I'd like to replace my Honeywell CT87A thermostat with a Nest thermostat. I see that Nest has a page to check system compatibility. Is it possible to identify if my system is compatible without taking it off of the wall, perhaps by the fact that I have a CT87A? It's bitter cold out and I don't want to turn off the fuse for the furnace.
Possible to check NEST system compatibility by looking at current thermostat model
furnacenestthermostat
Best Answer
According to the installation instructions in your link, the Honeywell CT87A requires only two or three wires (R,W,[Y]) to operate. The Nest compatibility checker shows that a system using those wires is compatible. You should be good to go.