Adding C wire for thermostat
Got a new thermostat that requires a 24v common C wire. The current cable is a 3 conductor that I had previously labeled Rh, W and G when replacing the old round mercury thermostat a few years ago.
Looking for some advice before I get started.
Running the new wire shouldn't be a problem as it's pretty much a straight run through an interior wall and I can see where the wire comes out in the basement.
There is a small panel mounted on a wall which I believe houses the transformer (will double check when there) that has armored cable coming into it from the main breaker panel and going out through armored cable to the gas fired boiler.
The three conductor cable runs directly from the thermostat to the the boiler.
Old house, old wiring but in good shape. Boiler was replaced a few years ago.
Should I replace the existing wiring completely or is it ok to just add a single wire for the C wire?
What gauge wire is recommended?
Where does the other end of the C wire attach to? Somewhere on the boiler with the other thermostat wires or somewhere in that box on the wall?
Anything else I should consider?