The part about the "12hr power on" assumes a crankcase heater is present.

Also, many manuf's require the period to be 24 hours but then again, assuming a crankcase heater is installed.

These are not installed in many areas.


My bryant/carrier heat pump unit says no heat above 66 deg and no A/C below 55 deg. It actually prevents cooling automatically via the outside air temp sensor installed when its lower than 55 deg.