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Erratic Heating Nest Heat Pump

tacop42please
Community Member

‎01-08-2024 11:04 PM - edited ‎01-08-2024 11:07 PM

Hello,
Had a Honeywell T4 Pro Thermostat that worked flawlessly. Purchased the google nest hoping to use the app interface, set a schedule and get remote control of the thermostsat. 

I have a heat pump system with auxiliary heat strips (in the air handler). 

I installed the Nest as instructed and the heating has been "sporadic". One thing to note, during the install the Nest app let me know it did not detect W1.  There has been no observable constant behavior that makes sense. 

Issues during heating :  Summarized , will not reliably heat 

  • When the thermostat is set to 73 and it's 71, it will blow room temperature air or slightly cooler causing the temp to drop or never reach the 73 SP
  • When the thermostat is close to temp it'll blow cold air
  • If I let it drop to 52 overnight, it wont ever get to 72 in the morning. It just keep running and running. 
  • If I turn it off and turn it back on sometimes it will heat.
  • Sometimes the air comes out warm, sometimes it comes out lukewarm, sometimes cold

I put my honeywell T4 back in and the thing is a beast. It just works. I have hot air coming out of the registers. 

I've contacted support in the chat but I get the same low-level basic trouble shoot run around. 
I have a feeling there is an issue with the W2 (on honeywell) being plugged into the W into the nest. 
It won't let me post image but the wiring for the Honeywell was Y G C O/B W2 R.
Nest wiring recommendation from the install Y G C O/B W RT

Not sure why the Nest just doesn't work. Maybe I need the nest learning with a W2 port. 

I feel like it has to do with this W wire somehow as W gets signal from the defrost board, and for aux heat

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zoeuvre
Community Specialist
Community Specialist

‎01-20-2024 09:43 AM

Hi tacop42please, 

 

Uh-oh! It sounds like you're experiencing heating issues with your Nest Thermostat after switching from a Honeywell T4 Pro thermostat. The Nest Thermostat may be experiencing erratic heating behavior due to a missing "W1" wire during installation. This indicates that the thermostat is not receiving a signal from the primary heating stage, potentially causing issues. Proper configuration is crucial for optimal performance in heat pump systems, and the Nest Thermostat may require specific settings or adjustments to work effectively with your specific heat pump system. The "W" wire connection may also be causing issues, especially if it controls auxiliary heat.

 

To address these issues, review the wiring connections at both the thermostat and the air handler/furnace to ensure they match the Nest Thermostat's recommended wiring configuration. You can send us the wiring photo of your control board or previous thermostat and photo of how you connected the wires to the Nest Thermostat.  Once the wiring is verified, make sure the Nest Thermostat settings are properly configured for your heat pump system. Pay attention to options such as "O/B" (which controls the reversing valve for heating/cooling mode) and "W1/W2" (for auxiliary heat). Adjusting these settings correctly is crucial for proper heat pump operation.

 

Let us know if that helps.

 

Best,

Zoe

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