Nest thermostat continues to heat after it reaches the set temp

[Csoule]

I set the heat to 68 and it continues to heat beyond 75-78. It will not shut off, even after pulling the nest off the wall. I had to shut the unit off instead. Any idea how I can fix this? Thank you

[Scott_R]

Maybe a stuck relay on your heating device (boiler, furnace, heat pump). At least, I had that once with the air conditioning and my HVAC people had to replace a relay on the air circulator.

[Csoule]

Thanks Scott....I will check that out!

[Markjosephp]

Hello folks,

@Scott_R, I appreciate your help here on what you've done to have your concern rectified.

@Csoule, I wanted to ensure that everything was covered here. How's it going with your thermostat? Have you had a chance to reach out to an HVAC technician for consultation? I also found an article that might help about the Common Wire. Please let us know if you have any other questions or concerns.

Regards,

Mark

[Scott_R]

Nest/Google seems to blame the common wire for every problem. Nest battery failing? It's the common wire. Unit not turning off? Common wire. House on fire? Common wire.

When I was trying to figure out the issue with the blower staying on, Nest support insisted it was the c-wire. They set me up with an appointment with one of their pros to come and do the install. The "pro" did some weird reconfiguration of the wires, which didn't fix anything but actually started making things work even more strangely. I got my HVAC people over; they replaced the stuck relay on the blower (the actual problem) and fixed the mess the Nest/Google -referred "pro" made of the wiring.

[Csoule]

Thank you...Scott,  Its crazy, I shut the unit off and didn't have time to mess with it, when I went back and restarted the unit and plugged the nest back in things seem normal again...really frustrating

[Scott_R]

Still not dispositive, but I had a similar issue with the relay; physically shutting the power off at the air handler fixed things for a bit, but it started getting stuck on again. Control relays are electromagnetic--physical as much as electronic, so can literally get stuck. 

Since you said it was still heating even with the Nest pulled, in my limited experience that made me think the issue was with the heating unit and not the Nest itself.

[Csoule]

Thank you Scott...I have 5 units/air-handlers and 5 nests tstats on my second floor for each bedroom...my HVAC person who installed them could not get them to work right with the Nest...he had originally installed square white ones...can't recall the brand right now, but they stood out like a sore thumb. I have an old historic home, and the nest is not as intrusive. I have unico system on the 1st floor with 3 nests and that system is working including steam heat from a gas boiler as my main source of heat. Lends me to think what your saying is correct because I have not had problems with those 3...the problems are with the 5 LG units. However my 1st problem I had was the hvac person did have them wired correctly (only blowing cold even when in heat mode and nest on off) and I got that info/fixed through this site, once I changed the white wire it was good...but then this happened... Thanks Scott, you probably hit the nail on the head! I appreciate your insight, this has been frustrating especially since my hvac "specialist" and the LG rep could not figure it out! Honestly they were negative abt the nest from the beginning and even though they spent HOURS trying to fix the issues I really think they wanted me to give up on the nest.  thanks again!

[Markjosephp]

Hi there,

I'm sorry for the late reply, and I appreciate all the steps you've taken to rule out what could be the possible cause. A power-related concern usually could cause an odd heating behavior due to insufficient power coming from the HVAC system, which results in power sharing for the available wires. But I wanted to ensure that everything was covered here. Please let me know if you have any other questions or concerns.

Regards,

Mark

[Scott_R]

Not the OP but my Nests have c-wires and still do this.

[Markjosephp]

Hi Scott_R,

I'm sorry to hear the issue still persists. Let's sort this out:

1. Check the target temperature. The unexpected heating or cooling may have been the result of someone changing the target temperature without realizing it.
2. Check whether the thermostat is set to automatically adjust temperatures when family members leave and come home (for example, switching to Eco temperatures when the home is set to Away). If desired, you can disable it from switching automatically from the Nest app or in the actual thermostat.
3. Make sure that auto-schedule is off.

Let me know how it goes.

Regards,

Mark

[Jenelyn_O]

Hi there,

Checking in — were you able to try the troubleshooting steps provided above? Please let us know how it goes. 

I appreciate your help, Mark.

Thanks,
Jenelyn

[Scott_R]

No one else is touching the thermostat. The only one it would be automatically adjusting to is me. Plus, I can see the temperature it's set to, and it keep heating (or cooling) past that. 

[Jenelyn_O]

Hi folks,

@Csoule, that's good to hear. How's your Nest Thermostat?

@Scott_R, have you already tried turning off your Auto Schedule? You can visit this support article for more information.

Best,
Jenelyn

[Markjosephp]

Hello everyone,

It's me again. I'm checking back in — how's it going? Still need our help? Let us know so we can assist you right away.

Regards,

Mark

[Scott_R]

I don't really have a way to test this, as it occurs on its own--I have no way to make it happen.

[Jenelyn_O]

Hi Scott_R,

I'm sorry for the delay. We totally understand that troubleshooting is a little out of the way, but it's a great start to figure out what's going on with your device. Let's give them a try!

I appreciate your help, Mark.

Best,

Jenelyn

[Markjosephp]

Hi Scott_R,

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

Regards,

Mark

[Jenelyn_O]

Hi  there,

Chiming in — we haven't heard from you in a while so we'll be locking this thread if there is no update within 24 hours. If you need assistance or want to discuss topics, feel free to start a new thread.

Best,

Jenelyn

[Csoule]

Hi, I have had a new HVAC company come in to troubleshoot the situation, They are returning tomorrow. I can fill you in afterwards on the findings