I have 3 wires coming out from the wall at my new house (red, white, blue). It is a water boiler heat only system. The tstat was already removed unfortunately.
I thought the blue wire was the C wire, so I hooked it up to a nest but it didn't work. It said there was no power.
I checked the voltage as following:
- red and white: 24V
- red and blue: 0V
- white and blue: 24V
I put R and W together and the heat is on.
So I think the blue wire is not a C wire? because it looks like it is hot. So what is this blue wire for? or I think the red and white are somehow swapped... so white is hot and red is neutral? At the relays, does it matter which wire goes to the terminals? It is a heat only boiler system, no cooling.
These are the wires from the relays. Zone 3 is the zone. I don't even see any blue wire.