT. HEAT OFF COOL RESET 12 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 FACTORY-INSTALLED JUMPER. AUX. HT. LED (YELLOW) CHECK LED (RED) O COOL CHANGEOVER VALVE G FAN RELAY R L1 (HOT) L2 1 W1 2 EM. HT. RELAY E X COMPRESSOR FAILURE C C815A OUTDOOR THERMISTOR SYSTEM LED (GREEN) T COMPRESSOR CONTACTOR Y M1628A Fig. 130. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 60-2485--8 148 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT H1/C1 ANTICIPATOR 2 SUBBASE FAN AUTO SWITCH ON SYSTEM COMPONENTS L1 (HOT) L2 R 1 3 H1 C1 FALL RESET HEATER 4 6 H2 ANTICIPATOR H2 FALL SYSTEM SWITCH SUPL. HT. HEAT 2 COOL W2 L C SUPL. HT. LED (RED) G O HCR 1 ODT FAN RELAY COOL CHANGEOVER VALVE E Y 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 FOR Q674L1454, IS "OFF". HCR 2 HCR 3 COMPRESSOR CONTACTOR HCR 1 HCR 2 M4723 Fig. 131. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 149 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 2 FALL H1 C1 H1/C1 ANTICIPATOR 3 4 H2 FALL 5 6 H2 ANTICIPATOR FAN SWITCH AUTO ON SYSTEM SWITCH EM. HT. HEAT OFF COOL 11 O COOL CHANGEOVER VALVE FAN RELAY G R 3R L1 (HOT) 1 L2 W1 AUX. HT. LED (YELLOW) 2 E EM. HT. LED (RED) SYSTEM LED (GREEN) 4R X C C815A OUTDOOR THERMISTOR SEQ 2 SEQ 1 EM. HT. RELAY 4R 5R HPS 4R 12 T RESET Y 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 REMOVE JUMPER FOR INDEPENDENT CONTROL OF W1 AND E TERMINALS. COMPRESSOR CONTACTOR 4R M1858 Fig. 132. Schematic and hookup of T874R with Q674L. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 H1/C1 ANTICIPATOR 2 H1 C1 FALL 3 4 5 6 H2 ANTICIPATOR H2 FALL FAN SWITCH AUTO ON SYSTEM SWITCH EM. HT. HEAT OFF COOL 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. FAN G RELAY L1 (HOT) R L2 1 K AUX. HT. EM. HT. RELAY RELAY W2 EM. HT. LED (YEL) L COMPRESSOR C FAILURE Z RESET LED (RED) W1 Y CO W1 RELAY COMPRESSOR CONTACTOR M2018 Fig. 133. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 60-2485--8 150 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS RTD 1 ODT 1 1 H1 C1 FALL 2 EHR 1 ODT 2 RTD 2 H1/C1 ANTICIPATOR 3 4 H2 ANTICIPATOR 5 6 FALL H2 8 10 FAN SWITCH AUTO ON SYSTEM SWITCH EM. HT. HEAT OFF COOL G R W2 AUX. HT. LED (GREEN) E COMP. FAILURE L EM. HT. LED (RED) B X LACO Y EHR 2 RDT 3 FAN RELAY L1 (HOT) 1 L2 RTD 1 EM. HT. RELAY RD CHANGEOVER VALVE (HEAT) COMPRESSOR CONTACTOR CHP 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. CHANGEOVER VALVE (COOL) O M106A Fig. 134. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 151 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT H1/C1 ANTICIPATOR 2 FAN SWITCH AUTO ON SUBBASE 3 H1 C1 RESET FALL HEATER 4 6 H2 ANTICIPATOR H2 FALL SYSTEM SWITCH SUPL. HT. HEAT OFF COOL 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. R W2 L SUPL. HT. LED (RED) C G O SYSTEM COMPONENTS L1 (HOT) L2 1 HCR 1 ODT HCR 1 HCR 2 FAN RELAY COOL CHANGEOVER VALVE E HCR 2 Y HCR 3 COMPRESSOR CONTACTOR M2017 Fig. 135. Schematic and hookup of T874R with Q674L. Used in heat pump applications. THERMOSTAT 1 C1 ANTICIPATOR H1 ANTICIPATOR 2 H1 C1 FALL 3 4 RESET 5 6 SUBBASE FAN SWITCH AUTO ON AUX. HT. LED (GRN) EM. HT. LED (RED) SYSTEM COMPONENTS G FAN RELAY W U1 AUX. HEAT RELAY B F COMP. FAILURE R T 2 L2 L1 (HOT) H2 FALL SYSTEM SWITCH EM. HT. HEAT OFF COOL 1 FIELD REMOVABLE JUMPER 2 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. X2 O.D. STAT C815A OUTDOOR THERMISTOR COOL CHANGEOVER VALVE O COMPRESSOR CONTACTOR Y M2012 Fig. 136. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 60-2485--8 152 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS RTD 1 ODT 1 1 H1 C1 FALL 2 EHR 1 ODT 2 RTD 2 H1/C1 ANTICIPATOR 3 4 H2 ANTICIPATOR 5 FAN SWITCH AUTO ON FALL H2 6 SYSTEM SWITCH EM. HT. HEAT W3 G R W2 AUX. HT. LED (GREEN) E EM. HT. LED (RED) COMP. FAILURE L CHECK LED (RED) B EHR 2 RDT 3 FAN RELAY L1 (HOT) 1 L2 RTD 1 EM. HT. RELAY RD CHANGEOVER VALVE (HEAT) OFF COOL X LACO Y COMPRESSOR CONTACTOR CHP 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. CHANGEOVER VALVE (COOL) O Fig. 137. Schematic and hookup of T874R with Q674L. Used in heat pump applications. M105A 153 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 FALL 1 2 H1 ANTICIPATOR 3 FAN SWITCH AUTO ON J R1 NO2 S SOLIENOID RELAY G R 2 S1 RELAY S1 NC FAN RELAY L1 (HOT) L2 1 FALL 4 H2 ANTICIPATOR 5 H2 7 RISE 8 C1 9 C1 ANTICIPATOR 10 SYSTEM SWITCH HEAT OFF COOL 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 FIELD REMOVABLE JUMPER C H2 R1 NC1 H1 R2 NO1 O AUX. HT. RELAY COMPRESSOR CONTACTOR REVERSING VALVE R1 RELAY M103A Fig. 138. Schematic and hookup of T874L with Q674B. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 H1 ANTICIPATOR 2 FALL H1 4 H2 ANTICIPATOR 6 H2 FALL 8 RISE C1 C1 ANTICIPATOR 10 C2 ANTICIPATOR AUTO FAN ON SWITCH SYSTEM SWITCH AUX. HT. HEAT PUMP 2 STG. HEAT OFF COOL 11 C2 RISE 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. FAN RELAY G R L1 (HOT) L2 B 1 W1 HEAT PUMP LED (GREEN) COMPRESSOR RELAY AUX. HT. RELAY W2 AUX. HT LED (RED) C O COOL CHANGEOVER VALVE Y1 COMPRESSOR CONTACTOR 1 Y2 COMPRESSOR CONTACTOR 2 M4730 Fig. 139. Schematic and hookup of T874D with Q674F. Used in heat pump applications. 60-2485--8 154 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT 1 FALL H1 ANTICIPATOR H1 2 FALL H2 H2 ANTICIPATOR 3 FALL H3 ANTICIPATOR 4 H3 5 SUBBASE FAN SWITCH AUTO ON SYSTEM COMPONENTS L1 (HOT) L2 1 T C815A OD THERMISTOR W3 AUX. HT. U LED (GREEN) G AUX. HT. RELAY EM. HT. R LED (RED) FAN RELAY 6 RESET RISE 8 C1 9 C1 ANTICIPATOR 10 RISE C2 ANTICIPATOR 11 C2 12 SYSTEM SWITCH EM.HT. HEAT OFF COOL E L CHECK LED (RED) X COMPRESSOR MONITOR EM. HT. RELAY B 2 O Y1 Y2 HEAT CHANGEOVER RELAY COOL CHANGEOVER RELAY COMPRESSOR CONTACTOR 1 COMPRESSOR CONTACTOR 2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 CONNECT CHANGEOVER RELAY TO 'O' TERMINAL FOR CHANGEOVER IN COOLING OR TO 'B' TERMINAL FOR CHANGEOVER IN HEATING. Fig. 140. Schematic and hookup of T874W with Q674L. Used in heat pump applications. M156A 155 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL 1 H1 H1 ANTICIPATOR 4 FALL 6 H2 H2 ANTICIPATOR C1 C2 RISE RISE 8 9 C1 ANTICIPATOR 10 C2 ANTICIPATOR 11 FAN SWITCH AUTO ON SYSTEM SWITCH OFF EM. HT. HEAT AUTO COOL R HEAT RELAY 1 W1 FAN RELAY G W2 EM. HT. LED (RED) X2 E HEAT RELAY 2 EM. HT. RELAY COMPRESSOR CONTACTOR 2 Y2 COMPRESSOR CONTACTOR 1 Y1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M8376 Fig. 141. Schematic and hookup of T874C with Q674F. Used in standard applications. L1 (HOT) L2 1 THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL H1 1 H1 ANTICIPATOR 4 FAN SWITCH AUTO ON L1 R (HOT) L2 1 W1 HEAT RELAY 1 H2 ANTICIPATOR W2 6 FALL H2 SYSTEM SWITCH B X2 CHECK LED (RED) X1 HEAT RELAY 2 RISE C1 8 9 C1 ANTICIPATOR 10 OFF EM. HT. HEAT AUTO COOL E EM. HT. RELAY G FAN RELAY Y2 COMPRESSOR CONTACTOR 2 C2 Y1 ANTICIPATOR 11 COMPRESSOR CONTACTOR 1 O RISE C2 1 POWER SUPPLY. PROVIDE DISCONECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M5985 Fig. 142. Schematic and hookup of T874C,D with Q674F. Used in standard applications. 60-2485--8 156 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL H1 1 H1 ANTICIPATOR 2 4 FALL 6 H2 H2 ANTICIPATOR RISE 8 CO C1 RISE 9 C1 ANTICIPATOR 10 Y1 FAN SWITCH AUTO G ON R SYSTEM SWITCH OFF AUTO W1 C AUX. HT. LED (RED) O 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COMPRESSOR CONTACTOR FAN RELAY L1 (HOT) L2 1 AUX. HT. RELAY COOL CHANGEOVER VALVE M8378 Fig. 143. Schematic and hookup of T874G with Q674B. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS L1 L2 (HOT) FALL H1 2 3 H1 ANTICIPATOR 4 H2 ANTICIPATOR 5 H2 FALL 6 RISE CO 8 9 C1 ANTICIPATOR 10 RISE C1 CO 11 FAN SWITCH AUTO ON SYSTEM SWITCH SUPL. HT. ON OFF R Y G W2 SUPP. HT. LED (RED) L C E X P O 1 COMPRESSOR CONTACTOR FAN RELAY HEAT RELAY 1 OUTDOOR THERMOSTAT HEAT RELAY HEAT RELAY 2 CONTACT 1 HEAT RELAY HEAT RELAY 3 CONTACT 2 "P" RELAY "X" RELAY COOL CHANGEOVER VALVE 12 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M5956 Fig. 144. Schematic and hookup of T874J with Q674J. Used in heat pump applications. 157 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS (HOT) L1 L2 H1 FALL H1 ANTICIPATOR 1 2 4 FAN SWITCH AUTO ON 1 V DEFROST RELAY SUP. ELEC. HT. RELAY Y OUTDOOR THERMOSTAT TIME DELAY EM. HT. RELAY FAN RELAY FALL H2 ANTICIPATOR 6 H2 FALL CO 8 9 C1 ANTICIPATOR SYSTEM SWITCH OFF EM. HT. HEAT AUTO COOL 10 RISE C1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. FAN RELAY F E EM. HT. LED (RED) EM. HT. RELAY COOL CHANGEOVER VALVE R COMPRESSOR CONTACTOR M INTERNAL THERMOSTAT OVERLOAD HIGH PRESSURE SWITCH M8375 Fig. 145. Schematic and hookup of T874G with Q674F. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 H1 FALL H1 ANTICIPATOR H2 FALL 3 4 H2 ANTICIPATOR 6 FAN SWITCH AUTO ON W1 EHR LPCO Y1 RVR RVR G R ODT 3 C1 RISE RISE C2 8 SYSTEM SWITCH OFF W2 EHT ODT 2 9 C1 ANTICIPATOR 10 C2 ANTICIPATOR 11 SUPL. HT. HEAT AUTO COOL E X SUPL. HEAT C LED (RED) SUPL. HT. RELAY DFR 2 Y2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. EHR REVERSING RELAY DFR 2 COMPRESSOR CONTACTOR 1 FAN RELAY HEAT RELAY 2 L1 (HOT) L2 1 HEAT RELAY 1 HEAT RELAY 3 COMPRESSOR CONTACTOR 2 M7010 Fig. 146. Schematic and hookup of T874D with Q674F. Used in heat pump applications. 60-2485--8 158 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 FALL FALL H2 2 H1 ANTICIPATOR 3 4 5 H2 ANTICIPATOR 6 8 CO RISE 9 FAN SWITCH AUTO ON SYSTEM SWITCH OFF COOL AUTO HEAT EM. HT. RISE C1 C1 ANTICIPATOR 10 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 CONNECT TO Y OR W TERMINAL WITH FACTORY INSTALLED JUMPER. A MODE SIGNAL 1 3 2 SERVICE LED (RED) AUX. HT. LED (GRN) EM. HT. LED (YEL) G FAN RELAY R S2 L1 (HOT) L2 1 W3 HEAT RELAY 1 W2 HEAT RELAY 2 X COOL L CHANGEOVER VALVE O COMPRESSOR CONTACTOR Y EM. HT. RELAY E T MODE SIGNAL 3 JUMPER FACTORY INSTALLED. M7024 Fig. 147. Schematic and hookup of T874G with Q674F. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR 1 2 H1 FALL 4 FAN SWITCH AUTO ON COOL CHANGEOVER VALVE O DEFROST BLOWER SPEED RELAY RELAY BLOWER RELAY G L1 R (HOT) L2 1 FALL H2 CO RISE C1 RISE 6 H2 ANTICIPATOR 8 SYSTEM SWITCH OFF EM. HT. EM. HT. W2 LED (RED) DEFROST RELAY AUX. HT. RELAY EM. HT. RELAY HEAT E 9 AUTO C C1 ANTICIPATOR 10 COOL LOCKOUT THERMOSTAT Y 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COOL CONTRACTOR M8382 Fig. 148. Schematic and hookup of T874G with Q674F. Used in heat pump applications. 159 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT FALL 1 H1 H1 ANTICIPATOR 4 FALL H2 H2 6 ANTICIPATOR RISE 8 C1 RISE 3 C2 9 C1 ANTICIPATOR 10 C2 ANTICIPATOR 11 FAN SWITCH AUTO ON SYSTEM SWITCH 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 OPTIONAL FIELD WIRE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER. 3 FOR Q674F1048, DELETE C2 STAGE. OFF EM. HT. HEAT AUTO COOL SUBBASE W1 Y1 G W2 EMR2 SYSTEM COMPONENTS EMR4 2R 1R 4R2 EMR4 2R2 5R 3R THERMAL SWITCHES FOR HEATING ELEMENTS HTR 1 HTR 2 HTR 3 EMR3 EM. HT. LED RC 2 X1 OUTDOOR THERMOSTAT 3R1 Z EMR1 EMR1 RH EM. HT. RELAY E L1 (HOT) L2 1 L1 L2 (HOT) 1 M8380 Fig. 149. Schematic and hookup of T874C with Q674F. Used in heat pump applications. 60-2485--8 160 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT H1 ANTICIPATOR 1 SUBBASE R SYSTEM COMPONENTS COOL CHANGEOVER VALVE FALL 2 H1 3 FALL 5 H2 H2 ANTICIPATOR FAN SWITCH AUTO ON COMPRESSOR CONTACTOR M INTERNAL THERMOSTAT OVERLOAD SWITCH FAN RELAY F HI PRESSURE SWITCH OUTDOOR THERMOSTAT Y SUPL. ELEC. HT. RELAY EM. HT. RELAY CONTACT TIME DELAY FAN RELAY 6 RISE 8 C1 RISE CO 9 C1 ANTICIPATOR SYSTEM SWITCH OFF EM. HT. HEAT COOL AUTO E EM. HEAT LED (RED) X SYSTEM MONITOR VR TIME DELAY FAN RELAY 1 L1 HOT L2 10 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 V 2 REMOVE FACTORY INSTALLED V-VR JUMPER WHEN CONNECTING A TWO TRANSFORMER SYSTEM. L2 1 L1 HOT M2852A Fig. 150. Schematic and hookup of T874G with Q674F. Used in heat pump applications. 161 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT H1 ANTICIPATOR 1 SUBBASE SYSTEM COMPONENTS L1 L2 (HOT) R 1 EM. HT. RELAY CONTACT 1 2 FALL H1 4 6 H2 ANTICIPATOR FALL H2 8 CO RISE 9 FAN SWITCH AUTO ON SYSTEM SWITCH OFF EM. HT. HEAT AUTO COOL W2 EM. HT. LED (RED) E 2 X H Y G O C1 ANTICIPATOR 10 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD C1 RISE PROTECTION AS REQUIRED. 2 OPTIONAL FIELD WIRE JUMPER TO CYCLE W2 WITH H1 IN EM. HT. (FASTER RESPONSE). T6031 REFRIGERATON/ TEMPERATURE CONTROLLER EM. HT. EM. HT. RELAY R8233B Y R G W COM EM. HT. O FAN C DF RS COMPRESSOR CONTACTOR SEQUENTIAL RELAY 1 L1 L2 (HOT) REVERSING SOLENOID FAN M4710 Fig. 151. Schematic and hookup of T874G with Q674F. Used in heat pump applications. 60-2485--8 162 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT 1 FALL H1 H1 ANTICIPATOR 4 FALL H2 ANTICIPATOR 6 H2 RISE C1 RISE C2 8 9 10 C1 ANTICIPATOR 11 C2 ANTICIPATOR SUBBASE FAN SWITCH AUTO ON SYSTEM SWITCH OFF EM. HT. HEAT AUTO COOL SYSTEM COMPONENTS 1 L1 L2 (HOT) HEAT RELAY W1 COMPRESSOR CONTRACTOR 1 Y1 FAN RELAY G RC 3 HEAT RELAY 2 W2 RH EM. HT. RELAY E EM. HEAT LED (RED) B 2 X2 X1 O COMPRESSOR CONTRACTOR 2 Y2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 FACTORY SUPPLIED FIELD INSTALLED JUMPER TO E-X2 FOR CONSTANT POWER TO EM HT LIGHT IN EM HT POSITION. 3 OPTIONAL FIELDWARE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER. 1 L1 L2 (HOT) M8377 Fig. 152. Schematic and hookup of T874D with Q674F. Used in standard applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 FALL 1 H1 ANTICIPATOR 2 4 AUTO ON FAN SWITCH COOL CHANGEOVER VALVE O FAN RELAY G L1 (HOT) L2 1 R OUTDOOR THERMOSTAT FALL C1 CO H2 RISE RISE 1 6 H2 ANTICIPATOR 8 SYSTEM SWITCH OFF EM. HT. HEAT W2 AUX. HT. RELAY E AUX. HT. RELAY CONTACT EM. HT. RELAY 9 C1 ANTICIPATOR 10 AUTO COOL EM. HT. LED (RED) X Y POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COMPRESSOR CONTACTOR M8381 Fig. 153. Schematic and hookup of T874G with Q674F. Used in heat pump applications. 163 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL 1 H1 ANTICIPATOR 2 H1 4 H2 ANTICIPATOR 6 H2 FALL 8 CO RISE 9 H1 ANTICIPATOR 10 FAN SWITCH AUTO ON SYSTEM SWITCH OFF EM. HT. HEAT AUTO COOL R W2 E EM. HT. LED (RED) X 2 H A COMP. FAULT LED (YELLOW) Y G O C1 RISE 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 OPTIONAL FIELD WIRE JUMPER TO CYCLE W2 WITH H1 IN EM. HEAT(FASTER RESPONSE). 1 L1 L2 (HOT) EM. HT. RELAY CONTACT 1 T6031 REFRIGERATION TEMPERATURE CONTROLLER EM. HT. EM. HT. RELAY COMPRESSOR CONTACTOR YR COM G R8233B SEQUENTIAL RELAY W EH O FAN C DF RS L1 L2 (HOT) FAN REVERSING SOLENOID M2858 Fig. 154. Schematic and hookup of T874G with Q674F. Used in heat pump applications. 60-2485--8 164 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT H1 ANTICIPATOR 2 3 H1 FALL 4 H2 ANTICIPATOR H2 5 FALL 6 8 9 RISE CHANGEOVER C1 ANTICIPATOR 10 RISE C1 SUBBASE FAN SWITCH AUTO ON SYSTEM SWITCH OFF COOL AUTO HEAT EM. HT. 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 W3 TERMINAL ON SELECT MODELS. SYSTEM COMPONENTS R RTD1 2 W3 W2 OTD1 EHR1 ODT2 EHR2 L1 (HOT) L2 1 RTD2 RTD3 AUX. HT. LED (GRN) X EM. HT. L LED (RED) G O E Y RTD1 SYSTEM MONITOR FAN RELAY RD LACO COOL CHANGEOVER VALVE EM. HT. RELAY COMPRESSOR CONTACTOR CHP M1589 Fig. 155. Schematic and hookup of T874G with Q674F. Used in heat pump applications. 165 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR FALL 1 H1 2 FAN SWITCH ON ON L1 L2 (HOT) 1 COOL CHANGEOVER VALVE O FAN RELAY G R 4 FALL H2 H2 ANTICIPATOR 6 RISE 8 CO 9 RISE C1 ANTICIPATOR 10 SYSTEM SWITCH OFF EM. HT. HEAT AUTO COOL OUTDOOR THERMOSTAT E AUX. HT. RELAY CONTACT EM. HT. RELAY EM. HT. LED (RED) L1 COMPRESSOR FAILURE X EM. HT. LED (GREEN) W2 AUX. HT. RELAY COMPRESSOR CONTACTOR C1 Y 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M5720 Fig. 156. Schematic and hookup of T874G with Q674F. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL H1 FALL H2 CO RISE C1 RISE 2 H1 ANTICIPATOR 3 4 H2 ANTICIPATOR 6 8 9 C1 ANTICIPATOR 10 FAN SWITCH AUTO ON SYSTEM SWITCH OFF EM. HT. HEAT AUTO COOL COOL CHANGEOVER VALVE Y1 FAN RELAY G R CHECK LED (GREEN) X DEFROST RELAY W2 E EM. HT. LED (RED) C1 W1 LOCKOUT RELAY HI PRESSURE SWITCH 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 1 L1 (HOT) L2 TIME DELAY RELAY 2 TIME DELAY RELAY 1 COMPRESSOR CONTACTOR M2860 Fig. 157. Schematic and hookup of T874G with Q674F. Used in heat pump applications. 60-2485--8 166 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS L1 (HOT) L2 1 1 H1 ANTICIPATOR O COOL CHANGEOVER VALVE H1 FALL 2 FAN SWITCH AUTO ON E EM. HT. RELAY G 2 FAN RELAY 4 B H2 FALL 6 H2 ANTICIPATOR 8 CO RISE C1 ANTICIPATOR 9 C1 RISE 10 SYSTEM SWITCH OFF EM. HT. HEAT AUTO COOL R HEAT CHANGEOVER VALVE W2 AUX. HT. RELAY L1 EM. HT. LED (RED) COMPRESSOR FAILURE AUX. HT. LED (GREEN) X Y COMPRESSOR CONTACTOR 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 B TERMINAL ON SELECT MODELS. M5721 Fig. 158. Schematic and hookup of T874G with Q674F. Used in heat pump applications. 167 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 H1 ANTICIPATOR H1 FALL FAN SWITCH AUTO 2 OFF 4 FALL H2 6 H2 ANTICIPATOR 8 SYSTEM SWITCH COOL CHANGEOVER VALVE O L1 L2 (HOT) 1 FAN RELAY G HEAT RELAY CONTACT R W OUTDOOR THERMOSTAT E AUX. HT. RELAY HEAT RELAY EM. HT. CONTACT RELAY RISE CO RISE C1 9 C1 ANTICIPATOR 10 EM.HT. AUTO OFF EM. HT. LED (RED) X Y LIMIT COMPRESSOR CONTACTOR 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M5722 Fig. 159. Schematic and hookup of T874G with Q674J. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL H1 FALL H2 2 H1 ANTICIPATOR 3 4 H2 ANTICIPATOR 5 FAN SWITCH AUTO ON O COOL CHANGEOVER VALVE G FAN RELAY R L1 (HOT) L2 1 W AUX. HT. RELAY RISE CO RISE C1 6 8 9 C1 ANTICIPATOR 10 SYSTEM SWITCH EM. HT. AUTO OFF X EM. HT. LED (RED) B Y EM. HT. RELAY COMPRESSOR CONTACTOR 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M5723 Fig. 160. Schematic and hookup of T874G with Q674J. Used in heat pump applications. 60-2485--8 168 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 H1 ANTICIPATOR 2 H1 FALL 4 FAN SWITCH AUTO ON COOL CHANGEOVER VALVE O 1 L1 (HOT) L2 G R FAN RELAY OUTDOOR THERMOSTAT W2 EM. HT. RELAY 1 FALL RISE H2 6 H2 ANTICIPATOR 8 CO RISE C1 ANTICIPATOR 9 C1 10 SYSTEM SWITCH SUPL. HT. ON OFF E 2 L SUPL. HT. LED (RED) C Y EM. HT. RELAY EM. HT. RELAY 2 CONTACT 1 EM. HT. RELAY EM.HT. CONTACT 2 RELAY 3 COMPRESSOR CONTACTOR 1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS 2 N.O. SWITCH -- INSTALLER ADDED, TO LIGHT EM. HT. LED AND OVERLOAD PROTECTION AS REQUIRED. WHEN COMPRESSOR OPERATION IS NOT NORMAL. M5724 Fig. 161. Schematic and hookup of T874G with Q674J. Used in heat pump applications. 169 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THEROMSTAT 1 FALL H1 2 H1 ANTICIPATOR 3 FALL 4 H2 5 RESET HEATER 6 RISE 8 CO 9 SUBBASE FAN SWITCH AUTO ON SYSTEM SWITCH EM. HT. AUTO OFF AUX. HT. LED (GREEN) EM. HT. LED (RED) SYSTEM COMPONENTS C815A OUTDOOR THERMISTOR T FAN RELAY G COOL CHANGEOVER VALVE O R OUTDOOR THERMOSTAT X2 W 1 L1 (HOT) L2 AUX. HT. RELAY B EM. HT. RELAY F RISE C1 C1 10 ANTICIPATOR 1 Y COMPRESSOR CONTACTOR POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M5725 Fig. 162. Schematic and hookup of T874G with Q674J. Used in heat pump applications. 60-2485--8 170 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR 1 H1 FALL 4 H2 ANTICIPATOR 6 FALL 1 H2 CO FALL C1 RISE 8 9 10 C1 ANTICIPATOR FAN SWITCH AUTO ON SYSTEM SWITCH AUTO OFF RESET 1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 H2 HAS 10¡F FIXED SETBACK FROM H1 ON T874G1485, 0-12¡F ADJUSTABLE ON T874G1535. 3 RESET IN MOMENTARY POSITION, SPRING RETURN TO OFF UPON SWITCH RELEASE. L2 L1 (HOT) 1 HEAT DAMPER B HEAT RELAY 1 W1 FAN RELAY G HEAT RELAY 2 W2 R S1 RESET CIRCUIT COOL CHANAGEOVER VALVE O S2 RESET CIRCUIT Y SERVICE LED (RED) X ON LED (YELLOW) A C COMPRESSOR RELAY M1820C Fig. 163. Schematic and hookup of T874G with Q674C. Used in standard applications. 171 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 H1 ANTICIPATOR 2 O FALL H1 RISE CO RISE C1 3 Y FAN SWITCH AUTO 4 ON G 6 R 8 9 C1 ANTICIPATOR SYSTEM SWITCH OFF AUTO 2 L MALFUNCTION LED (RED) B 10 X 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 R-L JUMPER SUPPLIED BY HONEYWELL. L1 (HOT) L2 COOL CHANGEOVER VALVE COMPRESSOR CONTACTOR FAN RELAY HEAT CHANGEOVER VALVE MALFUNCTION SWITCH M5726 Fig. 164. Schematic and hookup of T874H with Q674C. Used in standard applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 FALL H1 3 2 H1 ANTICIPATOR 3 4 H2 ANTICIPATOR FAN SWITCH AUTO ON L1 (HOT) 1 L2 J R1 N.O.2 S1 RELAY S 2 SOLENOID RELAY S1 N.C. G R FAN RELAY 5 H2 FALL 7 8 3 C1 RISE 9 C1 ANTICIPATOR 10 SYSTEM SWITCH OFF AUTO 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 FIELD REMOVABLE JUMPER. 3 H1 AND C1 ARE DPST SWITCHES. C H2 AUX. HT. RELAY R1 N.C.1 COMPRESSOR CONTACTOR H1 R2 N.O. 1 REV. VALVE R1 RELAY O M5727 Fig. 165. Schematic and hookup of T874L with Q674C. Used in heat pump applications. 60-2485--8 172 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL H1 1 H1 ANTICIPATOR 4 FALL 6 H2 H2 ANTICIPATOR 8 RISE C1 9 10 C1 ANTICIPATOR FAN SWITCH AUTO ON SYSTEM SWITCH OFF EM. HT. HEAT AUTO COOL W1 AUX. HT. LED (GREEN) EM. HT. LED X (RED) W2 RH L1 (HOT) L2 1 HEAT RELAY 1 HEAT RELAY 2 L SYSTEM MONITOR E EM. HT. RELAY G FAN RELAY RC COMRESSOR CONTACTOR 1 Y1 C2 ANTICIPATOR 11 Y2 RISE C2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COMRESSOR CONTACTOR 2 L2 1 L1 (HOT) M5728 Fig. 166. Schematic and hookup of T874D with Q674F. Used in standard applications. 173 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL H1 ANTICIPATOR 2 H1 3 FAN SWITCH R RTD 1 ODT 1 (HOT) L1 L2 1 EHR 1 RTD 2 ODT 2 4 H2 ANTICIPATOR AUTO ON EHR 2 H2 FALL FALL 5 SYSTEM SWITCH OFF 7 EM. HT. HEAT W2 AUX. HT. LED (GREEN) X EM. HT. LED (RED) COMPRESSOR FAILURE RD L G CHANGEOVER 8 9 AUTO COOL B HEAT CHANGEOVER VALVE E 10 C1 ANTICIPATOR LACO Y EHT1 C1 RISE COMPRESSOR CONTACTOR 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. RTD 3 RTD 1 FAN RELAY EM. HT. RELAY CHP M1592A Fig. 167. Schematic and hookup of T874G with Q674F. Used in heat pump applications. 60-2485--8 174 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR 1 C ANTICIPATOR 2 FAN SWITCH AUTO ON H1 C FALL 3 4 5 H2 ANTICIPATOR H2 6 FALL SYSTEM SWITCH EM. HT. HEAT OFF COOL 11 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 REMOVE JUMPER WHEN W1 RELAY IS USED. 3 FACTORY-INSTALLED JUMPER. W3 W3 RELAY O COOL CHANGEOVER VALVE L COMPRESSOR MONITOR FAN RELAY G EM. HT. LED (RED) AUX. HT. LED (GRN) R W2 AUX. HT. RELAY E EM. HT. RELAY X 3 HEAT X2 CHANGEOVER VALVE B W1 RELAY W1 2 COMPRESSOR RELAY Y L1 (HOT) L2 1 M5067 Fig. 168. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 175 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT FALL 1 H1 ANTICIPATOR 2 H1 4 6 H2 ANTICIPATOR H2 FALL RISE 8 C1 9 C1 ANTICIPATOR 10 11 RISE CO 12 SUBBASE SYSTEM COMPONENTS FAN SWITCH AUTO ON SYSTEM SWITCH OFF EM. HT. HEAT AUTO COOL O COOL CHANGEOVER VALVE G B 3 W3 R FAN RELAY B RELAY AUX HT. RELAY E EM. HT. RELAY L EM. HT. LED (RED) 2 X AUX. HT. LED (GREEN) AUX. HT. RELAY W2 L1 (HOT) L2 1 Y 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 TERMINAL LABELED C/X ON SOME MODELS. 3 W3 TERMINAL ON SOME MODELS ONLY. COMPRESSOR CONTACTOR M5986A Fig. 169. Schematic and hookup of T874G with Q674F. Used in heat pump applications. 60-2485--8 176 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 FALL 2 H1 ANTICIPATOR 3 4 5 FAN SWITCH AUTO ON 6 H2 ANTICIPATOR H2 FALL CO 8 9 C1 ANTICIPATOR SYSTEM SWITCH OFF EM. HT. 3 HEAT AUTO COOL RISE 10 RISE C1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 ON SOME MODELS, Y TERMINAL MAY BE LABELED Y1. 3 EMERGENCY HEAT RUNS CONTINUOUSLY WHEN SWITCH IN IN EM. HT. POSITION. W3 W3 RELAY W1 W1 RELAY B RELAY B G FAN RELAY R W2 AUX. HT. LED (GREEN) AUX. HT. RELAY X EM. HT. LED (RED) L COMPRESSOR FAULT E COOL CHANGEOVER VALVE EM. HT. RELAY O COMPRESSOR 2 CONTACTOR Y M5987A Fig. 170. Schematic and hookup of T874G with Q674F. Used in heat pump applications. L1 (HOT) L2 1 177 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS R 2 FALL H1 3 FAN SWITCH Y H1 ANTICIPATOR AUTO G 4 ON H2 ANTICIPATOR 5 FALL H2 6 W1 EM. HT. LED (RED) F CO RISE 8 9 C1 ANTICIPATOR 10 SYSTEM SWITCH EM. HT. AUTO C 2 E X OFF P 11 C1 RISE CO O 12 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 EXTERNAL JUMPER SUPPLIED BY HONEYWELL. L1 (HOT) L2 1 O.D.T. COMPRESSOR CONTACTOR FAN RELAY HCR1 HCR1 HCR2 HCR2 HCR3 "X" RELAY "P" RELAY COOL CHANGEOVER VALVE M5729 Fig. 171. Schematic and hookup of T874J with Q674J. Used in heat pump applications. FALL THERMOSTAT 2 H1 ANTICIPATOR 3 4 H1 RISE CO 8 C1 ANTICIPATOR 9 10 11 SUBBASE FAN SWITCH AUTO ON SYSTEM SWITCH HEAT OFF COOL G R O FAULT LED 2 (RED) C CHECK FILTER 3 LED (YELLOW) SYSTEM COMPONENTS FAN RELAY COOL CHANGEOVER VALVE L1 (HOT) L2 1 C1 RISE 12 Y 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COMPRESSOR CONTACTOR Fig. 172. Schematic and hookup of T874H with Q674B. Used in heat pump applications. M1401 60-2485--8 178 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES FALL THERMOSTAT 2 H1 ANTICIPATOR 3 4 H1 RISE CO 8 C1 ANTICIPATOR 9 10 11 SUBBASE FAN SWITCH AUTO ON SYSTEM SWITCH OFF AUTO G R O FAULT LED 2 (RED) C CHECK FILTER 3 LED (YELLOW) SYSTEM COMPONENTS FAN RELAY COOL CHANGEOVER VALVE L1 (HOT) L2 1 C1 RISE 12 Y 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COMPRESSOR CONTACTOR Fig. 173. Schematic and hookup of T874H with Q674C. Used in heat pump applications. M1400 THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 HA 2 3 H1 FALL 4 H2 ODA 5 FALL 6 FAN SWITCH AUTO ON C1 8 RISE 9 CA 10 C2 SYSTEM SWITCH EM. HT. AUTO OFF RISE 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 REMOVABLE JUMPER. FAN RELAY G EM.. HT. RELAY X2 T C815A OUTDOOR THERMISTOR R "F" RELAY F 1 L1 (HOT) L2 W EM. HT. LED (RED) 2 AUX. HT. RELAY U AUX. HT. LED (GREEN) B O COOL CHANGEOVER VALVE COMPRESSOR CONTACTOR Y M1403 Fig. 174. Schematic and hookup of T874G with Q674J. Used in heat pump applications. 179 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR 1 2 FALL FALL 4 H2 ANTICIPATOR 6 FAN ON SWITCH AUTO O COOL FAN RELAY CHANGEOVER VALVE G L1 R (HOT) L2 1 O.D.T. H.C.R. 1 W2 H.C.R. 1 H.C.R.2 8 C1 ANTICIPATOR 9 RISE CO 10 SYSTEM SWITCH SUPL. HT. ON OFF RISE HEAT PUMP C1 (GRN) 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. AUTO (YEL) E L MANUAL (RED) C Y DEFROST (RED) D H.C.R. 2 H.C.R.3 COMPRESSOR CONTACTOR M2112A Fig. 175. Schematic and hookup of T874G with Q674J. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL 2 H1 ANTICIPATOR H1 Y1 COOL CHANGEOVER VALVE 3 Y2 FALL SETBACK 2 RISE CO RISE C1 1 4 6 8 9 10 C1 ANTICIPATOR AUTO ON FAN SWITCH SYSTEM SWITCH OFF AUTO COMPRESSOR CONTACTOR G FAN RELAY OPEN-NIGHT CLOSED-DAY R SETBACK RELAY L X1 LED 3 C LED X2 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 SETBACK STAGE OFFSET 12°F (7°C) FROM H1 STAGE. 3 LEDS ON SOME MODELS. M5730 L2 1 L1 (HOT) Fig. 176. Schematic and hookup of T874G with Q674C. Used in standard applications. 60-2485--8 180 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT H1 ANTICIPATOR 1 H1 FALL 4 SUBBASE FAN SWITCH AUTO ON X RESET LED (RED) G SYSTEM COMPONENTS LOCKOUT (RESET) RELAY FAN RELAY 3 H2 FALL CO RISE 6 SYSTEM SWITCH OFF 7 AUTO 8 9 R1 R2 2 B 2 O HEAT CHANGEOVER VALVE COOL CHANGEOVER VALVE RISE C1 ANTICIPATOR Y 10 COMPRESSOR CONTACTOR C1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 USE EITHER 'B' OR 'O' ONLY FOR SYSTEM CHANGEOVER. 0.8A AT 30 VAC MAXIMUM LOAD CURRENT. 3 SECOND STAGE HEAT MAKES 12oF (7oC) AFTER FIRST STAGE HEAT TO PROVIDE SETBACK M114C Fig. 177. Schematic and hookup of T874G,H with Q674C. Used in standard applications. L1 (HOT) L2 1 THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL H1 1 H1 ANTICIPATOR 3 4 FALL 6 H2 H2 ANTICIPATOR 8 C0 RISE 9 C1 ANTICIPATOR 10 FAN SWITCH AUTO ON SYSTEM SWITCH OFF COOL AUTO HEAT EM.HT. W1 W2 R L SERVICE LED (RED) X EM, HT. LED (YELLOW) G C K 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. CHANGEOVER RELAY AUX.HT. RELAY L1 (HOT) 1 L2 FAN RELAY COMPRESSOR RELAY EM.HT. RELAY M18623 Fig. 178. Schematic and hookup of T874N with Q674F. Used in heat pump applications. 181 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 H1 ANTICIPATOR 2 W1 DEFROST RELAY OUTDOOR THERMOSTAT REVERSING VALVE EM.HT. RELAY CONTACT HEAT RELAY 2 H1 FALL 4 H2 ANTICIPATOR 5 H2 FALL 6 FAN SWITCH AUTO ON 8 RISE C1 9 C1 ANTICIPATOR CO 10 SYSTEM SWITCH OFF EM. HT. HEAT AUTO COOL EM.HT. RELAY CONTACT W3 HEAT RELAY 3 FAN RELAY G R W2 E EM. HT. LED (RED) X CHECK LED (GREEN) L Y 1 L1 (HOT) L2 HEAT RELAY 1 EM. HT. RELAY HIGH PRESSURE SWITCH OPTIONAL COMPRESSOR FAILURE DEVICE COMPRESSOR CONTACTOR 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M3686 Fig. 179. Schematic and hookup of T874N with Q674F. Used in heat pump applications. 60-2485--8 182 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS R-11 FAN DELAY RELAY L1 L2 (HOT) 1 FALL H1 H1 ANTICIPATOR 1 FAN SWITCH AUTO ON W1 R-10 Y1 G R-1 R-11 CHANGEOVER VALVE ELEC. HT. RELAY STG. 1 COMPRESSOR R-8 CONTACTOR R-6 OVERLOAD FAN RELAY R-6 4 FALL H1 H2 ANTICIPATOR 6 8 C1 RISE RISE C2 9 C1 ANTICIPATOR 10 C2 ANTICIPATOR SYSTEM SWITCH EM. HT. AUTO OFF 11 R-2 R W2 E EM. HT. LED (RED) X2 2 FILTER LED (YELLOW) R-10 R-6 R-3 Y2 ELEC. HT. RELAY STG. 2 EM. HT. RELAY R-5 T2 R-5 RANDOM START R-8 (OPT.) (HEAT PUMP OPERATION) R-10 (BIOLERLESS OPERATION ) R-11 X1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 FILTER LED ON SOME MODELS. M5957 Fig. 180. Schematic and hookup of T874A,D with Q674J. Used in heat pump applications. 183 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENT FALL 2 CO 3 H2 FALL 4 FALL 6 H1 H1 ANTICIPATOR 8 RISE C1 9 C1 ANTICIPATOR 10 FAN SWITCH AUTO ON SYSTEM SWITCH OFF AUTO TIME CLOCK L1 L2 (HOT) 1 Y COMPRESSOR RELAY G FAN RELAY R W W2 COMPRESSOR FAULT LED (RED) REVERSING VALVE COMPRESSOR FAULT A 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M18587 Fig. 181. Schematic and hookup of T874K with Q674C. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 FALL H2 FALL H1/C ANTICIPATOR H2 ANTICIPATOR RESET 1 2 FAN SWITCH 3 AUTO 4 ON 5 6 SYSTEM SWITCH EM. HT. HEAT OFF COOL T W2 G R E B EM. HT. LED (YELLOW) X SERVICE LED (RED) L O Y OUTDOOR RESET AUX. HT. FAN EM. HT. EM. HT. LIGHT W89 HEAT PUMP CONTROL PANEL SERVICE LIGHT COOL/HEAT COMPRESSOR M3951 Fig. 182. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 60-2485--8 184 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL H1 1 H1 ANTICIPATOR 2 FALL H2 4 H2 ANTICIPATOR 6 RISE CO RISE C1 8 9 C1 ANTICIPATOR 10 FAN SWITCH AUTO ON SYSTEM SWITCH EM. HT. ON OFF O COOL CHANGEOVER VALVE G 2BH FAN RELAY R O. D. S. 1BH SH E L1 EM. HT. LED (RED) X AUX. HT. LED (GREEN) W COMPRESSOR FAILURE 1BH Y COMPRESSOR CONTACTOR 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 1 L1 L2 (HOT) M3950 Fig. 183. Schematic and hookup of T874G with Q674J. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR 1 FALL H1 FALL H2 4 H2 ANTICIPATOR 6 RISE C1 8 9 C1 ANTICIPATOR 10 C2 ANTICIPATOR NO FAN SWITCH SYSTEM SWITCH OFF AUTO HEAT RELAY 1 W1 W2 HEAT RELAY 2 RH RC COMPRESSOR CONTACTOR 1 Y1 1 L2 L1 (HOT) L1 (HOT) L2 1 RISE C2 11 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Y2 COMPRESSOR CONTACTOR 2 M3953 Fig. 184. Schematic and hookup of T874A,F with Q674G. Used in standard applications. 185 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT H1 ANTICIPATOR FALL H1 SUBBASE 1 FAN AUTO SWITCH ON SYSTEM COMPONENTS HEAT RELAY W1 L1 L2 (HOT) 1 G FAN RELAY RC FALL H2 4 H2 ANTICIPATOR 6 RISE C1 RISE C2 8 9 C1 ANTICIPATOR 10 C2 ANTICIPATOR 11 SYSTEM SWITCH OFF HEAT AUTO COOL 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. W2 HEAT RELAY 2 RH IGNITION RELAY B COMPRESSOR CONTACTOR 1 Y1 Y2 COMPRESSOR CONTACTOR 2 1 L1 L2 (HOT) M3954 Fig. 185. Schematic and hookup of T874D with Q674E. Used in standard applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL H1 H1 1 ANTICIPATOR 4 FALL H2 5 H2 ANTICIPATOR 6 7 RISE C1 8 9 C1 ANTICIPATOR 10 RISE C2 11 C2 ANTICIPATOR 12 NO FAN SWITCH SYSTEM SWITCH OFF AUTO 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. W1 HEAT RELAY 1 RH HEAT RELAY 2 W2 FAN RELAY B FAN RELAY O RC Y2 COMPRESSOR CONTACTOR 2 Y1 COMPRESSOR CONTACTOR 1 1 L2 L1 (HOT) L2 L1 (HOT) 1 M3955 Fig. 186. Schematic and hookup of T874D with Q674G. Used in standard applications. 60-2485--8 186 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL H1 2 H1 ANTICIPATOR 3 4 H2 ANTICIPATOR 5 FALL H2 RISE C1 8 C1 ANTICIPATOR 10 FAN SWITCH HIGH LOW SYSTEM SWITCH HEAT OFF COOL R4 HEAT RELAY 2 R3 HEAT RELAY 1 R2 HI SPEED FAN RELAY R1 LO SPEED C FAN RELAY HIGH HIGH LR PRESSURE TEMP. SWITCH SWITCH R5 COOL LOCKOUT X CONTACTOR RELAY R 1 L2 L1 (HOT) 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M3956 Fig. 187. Schematic and hookup of T874C with Q674B. Used in standard applications. THERMOSTAT H1 ANTICIPATOR FALL 1 H1 FALL H2 4 5 H2 ANTICIPATOR 6 7 SUBBASE NO FAN SWITCH SYSTEM COMPONENTS HEAT RELAY 1 W1 1 RH HEAT RELAY 2 L2 L1 (HOT) W2 T RISE 8 C1 9 RISE C2 C1 ANTICIPATOR 10 11 C2 ANTICIPATOR 12 SYSTEM SWITCH AUTO 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. FAN RELAY B O RC Y2 COMPRESSOR CONTACTOR 2 Y1 COMPRESSOR CONTACTOR 1 L2 L1 (HOT) 1 M3958 Fig. 188. Schematic and hookup of T874D with Q674G. Used in standard applications. 187 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL H1 1 4 ANTICIPATOR FALL 5 H2 6 8 9 10 11 NO FAN SWITCH NO SYSTEM SWITCH W1 B M839 MOTOR L1 W2 Y L2 RH R RC Y2 Y1 M3960 Fig. 189. Schematic and hookup of T874F with Q674D. Used in standard applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 RESET H1 ANTICIPATOR FALL 2 H1 3 4 H2 FALL 5 H2 ANTICIPATOR 6 7 RISE C1 8 C1 ANTICIPATOR 10 FAN SWITCH AUTO ON SYSTEM SWITCH EM. HT. HEAT OFF COOL V 2 VR OG IN STAT M COMPRESSOR CONTACTOR F SERVICE RELAY FAN RELAY L HI PR 3 O. D. S. EM. HT. RELAY SERVICE LED (RED) EM. HT. ELEC. HT. RELAY Y E EM. HT. LED (YELLOW) ELEC. HT. RELAY X A C815A OUTDOOR THERMISTOR R 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 OPTIONAL REMOVABLE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER. COOL CHANGEOVER VALVE 3 WIRE JUMPER FOR SERVICE LIGHT. 1 L1 (HOT) L2 L1 (HOT) L2 1 M3978 Fig. 190. Schematic and hookup of T874C with Q674L. Used in heat pump applications. 60-2485--8 188 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 2 FAN FALL H1/C1 SWITCH H1 C1 ANTICIPATOR AUTO LO 3 HI CONT. FALL H2 4 H2 ANTICIPATOR 6 SYSTEM SWITCH HEAT Z "Z" RELAY O COOL CHANGEOVER VALVE G FAN RELAY R AUX. HT. RELAY W2 C W1 HEAT RELAY OFF COOL COOL RELAY Y 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. L2 L1 (HOT) 1 M3965 Fig. 191. Schematic and hookup of T874R with Q674B. Used in heat pump applications. THERMOSTAT H1 ANTICIPATOR FALL 1 H1 FALL H2 4 H2 ANTICIPATOR 6 RISE C1 8 9 C1 ANTICIPATOR 10 C2 ANTICIPATOR SUBBASE OFF AUTO SYSTEM SWITCH FAN SWITCH AUTO ON 2 SYSTEM COMPONENTS HEAT RELAY 1 W1 FILTER LED (YELLOW) SERVICE LED (RED) HEAT RELAY 2 W2 X A G R FAN RELAY O MOMENTARY O CIRCUIT COMPRESSOR CONTACTOR 1 Y1 L2 L1 (HOT) 1 RISE C2 11 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Y2 COMPRESSOR CONTACTOR 2 2 MOMENTARY POSITION. SPRING RETURN TO "ON" UPON SWITCH RELEASE. M3959 Fig. 192. Schematic and hookup of T874D with Q674C. Used in standard applications. 189 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 H1 ANTICIPATOR FALL H1 4 FALL H2 6 H2 ANTICIPATOR FAN SWITCH AUTO ON RH W1 HEAT RELAY 1 W2 HEAT RELAY 2 B CHANGEOVER RELAY (HEAT) 8 RISE C1 9 10 C1 ANTICIPATOR SYSTEM SWITCH OFF HEAT AUTO COOL RISE C2 ANTICIPATOR 11 C2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 JUMPER RH, RC FOR SINGLE TRANSFORMER. O CHANGEOVER 2 RELAY (COOL) G FAN RELAY Y2 COMPRESSOR CONTACTOR 2 Y1 COMPRESSOR CONTACTOR 1 RC Fig. 193. Schematic and hookup of T874D with Q674E. Used in standard applications. L1 (HOT) L2 1 1 L2 L1 (HOT) M3203B THERMOSTAT SUBBASE SYSTEM COMPONENTS 2 FALL H1 H1 ANTICIPATOR 3 4 AUTO ON FAN SWITCH Y1 G R CHECK LED (GREEN) COOL FAN RELAY CHANGEOVER VALVE DR TDR 2 FALL H2 H2 ANTICIPATOR 6 X HBTH W2 RISE CO 8 9 C1 ANTICIPATOR 10 RISE C1 SYSTEM SWITCH OFF EM. HT. HEAT AUTO COOL E C EM. HT. LED (RED) W1 TDR 1 COMPRESSOR CONTACTOR HPA 1 L1 L2 (HOT) 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M3977 Fig. 194. Schematic and hookup of T874G with Q674F. Used in heat pump applications. 60-2485--8 190 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL H1 ANTICIPATOR 1 H1 2 4 H2 H2 6 FALL ANTICIPATOR 8 CO RISE 9 C1 ANTICIPATOR 10 FAN SWITCH AUTO ON SYSTEM SWITCH OFF EM. HT. HEAT AUTO COOL EM. HT. LED (RED) AUX. HT. LED (GREEN) RISE C1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COOL CHANGEOVER VALVE O FAN RELAY G "B" RELAY B R EM. HT. RELAY E L COMPRESSOR FAULT X W2 AUX. HT. RELAY Y COMPRESSOR CONTACTOR L1 (HOT) L2 1 M2974 Fig. 195. Schematic and hookup of T874G with Q674F. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL H1 ANTICIPATOR 1 H1 2 4 H2 H2 6 FALL ANTICIPATOR 8 CO RISE 9 C1 ANTICIPATOR 10 FAN SWITCH AUTO ON SYSTEM SWITCH SUPL. HT. ON OFF SUPL. HT. LED (RED) RISE C1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COOL CHANGEOVER VALVE O FAN RELAY G L1 (HOT) L2 1 R H.C.R.1 W2 O.D.T. E H.C.R.1 H.C.R.2 L H.C.R.2 H.C.R.3 C Y COMPRESSOR CONTACTOR M2975 Fig. 196. Schematic and hookup of T874G with Q674J. Used in heat pump applications. 191 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 2 H1 C1 FALL 3 4 H2 FALL 5 6 11 AUTO ON FAN SWITCH SYSTEM SWITCH EM. HT. HEAT OFF COOL 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 FIELD REMOVABLE JUMPER. AUX. HT. LED (GREEN) EM. HT. LED (RED) G FAN RELAY W 2 U AUX. HEATER RELAY B COMPRESSOR MONITOR F R 1 L1 (HOT) L2 T X2 OUTDOOR THERMOSTAT O COMPRESSOR RELAY Y OUTDOOR THERMISTOR COOL CHANGEOVER VALVE M2970 Fig. 197. Schematic and hookup of T874R with Q674L. Used in heat pump applications. THERMOSTAT SUBBASE 1 H1 FALL H1 ANTICIPATOR 3 4 H2 H2 6 FALL ANTICIPATOR 7 C1 RISE 8 9 10 C2 ANTICIPATOR FAN SWITCH AUTO ON SYSTEM SWITCH OFF HEAT AUTO COOL 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. SYSTEM COMPONENTS STAGE 1 HEAT RELAY W1 L1 (HOT) L2 1 COMPRESSOR CONTACTOR Y1 FAN RELAY G R STAGE 2 HEAT RELAY W2 M2976 Fig. 198. Schematic and hookup of T874L with Q674E. Used in standard applications. 60-2485--8 192 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL H1 ANTICIPATOR 2 H1 3 H2 FALL 4 H2 ANTICIPATOR 5 FAN SWITCH AUTO ON SYSTEM SWITCH 8 CO RISE 9 C1 ANTICIPATOR 10 OFF EM. HT. HEAT AUTO COOL RISE C1 11 12 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. AUX. HT. LED (GREEN) EM. HT. LED (RED) CHECK LED (RED) W3 RELAY W3 FAN RELAY G R AUX. HT. RELAY W2 EM. HT. RELAY E COMPRESSOR FAULT L X B HEAT CHANGEOVER VALVE O COOL CHANGEOVER RELAY Y COMPRESSOR CONTACTOR L1 (HOT) L2 1 M2977 Fig. 199. Schematic and hookup of T874G with Q674F. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 RISE 1 C1 H2 ANTICIPATOR 2 FAN SWITCH AUTO T OUTDOOR THERMOSTAT W2 L1 (HOT) L2 1 SEQ 2 FALL 3 4 H2 5 C1 ANTICIPATOR 6 11 H1 ANTICIPATOR 12 ON SYSTEM SWITCH EM. HT. HEAT OFF COOL SERVICE LED (YELLOW) EM. HT. LED (RED) 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. OUTDOOR THERMOSTAT FAN RELAY G R X SERVICE Z SEQ 1 K COMPRESSOR CONTACTOR Y HEAT CHANGEOVER VALVE W1 M2978 Fig. 200. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 193 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 RISE RESET 1 C1 H2 ANTICIPATOR 2 FAN SWITCH AUTO C815A OUTDOOR THERMISTOR T W2 OUTDOOR THERMOSTAT L1 (HOT) L2 1 SEQ 2 RISE 3 4 H2 5 C1 ANTICIPATOR 6 11 H1 ANTICIPATOR 12 ON SYSTEM SWITCH EM. HEAT HEAT OFF COOL SERVICE LED (YELLOW) EM. HT. LED (RED) 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. FAN RELAY OUTDOOR THERMOSTAT G R X SERVICE Z K COMPRESSOR CONTACTOR SEQ 1 Y HEAT CHANGEOVER VALVE W1 M2979 Fig. 201. Schematic and hookup of T874R with Q674L. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 FALL 1 H1 ANTICIPATOR 4 5 H2 FALL H2 6 ANTICIPATOR 7 C1 8 RISE 9 RISE 10 C1 ANTICIPATOR 11 C2 12 C2 ANTICIPATOR NO FAN SWITCH SYSTEM SWITCH OFF AUTO 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED SERVICE LED (RED) A2 HEAT RELAY 1 W1 SERVICE LED (RED) A1 HEAT RELAY 2 W2 "T" RELAY T RC FAN RELAY B B RH FAN RELAY O O Y2 COMPRESSOR CONTACTOR 2 Y1 COMPRESSOR CONTACTOR 1 Fig. 202. Schematic and hookup of T874D with Q674G. Used in standard applications. L1 (HOT) L2 1 1 L1 (HOT) L2 M2980 60-2485--8 194 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS CO FALL 2 3 FALL RISE 4 H1 6 H1 ANTICIPATOR 8 C1 9 FAN SWITCH AUTO ON SYSTEM SWITCH OFF AUTO COMP. FAULT (RED) COMPRESSOR CONTACTOR Y FAN RELAY G R HEAT CHANGEOVER VALVE W W2 COMPRESSOR FAULT A 10 C1 ANTICIPATOR 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. L1 (HOT) L2 1 M2981 Fig. 203. Schematic and hookup of T874L with Q674C. Used in heat pump applications. THERMOSTAT 1 H1 FALL H1 ANTICIPATOR SUBBASE FAN SWITCH AUTO ON SYSTEM COMPONENTS HEAT RELAY 1 W1 HEAT RELAY 2 W2 L1 (HOT) L2 1 R 4 H2 H2 6 FALL ANTICIPATOR 8 C1 RISE 9 10 C1 ANTICIPATOR SYSTEM SWITCH OFF EM. HT. HEAT AUTO COOL LED (RED) X2 B EM. HT. RELAY E FAN RELAY G COMPRESSOR CONTACTOR 2 Y2 COMPRESSOR CONTACTOR 1 Y1 C2 ANTICIPATOR 11 RISE C2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 LED IS NOT LABELED. JUMPER W2 TO X FOR AUXILIARY HEAT INDICATION. JUMPER E TO X FOR EMERGENCY HEAT INDICATION. CONNECT SYSTEM MONITOR TO X TO IDENTIFY WHEN SYSTEM NEEDS TO BE CHECKED. M2982A Fig. 204. Schematic and hookup of T874D with Q674F. Used in standard applications. 195 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT FALL H1 ANTICIPATOR 2 H1 3 4 6 SUBBASE FAN SWITCH AUTO ON SYSTEM COMPONENTS COOL CHANGEOVER VALVE Y1 COMPRESSOR CONTACTOR Y2 FAN RELAY G R L1 (HOT) L2 1 RISE 8 CO 9 C1 ANTICIPATOR 10 SYSTEM SWITCH OFF AUTO L LED (RED) X1 LED (RED) C2 X2 RISE C1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 LEDS ON SOME MODELS. M2983 Fig. 205. Schematic and hookup of T874H with Q674C. Used in heat pump applications. THERMOSTAT SUBBASE FALL 2 H1 H1 ANTICIPATOR 3 H2 FALL 4 H2 ANTICIPATOR 5 6 RISE 8 CO 9 C1 ANTICIPATOR 10 FAN SWITCH AUTO ON SYSTEM SWITCH SUPL. HT. ON OFF R Y G W2 SUPL. HT. LED (RED) L C E 11 O 12 RISE C1 CO 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. SYSTEM COMPONENTS COMPRESSOR CONTACTOR L1 (HOT) L2 1 FAN RELAY H.C.R.1 O.D.T. H.C.R.1 H.C.R.2 H.C.R.2 H.C.R.3 COOL CHANGEOVER VALVE M2984 Fig. 206. Schematic and hookup of T874J with Q674J. Used in heat pump applications. 60-2485--8 196 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 2 R H1 H1 ANTICIPATOR FAN SWITCH FALL Y 3 AUTO H2 FALL RISE 4 H2 ANTICIPATOR 5 6 8 CO 9 ON SYSTEM SWITCH SUPL. HT. HEAT G W2 SUPL. HT. LED (RED) L C C1 ANTICIPATOR 10 OFF E COOL 11 O 12 RISE C1 CO 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COMPRESSOR CONTACTOR FAN RELAY H.C.R.1 L1 (HOT) L2 1 O.D.T. H.C.R.1 H.C.R.2 H.C.R.2 H.C.R.3 COOL CHANGEOVER VALVE M2985 Fig. 207. Schematic and hookup of T874J with Q674L. Used in heat pump applications. THERMOSTAT 1 H1 FALL H1 ANTICIPATOR 4 SUBBASE NO FAN SWITCH SYSTEM COMPONENTS HEAT RELAY 1 W1 HEAT RELAY 2 W2 L1 (HOT) L2 1 RH 5 H2 H2 6 FALL ANTICIPATOR 8 C1 RISE 9 RISE 10 C1 ANTICIPATOR C2 ANTICIPATOR 11 C2 NO SYSTEM SWITCH 2 RC Y2 COMPRESSOR CONTACTOR 2 Y1 COMPRESSOR CONTACTOR 1 1 L1 (HOT) L2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 RC-RH REMOVABLE JUMPER WHEN SPECIFIED. M2986 Fig. 208. Schematic and hookup of T874D with Q674D. Used in standard applications. 197 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 C1 R EM. HT. LED (RED) L EM. HT. RELAY RISE H1/C1 ANTICIPATOR 2 3 4 6 FALL H2 ANTICIPATOR H2 FAN SWITCH AUTO ON SYSTEM SWITCH EM. HEAT HEAT OFF COOL AUX. HT. LED (GREEN) 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. X AUX. HT. RELAY W2 FAN RELAY G COOL CHANGEOVER VALVE O EM. HT. RELAY E COMPRESSOR CONTACTOR Y '"B" RELAY B L1 (HOT) L2 1 M2987 Fig. 209. Schematic and hookup of T874R with Q674L. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 FALL 1 H1 ANTICIPATOR 2 3 FAN SWITCH AUTO ON FAN RELAY G COOL R CHANGEOVER VALVE O HCO CCO FALL 4 H2 H2 6 FALL ANTICIPATOR 8 C1 RISE 9 10 C1 ANTICIPATOR C2 ANTICIPATOR 11 SYSTEM SWITCH OFF HEAT AUTO COOL FILTER B LED (YELLOW) F HEAT CHANGEOVER VALVE RESET LED (RED) L COMPRESSOR CONTACTOR 1 Y1 COMPRESSOR CONTACTOR 2 Y2 RISE C2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. L1 (HOT) L2 1 M2988 Fig. 210. Schematic and hookup of T874Y with Q674E. Used in heat pump applications. 60-2485--8 198 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE FALL H1 ANTICIPATOR 2 H1 3 4 H2 H2 6 FALL ANTICIPATOR 8 RISE C1 C1 ANTICIPATOR 10 FAN SWITCH AUTO ON SYSTEM SWITCH OFF EM. HT. HEAT AUTO COOL AUX. HT. LED (GREEN) EM. HT. LED (RED) 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. SYSTEM COMPONENTS W1 RELAY W1 FAN RELAY G R AUX. HT. RELAY W2 L1 (HOT) L2 1 X L COMPRESSOR FAULT Y1 COMPRESSOR CONTACTOR M2989 Fig. 211. Schematic and hookup of T874G with Q674F. Used in standard applications. THERMOSTAT 1 H1 FALL H1 ANTICIPATOR 4 H2 H2 6 FALL ANTICIPATOR 8 C1 RISE 9 RISE 10 C1 ANTICIPATOR C2 ANTICIPATOR 11 C2 SUBBASE SYSTEM COMPONENTS FAN SWITCH AUTO ON HEAT RELAY 1 W1 HEAT RELAY 2 W2 RH L1 (HOT) L2 1 SYSTEM SWITCH OFF HEAT AUTO COOL 2 RC FAN RELAY G Y2 COMPRESSOR CONTACTOR 2 Y1 COMPRESSOR CONTACTOR 1 1 L1 (HOT) L2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 RC -RH REMOVABLE JUMPER WHEN SPECIFIED. M2990 Fig. 212. Schematic and hookup of T874A with Q674E. Used in standard applications. 199 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 FALL 2 H1 H1 ANTICIPATOR 3 4 H2 FALL 5 H2 ANTICIPATOR SYSTEM SWITCH OFF AUTO RELAY 1 N.O. 2 H1 S1 RELAY L1 (HOT) L2 1 COMPRESSOR S1 CONTACTOR RELAY N.C. Y R RISE 7 8 CO 9 10 C1 ANTICIPATOR FAN SWITCH LO MED HIGH ON C FIELD REMOVABLE JUMPER H2 AUX. HT. RELAY CHECK LED (RED) L R1 RELAY N.C. 1 COMPRESSOR CONTACTOR R2 RELAY N.O 1 COOL CHANGEOVER VALVE O 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. R1 RELAY K1 RELAY G1 K2 RELAY G2 M2991 Fig. 213. Schematic and hookup of T874L with Q674C. Used in heat pump applications. 60-2485--8 200 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE H1 1 FALL H1 ANTICIPATOR 2 C1 ANTICIPATOR 3 4 C1 RISE 5 11 SYSTEM SWITCH HEAT OFF COOL FAN SWITCH LO MED HIGH ON 12 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. SYSTEM COMPONENTS L1 (HOT) L2 1 AUX. HT. RELAY H1 R R1 RELAY O COOL CHANGEOVER L VALVE C CHECK LED (RED) R2 RELAY N.O. 1 COMPRESSOR CONTACTOR COMPRESSOR CONTACTOR S1 RELAY N.C. Y K1 RELAY G1 K2 RELAY G2 M2992 Fig. 214. Schematic and hookup of T874A with Q674B. Used in standard applications. 201 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT 1 FALL 2 H1 H1 ANTICIPATOR 3 4 H2 FALL 5 H2 ANTICIPATOR RISE 7 8 C1 9 10 C1 ANTICIPATOR 11 SUBBASE SYSTEM SWITCH HEAT OFF COOL FAN SWITCH LO MED HIGH ON 12 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. SYSTEM COMPONENTS RELAY 1 N.O. 2 H1 S1 RELAY L1 (HOT) L2 1 COMPRESSOR S1 CONTACTOR RELAY N.C. Y R C FIELD REMOVABLE JUMPER H2 AUX. HT. RELAY CHECK LED (RED) L COMPRESSOR R1 RELAY N.C. 1 CONTACTOR R2 RELAY N.O. 1 COOL CHANGEOVER VALVE O R1 RELAY K1 RELAY G1 K2 RELAY G2 M2993 Fig. 215. Schematic and hookup of T874L with Q674B. Used in heat pump applications. 60-2485--8 202 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS COOL CHANGEOVER VALVE O H1 FALL 1 H1 ANTICIPATOR 2 FAN SWITCH AUTO ON G FAN RELAY R L2 L1 1 (HOT) 4 3R SEQ 2 6 FALL H2 H2 ANTICIPATOR SYSTEM SWITCH W1 AUX. HT. LED 2 (YELLOW) E 4R SEQ 1 EM. HT. RELAY RISE 8 CO 9 EM. HT. AUTO OFF X CHECK LED (RED) C 4R 5R SYSTEM 10 LED (GREEN) C1 ANTICIPATOR RISE Y C1 COMPRESSOR 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. CONTACTOR 2 REMOVE JUMPER FOR INDEPENDENT CONTROL OF W1 AND E TERMINALS. HPS 4R 4R M1629 Fig. 216. Schematic and hookup of T874G with Q674J. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 H1 FALL 2 H1 ANTICIPATOR D. P. W1 W3 4 FAN SWITCH AUTO G 5 H2 ON ANTICIPATOR R H2 FALL C1 RISE CO 6 SYSTEM SWITCH OFF 8 AUTO 9 W2 X CHECK LED (GREEN) L Y C1 ANTICIPATOR 10 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. HEAT CHANGEOVER VALVE ODT EHR HEAT CONTACTOR #2 EHR HEAT CONTACTOR #3 1 FAN RELAY HEAT CONTACTOR #1 L2 L1 (HOT) OPTIONAL COMPRESSOR FAILURE COMPRESSOR CONTACTOR M5900 Fig. 217. Schematic and hookup of T874N with Q674C. Used in heat pump applications. 203 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 2 H1/C1 ANTICIPATOR 3 H1 FALL FALL C1 4 H2 ANTICIPATOR H2 6 FAN SWITCH AUTO ON SYSTEM SWITCH EM. HT. HEAT OFF COOL R L EM. HT. LED (RED) 3 W3 AUX. HT. RELAY 2 X AUX. HT. LED (GRN) W2 AUX. HT. RELAY FAN RELAY G COOL CHANGEOVER VALVE O E L1 (HOT) L2 1 EM. HT. RELAY Y COMPRESSOR CONTACTOR B "B" RELAY 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 TERMINAL LABELED C/X ON SOME MODELS. 3 W3 TERMINAL AVAILABLE ON SOME MODELS ONLY. M3683A Fig. 218. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 60-2485--8 204 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS CONTROL MODULE 1 H1 FALL 2 H1 ANTICIPATOR FALL 3 H2 C1 4 5 6 H2 7 ANTICIPATOR 8 SYSTEM SWITCH OFF AUTO FAN SWITCH AUTO ON W1 HEAT RELAY 1 W2 HEAT RELAY 2 W3 Y2 A SERVICE LED (RED) G R FAN RELAY L1 (HOT) L2 1 RISE 2 9 O MONENTARY CIRCUIT 10 Y1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COMPRESSOR CONTACTOR 1 2 MOMENTARY POSITION. SPRING RETURN TO "ON" UPON SWITCH RELEASE. 3 H2 OFFSET 12oF FROM H1. M5901 Fig. 219. Schematic and hookup of T874C with Q674C. Used in standard applications. 205 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 H1 FALL 2 H1 ANTICIPATOR H3 H2 4 5 FALL 6 H2 ANTICIPATOR FALL 7 C1 RISE 8 9 10 RISE C2 SYSTEM SWITCH OFF AUTO FAN SWITCH AUTO ON 2 SERVICE LED (RED) CONTROL MODULE HEAT RELAY #1 W1 HEAT RELAY #2 W2 HEAT RELAY #3 W3 COMPRESSOR CONTACTOR #2 Y2 SYSTEM MONITOR A FAN RELAY G L2 1 R L1 (HOT) MOMENTARY O CIRCUIT COMPRESSOR CONTACTOR #1 Y1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 MOMENTARY POSITION. SPRING RETURN TO "ON" UPON SWITCH RELEASE. M5929 Fig. 220. Schematic and hookup of T874W with Q674C. Used in standard applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 FALL 2 H1 ANTICIPATOR 3 4 FAN SWITCH AUTO ON RISE CO 8 9 C1 ANTICIPATOR 10 C1 RISE SYSTEM SWITCH OFF AUTO 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Y1 COOL CHANGEOVER VALVE G FAN RELAY R COMPRESSOR CONTACTOR Y2 B O X SERVICE LED (YELLOW) X1 C FILTER LED (RED) X2 24 VAC 1 L2 L1 (HOT) M5902 Fig. 221. Schematic and hookup of T874H with Q674C. Used in heat pump applications. 60-2485--8 206 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR 2 FALL H1 3 4 8 C1 RISE C2 RISE 9 C1 ANTICIPATOR 10 C2 ANTICIPATOR 11 FAN SWITCH AUTO ON SYSTEM SWITCH OFF HEAT AUTO COOL R SYSTEM MONITOR 1 L FAN RELAY G W MALFUNCTION HEAT RELAY LED (RED) C LOW SPEED LED (GREEN) HIGH SPEED LED (YELLOW) Y1 COMPRESSOR CONTACTOR 1 COMPRESSOR CONTACTOR 2 Y2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Fig. 222. Schematic and hookup of T874B with Q674E. Used in standard applications. L1 (HOT) L2 M5920 THERMOSTAT SUBBASE SYSTEM COMPONENTS 2 H1 H1 FALL ANTICIPATOR 3 4 H2 H2 ANTICIPATOR FALL 5 7 RISE C1 8 C2 RISE CO 9 C1 ANTICIPATOR 10 C2 ANTICIPATOR 11 FAN SWITCH AUTO ON SYSTEM SWITCH OFF EM. HT. HEAT AUTO COOL R L G W2 AUX. HT. LED (RED) E MALFUNCTION LED (RED) C LOW SPEED LED (GREEN) HIGH SPEED LED (YELLOW) Y1 Y2 L1 (HOT) L2 1 FAN RELAY AUX. HT. RELAY EM.HT. RELAY COMPRESSOR CONTACTOR 1 COMPRESSOR CONTACTOR 2 RISE 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. O COOL CHANGEOVER VALVE M5923 Fig. 223. Schematic and hookup of T874S with Q674F. Used in heat pump applications. 207 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL 1 H1 H1 ANTICIPATOR 4 H2 ANTICIPATOR H2 6 FALL 8 C1 RISE 9 10 11 FAN SWITCH AUTO ON SYSTEM SWITCH OFF HEAT AUTO COOL B W1 Y1 G RC W2 RH SERVICE LED (RED) A Y2 CONTROL MODULE HEAT CHANGEOVER VALVE HEAT RELAY #1 COMPRESSOR CONTACTOR #1 FAN RELAY L1 (HOT) L2 1 HEAT RELAY #2 L1 (HOT) L2 1 SYSTEM MONITOR COMPRESSOR CONTACTOR #2 C2 RISE COOL CHANGEOVER VALVE O 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M5927 Fig. 224. Schematic and hookup of T874A,D with Q674E. Used in standard applications. 60-2485--8 208 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL 1 W1 H1 W2 H1 FAN ANTICIPATOR SWITCH B AUTO 4 ON RH H2 6 ANTICIPATOR RC H2 FALL O SYSTEM 8 SWITCH G C1 RISE 9 OFF AUTO Y2 10 11 Y1 C2 RISE SERVICE LED (RED) A 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. CONTROL MODULE HEAT RELAY #1 HEAT RELAY #2 HEAT DAMPER L1 (HOT) 1 L2 L2 1 L1 (HOT) COOL DAMPER FAN RELAY COMPRESSOR CONTACTOR #2 COMPRESSOR CONTACTOR #1 SYSTEM MONTIOR M5928 Fig. 225. Schematic and hookup of T874D with Q674C. Used in standard applications. 209 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL H1 1 H1 ANTICIPATOR NO FAN SWITCH A2 SERVICE LED (RED) W1 SERVICE LED (RED) A1 4 W2 5 T 6 H2 RC H2 FALL ANTICIPATOR SYSTEM SWITCH 7 B OFF 8 AUTO RH C1 RISE 9 O 10 Y2 11 C2 RISE 12 Y1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. CONTROL MODULE SYSTEM MONITOR HEAT RELAY #1 SYSTEM MONITOR HEAT RELAY #2 T RELAY L1 (HOT) 1 L2 FAN RELAY B L2 L1 1 (HOT) FAN RELAY O COMPRESSOR CONTACTOR #2 COMPRESSOR CONTACTOR #1 M5930 Fig. 226. Schematic and hookup of T874G with Q674G. Used in standard applications. 60-2485--8 210 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 CO (HEAT) FALL 2 H1 ANTICIPATOR FAN SWITCH AUTO ON W3 FAN RELAY G W3 RELAY 1 L1 L2 (HOT) 3 R FALL 4 H2 5 H2 ANTICIPATOR H1 FALL 6 CO 8 (COOL) 9 RISE RISE 10 C1 ANTICIPATOR C1 11 SYSTEM SWITCH OFF EM. HT. HEAT AUTO COOL W2 E AUX. HT. LED (GREEN) X1 EM. HT. RELAY CHECK LED (RED) X2 EM. HT. LED (RED) AUX. HT. RELAY COMPRESSOR FAULT X COOL CHANGEOVER RELAY O B W1 RELAY W1 HEAT CHANGEOVER RELAY 2 Y1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 W1 - Y1 JUMPER IS Y TERMINAL; REMOVE JUMPER WHEN W1 RELAY IS USED. COMPRESSOR CONTACTOR M1230B Fig. 227. Schematic and hookup of T874G with Q674F. Used in heat pump applications. 211 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS L1 L2 (HOT) 1 1 H1 C1 FALL 2 H1/C1 ANTICIPATOR 3 4 H2 ANTICIPATOR 5 FALL H2 6 FAN SWITCH AUTO ON EM. HT. HEAT OFF SYSTEM SWITCH SENSOR LED (RED) 2 AUX. HT. LED (GREEN) R Y1 COMP. RELAY G L O.L. IN. STAT. HI. PRO. FAN RELAY SERVICE O.D.S. W1 EM. HT. E EM. HT. LED (YELLOW) EM. HT. RELAY ELECTRIC HEAT RELAY ELECTRIC HEAT RELAY C C815A OUTDOOR THERMISTOR COOL T 11 RESET O 12 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 REMOVABLE JUMPER (INSTALLED). COOL CHANGEOVER VALVE M3259 Fig. 228. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 60-2485--8 212 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS R L1 (HOT) 1 L2 1 H1 ANTICIPATOR 2 H2 ANTICIPATOR 3 H1 FALL 4 5 FAN SWITCH AUTO ON COMP. RELAY O.L. Y1 IN. STAT. HI. PRO G SERVICE LED (RED) L FAN RELAY SERVICE H2 CO FALL 6 RESET RISE 8 RISE 9 C1 ANTICIPATOR 10 SYSTEM SWITCH OFF EM. HT. HEAT COOL AUTO AUX. HT. LED (GREEN) 2 W1 O.D.S. EM. HT. E EM. HT. LED (YELLOW) C T EM. HT. RELAY ELECTRIC HT. RELAY ELECTRIC HT. RELAY C815A OUTDOOR THERMISTOR C1 11 O 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 REMOVABLE JUMPER (INSTALLED). COOL CHANGEOVER VALVE M3264 Fig. 229. Schematic and hookup of T874G with Q674F. Used in heat pump applications. THERMOSTAT SUBBASE H1 ANTICIPATOR 1 C ANTICIPATOR 2 H1 C FALL 3 4 H2 FALL 5 H2 ANTICIPATOR 6 FAN SWITCH AUTO ON SYSTEM SWITCH EM .HT. HEAT OFF COOL 11 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. SYSTEM COMPONENTS W3 RELAY W3 O L CHECK LED (RED) G R COOL CHANGEOVER VALVE COMPRESSOR MONITOR FAN RELAY 1 L1 (HOT) L2 EM. HT. LED (RED) AUX. HT. LED (GREEN) W2 AUX. HT. RELAY E EM. HT. RELAY X B HEAT CHANGEOVER VALVE Y COMPRESSOR RELAY M5068 Fig. 230. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 213 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 2 H1 FALL H1 ANTICIPATOR 3 4 H2 ANTICIPATOR 5 H2 FALL 8 FAN SWITCH AUTO ON SYSTEM SWITCH EM. HT. LED (RED) O L COMPRESSOR FAULT G R EM. HT. RELAY E COOL CHANGEOVER VALVE FAN RELAY 1 L1 (HOT) L2 9 C1 ANTICIPATOR 10 C1 RISE 11 12 OFF EM. HT. HEAT AUTO COOL X AUX. HT. LED (GREEN) W2 AUX. HT. RELAY 2 B HEAT CHANGEOVER VALVE W3 RELAY W3 Y COMPRESSOR RELAY H1 CO RISE 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 ONLY TERMINAL B OR O TO BE USED. 0.8A MAX. M5152 Fig. 231. Schematic and hookup of T874G with Q674F. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR FALL 1 H1 4 FALL H2 5 H2 ANTICIPATOR 6 7 NO FAN SWITCH HEAT RELAY 1 W1 1 RH HEAT RELAY 2 W2 L2 L1 (HOT) T RISE 8 C1 9 RISE C2 C1 ANTICIPATOR 10 11 C2 ANTICIPATOR 12 SYSTEM SWITCH OFF AUTO 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. FAN RELAY B O RC Y2 COMPRESSOR CONTACTOR 2 Y1 COMPRESSOR CONTACTOR 1 L2 L1 (HOT) 1 M3957 Fig. 232. Schematic and hookup of T874D with Q674G. Used in standard applications. 60-2485--8 214 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL H1 1 H1 ANTICIPATOR 2 H2 ANTICIPATOR 3 FALL 4 H3 5 H3 ANTICIPATOR FALL H2 6 RISE C1 8 9 C1 ANTICIPATOR RISE C2 10 C2 ANTICIPATOR 11 RESET 12 AUTO ON FAN SWITCH SYSTEM SWITCH EM. HT. HEAT OFF COOL COMPRESSOR HIGH SPEED Y1 AUX. HT. W2 FAN G R EM. HT. E B EM. HT. LED (YELLOW) EM. HT. LIGHT X SERVICE LED (RED) L O Y T SERVICE LIGHT COOL CHANGEOVER COMPRESSOR LOW SPEED OUTDOOR RESET W89 HEAT PUMP CONTROL PANEL M3952 Fig. 233. Schematic and hookup of T874W with Q674L. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL H1 H1 ANTICIPATOR 1 2 FALL H2 RISE CO 4 H2 ANTICIPATOR 6 8 9 RISE C1 10 C1 ANTICIPATOR FAN SWITCH AUTO ON SYSTEM SWITCH HEAT OFF COOL COMPRESSOR CONTACTOR Y1 FAN RELAY G R W1 AUX. HT. RELAY C AUX. HEAT LED (RED) COOL CHANGEOVER VALVE O 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. L2 L1 (HOT) 1 M3961 Fig. 234. Schematic and hookup of T874G with Q674B. Used in heat pump applications. 215 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT H1 ANTICIPATOR 2 3 H1 FALL 4 SUBBASE FAN SWITCH AUTO ON SYSTEM COMPONENTS R RTD1 OTD1 L1 (HOT) L2 1 EHR1 RTD2 W2 ODT2 H2 ANTICIPATOR 5 AUX. HT. LED (GRN) EHR2 RTD3 FALL H2 8 9 RISE CHANGEOVER C1 ANTICIPATOR 10 RISE C1 SYSTEM SWITCH OFF COOL AUTO HEAT EM. HT. 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. EM. HT. LED (RED) X L G O E Y RTD1 RD LACO SYSTEM MONITOR FAN RELAY COOL CHANGEOVER VALVE EM. HT. RELAY COMPRESSOR CONTACTOR CHP M7064 Fig. 235. Schematic and hookup of T874G and Q674F. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS CONTROL MODULE 1 H1 ANTICIPATOR H1 FALL 4 FAN SWITCH AUTO ON W1 HEAT RELAY 1 W2 HEAT DAMPER HEAT RELAY 2 B FALL H2 6 H2 ANTICIPATOR 8 C1 RISE 9 10 RISE 11 C2 SYSTEM SWITCH OFF AUTO 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. RH 1 RC 1 COOL DAMPER O SERVICE LED (RED) G Y2 COMPRESSOR RELAY 2 Y1 A FAN RELAY COMPRESSOR RELAY 1 M7570 Fig. 236. Schematic and hookup of T874A-D with Q674C. Used in standard applications. 60-2485--8 216 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR 1 FALL H1 FALL 2 3 H2 ANTICIPATOR 4 5 H2 6 8 C1 RISE 10 FAN SWITCH AUTO ON SYSTEM SWITCH HEAT OFF COOL R G B LOW LED (YELLOW) W1 HI LED (GREEN) W2 C1 ANTICIPATOR Y 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. L1 (HOT) L2 1 FAN RELAY HEAT 1 HEAT 2 COMPRESSOR CONTACTOR M7716 Fig. 237. Schematic and hookup of T874C with Q674B. Used in standard applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 1 ANTICIPATOR 2 H1 FALL 4 6 H2 ANTICIPATOR FALL H2 C1 RISE 8 C1 ANTICIPATOR FAN SWITCH AUTO ON SYSTEM SWITCH AUX. HT. HT. PUMP 2 STAGE HT. OFF COOL X CHECK LED (RED) G FAN RELAY R B RELAY L1 (HOT) L2 1 B HEAT PUMP RELAY W1 AUX. HT. RELAY W2 AUX. HT. LED (RED) C 2 O COOL CHANGEOVER VALVE 10 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 FACTORY INSTALLED JUMPER BETWEEN TERMINALS W1 AND Y1. Y1 COMPRESSOR CONTACTOR M7719 Fig. 238. Schematic and hookup of T874C with Q674F. Used in heat pump applications. 217 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 FALL C1 H2 FALL 1 H1 ANTICIPATOR 2 3 4 5 6 11 RESET FAN SWITCH AUTO ON SYSTEM SWITCH EM. HT. HEAT OFF COOL AUX. HT. LED (GREEN) EM. HT. LED (RED) 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 FIELD REMOVABLE JUMPER. G FAN RELAY W 2 U B COMPRESSOR MONITOR F R OUTDOOR SENSOR T AUX. HT. RELAY L1 (HOT) L2 1 X2 COOL CHANGEOVER OUTDOOR VALVE THERMOSTAT O COMPRESSOR CONTACTOR Y M7744 Fig. 239. Schematic and hookup of T874R with Q674L. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 1 ANTICIPATOR 4 H1 FALL SYSTEM OFF 2 ON 8 FAN LO C1 RISE 9 C1 ANTICIPATOR 10 MED HI 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 FAN CONTINUOUS IN ON POSITION. W1 HEAT RELAY B B RELAY L1 R (HOT) L2 1 G1 K1 RELAY G2 K2 RELAY Y1 COMPRESSOR CONTACTOR L2 L1 K1 K1 K2 K2 K2 HI MED LO 3 SPEED FAN SCHEMATIC M7745 Fig. 240. Schematic and hookup of T874A with Q674W. Used in standard applications. 60-2485--8 218 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE 2 H1 ANTICIPATOR 3 H1 FALL 4 H2 ANTICIPATOR 5 FAN SWITCH AUTO ON 6 H2 FALL 8 C1 ANTICIPATOR 9 CO 10 RISE 11 C1 RISE CO 12 SYSTEM SWITCH SUPL. HT. HEAT OFF COOL 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. R Y G W2 SUPL. HEAT LED (RED) L C SYSTEM COMPONENTS L1 (HOT) L2 1 COMPRESSOR CONTACTOR FAN RELAY HEAT CHANGEOVER VALVE NO. 1 O.D.T. HEAT HEAT CHANGEOVER CHANGEOVER VALVE NO. 1 VALVE NO. 2 E HEAT HEAT CHANGEOVER CHANGEOVER VALVE NO. 2 VALVE NO. 3 X X RELAY P P RELAY O COOL CHANGEOVER VALVE M7742 Fig. 241. Schematic and hookup of T874J with Q674L. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR 1 H1 FALL 4 6 H2 ANTICIPATOR H2 FALL 8 RISE C0 9 C1 ANTICIPATOR FAN SWITCH AUTO ON SYSTEM SWITCH OFF AUTO OVERRIDE 2 10 RISE C1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 OVERRIDE IS MOMENTARY POSITION. SPRING RETURN TO (OFF) UPON SWITCH RELEASE. B HEAT DAMPER W1 HEAT RELAY 1 G HEAT RELAY 2 W2 R FAN RELAY L1 (HOT) L2 1 S1 OVERRIDE CIRCUIT CHANGEOVER VALVE O S2 OVERRIDE CIRCUIT Y SERVICE LED (RED) COMPRESSOR RELAY X ON LED (YEL) A C M7212 Fig. 242. Schematic and hookup of T874G with Q674C. Used in standard applications. 219 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL H1 1 H1 ANTICIPATOR 2 4 6 H2 ANTICIPATOR H2 FALL RISE 8 C1 9 C1 ANTICIPATOR 10 11 RISE CO 12 FAN SWITCH AUTO ON SYSTEM SWITCH OFF EM. HT. HEAT AUTO COOL O COOL CHANGEOVER VALVE G FAN RELAY B B RELAY R E L EM. HT. LED (RED) EM. HT. RELAY 2 X AUX. HEAT LED (GREEN) AUX. HEAT RELAY W2 L1 (HOT) L2 1 Y 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 TERMINAL LABELED C/X ON SOME MODELS. COMPRESSOR CONTACTOR M7715 Fig. 243. Schematic and hookup of T874G with Q674F. Used in heat pump applications. THERMOSTAT SUBBASE 2 H1 ANTICIPATOR 3 H1 FALL 4 H2 ANTICIPATOR 5 FAN SWITCH AUTO ON 6 H2 FALL 8 C1 ANTICIPATOR 9 CO 10 RISE 11 C1 RISE CO 12 SYSTEM SWITCH SUPL. HT. ON OFF 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. R Y G W2 SUPL. HEAT LED (RED) L C SYSTEM COMPONENTS L1 (HOT) L2 1 COMPRESSOR CONTACTOR FAN RELAY HEAT CHANGEOVER VALVE NO. 1 O.D.T. HEAT HEAT CHANGEOVER CHANGEOVER VALVE NO. 1 VALVE NO. 2 E HEAT HEAT CHANGEOVER CHANGEOVER VALVE NO. 2 VALVE NO. 3 X X RELAY P P RELAY O COOL CHANGEOVER VALVE M7743 Fig. 244. Schematic and hookup of T874J with Q674J. Used in heat pump applications. 60-2485--8 220 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 2 H1/C1 ANTICIPATOR 3 H1 FALL C1 4 6 H2 ANTICIPATOR FALL H2 FAN SWITCH AUTO ON SYSTEM SWITCH EM. HT. HEAT OFF COOL 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 TERMINAL LABELED C/X ON SOME MODELS. O COOL CHANGEOVER VALVE G FAN RELAY B B RELAY R E L EM. HT. LED (RED) EM. HT. RELAY 2 X AUX. HT. LED (GREEN) AUX. HT. RELAY W2 Y COMPRESSOR CONTACTOR Fig. 245. Schematic and hookup of T874R with Q674L. Used in heat pump applications. L1 (HOT) L2 1 M7718 THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR 1 H1 FALL 4 6 H2 ANTICIPATOR H2 FALL 8 NO FAN SWITCH SYSTEM SWITCH OFF AUTO C1 RISE 9 10 11 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. W1 HEAT RELAY 1 W2 HEAT RELAY 2 RH L2 L1 1 (HOT) RC Y1 COOL CHANGEOVER Y2 VALVE L1 (HOT) L2 1 M7717 Fig. 246. Schematic and hookup of T874C with Q674G. Used in standard applications. 221 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 FALL H1 ANTICIPATOR H1 2 FALL H2 H2 ANTICIPATOR 3 FALL H3 ANTICIPATOR 4 H3 5 6 RESET RISE 8 C1 9 C1 ANTICIPATOR 10 RISE C2 ANTICIPATOR 11 C2 12 FAN SWITCH AUTO ON SYSTEM SWITCH EM.HT. HEAT OFF COOL T C815A OUTDOOR THERMISTOR W3 AUX. HEAT LED (GREEN) AUX. HT. RELAY G R EM. HEAT LED (RED) E X1 CHECK LED (YELLOW) C B FAN RELAY EM. HT. RELAY CHANGEOVER RELAY (HEAT) 2 CHANGEOVER RELAY (COOL) O X2 COMPRESSOR CONTACTOR 1 Y1 COMPRESSOR CONTACTOR 2 Y2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 CONNECT CHANGEOVER RELAY TO 'O' TERMINAL FOR CHANGEOVER IN COOLING OR TO 'B' TERMINAL FOR CHANGEOVER IN HEATING. Fig. 247. Schematic and hookup of T874W with Q674L. Used in heat pump applications. L1 (HOT) L2 1 M6999 60-2485--8 222 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 2 H1 H1 FALL ANTICIPATOR 3 4 H2 H2 ANTICIPATOR FALL 5 7 RISE C1 8 C2 RISE CO 9 C1 ANTICIPATOR 10 C2 ANTICIPATOR 11 FAN SWITCH AUTO ON SYSTEM SWITCH OFF EM. HT. HEAT AUTO COOL R L G W2 AUX. HT. LED (RED) E MALFUNCTION LED (RED) C LOW SPEED LED (GREEN) HIGH SPEED LED (YELLOW) Y1 Y2 L1 (HOT) L2 1 FAN RELAY AUX. HT. RELAY EM.HT. RELAY COMPRESSOR CONTACTOR 1 COMPRESSOR CONTACTOR 2 RISE 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. O COOL CHANGEOVER VALVE M5923 Fig. 248. Schematic and hookup of T874Y with Q674F. Used in heat pump applications. 223 60-2485--8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT FALL H1 1 H1 ANTICIPATOR 3 4 FALL 6 H2 H2 ANTICIPATOR SUBBASE FAN SWITCH AUTO ON W1 G RC 2 W2 B SERVICE LED (RED) C SYSTEM COMPONENTS HEAT RELAY 1 FAN RELAY HEAT RELAY 2 HEAT DAMPER X SYSTEM 8 SWITCH L1 (HOT) 1 L2 RH C1 HEAT COOL DAMPER RISE 9 OFF O RISE C2 C1 ANTICIPATOR 10 C2 ANTICIPATOR 11 COOL COMPRESSOR CONTACTOR 1 Y1 COMPRESSOR CONTACTOR 2 Y2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 FIELD WIRE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER. M18622 Fig. 249. Schematic and hookup of T874C with Q674B. Used in heat pump applications. Home and Building Control Honeywell 1985 Douglas Drive North Golden Valley, MN 55422 Home and Building Control Honeywell Limited-Honeywell Limitée 35 Dynamic Drive Scarborough, Ontario M1V 4Z9 60-2485--8 J.H. 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