Educate me on the 3 way RV fridge.

[Pacific Northwest yetti]

I have a 2007 outfitter Apex 8, that currently has the standard 3 way RV fridge. So 120, propane and 12 volt. I'm used to the other two, but am wondering about the 12volt portion. And why people pull them out, is the 12volt just really inefficient? Etc, I was planning on eventually replacing it with a 12volt only. I currently have abou 250amp/hr capacity.

Thanks,

 

[Joe917]

3 way fridges work by heating the refrigerant to operate. heating electrically draws a lot, the 12 volt element is normally used with the engine running, it quickly draws down the battery otherwise. Run the fridge on propane when parked.
12 volt compressor fridges are far more efficient electrically

 

[LeftCoastKiteboarding]

Or just stick with propane. Super efficient. My large fridge/freezer sips propane like a fine scotch. Can run for weeks on a 20lb tank.

12v is just about worthless on a 3 way. Can be used while driving if the propane pilot keeps blowing out but other than that not much point.

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[java]

As others have said on a 3way fridge on 12v its actually a heating element, not a compressor like the popular "12V" fridges. Sucks down power in a hurry!

 

[Mighty Dodge Ram]

What others have said...just run it on propane. Keep the outside compartment clean and carefully use compressed air to dissuade spiders from taking up residence in the burner orifice.

 

[GHI]

I have a 3-way fridge in my van. The 12 volt option will suck my house battery dry in a very short couple of hours if the engine isn't running. I will sometimes use that option if I'm packing in a bunch of windshield time trying to get to a destination. It is not as efficient as propane though.

 

[Pacific Northwest yetti]

Thanks guys! I gad it running on propane when at work, switched to 12volt to drive, and top off fuel. Got to Northwest Overland Rally yesterday and now the dang propane portion won't work. Pulled the fridge cleaned everything out, and tried again. I think it's the valve at the top you push to get the propane lit. I've buggered with it quite a bit so it should not be air in the lines. I think the valve itself is not working like it should be. I suppose I'll keep trouble shooting it, or may replace it sooner then expected.

 

[Mighty Dodge Ram]

Good luck with the fix. Be sure that the fridge is sitting mostly level...some are more tolerant than others.

 

[Pacific Northwest yetti]

Thanks, she is pretty level right now. And apparently after hearing about me replacing it w/ the dometic guy she fired right up. Go figure...

 

[LeftCoastKiteboarding]

If you can possibly keep it working it’s worth it. Propane is the absolutely most efficient system for off grid use!


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[boltzaction]

I have a 2007 outfitter Apex 8, that currently has the standard 3 way RV fridge. So 120, propane and 12 volt. I'm used to the other two, but am wondering about the 12volt portion. And why people pull them out, is the 12volt just really inefficient? Etc, I was planning on eventually replacing it with a 12volt only. I currently have abou 250amp/hr capacity.

Thanks,

OK, 1st, I expect to see these 3 way refrigerators largely go away over the next decade. These are not efficient as others here have claimed, the efficiency of these tends to be a C.O.P. of 1, (coefficient of performance) this is quite poor, it represents the number of BTU's output for the BTU input. Any vapor compression air conditioner, for example will have a C.O.P. of 3, minimum, a VC frig should be 2 or more. Propane is convenient and traditionally has been used in mobile and off grid applications, today better technology is being developed for this type of use.

To your question, Propane, 120v or 12v are all used to heat the solutions in an absorption refrigeration unit. (that is what you have) The way they work is interesting but not efficient as previously noted. In commercial systems absorption is generally used for comfort cooling utilizing waste heat. Resistance heating is the least efficient way to make something hot. At 120v an amp draw of 1 amp equates to 10 amps at 12v, therein lies the problem. These units have to be level to perform properly as you must be well aware. Over time crystallization problems often develop because of this issue. Propane is very convenient and harder to determine how much you are using, as well as being a fire hazard if running while you are moving. Probably illegal as well. I recommend you check out the Avanti superconductor frig. It can be 120 or 12v, (both plugs on the back of the unit) does not have a freezer, which saves energy and draws about 85 watts running, that is about 7 amps at 12v, should you have a 10 amp supply to the trailer from your vehicle you will be able to easily run the frig and still get a bit of battery charge. They sell for about 125 - 150 bucks and are very lightweight.

I have noticed lately at least one mfr. is going away from gas, this makes good sense, a very modest solar system can easily handle this demand.

Is your 250AH represent the full capacity of your battery pack, or have you already taken the 50% capacity reduction to make your pack last?

 

[LeftCoastKiteboarding]

While your analysis of the technology is likely correct, from a practical standpoint I disagree. Having had and used both solar and propane systems I still think propane is a better choice for a number of applications, especially overlanding. My last fridge/freezer drew about 5.5 amps. Worked great on a modest solar system....when not parked in the shade, and the sky was clear at least during peak generation hours, and other battery loads were not excessive, etc. Solar/compressor fridge systems work great when they work. But when the stars don’t align, they can cause problems. Heavy battery drawdown will damage future capacity, loss of cooling due to issues above can cause loss of food. Finding system components can be challenging in some places.
While propane may not be more efficient on a purely BTU basis, from a practical standpoint it is very functional. Works day and night, cloudy or not. Runs for a loooong time on a tank. Full tank drawdown does not cause damage. Fuel is available in a lot of places.

Given those limitations, everyone will have a different idea of what is best for them, but at this point I really think that for long term reliable off grid cooling propane is still one of the best choices. However I’m looking forward to the tipping point where solar/electric becomes the better option.


Edit: also consider system costs. Solar systems are getting cheaper and cheaper to buy. Solar capacity has gotten very affordable, but battery storage costs are still very high. A bank of durable and long lived batteries capable of running a fridge for a long time reliably will cost around $500...just for the batteries! They will not last forever and must be disposed of and replaced. On the other hand my current propane unit is from 1996 and still runs flawlessly.


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[Coachgeo]

just do not DRIVE on propane and keep it clean.

 

[LeftCoastKiteboarding]

I hear that from time to time but don’t know why folks are told not to drive while on propane. No manual for any of my propane fridges has said that. All modern units have a thermocouple that will shut off the gas if the pilot goes out. I can attest that they work. My fridge will sometime lose pilot while driving or in heavy wind. The thermocouple does its job and the gas goes off. As a retired firefighter I am by no means advocating taking unnecessary risks, but propane systems are built to be quite safe. While I can’t say it’s never happened, I have not heard of a properly operating propane fridge causing a fire in a moving vehicle.


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[JaSAn]

I have a 2007 outfitter Apex 8, that currently has the standard 3 way RV fridge. So 120, propane and 12 volt. I'm used to the other two, but am wondering about the 12volt portion. And why people pull them out, is the 12volt just really inefficient? Etc, I was planning on eventually replacing it with a 12volt only. I currently have abou 250amp/hr capacity.

Thanks,

My advice, since you have a working 3 way refrigerator, is to try it. Some people love them, some hate them. You must understand there is a fundimental difference between absorption refrigerators (running on propane) and compressor refrigerators. On a refrigerator running on propane you set the amount of cooling by controlling flame height (taking more or less heat out of the box), on a compressor fridge you set interior temperature (via thermostat). It takes a little getting used to.

As to driving with propane on:

• There is a slight risk, the big one is a ruptured fuel line in an accident.
• It is illegal to be 'near' a fuel dispensing station with an open flame. Near has different meanings in different locals. In Minnesota one is supposed to shut off all flames before entering a fuel island.
• It is illegal to go through some tunnels with an open flame.
• Most ferries will not let you on with an open flame.

jim