I have a 2400 sqft house that uses two Goodman heat pumps. I bought the place two years ago and the systems were installed by the previous owner before they moved. Below are the model numbers as listed on the equipment. When it gets cold out, below about 18 degrees, the thermostats will switch to aux heat. When this occurs, you can hear a click at the thermostat. However, the air stream does not feel any warmer. As an experiment I put one of the units into emergency heat. When I did this the outside compressor turned off and the air stream was immediately warmer. As a test I measured the current to the air handler. In normal heating it pulled 0.7 amps, which I suspect is the blower load. When the thermostat called for aux heat, the current reading was the same at 0.7 amps. When the unit goes into a defrost cycle, the current reading jumps to 42 amps. As soon as the defrost ends, the current drops back to 0.7 amps, even though the thermostat is still reading “aux heat.” If I put the unit into emergency heat, the current reading jumps to 42 amps. Additionally, if it gets cold enough, the units will drop below their set points, while in aux heat. The lowest I have seen was 3 degrees below the set point. I checked the CPH settings and found that both thermostats are set to: “aux heat” = 5, “emergency heat” = 9, “compressor” = 3.

It seems to me that even though the thermostat is calling for aux heat the heating strips are not turning on. However, the heating strips will turn on if I force the units into emergency heat or the units go into a defrost cycle. To me, this doesn’t make any sense. I can’t understand why the thermostats would list aux heat, yet the heating strips are not turning on. In searching the web, I found some comments that aux heat won’t start until the thermostat drops to 2-3 degrees below the set point, but why would the thermostat say “aux heat” when it is not on at that point. Does this behavior seem normal?

1st floor system
Thermostat: Honeywell Pro TH3210D
Compressor Unit: GSZ130241AB
Air Handler: ARUF182416BA
Heating Kit: HKR-10

2nd floor system
Thermostat: Honeywell Pro TH3210D
Compressor Unit: GSZ130301AC
Air Handler: GSZ130301AB
Heating Kit: HKR-10