How-to: Minimize use of Auxiliary Heat with Heat-pump


We have a heat pump and recently installed the ecobee 3. Now I keep on getting alerts that the Aux heat is running. It does seem to be kicking in frequently instead of normal heat and got an alert that my "Aux Heat was running for more than 180 minutes". What could be the problem?


There is a setting in your "thresholds" section that you can change; most likely it is set to default at the moment which relies on the feedback of your heatpump system and how long it takes to warm up the home. Some heatpumps can take longer than others to warm up and finally start giving heat. In these cases you can manually enter a higher differential to avoid the auxiliary heat coming on for a certain time or temperature difference (it is up to you what value you would like to keep it at). I would recommend to set a value for these thresholds first and that should eliminate the aux heat turning on sooner than needed.

This can be done by going to MENU > SETTINGS > INSTALLATION SETTINGS > THRESHOLDS > COMP TO AUX DELTA. Now this 'COMP TO AUX DELTA' option is asking for how many degrees the indoor temperature should drop before using the auxiliary heat.

In this option, please select what you find best fits for you. For heatpump systems, its also crucial to know and set the minimum outdoor temperature that the heat pump can run with - otherwise the thermostat will lock out the heatpump and change over to aux heat as the weather outside will be too cold to run the heatpump unit that's sitting outside.

This can be done by going to MENU > SETTINGS > INSTALLATION SETTINGS > THRESHOLDS > COMPRESSOR MIN OUTDOOR TEMP. This is set at a default 35F (1.7C), so the heatpump will not be used when the weather outside is below 35 degrees Fahrenheit and only aux heat will be used in this case.

To also avoid short cycling and increase equipment efficiency, you can go to MENU > SETTINGS > INSTALLATION SETTINGS > THRESHOLDS > ​HEAT DIFFERENTIAL TEMP > and change this to a higher value so that the system turns on for a bigger temperature drop and reduces short cycling.