In our previous 2003 Adventurer, the heat pump would quit running for 2 conditions.
First-The Heat pump could not maintain the set temperature. If the coach is losing heat faster than the HP can produce, then the LP furnace is activated. In this case the tstat will indicate DIFF, that the 2nd stage heat stage is activated.
If this happens 3 times in a row, then the HP is locked out for 2 hours. Only the LP furnace will run during that time.
The tstat uses 20 min as a criteria. If the HP can't satisfy the set point for 20 min, the lp is turned on.
Second- The HP shuts off because the outdoor coil Thermister cuts-off due to low freon temp. This usually occurs due to ice build up on the coils. In this case the lp furnace is in a safe mode. It will come on at 45 deg and shut off at 60 deg.
Setting the mode to gas will let the lp furnace operate to the set temp.
In my experience, the heat pump can operate at low outside temps, below 32 deg F. A lot depends on the humidity, and how long it take ice to form on the outside coils.
These basement units do not have any defrost circuitry built in, as do home units.
