Hey everyone! I'm living in a 1960s condo and I'm thinking about upgrading to a smart thermostat for my heating system, which only uses 2 wires. I understand I won't be able to access all features, but ideally, I want to control the heating through Home Assistant. I've got some images showing my current set-up and a wiring diagram for how I'm envisioning connecting an Ecobee 3 Lite.
From what I can see, it looks like I might need an additional wire for power. There's this conduit or sheathing that seems to run from the wall transformer to the thermostat, so it might not be too complicated—probably around 7-9 feet of wire needed.
I'm curious if the existing transformer can be used for this setup? Any help or explanations would be greatly appreciated!
2 Answers
You should try connecting R to Rc, and W to W, but you’ll need to add a third wire to C for a complete setup.
Before making any connections, first confirm the voltage of your wires. Old systems often used 120v, which won’t work with smart thermostats like the Nest. However, if you find out that you’re running 24v to the thermostat, then you're in luck! The Nest Gen 3 can be used with just the 2 wires for heating.
The first image shows a transformer, so I think it's 24v going to the thermostat. I still need to check if that’s functioning, though.
Sounds simple enough! What type of wire do I need for this connection?