Switching Refigerator Modes?

My rule of thumb is use AC when available, LP the rest of the time, DC when you have to.
You need to have a big healthy battery bank and/or a bunch of solar to get alot out of DC fridge mode, IMO. 2 new 12V deep cycles will run my fridge for about 8 hours in hot weather before it drains the batteries.
LP on the road with DC backing it up if the flame gets blown out.

Doesn't your Dometic Fridge have AUTO mode?
AUTO...selects available energy source as available
IE: 120V AC....GAS....12V DC

Run it in AUTO and it will swap to available energy source with 120V AC having priority

If no AUTO mode..select 120V AC when available ...swap to gas when AC not available----use DC only when you have engine running as it will drain battery otherwise


AC and Gas provide SAME heat energy to cool fridge from initial start to shutdown
DC only good enough to 'maintain' temps WHILE in transit

The fridge stays on auto all the time. We let the fridge figure it out.

I agree with using auto mode if you have it.
There's no advantage to putting it on electric mode if your electric is coming from an onboard propane generator. That's really still using propane, just going thru an inefficient conversion process. If you are talking about running a gasoline generator then I guess it might make sense to conserve your onboard propane but in reality the amount we're talking about is so small you'll never notice the difference.

NoVa RT wrote:
Is it worth it to switch the refrigerator to AC if the generator is in use, or do you lose cooling efficiency by stopping & starting so that it’s better to run on propane continuously?

Anytime you don't have campground shore power available run your gas absorption fridge on propane, after all that's what it's designed for. Aside from powering A/C use the genset for maintaining adequate battery charge.

Old-Biscuit wrote:
Doesn't your Dometic Fridge have AUTO mode?

We have no idea what this fridge is because the OP never said, whether it's DSI or strictly manual. All I've figured out it's in a Road Trek Class B vehicle.

I would say propane most likely beats Grenerator but I"m not sure. Depends on the cost of fuels.

I will give you HALF the information you need.
Thomas Edison achieved, as I recall an efficiency of about 80% both on Generators and on electric motors. Though there may have been SOME improvement since. not a whole lot.

SO you burn Fuel (Gas D or P) it makes mechanical energy (There is some loss) Which then makes electricity (Again 20% loss) this heats a wire (At last we have something that APPROACHES 100% efficiency (There is a small loss in the wires leading to the heat element) to run the Absorption Cooling Boiler

Now think of Mr. Rube Goldberg.

Next we have the propane method...
You burn propane to make heat which heats the boiler.. End of list.

That said. If you are paying like 5.00/gallon for propane and 2.50 for gas.. Well makes a difference don't you know .

OPs Signature line

2013 RT 190-Popular


They use Dometic compact fridges....3 cu/ft and 5 cu/ft
Some models do not have AUTO mode..............MOST do

If OPs has AUTO..they should use it

If you'd be running the generator solely for the fridge, use propane.

If you'll be running the generator for other reasons such as air conditioning, use AC power. If it's just a quick run of the generator (make coffee or microwave lunch) it's probably not worth the hassle of switching back and forth manually. It generally makes no sense to run the generator just to power an absorption fridge, and doubly so if it's a propane fueled generator.

If the fridge has an automatic setting (many do), that will switch between propane and AC power based on whether or not electric power is available at the moment, and it usually works out best just to leave it on automatic most or all the time.

While there are a great many variables, a handy rule of thumb in the absense of any better information is to guess that an RV fridge uses a pound of propane a day on propane power, maybe a little less in your this case as it's a quite small fridge. It's not a large consumer of propane relatively speaking.

SoundGuy wrote:

Old-Biscuit wrote:
Doesn't your Dometic Fridge have AUTO mode?

We have no idea what this fridge is because the OP never said, whether it's DSI or strictly manual. All I've figured out it's in a Road Trek Class B vehicle.

In your case, I suspect you have to adjust from electric, to gas, to DC. Also in your case, you should only use DC when driving. DC has a hard tine keeping stuff cold, and certainly can't cool down one of those little fridges.

I've owned 3 Class B's in the past.