furnacethermostatthermostat-c-wire
I’m installing a new WiFi thermostat that needs the c wire. I ended up running new thermostat wires that contained the common wire but now I’m stuck on where to connect it to the furnace.
Can someone take a look at the wiring diagram to help me figure out if I have a place on my furnace to connect the c wire?
First off, the green wire should connect to the G terminal on the thermostat. It's connected to the G terminal in the furnace, and so should also go to the G terminal on the thermostat.
At the thermostat, the extra blue wire should connect to the C terminal. Depending on the furnace (read the documentation, and analyze the schematic to be sure), you should be able to connect the other end of the blue wire to either of the C terminals in the furnace.
After looking closely at the images you've supplied, this is what it appears is going on in the last photo.
From what I know about HVAC systems, I would guess a broader view of the system would look something like this.
COOL call from the thermostat.C).When the thermostat calls for COOL, the BLUE wire is energized. This energizes the WHITE wire leading to the contactor, which pulls the contactor closed. The GREEN wire connects to the BROWN wire, which leads back to the transformer, thus completing the circuit.
Therefore, if you want to use the YELLOW wire as C. You should include it in the twist-on wire connector with the GREEN and BROWN wire.
You'll just want to make sure the transformer is sized properly to supply the additional current draw of the thermostat.
If it were me, I'd rewire it so that the YELLOW wire was the COOL call, and the BLUE wire was C. As that's a more common color coding.
Best Answer
The AR861 doesn't provide that functionality, sorry!
Unfortunately, the AR861 does not provide a C wire from its internal transformer, so you'll have to use an external transformer on Rc and C with the supply from the AR861 connected to Rh on the thermostat.