topic Nest C Wire in Nest Thermostats

Nest C Wire

Brooklyn1 — Thu, 21 Apr 2022 21:42:37 GMT

I have a wire that is giving off 24 volts; however, it is NOT connected to the boiler--it's just a power source. Do I NEED it to be connected to the boiler in order for the system to read it as a C wire?

Currently I have an R wire, and W wire and I have the 24 volt wire hooked up as the C wire. But it is saying I don't have a C wire.

Readings on the power say:

Vin: 35.133v

lin:385 (W)

PS: W-385, WP-2

Re: Nest C Wire

Patrick_Caezza — Fri, 22 Apr 2022 04:16:06 GMT

The C wire is not just 24Vac. It is the return (common) of the 24Vac for your system.

One problem with boilers is their red and white wires are mostly just used for a switch closure and there isn't any voltage on them.

Normally 24Vac is supplied by the R wire and the C wire is the return just for powering the thermostat.

Re: Nest C Wire

Ryan_G — Tue, 26 Apr 2022 00:14:02 GMT

Hey Brooklyn1,

Thanks for reaching out here at the Google Nest Community.

I'd like to jump in here and check if you've seen Patrick_Caezza's response about the common wire.

Let us know how it goes with your system by replying to this thread.

Thanks for your help, Patrick_Caezza.

Best regards,

Ryan

Re: Nest C Wire

Ryan_G — Mon, 06 Jun 2022 04:33:49 GMT

Hey folks,

Thanks for visiting the Google Nest Community.

Since this thread hasn't had activity in a while, we're going to close it to keep content fresh.

If you have additional questions, feel free to submit another post and provide as many details as possible so that others can lend a hand.

Hope this helps!

Kind regards,

Ryan