topic Re: Nest wiring with two red wires in Nest Thermostats

Nest wiring with two red wires

Marco1955 — Fri, 19 Nov 2021 18:17:21 GMT

I’m installing a Nest Thermostat for my HVAC system. I have two red wires coming from the system. One is connected to R(heat) and the other RC(cooling) on the old thermostat. The Nest thermostat only has a connection for R . How do I connect the RC wire. Thanks

Re: Nest wiring with two red wires

laurentbourg — Fri, 19 Nov 2021 21:03:53 GMT

I assume you have a Nest E or a Nest 2020 thermostat, those only have one R, previous versions of Nest thermostats used to show Rc and Rh separately. If you have a different system for your heat and cooling (for example, forced air for cooling and radiator for heating), you will need to get a Nest thermostat 3rd generation, the thermostat you currently have won’t work. If it’s the same system, then you can just use either Rc or Rh wires because they most likely come from the same transformer and put electric tape on the one you don’t use.

Re: Nest wiring with two red wires

Marco1955 — Fri, 19 Nov 2021 21:27:46 GMT

Thanks for the quick response. I looked at the wiring plate for the Nest Learning thermostat and that shows a R and RC terminal so I assume that would work too correct ? It’s cheaper than the 3rd generation

Re: Nest wiring with two red wires

laurentbourg — Fri, 19 Nov 2021 21:29:44 GMT

Which Nest thermostat model do you currently have?

Re: Nest wiring with two red wires

Marco1955 — Fri, 19 Nov 2021 22:07:25 GMT

I have a Nest thermostat 1.4 Only has R terminal

Re: Nest wiring with two red wires

laurentbourg — Fri, 19 Nov 2021 22:24:31 GMT

Ok that is the one with the mirror faceplate, it’s also called Nest wifi or Nest 2020. You cannot use that one if you have 2 different furnaces for cooling and heating. Do you have 2 different systems?

Re: Nest wiring with two red wires

Marco1955 — Fri, 19 Nov 2021 22:49:08 GMT

Yes that’s the one. Yeah I have a separate gas boiler and electric A/C unit with air handler unit which I assume is the reason for the two R wires.

Re: Nest wiring with two red wires

laurentbourg — Fri, 19 Nov 2021 23:02:53 GMT

Yes correct, there are 2 independent transformers so 2 R wires are needed. I do not believe there is a way around it, you will need either Nest 2nd or 3rd generation to solve this.

Re: Nest wiring with two red wires

Marco1955 — Fri, 19 Nov 2021 23:05:44 GMT

Last question. Will the Nest Learning work as well as the 2nd or 3rd gens?

Re: Nest wiring with two red wires

laurentbourg — Sat, 20 Nov 2021 16:52:46 GMT

The nest learning thermostats 1st gen/2nd gen/3rd gen will work. See enclosed link for all available types of nest thermostats. https://support.google.com/googlenest/answer/9246551?hl=en

Re: Nest wiring with two red wires

Marco1955 — Sat, 20 Nov 2021 23:46:42 GMT

Thanks very much for your help.

Re: Nest wiring with two red wires

cchristenbury — Wed, 22 Dec 2021 04:09:31 GMT

Will this set-up (2 wires) work with a gas furnace heating system with no cooling system?

Re: Nest wiring with two red wires

Marco1955 — Wed, 22 Dec 2021 12:48:59 GMT

I could not get it to work with just two wires R+W using a Nest Thermostat. I even tried a Nest Power Connector and a separate 24v transformer. Couldn’t get it to work. I have a three wire thermostat cable so I’m going to get an electrician to try and power the third wire.

Re: Nest wiring with two red wires

pippo047 — Thu, 17 Mar 2022 04:13:57 GMT

you can run a separate transformer with one wire going piggy back to the r and the second wire in the c (common) this will work...

Re: Nest wiring with two red wires

Fletch94 — Sat, 16 Jul 2022 15:24:15 GMT

My nest doesn't have a RC spot for a wire, it does have an *OB spot?

Re: Nest wiring with two red wires

Keithlac — Tue, 20 Dec 2022 02:01:56 GMT

I have a rc and a rw wire on my thermostat but I only heating no ac.

Re: Nest wiring with two red wires

EdwardT — Sat, 24 Dec 2022 00:27:39 GMT

Hi Keithlac,

Thanks for reaching out. I'd love to know more about this. Could you share a photo of your previous thermostat's wiring?

Thanks,

Edward

Re: Nest wiring with two red wires

EdwardT — Tue, 27 Dec 2022 00:41:04 GMT

Hi Keithlac

It's me again. I wanted to check back in to see if you have other questions and concerns. Feel free to let me know if you do.

Thanks,

Edward

Re: Nest wiring with two red wires

EdwardT — Wed, 28 Dec 2022 03:50:09 GMT

Hi Keithlac,

I'm just checking in to make sure that you've seen our response. Please let us know if you have any other questions or concerns as I will be locking this in 24 hours.

Thanks,

Edward