11-19-2021 10:17 AM
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
Answered! Go to the Recommended Answer.
11-19-2021 01:03 PM
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.
11-20-2021 08:52 AM
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
11-19-2021 01:03 PM
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.
11-19-2021 01:27 PM
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
11-19-2021 01:29 PM
Which Nest thermostat model do you currently have?
11-19-2021 02:07 PM
I have a Nest thermostat 1.4 Only has R terminal
11-19-2021 02:24 PM
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?
11-19-2021 02:49 PM
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.
11-19-2021 03:02 PM
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.
11-19-2021 03:05 PM
Last question. Will the Nest Learning work as well as the 2nd or 3rd gens?
11-20-2021 08:52 AM
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
11-20-2021 03:46 PM
Thanks very much for your help.
12-21-2021 08:09 PM
Will this set-up (2 wires) work with a gas furnace heating system with no cooling system?
12-22-2021 04:48 AM
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.
03-16-2022 09:13 PM
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...
07-16-2022 08:24 AM
My nest doesn't have a RC spot for a wire, it does have an *OB spot?
12-19-2022 06:01 PM
I have a rc and a rw wire on my thermostat but I only heating no ac.
12-23-2022 04:27 PM
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
12-26-2022 04:41 PM
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
12-27-2022 07:50 PM
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