getting 24 volt to nest thermostat

[stephen777]

I have a new, second Nest thermostat (not a learning Nest) controlling heat source with only two wires used with the old thermostat. My other Nest thermostat, controlling an older oil furnace, had the same issue. I purchased a 24 volt transformer so I could provide the C wire and that learning Nest has 10 connections, which provided both the C and the Rc connections to use with the 24 volt transformer power. Works perfectly. My second and new Nest thermostat only has 6 connections. the W and R for the wires to the heat source and it has a C for the new common from my 24 volt transformer, but there is no Rc terminal (why?!). The only other open terminals for the Nest are Y, G, and OB. Where do I connect the other wire from my 24 volt transformer so the Nest will have its necessary constant power?

[RenzJ]

Hi stephen777,

Thanks for bringing this up here in the Google Nest community. Let's check this out. The Nest Thermostat 2020 and Nest Learning Thermosatt have different bases. The Nest Learning Thermostat can support both single and dual transformer systems, while the Nest Thermostat 2020 can only support single transformer systems. RC and RH on the Nest Learning Thermosat have the same function as the R Terminal of the Nest Thermostat 2020. I wanted to make sure that we could wire this correctly. Could you send us a photo of your current wiring?

I look forward to your response.

Cheers,

Renz

[stephen777]

I replied to your above message just below.

[zoeuvre]

Hi folks.

@stephen777, I'm sorry for the late reply. After installing the Nest Power Connector, if the heat does not shut off, remove the thermostat display from the base, wait about five minutes, and check if the system turns off or stays on.

Thanks for your help, Renz. 

Best,

Zoe 

[stephen777]

I bought the nest power connector and wired it according the the attached image. The thermostat is happy and works. the problem is now the heater will not shut off, even when I set the thermostat to shut it off. I tried reversing the red and white terminals from the heater. No change. Thought ion trying reversing the two transformer wires but have not done that. What would be causing this?