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Fantom O/B Hest Pump Wire (E413)

Noheatpump
Community Member

‎09-28-2025 03:13 PM

I am replacing a nest learning thermostat gen 1 to gen 4. Wiring should be the exact same. we have a gas, furnace (wires W1 and W2) and electric air-conditioning system (wire Y1). I have no heat pump and so no wire is connected to O/B. Yet when I try to install the new nest thermostat, it recognizes an O/B wire and therefore things there is a heat pump in the system and wires W1 and W2 are redundant. so I am unable to put my heating system online. 

I have tried everything for it to not recognize that O/B port or wire. is this a known issue or could this be a faulty/defective unit?

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GabrielaG
Community Specialist
Community Specialist

‎10-02-2025 05:58 PM - edited ‎10-03-2025 08:57 AM

Hi @Noheatpump,

 

Thanks for reaching out to the Google Nest Community. I'm sorry to hear that you're having problems with your Nest Learning Thermostat not recognizing your conventional system and incorrectly detecting an O/B wire. I'm glad to help you.

To make sure I provide you with the most accurate and effective troubleshooting steps, I just need a little more information. Could you please answer the following questions for me? 

  • When did you install your Nest Thermostat?
  • Do you have a C wire connected?
  • Do you see error codes on the screen of the Nest Thermostat or app?
  • Have there been any recent changes or upgrades to your HVAC system?

If you have any additional details that might be helpful, feel free to share them with me.

 

Regards,

Gabriela

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