Geothermal heat pump shuts down when it is working fine and switches to aux heat.

[rebe]

Ok here goes my first post here.  I already feel bad if this is answered elsewhere else.  I have two geothermal heat pumps in my home, both hooked up to Nest Gen 3 thermostats.  This is a well water pump and dump system and all is good with both systems.  There are no outside units.  Our backup heat is electric heat strips for each.  Recent temperatures here got down to minus 20 degrees F and the heat pumps both shut off.  The inside temperature was just fine, 70 degrees.  Aux heat strips came on and could not keep up as well as the heat pumps.  I want the aux heat to stay off while the heat pumps are keeping inside temperature is comfortable.  The heat pump balance allows me to switch on aux heat but then shuts off the nicely working heat pumps based on the outside temperature.  I would really like to control aux heating based on the inside temperature not the outside temperature.  What am I missing?

[GabrielaG]

Hi @rebe,

Thanks for reaching out to the Google Nest community. I'm sorry to hear your Nest Learning Thermostat 3rd gen is not working as expected, shutting down your two Geothermal Heat pumps and switching to the Aux Heat, but there's no need to worry; I'm happy to help you right now.

To get a better understanding of the situation, please help me out by answering the following questions:

• When did the issue first occur?
• When was the Nest Thermostat installed?
• Do you see an error code on the screen of the Nest Learning Thermostat 3rd gen?
• Have you done troubleshooting steps? If so, can you list them?
• Can you please send me a picture of the wiring of the Nest Learning Thermostat 3rd gen?

Any additional details you can provide will be helpful.

Regards,

Gabriela

[rebe]

The issue was noticed about 2 weeks ago when the nest sent me an emergency alert that our home was 43 degrees.  The nest thermostats were installed about 4 years ago.  I never saw an error code on either of the nest screens.  As far as trouble shooting this issue I have spent considerable amounts of time on the web which has greatly improved my understanding of Nest and thermostats in general.  I have tried different configurations for primary and aux heat sources.  I was unable to get into the pro settings and was hoping there would be a way to set my 'delta' but no luck.  I apparently do not have permission to upload photos here but both nests are wired the same. 

Y1 - yellow

G - green

OB - orange

W1 - white

C - blue

Rh - red

Thanks for your help.

[GabrielaG]

Hi @rebe,

Thank you for your reply. I appreciate the important information you provided me about your Nest Learning Thermostat 3rd gen. I'm happy to continue assisting you.

We need to check the Heat Pump orientation. Please change the orientation following the steps below:

• On your thermostat, go to Settings.
• Select Equipment.
• Select Continue > Continue.
• Select Heat Pump.
• The Nest Thermostat defaults to an O setting for heat pumps. 
• If the O option is highlighted, select B.
• If the B option is highlighted, select O.
• To make sure the issue is resolved, test your heating and cooling again.

Let me know how it goes.

Best regards,

Gabriela

[rebe]

Hi GabrielaG  Switching the O to B changes the heat pump so it cools when I need heat.  

I would like to fine tune when the auxiliary heat comes on and not have the heat pump shut off when the outside temperature is cold.  

Are these settings in the pro setup?

[GabrielaG]

Hi @rebe,

I appreciate your response. Thank you for following my troubleshooting steps. I understand that you want to use the Auxiliary heat when it's cold on the outside without having the heat pump turn off. I'm happy to continue assisting you.

To change the Auxiliary heat, we need to check the Heat Pump Balance settings in your Nest Learning Thermostat 3rd gen. Please follow the steps below.

• On your thermostat
• Press your thermostat ring to open the Quick View menu.
• Select Settings.
• Select Nest Sense.
• Select Heat Pump Balance, then choose the setting you want.

You can check this article to learn more about Heat Pump Balance options.

Let me know how it goes.

Best regards,

Gabriela

[rebe]

Yes thankyou for the link.  I have the heat pump balance set to off.  The nest then uses 0 degrees as the point it is shutting my heat pumps off.  This makes no sense when they are working fine.  Aux heat then is unable to keep up and my home gets verry cold.  We are able to burn wood to help but the home is quite large.  The link you provided discusses droop.  for gen4 Nests.  That feature would be nice.  I do not want the Nest to shut off the heat pumps when I need them the most.  Looking for ideas in Iowa.   

[GabrielaG]

Hi @rebe,

Thank you for your reply. I'm sorry to hear your Nest Learning Thermostat 3rd gen is still not working as expected. I appreciate your time performing the troubleshooting steps with me. I'm happy to continue assisting you.

We need to troubleshoot some wires on the Nest Learning Thermostat 3rd gen to see if there's a problem with the Nest Learning Thermostat 3rd gen backplate. If you feel comfortable, please follow the steps below:

• Turn HVAC system power off through the breakers.
• Remove the Y1 and OB wires, and treat the system as a conventional heating system.
• Turn on the breakers.
• Check if the issue is resolved.
• Troubleshoot the G terminal.

• Stop any call for heat or cool.
• Turn on the fan and verify if it activates.

• Turn HVAC system power off through the breakers.
• Put Y1 back and swap the OB and G wires.
• Turn the power back on the HVAC system through the breakers.
• Stop the call for heat or cool, turn on the fan, and verify if it activates. For heat pumps with O-orientation: Call for cool, but expect heat. For heat pumps with B-Orientation: Call for heat.
• Reset the thermostat to factory defaults, then set it up again.
• Please let me know if you're still having the same issue or if you start to receive heating or cooling after all these troubleshooting steps. 

Let me know how it goes.

Best regards,

Gabriela