Nest Thermostat won't stop heating even when temperature is reached

[itsdingee]

I moved into a house which has 1950's wiring. The existing thermostat only provides heat and had a red wire connected the the R and a green wire connected to the W. I installed my nest with the red wire connecting to the RH and the green wire connecting to the W. It powers on and seems to function well but it wont stop heating my house even once its reached the set temperature. Even when its set to OFF it still seems to be heating. I took the nest off the wall and my furnace stops so I assume its something to do with the nest settings. Please help. I really want to have my nest back so I can set a heating schedule.

[Mikemoore1127]

I had a similar issue with my house where the previous thermostat only required regular power. When I also connected the additional power, the nest functioned properly and the HVAC responded accurate. Try add the supplemental power wire and see if that fixes it.

[itsdingee]

Is this what you purchased? Nest Power Connector Or did you have an electrician rerun wiring with a C wire?

[furqanhamid]

The issue could be related to the 1950s wiring and how it's interacting with your Nest thermostat. Since the heating stops when the Nest is removed, it's likely that the thermostat is incorrectly sending a continuous signal to the furnace. Check the wiring setup to ensure it's compatible with the Nest and confirm that the system is configured correctly in the Nest settings (go to Settings > Equipment). You might also try installing a common wire (C-wire) or using a Nest Power Connector to stabilize the power flow. If you're unsure, consulting an HVAC technician would be a good next step.

[maedacortez]

Hi itsdingee,

Thanks for reaching out. I understand that the heating does not turn off even when it reaches the desired temperature.

To help me understand the situation better, I have a few questions:

• When did this issue start?
• Have you noticed any other unusual symptoms since the problem began?
• Are you receiving any error messages? If so, please provide the exact messages.
• Is this a newly installed heating system?
• When was the last maintenance check performed on your HVAC system?

I look forward to your response.

Regards,

Manuel

[itsdingee]

Thanks for the reply Manuel.

The issue started immediately upon installing the Nest Thermostat. My old thermostat does not cause this issue. There are no error messages in the Nest Thermostat when installed. My furnace is not new but I am unsure of the age since I just moved into the house and haven't had an HVAC inspection yet. 

[maedacortez]

Hi itsdingee,

Thank you for your reply. Could you please send me a picture of your wire connections so I can check if everything is connected correctly?

I look forward to your response.

Regards,

Manuel

[itsdingee]

Hi Manuel,

I had to uninstall it because it woudn't stop heating so I cant show a picture but I can explain how I had it installed. I had 2 wires (red and green). I attached the red wire to the RH connection and the green wire to the W connection. When I was troubleshooting, I tried to connect the green wire to the G connection but then the Nest gave me an error message that there was no power to the device.

Thanks,

Emily