Aux Heat Not Engaging with Electric Heat Pump

[Cm18cam]

I have an electric heat pump with auxiliary heat (no gas or other heat source). My heat runs fine, however when I jump the temperature 20 degrees just to see if my auxiliary heat will engage it does not. I had a professional install my heat pump (thermostat was already installed) and they could not figure out the issue and suggested it may be an issue with the thermostat itself as they could manually jump the wires and engage the aux heat at the handler. Essentially whether I jump the temperature or whether the outside temperature is cold (15 degrees) the aux heat never engages to assist the heat pump and my heat pump ends up running constantly. I have turned off nest balance and switched the setting to (aux heat as needed), uninstalled the thermostat and reinstalled it, yet the problem continues. I contacted nest support but the technician said he had never seen this issue before. Any help aside from replacing the thermostat would be greatly appreciated. 

[zoeuvre]

Hi Cm18cam, 

Uh-oh! I'm sorry to hear about the issues you're experiencing with your electric heat pump and auxiliary heat. Try to directly connect the auxiliary heat at the handler, as your professional installer did. This will help determine if the issue lies with the thermostat or the heat pump system itself. If the auxiliary heat engages successfully when bypassing the thermostat, it suggests a potential problem with the thermostat or its configuration. Take note to turn off the power to your heat pump system before touching any wires. 

Let us know how it goes.

Best,

Zoe