topic Re: Wiring photo to check compatibility in Nest Thermostats

Re: Wiring photo to check compatibility

slava1 — Thu, 03 Aug 2023 19:41:01 GMT

The red wire is not connected. What should I do?

Re: Wiring photo to check compatibility

CoolingWizard — Thu, 03 Aug 2023 20:37:05 GMT

if your current thermostat does not have a wire attached to R, there is not a possibility that it is capable of activating your furnace.

AC Cooling Wizard

Re: Wiring photo to check compatibility

slava1 — Thu, 03 Aug 2023 23:19:20 GMT

Furnace works fine.

Re: Wiring photo to check compatibility

CoolingWizard — Fri, 04 Aug 2023 04:24:00 GMT

Your furnace absolutely will not work with the thermostat you posted, without the wire connected to R/Rc. The B wire is for the Power Common and the W wire is the furnace activation wire. In order for your furnace to work, you must have 24VAC a power incoming on R and the thermostat connects that to W for heating.

AC Cooling Wizard

Re: Wiring photo to check compatibility

slava1 — Fri, 04 Aug 2023 18:34:08 GMT

I traced the wires to a transformer on the boiler. I found the white wire connected to a terminal labeled G and the white wire to a terminal labeled Y. The red was was not connected. There is no circuit board.

I measured the voltage between the black and white wires and found it to be 26.5 VAC.

Re: Wiring photo to check compatibility

CoolingWizard — Fri, 04 Aug 2023 22:05:04 GMT

The Black wire connected to B on your thermostat is supposed to be connected to the Common side of your transformer. And the White Wire attached to your thermostat W, should be attached to your boiler T terminal of the control box. The red wire should be attached to Line side of the transformer and attached to R in your thermostat. When you thermostat call for heat, it connects the R power to the W terminal, which travels to the other T of the boiler thus energizing the gas valve and starting the heating cycle. The B terminal on the thermostat is never connected to any other terminal on the thermostat. It I used by smart thermostats to provide power to the thermostat itself by using R and B.

Can you provide a screen shot of your boiler showing the wire connections from the thermostat and the manufacturer model number of your furnace? Thank you.

AC Cooling Wizard