I am upgrading my thermostat to a Nest, and would like to add a common wire. My current furnace controller doesn't have a C terminal, but the current thermostat wire has 2 unused wires (black and blue)
what's the best way to do this?
On the 24V side of the transformer there is:
1 Red Wire
3 Blue Wire
– 1 Blue is ground
– 1 Blue goes to gas valve
– 1 Blue goes to furnace controller
Can I cut one of the blue wires, lets say the one to the controller, strip the ends and connect both ends to the c-wire on my thermostat wire?
Best Answer
Since in your case, one side of the transformer is grounded. You can simply use a fork or ring terminal, to connect the
Cwire to the chassis. Though it appears there's already a wire that's attached to ground, and comes right over near the thermostat wiring. I'd just put myCwire in with the other two wires, in that twist-on wire connector near the bottom of the photo.