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Instruction Manual for MRCOOL models including: MGM96 96 Gas Furnace, MGM96, 96 Gas Furnace, Gas Furnace, Furnace
MRCOOL VersaPro 120K BTU, 96% AFUE, Multi-position, Gas Furnace (MGM96
MRCOOL VersaPro 80K BTU, 96% AFUE, Multi-position, Gas Furnace (MGM96E
File Info : application/pdf, 24 Pages, 6.95MB
DocumentDocumentVersaProTM 96% Gas Furnace Service Manual MODELS: · MGM96EE060B3NB · MGM96EE080B3NB · MGM96EE080C4NB · MGM96EE100C5NB · MGM96EE120D5NB Read this manual carefully before installation and keep it where the operator can easily find it for future reference. Due to updates and constantly improving performance, the information and instructions within this manual are subject to change without notice. Version Date: 05/30/24 Please visit www.mrcool.com/documentation to ensure you have the latest version of this manual. Contents CONTENTS 1 SAFETY PRECAUTIONS ......................................................................................... 2 2 TROUBLESHOOTING ............................................................................................ 3 2.1 Electrostatic Discharge (ESD) Precautions ............................................ 3 2.2 Resetting from Lockout........................................................................... 4 3 ERROR CODES ....................................................................................................... 4 3.1 No Light & No Fan ..................................................................................... 4 3.2 E7 System Lockout-Failed Ignition E8 System Lockout-Too Many Flame Dropouts .................................... 7 3.3 E1 Low Fire Pressure Switch Stuck Closed............................................. 9 3.4 E2 Low Pressure Switch Stuck Open E4 Pressure Switch Cycle Lockout E3 High Pressure Switch Stuck Open ................................................... 10 3.5 E5 Limit/Rollout Switch Open <> 5 minutes ........................................ 12 3.6 Pr Incorrect Polarity of L1/L2................................................................. 16 3.7 FL Low Flame ........................................................................................... 16 4 APPENDIX............................................................................................................ 17 4.1 Two-Stage Controller Logic ................................................................... 17 4.2 Ignition Failure & Re-Ignition Sequence.............................................. 19 4.3 Requirements for Refrigerant Leakage Sensors ................................ 20 1 mrcool.com 1 SAFETY Safety Precautions Read Before Using Incorrect usage may cause serious damage or injury. The symbols below are used throughout this manual to indicate instructions that should be followed closely or actions that should be avoided to prevent death, injury, and/or property damage. WARNING CAUTION Indicates the possibility of personal injury or loss of life. Indicates the possibility of property damage or serious consequences. NOTICE Used to address practices not related to personal injury. WARNING: FIRE OR EXPLOSION HAZARD 1. Do not store or use gasoline or other flammable vapors and liquids in the vicinity of this or any other appliance. 2. If you smell gas: · Do not try to light any appliance. · Do not touch any electrical switch; do not use any phone in the building. · Leave the building immediately. · Immediately call your gas supplier from a neighbor's phone. Follow the gas supplier's instructions. · If you cannot reach your gas supplier, call the fire department.\ 3. Installation and service must be performed by a qualified installer, service agency, or the gas supplier. 4. The furnace is designed and approved for use with Natural Gas and Propane (LP) Gas ONLY. 5. DO NOT BURN ANY LIQUID FUEL OR SOLID FUEL IN THIS FURNACE. 6. Burning any unapproved fuel will result in damage to the furnace's heat exchanger, which could result in Fire, Personal Injury, and/or Property Damage. 7. Improper installation, adjustment, alteration, maintenance, or use could cause carbon monoxide poisoning, explosion, fire, electrical shock, or other conditions which may cause personal injury or damage. Consult a qualified service agency, local gas supplier, or your distributor for information or assistance. 8. The furnace must be kept free and clear of insulating materials. Inspect surrounding area to ensure insulation material is at a safe distance when installing furnaces or adding insulation materials. Insulation materials ma be combustible. Maintain a 1 inch clearance from combustible materials to supply air ductwork for a distance of 36 inches horizontally from the furnace. See NFPA 90B or local code for further requirements. 9. The furnace SHOULD NOT be installed directly on carpeting, tile, or any other combustible material other than wood flooring. In downflow installations, a field supplied floor base MUST be used when installed on combustible materials and wood flooring. A special base is not required when this furnace is installed on industry-standard coil assembly matching correct furnace width. 10. Check entire gas assembly for leaks after lighting this appliance. 11. Never test for gas leaks with an open flame. Use a commercially available soap solution made specifically for the detection of leaks to check all connections, as specified in the installation and owner's manual. 12. See instructions for lighting/shutdown operation (as shown on a sticker directly on the inside of the furnace panel). Should the gas supply fail to shut off or if overheating occurs, shut off the gas valve to the furnace before shutting off the electrical supply. mrcool.com 2 2 TROUBLESHOOTING WARNING 1. Untrained personnel (homeowners) may only clean and replace filters and fuses as required for basic maintenance. All other operations, including installation, repair, and service must be performed by a qualified installer, service agency, or the gas supplier. 2. Do not use this furnace if any part has been under water. A flood-damaged furnace is extremely dangerous. Attempts to use the furnace can result in fire or explosion. A qualified service agent must inspect the furnace and replace all gas controls, control system parts, and electrical parts that have been wet, or the furnace if deemed necessary. 3. Wear safety glasses, protective clothing, and work gloves. Have a fire extinguisher available. 4. Read these instructions thoroughly and follow all warnings or cautions included in literature attached to the unit. 5. Consult local building codes as well as the current editions of the National Fuel Gas Code (NFGC) NFPA 54/ ANSI Z223.1 and the National Electrical Code (NEC) NFPA 70. 6. This product can expose you to chemicals including lead and lead components, which are known to the State of California to cause cancer and birth defects or other reproductive harm. Fore more information, go to www.P65Warnings.ca.gov. CAUTION: CUT HAZARD Failure to follow this caution may result in personal injury. Sheet metal parts may have sharp edges or burrs. Use care and wear appropriate protective clothing, safety glasses, and gloves when handling parts and servicing the furnace. 2.1 Electrostatic Discharge (ESD) Precautions NOTE Discharge body's static electricity before touching unit. An electrostatic discharge can adversely affect electrical components. Use the following precautions during furnace installation and servicing to protect the integrated control module from damage. By putting the furnace control and the person at the same electrostatic potential these steps will help avoid exposing the integrated control module to electrostatic discharge. This procedure is applicable to both installed and uninstalled (ungrounded) furnaces. 1. Disconnect all power to the furnace. Do not touch the integrated control module or any wire connected to the control prior to discharging your body's electrostatic charge to ground. 2. Firmly touch a clean unpainted metal surface of the furnace away from the control. Any tools held in a person's hand during grounding will be discharged. 3. Service integrated control module or connecting wiring following the discharge process in step 2. Use caution not to recharge your body with static electricity; (i.e. do not move or shuffle e your feet, do not touch ungrounded objects, etc.). If you come in contact with an ungrounded object, repeat step 2 before touching control or wires. 4. Discharge your body to ground before removing a new control from its container. Follow steps 1 through 3 if installing the control on a furnace. Return any old or new controls to their containers before touching any ungrounded object. 3 mrcool.com 3 ERROR CODES 2.2 Resetting from Lockout Furnace lockout results when a furnace is unable to achieve ignition after three attempts. Refer to the troubleshooting chart on the following pages for assistance in determining the source of unit operational problems. The red diagnostic LED blinks to assist in troubleshooting the unit. If the furnace is in "lockout" it will (or can be) reset in any of the following ways. 1. Automatic reset. The integrated control module will automatically reset itself and attempt to resume normal operations following a one hour lockout period. 2. Manual power interruption. Interrupt 115 volt power to the furnace for 1 - 20 seconds. 3. Manual thermostat cycle. Lower the thermostat so that there is no longer a call for heat for 1 - 20 sec. 3.1 No Light & No Fan Leave "Park" terminal unused. mrcool.com 4 3 ERROR CODES No Light and No Fan (Sy Figures & Tables t Normally) 1 1. Check for 18-31Vac power between these 2 terminals with multi-meter. Figure 3 1 1. Check for 115Vac power supply between L1 and common terminal Figure 1 1 1. Power off. 2. Press in the door switch. 3. Use a multi-meter to measure the resistance. If it is 0 , then the door switch is ok. Figure 2 1. Check for 18-31Vac power between "R" & "C" terminals with multi-meter. Figure 4 5 mrcool.com 3 ERROR CODES 1 1 1. Check for 18-31Vac power between "W/W1" & "C" terminals with multi-meter Figure 5 1. Check for 18-31Vac power between Hi-heat/lo-heat/hi-cool/lo-cool and COM with multi-meter 2. Check for 115Vac power supply between CIRC-H and N with multi-meter Figure 7 QCPASS 1 1. Check for 18-31Vac power between "G" & "C" terminals with multi-meter Figure 6 1 BLACK W 3 WHITE V 5 RED U M BK WH RD W V U 5 3 1 The resistance between motor U, V and W wires is 2~10 ohms Figure 8 mrcool.com 6 3 ERROR CODES 3.2 E7 System Lock-Out - Failed Ignition E8 System Lock-out - Too Many Flame Dropouts Start Are there any loose wires or wrong connections? No Correct wiring Yes according to wiring diagram Unit should Does the work No unit show 1 LED flash normally after restart? Yes Is the Yes ignitor "glowing" No red/orange? Is gas valve switched to No "On" position? Turn the gas Yes valve switch to "On" Is there a flame? (visual check) Yes No Replace the ignitor No Is the ignitor working properly? See Figure 8 Replace the PCB Board No Check the wire Is there connections Yes power to the ignitor? Yes between See Figure 9 ignitor and PCB Board Is flame reaching the flame sensor? (visual Yes check) Is the flame sensor dirty or broken? No Clean with Yes steel wool or replace the flame sensor Replace the Is there a PCB No signal to the gas valve? No board See Figure 10 Yes Check Does the Are orifices incoming gas supply Yes manifold gas pressure meet the requirement? No blocked or clogged? (check burner) quality See Table 1 No Yes Adjust gas valve to ensure it meets gas Yes pressure requirement Is the inlet gas pressure meeting the requirement? See Table 2 No Remove the blockage Replace the gas valve if the pressure cannot be adjusted Adjust the inlet gas pressure Is the wire Properly grounded properly? No ground the See Figure 11 wire Yes Replace the PCB board The flame sense signal should be 1-6 microamps. 7 mrcool.com E7 (System Lock-Out due to Failed Ignition) E8 (System Lock-Out due to too Many Flame Dropouts) Figures & Tables 3 ERROR CODES 1 1 1. Check for 9-17 between these two terminals with multi-meter. Figure 9 1. Check for 18-31Vac power between "M/HI"&"C" terminals with a multi-meter Figure 11 1 1 1. Check for proper grounding (green wire). 1. Check for 115Vac power supply between IG and IGN with multi-meter during preheating sequence. Figure 12 Figure 10 Manifold Gas Pressure Natural Gas 3.5 in. W.C. Propane Gas 10 in. W.C. Table 1 Manifold Gas Pressure Inlet Gas Supply Pressure Natural Gas Propane Gas Inlet Gas Supply Pressure Minimum: 4.5 in. W.C. Maximum: 10.5 in. W.C. Minimum: 11.0 in W.C. Maximum: 13.0 in. W.C. Table 2 Inlet Gas Supply Pressure mrcool.com 8 3 ERROR CODES 3.3 E1 Low Fire Pressure Switch Stuck Closed Start Are there any loose wires or wrong connections? No This error could also be caused by a blocked vent. Check vent for obstructions. If a vent is blocked, the unit's safety protection logic will turn off the unit. Does the resistance of low fire pressure switch show as " " ? See Figure 12 & 13 Yes Replace the PCB Board Correct wiring Yes according to the wiring diagram Replace the No pressure switch Figure 13 9 mrcool.com Figure 14 3.4 E2 Low Pressure Switch Stuck Open E4 Pressure Switch Cycle Lockout E3 High Pressure Switch Stuck Open 3 ERROR CODES Start Are there any loose wires or wrong connections? No Is the pressure switch closed? See Figure 14 & 15. No Is there blockage in the pressure hose or is the hose loose? See Figure 16. No Correct wiring Yes according to the wiring diagram Replace Yes the PCB Board Remove Yes blockage or fix the pressure hose Is there blockage in the exhaust pipe? Remove Yes blockage in the exhaust pipe No Is the pressure at the pressure switch correct? No See Figure 17. Replace the inducer Yes Replace the pressure switch mrcool.com 10 3 ERROR CODES E2 (Low Pressure Switch Stuck Open) E4 (Pressure Switch Cycle Lockout) E3 (High Pressure Switch Stuck Open) FigurTehse pressure switch that you are checking in this step depends on the number of LED flashes. Refer to the specTifhice fplraesshseusreasnwdittchhethiradt yeosucrairpetciohnesc.king in this step depends on the number of LED flashes. Refer to the specific flashes and their descriptions above. High fire pressure switch Low fire pressure switch Overflow pressure switch Figure 15 1 1. Check pressure hose for proper operating condition. Check for proper hose connections. Check and remove any blockages in the hose. Figure 17 High fire pressure switch 2 Low fire pressure switch 1 1 1. Check for 0Vac between these two terminals with multi-meter. Figure 16 Check to see if the pressure at pressure switch is correct by removing the hose and measuring with a manometer. (1) Low Pressure Switch Set Point: 0.55 in. WC (2) High Pressure Switch Set Point: 1.1 in. WC Figure 18 11 mrcool.com 3 ERROR CODES 3.5 E5 Limit/Rollout Switch Open Less than 5 Minutes E6 Limit/Rollout Switch Open More than 5 Minutes Remove blockage in the exhaust pipe Start Are there any loose wires or wrong connections? No Correct wiring Yes according to wiring diagram "SW2" is used for the fan delay after burner starts. · "SW2" is used for the fan delay after burner starts. · Verify that the temperature rise is between 40- 5V5e°rFif.y that the temperature rise is between 40-55°F. Turn off the equipment for 10 minutes to ensure sufficient cooling off period.Measure the resistance between two leads on the limit switches No Replace the (chamber/fan mounted) Limit Switch Are the limit switches working properly? See Figure 18 & 19. Replace the PCB Board Replace the Rollout Switch Replace the inducer Yes Yes Is there Is the rollout limit switch Yes blockage in the exhaust No showing resistance of Yes pipe? "0"? See Figure 20 & 21. Yes After manual reset of the limit switch(by pressing the button on switch),is the Yes error still present once the system starts up? Yes No Is the inducer working properly? Are (chamber/fan mounted) limited switches in right models? See Table 3 Yes Is the circulating fan motor turning on after 30s delay? Replace the No Limit Switch No Is there power to the circulating fan motor? Yes See Figure 7 Replace the circulating fan motor No Yes Is there blockage on the filter? Yes Clean/Replace the filter Is the circulating fan motor No speed correctly set? See Tables 4 &5 Yes Check the airflow duct for blockage Replace the PCB Board No Correct the circulating fan motor speed or replace the motor if necessary. mrcool.com 12 3 ERROR CODES 1 1 2 1. Chamber mounted limit switch (behind the gas valve) 2. Fan mounted limit switch (side of blower fan, behind PCB board) Figure 19 Figure 21 1. Rollout limit switch locations. 1 1 1. Power off and check for 0 resistance between these two terminals with multimeter. Figure 22 1. Check for 0 resistance between these two terminals with multi-meter. Make sure to do this check on both chamber and fan mounted limit switches. Figure 20 Model MGM96EE060B3NB MGM96EE080B3NB MGM96EE080C4NB MGM96EE100C5NB MGM96EE120D5NB Rollout Switch Resettable -- °F 300 Inlet High Temp. Limit Switch - Fixed Off/ On °F 150 / 120 M 150 / 120 M M 150 / 120 M 150 / 120 M 150 / 120 M 13 mrcool.com 3 ERROR CODES Furnace Size Return-Air Inlet Speed H Mid-H 60B Bottom or Sides Mid Mid-L Low H Mid-H 80B Bottom or Sides Mid Mid-L Low H Mid-H 80C Bottom or Sides Mid CFM Temp. Rise-1st Stage °F Temp. Ride-2nd Stage °F CFM Temp. Rise-1st Stage °F Temp. Ride-2nd Stage °F CFM Temp. Rise-1st Stage °F Temp. Ride-2nd Stage °F CFM Temp. Rise-1st Stage °F Temp. Ride-2nd Stage °F CFM Temp. Rise-1st Stage °F Temp. Ride-2nd Stage °F CFM Temp. Rise-1st Stage °F Temp. Ride-2nd Stage °F CFM Temp. Rise-1st Stage °F Temp. Ride-2nd Stage °F CFM Temp. Rise-1st Stage °F Temp. Ride-2nd Stage °F CFM Temp. Rise-1st Stage °F Temp. Ride-2nd Stage °F CFM Temp. Rise-1st Stage °F Temp. Ride-2nd Stage °F CFM Temp. Rise-1st Stage °F Temp. Ride-2nd Stage °F CFM Temp. Rise-1st Stage °F Temp. Ride-2nd Stage °F CFM Temp. Rise-1st Stage °F Temp. Ride-2nd Stage °F 0.1 1339 -37.3 1124 -44.2 880 36.7 56.3 779 41.4 -553 58.1 -1230 -53.9 1052 41.0 62.8 849 50.6 -754 56.9 -569 --1303 -50.8 1120 38.5 59.0 908 47.3 -- 0.2 1327 -37.7 1118 -44.5 870 37.2 57.0 768 42.0 -586 54.9 -1233 -53.8 1052 41.0 62.8 861 50.0 -771 55.7 -554 --1301 -50.9 1127 38.3 58.7 894 48.1 -- External Static Pressure (in. W.C.) 0.3 0.4 0.5 0.6 0.7 0.8 1338 1309 1321 1320 1342 1334 -- -- -- -- -- -- 37.5 38.3 38.1 38.1 37.6 37.9 1102 1106 1096 1099 1102 1109 -- -- -- -- -- -- 45.2 45.1 45.6 45.5 45.5 45.3 853 858 865 858 854 866 37.9 37.8 37.6 38.0 38.2 37.8 58.1 57.9 57.5 58.0 58.4 57.7 762 756 740 753 757 747 42.4 42.8 43.8 43.1 43.0 43.6 -- -- -- -- -- -- 543 569 552 562 584 572 59.3 56.74 58.5 57.6 55.5 56.8 -- -- -- -- -- -- 1222 1226 1214 1236 1255 1244 -- -- -- -- -- -- 54.4 54.3 54.8 53.9 53.2 53.7 1041 1044 1037 1034 1048 1046 41.5 41.5 41.8 42.1 41.5 41.7 63.6 63.5 64.0 64.3 63.4 63.7 854 853 855 844 855 848 50.4 50.5 50.5 51.2 50.6 51.2 -- -- -- -- -- -- 765 764 728 761 782 739 56.2 56.3 59.2 56.8 55.3 58.5 -- -- -- -- -- -- 571 572 568 572 598 594 -- -- -- -- -- -- -- -- -- -- -- -- 1281 1291 1289 1291 1290 1295 -- -- -- -- -- -- 51.8 51.5 51.6 51.6 51.7 51.6 1134 1130 1135 1138 1132 1143 38.1 38.3 38.2 38.2 38.5 38.2 58.4 58.7 58.5 58.4 58.8 58.3 896 902 896 894 864 891 48.0 47.8 48.2 48.4 50.1 48.7 -- -- -- -- -- -- 0.9 1316 -38.5 1089 -46.2 871 37.6 57.4 785 41.6 -575 56.5 -1249 -53.6 1024 42.7 65.1 834 52.1 -758 57.2 -572 --1298 -51.6 1107 39.5 60.3 935 46.5 -- 1.0 1335 -38.0 1105 -45.6 839 39.1 59.7 766 42.7 -567 57.4 -1251 -53.6 1076 40.7 62.1 859 50.7 -758 57.3 -548 --1253 -53.5 1112 39.4 60.1 880 49.5 -- Mid-L Low CFM Temp. Rise-1st Stage °F Temp. Ride-2nd Stage °F CFM Temp. Rise-1st Stage °F Temp. Ride-2nd Stage °F 818 819 825 800 813 803 831 838 791 802 52.4 52.4 52.1 53.8 53.1 53.8 52.1 51.8 54.9 54.2 -- -- -- -- -- -- -- -- -- -- 577 628 605 624 615 601 628 573 590 588 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- Table 4 - Air Delivery CFM (Without Filter) * ** * A filter is required for each return air inlet. This table shows the airflow performance without a filter. To determine airflow performance with a filter, if a 3/4 inch (19mm) washable media filter is used, assume an additional 0.1 in. W.C. available external static pressure. ** The manufacturer default fan settings are based on model, refer to Table 24. mrcool.com 14 3 ERROR CODES Furnace Size Return-Air Inlet Speed H Mid-H 100C Bottom or Sides Mid Mid-L Low H Mid-H 120D Bottom or Sides Mid Mid-L Low CFM Temp. Rise-1st Stage °F Temp. Ride-2nd Stage °F CFM Temp. Rise-1st Stage °F Temp. Ride-2nd Stage °F CFM Temp. Rise-1st Stage °F Temp. Ride-2nd Stage °F CFM Temp. Rise-1st Stage °F Temp. Ride-2nd Stage °F CFM Temp. Rise-1st Stage °F Temp. Ride-2nd Stage °F CFM Temp. Rise-1st Stage °F Temp. Ride-2nd Stage °F CFM Temp. Rise-1st Stage °F Temp. Ride-2nd Stage °F CFM Temp. Rise-1st Stage °F Temp. Ride-2nd Stage °F CFM Temp. Rise-1st Stage °F Temp. Ride-2nd Stage °F CFM Temp. Rise-1st Stage °F Temp. Ride-2nd Stage °F 0.1 1752 -47.5 1512 38.6 54.8 1354 42.9 61.1 1165 49.7 -994 58.1 -1926 -51.8 1721 -57.8 1489 46.7 66.5 1384 50.2 -1165 59.5 -- 0.2 1764 -47.3 1506 38.8 55.1 1354 43.0 61.1 1165 49.7 -1025 56.4 -1933 -51.7 1747 -57.0 1497 46.6 66.3 1360 51.1 -1175 59.0 -- External Static Pressure (in. W.C.) 0.3 0.4 0.5 0.6 0.7 0.8 1768 1781 1774 1786 1762 1802 -- -- -- -- -- -- 47.3 47.0 47.3 47.0 47.7 46.8 1536 1523 1514 1509 1529 1551 38.1 38.5 38.8 39.0 38.6 38.1 54.1 54.6 55.1 55.3 54.7 54.0 1362 1370 1357 1381 1389 1394 42.8 42.6 43.1 42.4 42.3 42.2 60.8 60.6 61.2 60.3 60.0 59.9 1176 1164 1185 1190 1186 1205 49.3 49.9 49.2 49.0 49.2 48.6 -- -- -- -- -- -- 1018 1024 1032 1026 1035 988 56.9 56.6 56.3 56.7 56.3 59.0 -- -- -- -- -- -- 1915 1923 1916 1929 1971 1941 -- -- -- -- -- -- 52.2 52.1 52.4 52.1 51.1 52.0 1716 1749 1760 1768 1778 1783 -- -- -- -- -- -- 58.1 57.1 56.8 56.6 56.4 56.3 1503 1504 1507 1488 1496 1518 46.4 465 46.5 47.1 47.0 46.4 66.1 66.1 66.1 67.0 66.7 65.8 1365 1384 1382 1383 1379 1401 51.0 50.4 50.6 50.6 50.8 50.1 -- -- -- -- -- -- 1162 1158 1158 1184 1186 1204 59.8 60.0 60.1 58.9 58.9 58.1 -- -- -- -- -- -- 0.9 1792 -47.2 1565 37.9 53.6 1416 41.7 59.0 1174 49.9 -1005 58.1 -2036 -49.8 1747 -57.5 1519 46.4 65.9 1421 49.5 -1201 58.4 -- 1.0 1786 -47.4 1532 38.8 54.8 1383 42.7 60.5 1199 49.0 -1041 56.2 -1998 -50.7 1788 -56.4 1568 45.1 64.0 1414 49.9 -1185 59.2 -- Table 5 - Air Delivery CFM (Without Filter) * ** * A filter is required for each return air inlet. This table shows the airflow performance without a filter. To determine airflow performance with a filter, if a 3/4 inch (19mm) washable media filter is used, assume an additional 0.1 in. W.C. available external static pressure. ** The manufacturer default fan settings are based on model, refer to Table 24. 15 mrcool.com 3.6 Pr (Incorrect Polarity of L1/L2) 3.7 FL (Low Flame) Figure 23 3 ERROR CODES NOTE Please refer to the wiring diagram to confirm whether the connection is normal. Please check whether the input power ground wire is correctly and reliably connected to the machine. mrcool.com 16 4 APPENDIX 4.1 Two-Stage Controller Logic There are two heating modes: 1. Low Fire Heating Mode: Only W1 signal 2. High Fire Heating Mode: Both W1 and W2 signal If you are using a single-stage thermostat, only a W1 signal will be sent. in this scenario, the furnace will upstage from low to high fire via a timing sequence. The time delay is set via the S1-1 and S1-2 dip switches on the control board. If the furnace fails to ignite, there is a separate logic for the re-ignition sequence. Low Fire Heating Mode Logic (only W1 signal): Figure 24 1. When there is a call for heat (W1), the inducer will start on high speed and the low pressure switch closes. This will last for 15 seconds. 2. Inducer will turn to low speed and the igniter will energize. This preheating sequences lasts for 17 seconds. 3. After preheating, the gas valve opens and the burners light. The igniter will turn off after 3 seconds. 4. There is a 30 second time delay before the blower motor starts. 5. The system is working properly. 6. When there is no call for heat (no W1 call) and no flame is sensed, post-purge begins. This will last for 15 seconds. 7. There is a fan delay to dissipate heat in the system. This time depends on the dip switch S1-3 and S1-4. The default time is 180 seconds. 17 mrcool.com High Fire Heating Mode (W1+W2 Signal): 4 APPENDIX Figure 25 1. When there is a call for heat (W1), the inducer will start on high speed and the low pressure switch closes. This will last for 15 seconds. 2. Inducer will turn to low speed and the igniter will energize. This preheating sequences lasts for 17 seconds. 3. After preheating, the gas valve opens and the burners light. The igniter will turn off after 3 seconds. 4. Before the gas valve, inducer, and pressure switch turn to high stage, there is a 5 second delay. 5. There is a time delay of 30 seconds before the blower motor starts. 6. The system is working properly in high stage. 7. When there is no call for heat, there is a time delay before the inducer shuts down. This will last for 15 seconds. 8. The blower motor will run at high speed for 30 seconds for fan delay. 9. There is a fan delay to dissipate heat in the system. This time depends on the dip switch S1-3 and S1-4. The default time is 180 seconds. mrcool.com 18 4 APPENDIX 4.2 Ignition Failure & Re-ignition Sequence If the furnace fails to ignite, there is a separate logic for the re-ignition sequence: Figure 26 1. When there is a call for heat (W1), the inducer will start on high speed and the low pressure switch closes. This will last for 15 seconds. 2. Inducer will turn to low speed and the igniter will energize. This preheating sequence lasts for 17 seconds. 3. After preheating, the gas valve opens and the burners light. The igniter will turn off after 3 seconds. 4. The gas valve will open for 4 seconds if there is no flame. 5. The inducer will run at high speed for 60 seconds. 6. Test of low pressure switch 7. Preheating occurs for 27 seconds. 8. After preheating, the gas valve opens. The igniter will turn off after 3 seconds. After two failed ignition attempts, the system will lock out. 19 mrcool.com 4.3 Requirements for Refrigerant Leakage Sensors W2 Delay DIP SW Nominal (Minutes) S1-1 S1-2 *OFF OFF OFF ON OFF 10 OFF ON AUTO ON ON 20 Heat Off Delay DIP SW Nominal S2-1 S2-2 (Minutes) *OFF OFF 90 ON OFF 120 OFF ON 150 ON ON 180 Cool Off Delay DIP SW Nominal (Minutes) S2-3 S2-4 *OFF OFF 60 ON OFF 90 OFF ON 120 ON ON 150 Option Switch Positions 4 APPENDIX mrcool.com 20 4 APPENDIX A B SW2-1 OFF OFF OFF OFF ON ON Series of Products OFF SW2-4 ON 80% Gas Furnace 96% Gas Furnace A 96% Machine Type DIP SW SW2-2 OFF SW2-3 OFF OFF ON ON OFF ON ON OFF OFF OFF ON Type * * 60B, 80B 80C 100C 120D SW1-1 SW1-2 B Fan Speed OFF Normal Speed ON Slow Speed OFF W/O Refrigerant Sensor ON W/ Refrigerant Sensor WARNING According to the safety requirements of UL 60335-2-40 on combustible refrigerant A2L, when the gas furnace is used with coil and the new type of combustible refrigerant is used in the coil, the unit must be equipped with the refrigerant gas detection sensor to monitor the refrigerant concentration around the unit in real time to prevent the danger of abnormal refrigerant leakage. Refrigerant gas detection sensors are manufactured under the coil manufacturing label and must be installed by a qualified local gas supplier, distributor or service organization. If the refrigerant gas detection sensor is not installed or is incorrectly installed, it does not meet the requirements of current regulations and cannot effectively warn of an emergency, which may cause personal injury. Therefore, follow the instructions provided in the manual. 21 mrcool.com 4 APPENDIX Installation of refrigerant gas detection sensor: For the use of a coil unit, connect the refrigerant gas sensor cable terminal to the CN30 Interface, as shown in "Gas Furnace Control Module" and move the drive plate SW1-2 to the "ON" position. Refer to the coil manual for installation locations of refrigerant gas sensors. Operation Indication of Refrigerant Gas Sensor: When the sensor detects a refrigerant leak, the unit will respond according to the following rules. LED2 Number of Green Flashes 1 Fault Location The refrigerant sensor communication fails Refrigerant 2 concentration exceeds the limit alarm value 3 Forget the dip reminder 4 Expiration reminder Fault Cause The communication with the refrigerant sensor fails for 2 minutes or the refrigerant sensor is faulty. The pipe is damaged or the refrigerant leaks. The sensor is connected and communication is normal, but SW1-2 is in the "OFF" position. The sensor expired or is faulty. Unit Response & Handling Method The LED2 indicator of the driver board blinks green once, and the Y signal is disconnected to stop cooling. Contact MRCOOL to check the sensor. The green light of the drive board LED2 flashes twice, disconnect the Y signal, stop the refrigeration, and the fan in the unit will continue to run until the refrigerant concentration is detected to decrease to a safe value. Maintain ventilation and avoid open flames. Contact MRCOOL to check the unit. LED2 of the driver board blinks green three times. Check whether SW1-2 is in the ON position. The LED2 indicator of the driver board blinks green four times to turn off the Y signal and stop cooling. Contact MRCOOL for a new refrigerant detection sensor. mrcool.com 22 VersaProTM 96% Gas Furnace Service Manual The design and specifications of this product and/or manual are subject to change without prior notice. Consult with the sales agency or manufacturer for details.