Ducane 20kw furnace with heat pump/ as long as the outdoor unit is running the indoor unit runs fine. If the outdoor temp falls below the setting on the outdoor units outside stat the 30amp breaker to the furnace breaks. Pulling 21amps. on the circuit when the outdoor unit is running. The wire is 10-2 w/gr. The 60amp circuit will pull 42amps or 21 depending on the number of strips that are on. It is on 8-2 w/gr. The unit is new. Of course didn't have the problem till outdoor temp dropped enough to show the problem

Grilling - Ducane