Spent $80 on a smart thermostat that doesn't work with my old furnace

Bought a Nest last month because everyone raves about them. Got home, pulled off my old thermostat, and the wiring was completely different. My furnace is from 1985 and uses a proprietary 3-wire system. Had to return the Nest and buy a basic programmable one for $24. Has anyone else run into this with older heating systems?

2 comments

2 Comments

grantthomas8d ago

My buddy Dave tried the same thing last year with his old oil furnace from the 70s. He spent two hours trying to match up wires and ended up frying the control board completely. Had to call an HVAC guy who charged him $150 just to tell him to buy a simple Honeywell programmable instead.

karent758d ago

I swapped out my parents' old furnace thermostat a few years back (the one with the mercury switch, remember those?) and took photos with my phone before I touched a single wire. Saved me a headache, and the new one was under 30 bucks at the hardware store.