I want to replace a dumb non-programmable thermostat in my home with a programmable one, but the one I’m looking to get requires a C wire.
At the moment, there’s no C connection at the stat, but there is an unused blue wire in the cable. Can I just connect this wire to the C terminal on the furnace and be done?
The existing wiring looks like the top (1 cool 1 heat) diagram here, except for the no connection from C to the stat.
Yes.
This is exactly what I did. There was a big obvious “C” post in my furnace that was unused and a spare wire in the cable.
I hooked the spare wire to “C” in the furnace and on the thermostat.
By the way, I got one of those wifi-enabled thermostats. I never imagined how convenient this would be, figuring it was more of a gimmick. It is so neat to be in bed and be able to whip out my iPhone and adjust the temperature.
Sure.
Just make sure you document the wiring, and leave a printout at both the thermostat and the furnace. You’ll appreciate this when it comes time to upgrade again.