Introduction
Congratulations on your purchase of the Honeywell Thermostat. This smart thermostat offers total comfort temperature management with Adaptive Intelligent Recovery™.
Key features include:
- Maintains comfort by automatically calculating furnace or air conditioning activation times for desired temperatures upon arrival.
- Saves energy and money by remembering to adjust settings when you leave or sleep.
- Offers convenience with a pre-programmed schedule, which you can customize.
This manual will guide you through the features and operation of your new thermostat.
Energy Savings Overview
The document includes a chart illustrating typical energy savings for representative cities in the U.S. and Canada. These savings are based on temperature decreases for heating and increases for cooling.
The chart displays approximate percentage of energy cost savings for different cities. It shows savings for a 10°F (5°C) decrease (once-a-day and twice-a-day settings) and savings for a 5°F (3°C) summer increase. The data is presented as bar graphs for various cities across the United States and Canada.
*Based on a 10°F (5°C) decrease. A 5°F (3°C) decrease gives approximately 55 percent of these savings.
Recycling Information
If this thermostat replaces a control containing mercury in a sealed tube, do not dispose of it in the trash. Contact your local waste management authority for proper recycling and disposal instructions.
For questions, call Honeywell Inc. at 1-800-468-1502.
Figure 1 shows the typical location of a mercury switch within a thermostat.
Table of Contents
- STEP 1: Prepare For Installation
- STEP 2: Remove Old Thermostat
- STEP 3: Before You Program
- Install the Batteries
- Adaptive Intelligent Recovery™ Selection
- STEP 4: Program The Thermostat
- STEP 5: Mount Thermostat Wallplate
- STEP 6: Adjust System On-Time, Clock Display, as Required
- STEP 7: Adjust Fan Operation Switch, As Required
- STEP 8: Wire Wallplate Terminals
- STEP 9: Mount The Thermostat
- STEP 10: Check Thermostat Operation After Programming and Installing
- STEP 11: Set The Fan And System Switches
- Troubleshooting Guide
- Index
- Limited One-Year Warranty
STEP 1: Prepare For Installation
Before installation, check the compatibility of this thermostat with your heating and cooling system using the chart below. If incompatible, return the thermostat to the retailer.
For more information, call Honeywell Customer Assistance, toll-free at 1-800-468-1502.
Table 1. Compatibility Chart
| System Type | Compatible with CT3400/3455 |
|---|---|
| Gas—Standing Pilot | Yes |
| Gas—Electronic Ignition | Yes |
| Gas-Fired Boilers | Yes |
| Gas—Millivolt | No |
| Oil-Fired Boilers | Yes ⚠️ |
| Oil-Fired Furnace | Yes |
| Electric Furnace | Yes |
| Electric Air Conditioning | Yes |
| Baseboard Electric (120/240 line volt) | No |
| Heat Pumps/Multistage Equipment | No |
Not compatible with any 120/240 volt circuit.
⚠️ Compatible with 2-wire Honeywell and Taco zone valves. Not compatible with 3-wire zone valves or 2-wire White Rodgers no. 1361 valves.
STEP 2: Remove Old Thermostat
Safety First:
- Test your heating and cooling systems to ensure they are working properly. If not, contact a dealer.
- To prevent compressor damage, do not operate the cooling system when outdoor temperature is below 50°F (10°C).
- Turn off power to the system at the furnace or circuit breaker panel.
Removal Process:
- Carefully unpack your new thermostat and wallplate; save screws, instructions, and receipt.
- Remove the cover from the old thermostat. If it's difficult to remove, check for a locking screw.
- Loosen screws holding the thermostat to its base, wallplate, or wall, and lift it away.
- Disconnect wires from the old thermostat or subbase.
- As you disconnect each wire, use masking tape to label it with its old terminal designation. If only two wires are present, labeling is not necessary.
- Wrap wires around a pencil to prevent them from falling back into the wall.
An illustration shows wires passing through a wall opening, with a pencil used to keep them from retracting.
Replacing a clock thermostat with C or C1 terminals? If you are replacing a Honeywell Chronotherm® Thermostat, you might find wires connected to the C or C1 terminals. Ensure these wires do not touch each other, as this could damage your transformer. Disconnect and wrap them separately with electrical tape. Place them where they won't interfere with the new thermostat. Record wire colors and terminal designations.
Six or more wires? If you have six or more wires (excluding clock wires), you likely have a heat pump or multistage system. This thermostat is not compatible. Return it to the place of purchase. For compatible programmable thermostats, contact Honeywell Customer Assistance at 1-800-468-1502.
Three thermostat wires? This thermostat works for heating-only systems if the fan can be operated via the FAN ON switch. For some hot water (zoned) heating systems with three wires, an isolating relay may be required. Contact Honeywell Customer Assistance at 1-800-468-1502 for details.
STEP 3: Before You Program
Install the Batteries
IMPORTANT: Three AA alkaline batteries are included and required for programming and operation.
- Install batteries in the back of the thermostat, ensuring positive (+) terminals face toward the right.
An illustration shows the back of the thermostat with three AA batteries being inserted, with the positive (+) terminals oriented to the right.
A REPL BAT indicator will flash 1-2 months before batteries run out. Replace them promptly.
If new batteries are installed within 20-30 seconds of removing old ones, reprogramming may not be necessary. If the display is blank, batteries may be dead or incorrectly installed; reprogram using pages 13-15. If not reprogrammed, factory settings will be used.
Battery Maintenance: Replace batteries annually to prevent leakage and system shutdown. When leaving home for over a month, change batteries before departing. Use fresh alkaline batteries; non-alkaline batteries may leak and cause damage. Energizer® batteries are recommended.
Adaptive Intelligent Recovery™ Selection
Decide whether to use the factory-set Adaptive Intelligent Recovery™ or conventional recovery. For conventional recovery, turn screw 3A on the back of the thermostat one turn outwards.
Adaptive Intelligent Recovery™ gradually brings your home to the programmed comfort temperature by the set time, optimizing energy savings and comfort.
More about Adaptive Intelligent Recovery™
This thermostat uses a small computer to calculate furnace/AC activation times, considering:
- Current air temperature
- Wall temperature
- Desired comfort temperature establishment time
During recovery, the thermostat gradually increases temperature and cycles equipment to avoid overshooting the target, saving energy. The CURRENT SETTING key displays the current control temperature during recovery.
The system learns and adjusts recovery start times daily. It typically takes 4-8 days after installation for the thermostat to adapt to your home's environment and lifestyle.
With conventional recovery, the programmed time is when the furnace/AC starts, so set it earlier than your desired comfort time (30 minutes is a good starting point).
Indicator: If screw 3A is adjusted for conventional recovery, a ? symbol appears in the lower right corner of the display as a reminder.
An image shows a thermostat display with the time and temperature, and a small indicator symbol in the corner labeled "INDICATES THERMOSTAT IS SET FOR CONVENTIONAL RECOVERY".
STEP 4: Program The Thermostat
You can program the thermostat while holding it or after it's mounted on the wall (skip to page 16 if programming after mounting).
A personal programming chart (pages 11-12) is available to help plan your schedule.
There are four programmable time periods:
- MORNING: For comfortable temperature when waking up and preparing for the day.
- DAYTIME: For energy-saving temperature while away at work or school.
- EVENING: For comfortable temperature during evening activities.
- NIGHT: For energy-saving temperature while sleeping.
You will set one schedule for weekdays, one for Saturday, and one for Sunday.
Fill in your desired times and temperatures. Factory pre-programmed settings are shown in parentheses and will be used if you do not program the thermostat. A MORNING period program is required. DAYTIME and EVENING can be left blank. NIGHT can be changed or canceled (see page 15).
Before programming, remove the clear plastic overlay from the display.
Use the ball of your finger or a soft pencil eraser to press keys. Sharp objects can damage the keypad.
If you make an error, press the RUN PROGRAM key and resume at the previous step.
Personal Programming Chart
This chart helps plan your schedule for weekdays, Saturdays, and Sundays.
Weekday Program
| PERIOD | START TIME | HEATING TEMPERATURE | COOLING TEMPERATURE |
|---|---|---|---|
| MORNING | (6:00 AM) | (70°F [21°C]) | (78°F [26°C]) |
| DAYTIME | |||
| EVENING | (10:00 PM) | (60°F [16°C]) | (78°F [26°C]) |
| NIGHT |
Saturday Program
| PERIOD | START TIME | HEATING TEMPERATURE | COOLING TEMPERATURE |
|---|---|---|---|
| MORNING | (6:00 AM) | (70°F [21°C]) | (78°F [26°C]) |
| DAYTIME | |||
| EVENING | (10:00 PM) | (60°F [16°C]) | (78°F [26°C]) |
| NIGHT |
Sunday Program
| PERIOD | START TIME | HEATING TEMPERATURE | COOLING TEMPERATURE |
|---|---|---|---|
| MORNING | (6:00 AM) | (70°F [21°C]) | (78°F [26°C]) |
| DAYTIME | |||
| EVENING | (10:00 PM) | (60°F [16°C]) | (78°F [26°C]) |
| NIGHT |
⚠️ The temperatures cannot be set any higher than 88°F (31°C) or any lower than 45°F (7°C).
NOTE: The factory-preprogrammed time and temperature settings are shown in parentheses.
Programming Steps
Follow these steps to program your thermostat. Batteries are required.
Set Present Day and Time
- Press and release Set Present Day/Time, then press Day until the present day shows.
- Press and release Set Present Day/Time, then press Time ↑ until the present time shows.
Heating Program
With the system switch at HEAT:
- Press and release Morning. Use Time ↑ and Temp ↑/↓ to program Mon-Fri MORNING time and temperature.
- Repeat for DAYTIME, EVENING, and NIGHT periods using their respective keys.
- For Saturday: Press Day to SAT. Press and release Morning; use Time ↑ and Temp ↑/↓ to program Saturday morning. Repeat for other periods.
- For Sunday: Press Day to SUN. Repeat steps as for Saturday.
Cooling Program
The times set for heating apply to cooling. You only need to program the temperatures.
With the system switch at COOL:
- Press and release Morning. Use Temp ↑/↓ to program Mon-Fri MORNING temperature.
- Repeat for DAYTIME, EVENING, and NIGHT periods.
- For Saturday: Press Day to SAT. Press and release Morning; use Temp ↑/↓ to program Saturday morning. Repeat for other periods.
- For Sunday: Press Day to SUN. Repeat steps as for Saturday.
After programming, adjust fan and system switches as desired.
Press and release RUN PROGRAM to start the program.
⬆️ Press ↓ to move number back; press ⬆️ to move number ahead.
Temporary and Permanent Changes
Temporarily Change Temperature: Press Temp ↑/↓. A TEMPORARY indicator shows on display. This change cancels at the next scheduled change. To cancel sooner, press RUN PROGRAM.
Hold Temperature Indefinitely (e.g., for vacation): Press Hold, then Temp ↑/↓. A Hold indicator appears. To cancel, press RUN PROGRAM.
Check Current Temperature Setting: Press Current Setting.
Cancel a Program: Press and hold Daytime, Evening, or Night for three seconds. Morning cannot be canceled (only changed).
Permanently Change a Program: Repeat the steps under Heating Program (page 13) or Cooling Program (page 14).
Return to Normal Program: Press RUN PROGRAM.
⬆️ Press ↓ to move number back; press ⬆️ to move number ahead.
STEP 5: Mount Thermostat Wallplate
Position the wallplate on the wall. Level it for appearance only. Use a pencil to mark the two mounting holes that best fit the application.
An illustration shows a wallplate being positioned on a wall, with wires coming through an opening. Mounting holes and wall anchors are indicated.
- Remove the wallplate from the wall.
- Drill 3/16 inch holes in drywall (or 7/32 inch for plaster/wood) at the marked locations.
- Gently tap in the provided anchors until flush with the wall.
- Reposition the wallplate over the holes, pulling wires through the opening.
- Loosely insert two mounting screws into the holes.
- Level for appearance only; the thermostat functions correctly even if not perfectly level.
- Tighten the mounting screws.
An illustration shows a level being used on a wallplate mounted on a wall.
STEP 6: Adjust System On-Time, Clock Display, As Required
The thermostat's on-time is factory-set for warm air, gas, or oil heating systems. For other system types, adjust screws 1A and 1B on the back of the thermostat according to the heating system table below to optimize system on-time and minimize temperature swings.
Turning a screw out one turn means approximately a 360° counterclockwise rotation.
System Type Adjustments:
- Hot Water or High Efficiency: Set at Gravity Air/Water (1A—out one turn, 1B—out one turn).
- Gas/Oil Warm Air: Set at Hot Water or High Efficiency (1A—leave in, 1B—out one turn).
- Electric Warm Air: Leave at Gas/Oil Warm Air (1A—leave in, 1B—leave in).
For longer furnace on-time, readjust screws 1A and/or 1B.
IMPORTANT: For high efficiency furnaces (90%+ AFUE), leave screw 1A IN and screw 1B OUT one turn.
The thermostat defaults to a 12-hour clock and Fahrenheit temperature display. To change to a 24-hour clock or Celsius readings, adjust screws 2A and 2B as shown in the illustration.
For an explanation of Recovery Selection screws (3A), see pages 7 and 8.
Diagram shows the back of the thermostat with labels for RECOVERY SELECTION (3A), SYSTEM (1A, 1B), and DISPLAY (2A, 2B) settings. A table details the settings for different system types and display options.
STEP 7: Adjust Fan Operation Switch, As Required
The fan operation switch is factory-set to the left (NON ELEC) position, suitable for most systems. If you have an electric furnace, set the switch to the right (ELEC) position. The ELEC position allows the fan to turn on immediately with heating or cooling if the G terminal is connected to a fan relay.
NOTE: The switch must be set before installing batteries, or the left battery must be removed to access it.
Diagram shows the back of the thermostat with the FAN OPERATION SWITCH labeled, indicating the NON ELEC and ELEC positions.
STEP 8: Wire Wallplate Terminals
NOTE: All wiring must comply with local codes and ordinances. If unsure, consult your local heating/air conditioning contractor.
Refer to the masking tape labels you placed on wires when removing the old thermostat.
Match the letter of your old thermostat wire with the corresponding terminal letter on your new thermostat. Refer to illustrations on pages 22 and 23.
- Loosen the terminal screws and slip each wire beneath its matching terminal. Straight or wraparound connections are acceptable. Tighten terminals.
- Plug the wall hole with insulation to prevent drafts that could affect thermostat operation.
Wire Stripping: For straight insertion, strip 5/16 in. (8mm) of insulation. For wraparound connections, strip 7/16 in. (11mm).
In 5-wire installations, be sure to remove the factory-installed jumper connecting terminals R and Rc.
Illustrations show wire stripping for straight insertion and wraparound connections.
Diagrams show wiring configurations for:
- 2-WIRE HEAT-ONLY (JUMPER INTACT): Shows connections to HEATING RELAY OR VALVE COIL.
- 4-WIRE HEAT/COOL (JUMPER INTACT): Shows connections to HEATING RELAY OR VALVE COIL, FAN RELAY, and COOLING CONTACTOR COIL.
- 3-WIRE HEAT ONLY (JUMPER INTACT): Shows connections to HEATING RELAY OR VALVE COIL.
- 5-WIRE HEAT/COOL (JUMPER REMOVED): Shows connections to HEATING RELAY OR VALVE COIL, FAN RELAY, and COOLING CONTACTOR COIL.
STEP 9: Mount The Thermostat
Attach the thermostat to the wallplate.
Diagram A shows engaging the tabs between the top of the thermostat and the wallplate.
Diagram B shows pressing the lower edge of the thermostat case to latch it.
Diagram C shows swinging the cover open for checkout and programming.
STEP 10: Check Thermostat Operation After Programming and Installing
Heating Check
Do not check heating system operation by jumpering terminals at the primary control. This can damage the thermostat. Instead, you can jumper R and W wires at the thermostat.
Procedure:
- Move the system switch to HEAT and the fan switch to AUTO.
- Press the Temp ↑ arrow until the setting is about 10°F (6°C) above room temperature.
- Heating should start, and the fan should run after a short delay (immediately if the fan switch is set to ELEC).
After the heating starts, press the Temp ↓ arrow until the setting is about 10°F (6°C) below room temperature. The heating equipment should shut off.
Cooling Check
To avoid compressor damage, do not operate the cooling system when the outdoor temperature is below 50°F (10°C).
When cooling settings are changed, the thermostat may delay up to five minutes before turning on the air conditioner to protect the compressor.
Procedure:
- Move the system switch to COOL and the fan switch to AUTO.
- Press the Temp ↓ arrow until the setting is about 10°F (6°C) below room temperature. The cooling equipment and fan should start.
- Press the Temp ↑ arrow until the setting is about 10°F (6°C) above room temperature. The cooling equipment and fan should stop.
Fan Check
- Move the system switch to OFF and the fan switch to ON.
- The fan should run continuously.
When the fan switch is in the AUTO position, the fan cycles with the heating or cooling system.
STEP 11: Set The Fan And System Switches
Set The Fan Switch
FAN ON: The fan runs continuously. Use for improved air circulation or more efficient electronic air cleaning. (In heat-only systems, fan runs continuously only if a fan relay is connected.)
FAN AUTO: Normal setting for most homes. A single-speed fan turns on automatically with the air conditioner or furnace. A two-speed fan usually runs on high with the air conditioner and on low with the furnace. Exception: If the fan operation switch on the back of the thermostat is set to ELEC (right position), the fan operates with the furnace only.
Diagrams show the FAN switch positions: ON and AUTO.
Set The System Switch
HEAT: The thermostat controls your heating system.
OFF: Both heating and air conditioning systems are off.
COOL: The thermostat controls your air conditioning system.
Diagrams show the SYSTEM switch positions: HEAT, OFF, and COOL.
Troubleshooting Guide
IF... Display does not come on.
THEN...
- Set the system switch to OFF. Remove batteries. Insert them backward for at least five seconds to reset the thermostat. Replace batteries correctly. The display should come on.
- Ensure batteries are fresh and installed correctly.
- Gently clean battery contacts with a soft pencil eraser. Do not use abrasive materials.
IF... Display flashes during programming.
THEN...
- You have reached the temperature setting limit (45°F to 88°F / 7°C to 31°C).
IF... Temperature change occurs at the wrong times.
THEN...
- Check program times for the period. Ensure AM/PM indications are correct. Verify current day and time are correct. Reprogram if necessary.
- If using Adaptive Intelligent Recovery™, start times may occur before programmed comfort periods.
IF... Heating does not come on.
THEN...
- Check that the switch is set to HEAT.
- Check the system fuse or circuit breaker. If the display is blank or shows REPL BAT, install fresh batteries.
- Check wiring and connections.
- Jumper R and W wires. If heat still doesn't come on, contact your heating dealer.
- If the temperature setting is higher than the current temperature and HEAT ON is displayed, contact Honeywell Customer Assistance at 1-800-468-1502.
IF... Cooling does not come on.
THEN...
- Check that the switch is set to COOL.
- Check the system fuse or circuit breaker. If the display is blank or shows REPL BAT, install fresh batteries.
- Check wiring and connections.
- Jumper Rc and Y wires. If cooling still doesn't come on, contact your cooling dealer.
- The thermostat has a built-in time delay on cooling (up to 10 minutes). Ensure the outdoor disconnect is energized (on).
- If the temperature setting is lower than the current temperature and COOL is displayed, switch from COOL to OFF for 10 minutes, then back to COOL. If the AC starts, your compressor may have reached its high-limit protection. If it doesn't start after 10 minutes and COOL is displayed, contact Honeywell Customer Assistance at 1-800-468-1502.
- For 2- or 4-wire installations, verify the R-Rc jumper is installed.
IF... The house is too warm or too cool.
THEN...
- Press CURRENT SETTING to check the current temperature setting.
- If desired, change the temperature setting (see page 15).
IF... HEAT ON is displayed, but no heat is coming from the registers.
THEN...
- Allow time for the furnace to heat up and the fan to come on. Note that on most gas/oil systems, the fan is controlled by a separate device, which may cause a delay.
IF... The system cycle length is too short or too long.
THEN...
- Readjust according to instructions on pages 18 and 19.
IF... The thermostat's current setting does not match the display temperature to within ± 1°.
THEN...
- Check that the wiring hole behind the wallplate is plugged with insulation to prevent drafts that might affect thermostat operation.
- Be aware that it's normal for the current setting and display temperature to differ occasionally.
IF... Incorrect room temperature is showing on thermostat display.
THEN...
- Ensure the hole behind the thermostat is plugged with insulation to prevent drafts.
- The thermostat is factory-calibrated and cannot be adjusted.
Index
- Adaptive Intelligent Recovery™: 7, 8
- Batteries, installation: 6
- Batteries, replacement: 6, 7
- Blinking display: 6
- Canceling programs: 15
- Change temperature: 15
- Checking current setting: 15
- Clock display: 19
- Conventional Recovery: 7, 8
- Cooling temperatures: 9, 11, 12, 14
- Current setting: 15
- Customer Assistance: 35
- Day: 13
- DAYTIME: 13, 14, 15
- Energy-saving temperature: 9
- EVENING: 13, 14, 15
- Fan operation switch: 20
- Fan switch: 29
- Flashing display: 6
- Heating temperatures: 9, 11, 12, 13
- Hold temperature: 15
- MORNING: 13, 14
- NIGHT: 13, 14, 15
- Operation: 15
- Period keys: 9
- Personal programming chart: 11, 12
- Preprogrammed schedule: 9, 10, 11, 12
- Programming steps: 13, 14
- Replacing batteries: 6, 7
- Saturday program: 10, 11, 12, 13, 14
- Set cooling temperatures: 14
- Set present day: 13
- Set present time: 13
- Set fan switch: 28
- Set cooling temperatures: 14
- Set heating temperatures: 13
- Setting limits: 11, 12
- Sunday program: 10, 11, 12, 13, 14
- System switch: 29
- Switch, fan: 28
- Switch, system: 29
- Table of Contents: 1
- Temporary program changes: 15
- Time: 13
- Time period: 9, 10, 11, 12
- Troubleshooting: 30, 31, 32, 33
- Warranty: 36
- Weekday program: 9, 10, 11, 13, 14
Limited One-Year Warranty
Honeywell warrants this product (excluding battery) to be free from defects in workmanship or materials under normal use and service for one (1) year from the date of purchase. If defective or malfunctioning during the warranty period, Honeywell will repair or replace it.
If the product is defective:
- Return it with proof of purchase to the retailer.
- Or, package it carefully with proof of purchase and a description of the malfunction, and mail it postage prepaid to: Honeywell Inc., Return Goods Department, 1050 Berkshire Lane, Plymouth, MN 55441-4437.
- In Canada: Honeywell Limited/Honeywell Limitee, Product Services ON30, 155 Gordon Baker Road, North York, Ontario M2H 3N7.
This warranty does not cover removal or reinstallation costs. It does not apply if damage occurred while the product was in the consumer's possession.
Honeywell's sole responsibility is to repair or replace the product. Honeywell is not liable for any incidental or consequential damages.
This is the only express warranty Honeywell makes. Implied warranties, including merchantability and fitness for a particular purpose, are limited to one year.
This warranty grants specific legal rights, which may vary by state.
For warranty questions, contact Honeywell Customer Assistance at 1-800-468-1502, Monday-Friday, 7:00 a.m. to 5:30 p.m., Central time. In Canada, write to the address above.
NOTICE: This equipment is a Class B digital apparatus, which complies with Canadian Radio Interference Regulations, CRC c.1374.
