Honeywell Thermostat Installation Guide

Always turn off power to your heating and cooling system before removing the old thermostat or touching any thermostat wires. Power is usually turned off at the circuit breaker, furnace switch or HVAC equipment service switch.

If you are unsure how to turn off power safely, if your wiring does not match the thermostat instructions or if your system uses high-voltage wiring, contact a licensed HVAC professional.

Start by turning off power to your heating and cooling system. This helps protect the thermostat, HVAC equipment and wiring during installation.

After turning off power, check the old thermostat display. If the display turns off, that is a good sign power has been disconnected. However, some battery-powered thermostats may still show information on the screen even after system power is off.

Do not begin disconnecting wires until you are confident the system power is off.

Carefully remove the faceplate or cover from the existing thermostat. Some covers pull straight off, while others may have screws or tabs that need to be loosened.

Once the cover is removed, you should be able to see the thermostat wires connected to labeled terminals on the old base plate.

Before disconnecting anything, take a clear photo of the existing wiring. This photo can be helpful if you need to double-check how the old thermostat was connected.

Label each wire based on the terminal letter it is connected to, not only by the wire color. For example, a wire connected to the R terminal should be labeled R, even if the wire color is not red.

Common thermostat terminals may include R, Rc, Rh, W, Y, G, C and O/B. Your system may not use every terminal.

If you are installing a smart thermostat, look for a C-wire, also called a common wire. Many smart thermostats need a C-wire or compatible power adapter to provide continuous power.

Once the wires are labeled, loosen the terminal screws or release the wire clips on the old thermostat base. Gently pull each wire free.

Be careful not to let the wires fall back into the wall. You can wrap the wires around a pencil or lightly tape them to the wall while you remove the old base plate.

After the wires are secure, remove the screws holding the old base plate to the wall.

Pull the labeled wires through the opening in the new Honeywell thermostat base plate. Position the base plate against the wall and use a level if needed.

Mark the screw holes, drill pilot holes if necessary and install wall anchors if the mounting location requires them. Then fasten the base plate securely to the wall.

Do not overtighten the screws, as this could bend or damage the base plate.

1. Match each labeled wire from the wall to the same terminal label on the new thermostat base.
2. Insert each wire fully into the correct terminal.
3. Tighten the terminal screw or close the wire clamp, depending on the thermostat design.
4. Gently tug each wire to confirm it is secure.
5. Make sure no bare wire is touching another terminal.
6. Install batteries if your thermostat model requires them.
7. Attach the thermostat faceplate to the base.

If your old thermostat had jumper wires, separate Rc and Rh wires or unused wires, follow the instructions for your specific Honeywell thermostat model.

A C-wire helps provide steady power to smart thermostats. If your existing thermostat wiring includes a wire connected to the C terminal, label it and connect it to the C terminal on the new thermostat base.

If you do not have a C-wire, your thermostat may require a C-wire adapter, power adapter or alternate wiring setup. Do not guess or force a connection. Use the instructions for your specific smart thermostat model.

After wiring is complete, many smart models will guide you through equipment setup, Wi-Fi connection and app pairing.

• Restore power to the HVAC system.
• Confirm the thermostat display turns on.
• Select the correct system type during setup.
• Set the date, time and temperature preferences if prompted.
• For programmable models, create your heating and cooling schedule.
• For smart models, connect to Wi-Fi and complete app setup.
• Test heating, cooling and fan operation.

Your HVAC equipment may take several minutes to respond after changing modes or adjusting the temperature. This delay can be normal and may help protect the system.

• Do not rely on wire color alone. Always use the old terminal labels.
• Do not skip the wiring photo before disconnecting the old thermostat.
• Do not let wires fall back into the wall.
• Do not connect a wire to a terminal unless your thermostat instructions support it.
• Do not ignore C-wire requirements for smart thermostat installation.
• Do not install a low-voltage thermostat on a high-voltage system.
• Do not continue if the wiring is damaged, unclear or different from the manual.

If the thermostat does not power on, does not control the system correctly or shows an error during setup, turn power back off and review the wiring against your original photo and model-specific installation guide.