Adding C wire for wifi Thermostat (2024)

Quick question, our river house has multiple unused wires going from the furnace to the thermostat. Can I tap into something at the furnace to get a C wire to the thermostat for our new wifi controller?

Yes, use the left over brown wire going to the thermostat, connect it to C at the stat and connect it to the orange/white wire with blue wire nut Which is common off the transformer

unplug the furnace before you do any wiring revisions so you don’t short stuff out.

River Dirt 2 said:

Yes, use the left over brown wire going to the thermostat, connect it to C at the stat and connect it to the orange/white wire with blue wire nut Which is common off the transformer

unplug the furnace before you do any wiring revisions so you don’t short stuff out.

Click to expand...

This is awesome info! I want to add a WIFI thermostat to my Parker pad and I have the same wiring on my Coleman furnace. I was going to add a C-wire transformer or pay someone to perform this wiring.

One question, to verify voltage on the white/orange wire, can I test voltage while the unit is running to verify 24v power?

River Dirt 2 said:

Yes, use the left over brown wire going to the thermostat, connect it to C at the stat and connect it to the orange/white wire with blue wire nut Which is common off the transformer

unplug the furnace before you do any wiring revisions so you don’t short stuff out.

Click to expand...

Thank you very much! Very clear instructions.

Bajastu said:

This is awesome info! I want to add a WIFI thermostat to my Parker pad and I have the same wiring on my Coleman furnace. I was going to add a C-wire transformer or pay someone to perform this wiring.

One question, to verify voltage on the white/orange wire, can I test voltage while the unit is running to verify 24v power?

Click to expand...

You can yes, in this case you can use a VOM and read 24v between the white/orange and the red/red wire with yellow wire nut on the far right of the picture. Red is hot from the transformer coming from the control box.

Everything coming out of the box thru the black connector is low voltage
everything coming out of the box thru the white connector will be line voltage.

The only confusing part on the low voltage wiring is the 2 white/wires coming out of the black connector, 1 is the common from the transformer and the other is the heating wire which goes to the white wire from the thermostat (white/white w yellow wire nut)

River Dirt 2 said:

You can yes, in this case you can use a VOM and read 24v between the white/orange and the red/red wire with yellow wire nut on the far right of the picture. Red is hot from the transformer coming from the control box.

Everything coming out of the box thru the black connector is low voltage
everything coming out of the box thru the white connector will be line voltage.

The only confusing part on the low voltage wiring is the 2 white/wires coming out of the black connector, 1 is the common from the transformer and the other is the heating wire which goes to the white wire from the thermostat (white/white w yellow wire nut)

Click to expand...

Thanks for the info!!!

Bajastu said:

Thanks for the info!!!

Click to expand...

Happy to help.
Remember my info is based on being able to see the current wiring. Someone else’s setup could be different. Best to test with VOM to confirm

Cheers

River Dirt 2 said:

Happy to help.
Remember my info is based on being able to see the current wiring. Someone else’s setup could be different. Best to test with VOM to confirm

Cheers

Click to expand...

Yeah, I don’t have a good picture. I can build engines, tig weld chassis, wire cars, and rig boats, but I’m clueless when it comes to house HVAC. Maybe I’ll pay someone to add it to the house in Parker.

Bajastu said:

Yeah, I don’t have a good picture. I can build engines, tig weld chassis, wire cars, and rig boats, but I’m clueless when it comes to house HVAC. Maybe I’ll pay someone to add it to the house in Parker.

Click to expand...

Yours looks about the same, the wire from above is to the thermostat, the wire from below follows the refrigerant lines out to the condensing unit.
the wire going to the condensing unit is 2 conductor, 1 will be the common wire off the transformer and 1 will connect to the Y terminal at the thermostat. If you can separate the wires a bit better and repost the pic I can tell you what goes where. Can’t tell from the pic if you have a spare wire going to the stat, you will need that for it to work. If no spare wire then yes call someone out, like @desertrider ‘s new company

Note, looks like the heavy wires on the right are exposed 220 line voltage so be very careful around those
Here’s a simple wiring diagram, it for a furnace but heatpumps are similar at least for this process.

River Dirt 2 said:

Yours looks about the same, the wire from above is to the thermostat, the wire from below follows the refrigerant lines out to the condensing unit.
the wire going to the condensing unit is 2 conductor, 1 will be the common wire off the transformer and 1 will connect to the Y terminal at the thermostat. If you can separate the wires a bit better and repost the pic I can tell you what goes where. Can’t tell from the pic if you have a spare wire going to the stat, you will need that for it to work. If no spare wire then yes call someone out, like @desertrider ‘s new company

Note, looks like the heavy wires on the right are exposed 220 line voltage so be very careful around those
Here’s a simple wiring diagram, it for a furnace but heatpumps are similar at least for this process.

Click to expand...

This is great over the top info.
There is definatly a spare wire, I belive its the blue wire. I'll be back out in a few weeks and take a look at it. If I can't figure it out, I'll deffinatly call Desertriders new company.