I have additional wires in my wall that were not connected to my old thermostat. Do I need them to install my new thermostat?

Last updated

5/12/23

An extra unused wire in the wall can be used as the C wire for your new thermostat. The extra wire will also need to be connected to the C (common) terminal at the heating and cooling system. This will provide power to your new thermostat.

Please note that the C-wire is only needed for WiFi connected thermostats [click here to see our WiFi thermostats]. Most standard thermostats do not need a C-wire.

Please refer to the videos below for more information:

What Is a C-Wire?

What if I Don't Have a C-Wire?

A C-Wire Adapter replaces the need for a C-Wire. The C-Wire Adapter is included in newer Honeywell WiFi Thermostats. If you own an older thermostat model, you can purchase a C-Wire Adapter here.