Nest says no power to the Rc, but old thermostat works fine

[JoelEblin]

I have a heat pump in my new place and tried installing a Nest Learning Thermostat. I keep getting an error saying no power to the Rc wire.

I put my old thermostat on and it works fine. I also know other people in this building have a Nest thermostat, so it's not the building.

I've attached pictures of the old wiring, new wiring, wiring diagram on the Nest, and the error report.

(I also tried the Rc wire in the Rh hole.)

 

 

 

 

[Markjosephp]

Hello JoelEblin,

Thank you for taking the time to let us know about your inquiry. I'd love to help.

The common wire may not be properly grounded, so the system uses power sharing but doesn’t get enough energy, which shows no power. Could you please gather the power readouts under Technical Info with and without C-wire connected? Turn off the power to your HVAC system at the breaker box before touching the wires.

I'll look forward to your response.

Regards,

Mark

[Markjosephp]

Hey there,

I wanted to see if you still needed help. Please let us know if you have any other questions or concerns.

Thanks,

Mark

[EmersonB]

Hi everyone,

@JoelEblin just one quick final check in here since activity has slowed down. We'll be locking the thread in the next 24 hours, but if you still need help, we would be happy to keep it open. If there's more we can do, just let us know.

I appreciate the help, Mark.

Best,
Emerson