You have a Heat Pump with Auxiliary Heat and Emergency Heat. The Nest Learning Thermostat E cannot support both auxiliary and emergency heat. You need to upgrade to Nest Learning Thermostat 3rd generation. Now you can check your system because sometimes auxiliary heat and emergency heat are the same heating elements. With an emergency heat capable Thermostat, the homeowner can activate the electric heat strips in the situation where the outdoor compressor has failed and you need HVAC service repair. So, with emergency heat, you will have a way that you’ll be able to have some heat, albeit electric heat strips, which are terribly inefficient. The thermostat that you have can support a heat pump with auxiliary heating. The auxiliary heating is used by the heat pump, defrost control board. When the heat pump needs to go into defrost mode, it will activate the auxiliary heat to keep the air warm while it is defrosting the outdoor unit. Additionally, with a nest learning thermostat can do it is if the heat pump is running and it’s not keeping up with the demand for heat, it can activate the auxiliary heat strips to boost amount of heat being produced..
AC Cooling Wizard
NestPro, Google Pro, Mechanical Engineer and HVAC service company owner.
