I recently installed a Bosch heat pump and an Ecobee 3 Lite thermostat, and I’m trying to understand how the auxiliary heater is functioning. The setup includes the auxiliary heater as a hydrocoil downstream of the heat pump coil, and it’s supposed to run alongside the heat pump. However, I’m observing some unexpected behavior that I’d like to understand better.
This morning, the auxiliary heater ran for 15 minutes, but the indoor temperature only increased by 0.5°F. The setpoint was 69°F, the indoor temperature was 67°F, and the outdoor temperature was 17.5°F when the auxiliary heater kicked in. From what I’ve read, automatic staging doesn’t perform reverse staging, and the minimum auxiliary run time is set to 2 minutes. My questions are:
- Why did the auxiliary heater activate at a 2°F differential instead of the 2.3°F differential set in the thermostat? I suspect the thermostat might not have updated the differential value correctly.
- More importantly, why did the auxiliary heater only run for 15 minutes and only raise the temperature by 0.5°F? I thought the auxiliary heater should run until the setpoint is reached, especially since automatic staging doesn’t reverse stage.
I’m curious if others have experienced similar issues or if there are specific settings I might have missed. Any insights or suggestions would be greatly appreciated!