I bought the Nest 2nd Gen Thermostat. When I went to install the thermostat, I found an "L" wire connected to the old Thermostat. Buried on the Nest site, there is a statement that Nest does not support Heat Pumps with an "L" wire (Even though the capability chart states that it does). So I am not sure what the correct answer is.

However, I opened the Furnace to check the control board. I found the "L" wire was combined with the "C" wire (they are wire-nutted together) and then that Wire is hooked into the "C" terminal.

Can I ditch the "L" wire since it is combined with the "C" wire - I assume they must serve the same purpose since they are combined.

Other Info: My set up is a heat pump with coils for emergency heat

Thanks for any help that can be provided.

 

Correction: I properly traced the wires. The "L" wire is NOT combined with the "C" wire as I first thought.

Is it safe to run the heat pump without the "L" - system fault indicator attached?

 

Yes, it is safe to run your system without the "L" wired.