Nest Thermostat Heats Instead of Cools

[JU757]

I have a two-zone system with two Nest thermostats - both have been working fine for about 6-9 months.

Over the past few weeks the thermostat in one of the zones has been acting very strange - instead of cooling, it turns on the heat. We came home from a weekend trip to find the house at 113 degrees! Fixed the problem by resetting the thermostat... it has happened two more times since then... it will work fine for about 5-8 days and then it will repeat the problem. Any suggestions? It's a safety issue now.

[Jenelyn_O]

Hi there,
 

Thanks for reaching out. I'm sorry for the delay. A few questions: what type of Nest Thermostat do you have? You can visit this link to check what type of thermostat you have. Also, in what country are you located? I'll leave this support article for your reference in regards to troubleshooting strange heating or cooling behavior.
 

Best,

Jenelyn

[JU757]

Thank you for the response - I have a Nest Learning Thermostat, 3rd Generation.

I read through the support article, but it does not seem to address my specific situation. Three times over the past month, the thermostat has turned on the heater instead of cooling the house. Each time, I reset the thermostat, and it works properly. Several days later it will repeat the same problem.

We have a second Nest Thermostat (same model) in another zone... it works properly 100% of the time. So I do not think that it is a problem with the HVAC system. Since it works properly after restart, it also does not seem like a wiring problem. Is there a way to run a diagnostic on the actual thermostat... or to get a replacement?

I would like to restate that this is a safety issue - we have not been turning the system on when we are away from our home because we are afraid that it will heat up the house to dangerous levels again.

[Jenelyn_O]

Hey JU757,

I'm sorry for the delay — I know it's been a while now. If unexpected heating occurs only in one zone, the fault is likely system-related. The motorized valve is stuck in the open position, or the relay is stuck in a closed position. In what states are you located?

Thanks,

Jenelyn

[JU757]

The problem hasn’t repeated in a couple months after the last time that we reset the thermostat. I’m cautiously optimistic that it is working fine now. We live in Virginia. 

[Jenelyn_O]

Hey JU757,

Cool, thanks for the update! I'm glad that it is working now. Please feel free to create a new thread if you have any questions or concerns, as i'll be locking this thread after 24 hours. 

Cheers,

Jenelyn