I have done quite a bit of research and have not been able to find an answer I am looking for. I currently have a manual digital thermostat that is not programmable made by Braeburn. My system is a Ground A/C unit outside, and my heater/air handler is up in the attic. My thermostat is wired the following way:
- Jumper wire between R and RC
- Red wire from wall to RC
- B terminal on thermostat is empty
- Blue wire from wall to O
- Jumper wire from Y to W
- Yellow wire from wall to Y
- No wire to W other than Jumper
- Green wire from wall to G
- There is a spare wire from the wall harness to nothing as well.
I have not had a chance to go in the attic to check the labels on the air handler, but I am hoping there is an extra wire up there too so I can use it as a C wire.
I am curious how, or if I can use a WiFi thermostat or any other programmable for that matter. I have not come up with any leads yet, and don't want to screw things up before I start.
Best Answer
The C wire, not to be confused with R or RC is the return path. Think of it as a ground, though technically not. Based on the information above, none of the wires O, B, W, G, R, Y, will work for C. So they can not be jumped over to the C connection. The C wire, usually the brown wire on the transformer, the low voltage (24v) is the common. However, no matter the color, there are only two low voltage wires on the transformer, one power (Red, Blk, Yel), one common. So what ever color not representing the power, is the common C. Of course, AC current flows both directions, but trying to make this simple. Anyway, that wire (the non power wire) needs to come in to the thermostat for the C connection. With an extra wire (any color on the wire loom at the thermostat can be traced back to the 24v transformer and connected to the common, usually color brown wire). That extra wire used, the new color will become the C wire. Just a note, one issue I have had with the WiFi thermostat is the fan ON and Auto don't work independently. So for example, if the thermostat is selected to run the fan ON - no cooling or heating, I've seen that not work. It can be fixed too, just not answering that.