cancel
Turn on suggestions
Auto-suggest helps you quickly narrow down your search results by suggesting possible matches as you type.
Showing results for 
Search instead for 
Did you mean: 
Help

Nest v2 to v4 upgrade with Fossil Fuel kit - not engaging alternate heat

mmercill
Community Member

3 weeks ago

Hello - 

I have had two Nest v2 thermostats working perfectly fine for more than a decade on two identical Trane heat pump/duel fuel (propane) systems.  Both systems have fossil fuel kits attached which presumably have outdoor temperature sensors.  Recently I was forced to upgrade to the Nest v4 thermostat, which I have heard handles duel fuel differently.  I wired both thermostats identically to how they were wired with the Nest V2 thermostats.  Neither system will engage alternate heat when the temperature falls below the lockout temperature of 30 degrees.  My wiring information is below.  I am looking for suggestions on what to try.

Y1 - Yellow

Y2 - Empty

G - Green

OB - Orange

Rc - Empty

AQ minus - Empty

W1 - Empty (I have tried to put white here with a factor reset but it didn't work)

W2 - White

C - Blue

* - Black (configured as Emergency)

Rh - Red

QQ plus - Empty

 

 

Labels:
0 Kudos
1 REPLY 1

moralesvicente
Community Specialist
Community Specialist

3 weeks ago

Hi @mmercill, 

 

Thanks for reaching out to the Google Nest Community Forum. I understand that you have upgraded to the Nest Learning Thermostat (4th gen) and are noticing that neither system engages alternate heat when the temperature falls below the lockout temperature of 30 degrees, despite using your previous wiring setup and HVAC system (Trane heat pump/dual fuel). I’m here to help.

To resolve this, please try the following troubleshooting steps:

  • Adjust the Wiring: For your safety, turn off the power to your HVAC system at the breaker box before proceeding. Move the white wire to the W1 terminal and the black wire to the W2 terminal.
  • Secure Connections: Ensure all wires are fully inserted and properly seated in their terminals.
  • Reconfigure the wires: Open the Google Home app to update your wiring settings. For guidance, you can review this article: Thermostat wire undetected, unconfigured, or unspecified.
  • Verify Heat Source: In the Google Home app, tap your thermostat tile > Settings > Equipment > Heat Type. Ensure the source is set correctly for your system.

Let me know if this helps or if you need further assistance.

 

Regards,

Daniel

0 Kudos