wifi thermostat help

[Gunnyart]

Spent a while in my attic this morning trying to add the common wire but my Payne air handler unit doesn’t have a terminal type board and I’m not sure where to tap in to get a constant 24 vac so I’m ordering a wall transformer and am going to power it locally.

[double bogey]

post a pic of the terminal board, and I can tell you which one to use. You should have a terminal marked C.

Add: if you cannot locate the common wire, you can use the furnace chassis. All modern furnaces have to have one side of the control circuit grounded*. Always the ground will be connected to the common wire at or near the control transformer.
Loosen a screw, strip an inch off of a wire, and put it under the screw and tighten. Then run the wire to the tstat and connect to the C terminal.

*its a national electric code thing

[Meatcutter]

You most likely will need to run a common wire for a wifi stat.
The nest stats I have ran into without a common wire have all been problems, that were solved with a common wire.
I don't know of any that don't require it.

Had to do the same.

[Gunnyart]

post a pic of the terminal board, and I can tell you which one to use. You should have a terminal marked C.

Add: if you cannot locate the common wire, you can use the furnace chassis. All modern furnaces have to have one side of the control circuit grounded*. Always the ground will be connected to the common wire at or near the control transformer.
Loosen a screw, strip an inch off of a wire, and put it under the screw and tighten. Then run the wire to the tstat and connect to the C terminal.

*its a national electric code thing

Thanks double bogey for the offer. It doesn't have a terminal board apparently. The stat wires are wire nutted to other wires and don't seem to follow the normal color coding or labeling.


You can see the unused blue wire in the first photo. I was hoping to find a c terminal and just connect it and be done.

Does this rat's nest mean anything to you?

[double bogey]

On the transformer, follow the brown and the red wires. The red wire should go to the "R" terminal on a board, and the brown wore should be common.

Another place to find common is on the wires that go to the condensing unit. One connects to the "y" or yellow wire from the tstat. The other connects to a common wire, you can use this connection. In the top left pic I see the yellow, but cannot see the common wire. give me a min to enlarge it and see if I can see it

[double bogey]

Is it a heat pump?

[Gunnyart]

Is it a heat pump?

not a heat pump

[double bogey]

Top left pic, the wire with the green wrapped around it appears to go to the ac. The red wire is connected to the yellow wire coming from your tstat, and the white wire from the ac is your common wire. (in the pic I can't see where it goes, but that will be the common wire)
If you are going to use the blue wire from the tstat for the common, connect it to the white wire coming from the ac, and the c terminal in the tstat. You should be good to go.

[double bogey]

not a heat pump

dang, you running electric heat? you need a heat pump.

[Gunnyart]

Thanks for the help.

[double bogey]

Anytime, if I can't physically do it, at least I can tell someone how to.

[Gunnyart]

Top left pic, the wire with the green wrapped around it appears to go to the ac. The red wire is connected to the yellow wire coming from your tstat, and the white wire from the ac is your common wire. (in the pic I can't see where it goes, but that will be the common wire)
If you are going to use the blue wire from the tstat for the common, connect it to the white wire coming from the ac, and the c terminal in the tstat. You should be good to go.

Hey brother,

I put my meter on the white coming from the AC and to the red and got 39vac. Am I going to have a problem with that much voltage?

[Gunnyart]

Hey brother,

I put my meter on the white coming from the AC and to the red and got 39vac. Am I going to have a problem with that much voltage?

Disregard my last...

I'll never buy a Harbor Freight multimeter again. It was reading way high. Everything is working correctly now.

[double bogey]

Good, sorry, I was out of pocket all day.