Heat pump only works after resetting Nest Thermostat

[Gordon2023]

Greetings.  I have an electric heat pump (Payne) with propane auxiliary heat. The auxiliary heat works great and the heat pump has worked well for the last two years with my Nest thermostat.  Recently though, I find that occasionally the outside compressor isn’t running while the house is trying to heat (particularly in the morning or after we’ve been gone—when we’re trying to heat the house from a cooler setting like 62 going up to 70) so the house is not heating. What I’ve found is if I do a reset on the Nest thermostat, the compressor then comes on and the heat pump begins working as it should (for several days).  

The software version says it’s up to date at 6.2-27 (“Model Display-4.8”, “Base Software version 1.4.11/4.0 Model backplate-7.6”). 

Does it sound like the thermostat may be going bad?  Any way to test that? Suggestions?

[Gordon2023]

Update: I’ve observed today that the heat pump works as normal until it goes into defrost mode.  At that point the compressor never comes back on, until I perform a reset/reboot of the Nest thermostat. Without the compressor running, the air does not heat (obviously).  So I’m wasting a lot of energy because the system runs continuously without heating the house when it’s in this mode. 

[Patrick_Caezza]

Have an HVAC tech out to check the operation of your system. The HVAC and not the thermostat control the Defrost mode.

[Gordon2023]

Thanks for the reply @Patrick_Caezza, my follow up question is—why does the compressor come on only after I do a Nest reset/reboot?

[Patrick_Caezza]

@Gordon2023 

I don't have an answer for that

[Jenelyn_O]

Hi there,

Thanks for reaching out — I just want to follow up if you were able to get an HVAC technician to check your system?

I appreciate your help, @Patrick_Caezza.

Best,

Jenelyn

[Gordon2023]

I called my HVAC technician and he thought the problem was either the thermostat or the wiring.  I decided it would be a waste of time for him to come out without further troubleshooting the system.  So I swapped out the Nest thermostat with an identical Nest thermostat (base and all) that I had on another system.  I’m going to give it a few days and see if the problem reoccurs.  If so, I’ll get the tech out to work on the heat pump. 

I’ll update this thread in a few days. 
Thanks!

[Jenelyn_O]

Hey Gordon2023,

That sounds like a plan! I would be happy to get an update from you. For now, I'll just keep this thread open. 

Regards,

Jenelyn

[Jenelyn_O]

Hi there,

Checking if there's any update — how was the monitoring? Do you still encounter the issue? 

Thanks,

Jenelyn

[Jenelyn_O]

Hello Gordon2023,

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

[Gordon2023]

The HVAC technician came out on Friday and replaced several boards on my heat pump —the fossil fuel kit and the outdoor thermostat. He also changed the dual fuel setting on the Nest so instead of using alternate heat (propane) when it’s below 30 degrees he set it to Never Use Alternate Heat.  His explanation was that the heat pump itself would switch over to propane when it’s thermostat told it to.  However the next morning it was 20

degrees outside and it was trying to heat with the heat pump only (never used Propane).  I’m thinking that last setting change was probably wrong.  Can anyone confirm that for me?
@Patrick3 

[Gordon2023]

I meant to also update you that when I swapped out the Nest thermostat last Thursday with the identical thermostat I had on my upstairs unit, the problem remained the same. So I was able to tell my HVAC guy that the thermostat wasn’t the problem.  That’s why he came out Friday and changed out the circuit boards I mentioned above.  

[zoeuvre]

Hey there,
 

I wanted to check in and see if you are still in need of any help. Please let me know, as I would be happy to assist, and answer any questions you may have.

Thanks,

Zoe

[Gordon2023]

Yes, I still have the outstanding question of whether it was wrong to set it to “Never Use Alternate Heat”.  can anyone confirm?

Also, my HVAC guy still seems convinced that the problem is the Nest thermostat, so he’s put in a more traditional thermostat

The problem we’re trying to address is the heat pump occasionally failing to restart after defrosting.  The unit keeps running without the compressor running , thereby failing to generate any heat.

[zoeuvre]

Hi Gordon2023, 

Alternate heat is used when your heat pump is not capable to generate enough heat when its cold outside. Therefore, using Alternate heat would help your heat pump to protect itself from freezing but is expensive rather than using your heat pump to heat up your home. You can learn more about this by checking this article. 

Let us know if you have any other questions. We're happy to help. 

Best, 

Zoe

[zoeuvre]

Hi there,

I wanted to check and see if you are still in need of any help. Please let me know, as I would be happy to assist, and answer any questions you may have.

Regards,

Zoe

[Gordon2023]

My HVAC tech switched out the nest thermostat with a traditional thermostat and we’re watching to see if the problem

is there a Nest thermostat that is particularly good for use with a heat pump with propane as the auxiliary heat source?  It has to handle two-stage heat with auxiliary heat.

The temporary thermostat we have Right Now will use propane if we need it to jump more than 2 degrees. Great feature that our Nest doesn’t do—it sometimes takes hours to get to a comfortable temperature  

[Gordon2023]

My HVAC tech switched out the nest thermostat with a traditional thermostat and we’re watching to see if the problem continues. 

is there a Nest thermostat that is particularly good for use with a heat pump with propane as the auxiliary heat source?  It has to handle two-stage heat with auxiliary heat?  The temporary thermostat we have Right Now will use propane if we need it to jump more than 2 degrees. Great feature that our Nest doesn’t do—it sometimes takes hours to get to a comfortable temperature. 

thanks, Gordon

[JaredOberhaus]

Try this:

Choose Equipment, and find Equipment Settings (navigate through some intermediate panels), then find Heat Pump. The setting "Use the heat pump auxiliary heat when the outdoor temperature is below:" might be too low. Auxiliary heat will not activate unless the outdoor temperature is below this setting. I assume that the value you choose here is dependent upon how efficient your heat pump is.

This setting is different than "Safety Temperature."