We have an old forced air gas furnace. Lennox from the 90s. Heat only - no AC. Current thermostat doesn't have a 'c' wire. There are extra unused wires in the wall - but I'll be damned if I know where they go because they don't seem to terminate at the furnace. I opened up the access panels last night. Definitely no easily identifiable control board. A bunch of zig zaging wire clusters attached to different things in the guts of the furnace.
Going through the compatibility process with a Google agent - they said its fine to run the Nest learning 3rd gen without the 'c' wire. Which I learned later is possible due to the power stealing feature that recharges the onboard battery. However, there seems to be a lot of internet chatter around how unadvisable it is to run it without a 'c' wire. With that said, some say in a simple heat only set up, it works just fine without.
I'm a handy guy, but looking into the belly of that furnace makes me weary to dive in. If it were a simple control board like I've seen in the dozens of 'hook up your own c wire' videos - I'd be game. But my situation seems more suited for the professionals.
So now I'm faced with either rolling the dice and getting a Nest and trying to run without the 'c', paying a steep price to have in professionally installed with the 'c' (assuming that's even possible with my aging furnace), or just foregoing a smart thermostat for the time being.
If any of you have thoughts, suggestions or positive experiences with a 'c'-less Nest set up - please share!
