Temporarily switch Nest thermostat with a different one

[brevoy]

We have two Nest thermostats in our house.  One for the downstairs furnace and one for the upstairs furnace and air conditioner.  The upstairs one is connected to a C-wire, the downstairs one is not.  The downstairs one is now showing low battery and because of this, our furnace is not properly heating our downstairs.  I have charged the thermostat mutliple times, but the battery is dying very quickly.  We are getting the C-wire installed in a week or so, but until then, we don't really have heat downstairs.  Would I be able to switch the upstairs Nest (which should have a full battery since it is connected to the C-wire) to the downstairs, then move the downstairs to the upstairs since it will then have a connection?  Does it matter that the upstairs is configured for heat and air con, meaning will it mess up the thermostats since we don't have air con downstairs?  Thank you in advance for advice!

[zoeuvre]

Hi brevoy, 

Thanks for posting here, and i'm sorry to hear about the situation you're in with your thermostat. 

Yes, you can switch the Nest Thermostats between the upstairs and downstairs locations to temporarily resolve the low battery issue. Since the upstairs thermostat is connected to a C-wire and has a continuous power supply, it should have a full battery. Here's how you can proceed:

1. Turn off the power to the heating and cooling systems at the circuit breaker before removing or installing the thermostats.
2. Carefully remove the upstairs and downstairs Nest Thermostats from their respective locations.
3. Switch the thermostats between the upstairs and downstairs locations. Install the upstairs thermostat in the downstairs location and vice versa. Make sure to reconnect the wiring properly and securely.
4. Once the thermostats are swapped, you may need to reconfigure some settings to match the new locations. The Nest app will guide you through the setup process, including selecting the correct HVAC system type (heat only for the downstairs thermostat).
5. Switch on the power at the circuit breaker and check the thermostats' functions after reconfiguring them. Confirm the operation of the heating systems on the upstairs and downstairs.

Take note that until you add the C-wire for the downstairs thermostat, this is only a temporary fix. The thermostats can be returned to their original positions after the C-wire is installed for your downstairs thermostat.

Let us know if you have any other questions.

Best,

Zoe