Fridge a/c receptacle rewired for Inverter

[SC RVer]

As most everyone has experienced rising temps in fridge while traveling in high temp season while on propane I was wondering if anyone has had the a/c receptacle converted to have output from the inverter while traveling? This is of course assuming that the wattage is sufficient and the t/v alternator output is enough. That part I have not yet researched. Thanks in advance for any thoughts good or bad.

[uncle_bob]

Hi

The fridge on AC pulls about 3A. Yes, that's a guess and yours could pull a bit more or a bit less. The only way to know what yours pulls is to measure it and see.

3A at 120 is around 30A off a 12V bus at 100% efficiency. Your inverter would need to be able to supply 3.6 KW "full time". Something up around 4KW probably would be a good idea. If you loose 10% in the inverter and 10% in the wiring, you would need about 36A at 12V to get the job done.

36A is well above what your normal 7pin adapter will handle. You are talking about some sort of custom wire job. Either you put the inverter in the TV and run 120V back or you put in some pretty big wires / connectors to get DC back to the trailer.

Swapping out to a compressor based fridge would take the 30-ish A number down to something in the < 10A range. You have some choices to make in terms of double vs single compressor. The singles pull half as much (peak) but the freezer does not get it's own separate cooling system.

The absorption fridge likely will do no better / no worse running on 120V than on propane. If anything, I'd bet it runs slightly better on propane. If the objective is to cool better, switching it to 120V is not going to help. The dual compressor with proper ventilation likely will do a better job in this regard.

Fun !!

Bob

[Al and Missy]

Originally Posted by uncle_bob

Hi

The fridge on AC pulls about 3A. Yes, that's a guess and yours could pull a bit more or a bit less. The only way to know what yours pulls is to measure it and see.

3A at 120 is around 30A off a 12V bus at 100% efficiency. Your inverter would need to be able to supply 3.6 KW "full time". Something up around 4KW probably would be a good idea. ...
Bob

As we used to say (in the pre-calculator slide rule past) there's that damn decimal point again....30A at 12 volts is 360 watts, not 3.6 kW. It will actually be a little more due to the low efficiency of the inverter....


Agreed it will probably do no better on AC than propane. My 2001 and 2002 had a recall to add baffles around the flame area. The reason was fire safety in case of an ammonia leak, but I think it also improved performance going down the road.

[uncle_bob]

Originally Posted by Al and Missy

As we used to say (in the pre-calculator slide rule past) there's that damn decimal point again....30A at 12 volts is 360 watts, not 3.6 kW. It will actually be a little more due to the low efficiency of the inverter....

Hi

There you go .... sorry about that

Bob

[BigSxyWhtGuy]

Ours is rewired but we just run it on propane as the drain on the battery is pretty serious. We do have a dc/dc charger with a 3000 watt inverter as well. Dc/dc does 500 watts in addition to the 600 watts of solar.

[vwii]

Since adding ventilation fans our propane fridge has operated much better in HOT temperatures. It sems even driving down the road that the vents are not circulating air as well as you'd think.

[Wazbro]

Originally Posted by uncle_bob

The absorption fridge likely will do no better / no worse running on 120V than on propane. If anything, I'd bet it runs slightly better on propane. If the objective is to cool better, switching it to 120V is not going to help. The dual compressor with proper ventilation likely will do a better job in this regard.

Fun !!

Bob

Actually this seems to vary from one fridge to the next. Some do better cooling on electric, others do better on propane (maybe some need tune-up/adjustment). Testing each way on his fridge would be needed to find out if it would help or hurt the cooling ability of his fridge.
Although I agree going to a properly vented 2 compressor fridge would be most helpful for maintaining temps.

[wulfraat]

I run my fridge off inverter / battery from time to time (have 600ah). Pulls about 350-400w when heater is running per Bob's post.



I do this to conserve propane on occasion or if I want to cycle my batteries.

[wcrockett]

Originally Posted by uncle_bob

Hi

The fridge on AC pulls about 3A. Yes, that's a guess and yours could pull a bit more or a bit less. The only way to know what yours pulls is to measure it and see.

3A at 120 is around 30A off a 12V bus at 100% efficiency. Your inverter would need to be able to supply 3.6 KW "full time". Something up around 4KW probably would be a good idea. If you loose 10% in the inverter and 10% in the wiring, you would need about 36A at 12V to get the job done.

36A is well above what your normal 7pin adapter will handle. You are talking about some sort of custom wire job. Either you put the inverter in the TV and run 120V back or you put in some pretty big wires / connectors to get DC back to the trailer.

Swapping out to a compressor based fridge would take the 30-ish A number down to something in the < 10A range. You have some choices to make in terms of double vs single compressor. The singles pull half as much (peak) but the freezer does not get it's own separate cooling system.

The absorption fridge likely will do no better / no worse running on 120V than on propane. If anything, I'd bet it runs slightly better on propane. If the objective is to cool better, switching it to 120V is not going to help. The dual compressor with proper ventilation likely will do a better job in this regard.

Fun !!

Bob

Hey Bob,

I have a 3000 watt inverter wired along with the shore power line through a transfer switch that powers the 30Amp converter for the entire electrical system in my 2012 27'FB. If I turn the inverter on when I am not on Shore Power, with the frig is set to Auto, it switches seamlessly to electricity. It works fine but I did not design the system with the intention of using electricity from the inverter to power my frig.. So I always set it back to run on Propane. I prefer propane because of the limited power from my solar panels and the 3 battle born batteries that power the inverter. All that said, my point is:

1) Yes. You can power the Frig. from a 3000 watt inverter in my 2012 27FB but not indefinitely.
2) I choose not to because it consumes more power than my battery and solar capacity over a prolonged period of time. I also only use my 3000 watt inverter when I need lot of AC power for things like the microwave. It is not on 24/7 when I boon dock.

As to the question in the original post: The Frig in my trailer does about the same in hot weather regardless of the power source. I think the real key is to keep cool air circulating through the refrigerator vent. I think that will do more for efficiency than the power source.

Of course everyone has their own experience to fall back on so take mine with a grain of salt. I am sure others have more experience and differing opinions.

[Gulliver72]

We always travel with the fridge on the 2000w inverter powered from the truck alternator thru a DC/DC charger. All outlets are live all the time. Everything powered through the inverter.