furnacewire
I am upgrading my thermostat to a Honeywell Wifi one, and would like to add a common wire. My current furnace controller has 3 blue wires at the 24 v end of the transformer. Which of these (blue) should I use to connect my blue C wire?
Circuit diagram below:
Since in your case, one side of the transformer is grounded. You can simply use a fork or ring terminal, to connect the C wire 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 my C wire in with the other two wires, in that twist-on wire connector near the bottom of the photo.
Yes, the terminal at the lower right in the photo is C.
Here's the wiring diagram from the documentation, which I highlighted in different colors.
Here's your wiring, which I highlighted using the same colors.
Best Answer
You can connect the
Cwire to any of the blue wires highlighted below, as they are all connected.