Originally Posted by handbuilder
The refrigerator in the A-Frame is a three way and can run on battery but will drain it in a day...therefore propane is recommended if no power to plug into - however keep in mind it will still use a little battery juice to maintain the temp...likewise, the furnace and water heater also run on propane but both also use a bit of battery power to maintain temp.
Actually, only some of the high wall A-frames and PUPs (OP does not have high wall) have fridges with thermostatic controls (and associated DC parasitic draw).
The smaller regular PUP and A-frame fridges are continuous run (no thermostat or control board). On gas, cooling is adjusted by varying the propane flow with a valve. On AC, cooling is adjusted with a device similar to your home wall dimmer switch. On DC, there is no cooling control at all because the heating element is not strong enough to cause the fridge to freeze. If camping in the same place for several days, I generally have to back off the AC or propane cooling or the fridge contents freeze.
Because the DC cooling is weak, I only use the fridge DC mode while towing. I don't have to worry about the propane flame blowing out (there is no auto restart for propane on a continuous run fridge), but the DC will only maintain the existing temp, not cool any more. That is why I always pre-cool the fridge for at least 12 hours before a trip.
I simply plug in the A-frame (also fully charges the batteries) the night before and set the fridge on max cool on AC. In the morning, when I unplug and hook up the A-frame for the trip, I turn the fridge on DC. The tow vehicle provides enough DC to run the fridge, trailering lights, and maintain the batteries.
just my smaller A-frame and PUP experiences
2014 Rockwood A122
2008 Hyundai Entourage (minivan)
camping Colorado and adjacent states one weekend at a time