Nest thermostat connecting to Trane XR80 no call for heat

[MonteBarlow]

I have a 5 wire system (Y, G, R, W, C) and after connecting my nest, the fan blows but it gives no heat. Error code on Trane unit says “no call for heat”. I have pictures of old connections with previous thermostat and the wiring in my Trane unit. To explain in words, on the C terminal in Trane unit is a blue wire that goes to thermostat, a white wire that goes to outside AC unit, and a black wire that goes to a wet sensor. On the Trane G terminal is a green wire to thermostat. On the Trane R terminal is a red wire from the wet sensor and a green wire to the wet sensor. On the Trane W terminal is a white wire from the thermostat. On the Trane Y terminal is a yellow wire to the thermostat and a red wire to the AC unit.  The red wire from the thermostat is wire nutted together with an orange wire to the wet sensor. 

[alejandom]

Hi @MonteBarlow,

It sounds like you've done a good job documenting the wiring! While I can't provide specific electrical troubleshooting advice due to safety concerns, I can offer some next steps based on the information you provided:

1. Double-check Nest wiring: Ensure your Nest thermostat wires match the wiring instructions for your specific Nest model and Trane furnace combination. You can find the Nest wiring guide in the Nest app or online https://support.google.com/googlenest/answer/9274936?hl=en.

2. Verify "C" wire connection: The "no call for heat" error could indicate the Nest isn't receiving sufficient power. In some cases, a "C" wire (common) is needed for proper communication. Check if your old thermostat had a "C" wire connected and if your Nest model requires one.

3. Review Trane unit wiring: While the Nest wiring is crucial, double-checking the Trane unit wiring against the original thermostat connections or a Trane manual wouldn't hurt.

4. Utilize Nest resources: Nest offers troubleshooting resources specific to error codes and common issues. Check their support website for your model https://support.google.com/googlenest/answer/9233319?hl=en.

5. Consider a qualified technician: If you're not comfortable troubleshooting further, contacting a qualified HVAC technician is the best course of action. They can diagnose the issue and ensure your furnace operates safely and efficiently.

Here are some additional tips:

• When consulting a technician, mention the "no call for heat" error and the fact you recently installed a Nest thermostat.
• Provide them with pictures of your old thermostat wiring and the Trane unit wiring (if comfortable).

Regards,

Mario.