Is a 3 (three) way fridge a real improvement?

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BadPennyKenny

BadPennyKenny

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Joined
Aug 30, 2020
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19
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Gary, S.D.-St.Louis, MO.
How do the newer 3 way RV fridge utilize land power, In my case 30 AMP service. Does it have an entirely separate cooling system then the 12V or LPG part of the system? Or is it just using the existing 2 way fridge systems but with the higher Amp/Wat.
I am trying to decide if the upgrade from 2-way to 3-way is worth it when I replace my RV fridge.
 
I think you are confused a bit here, a 2 way refrigerator runs on Propane or AC shore power, though it does also require DC battery power to run the control board in most places.  A 3 way refrigerator will also RUN on battery power, but really sucks the batteries down fast as it is about a 400 watt running load, though perhaps has a place when being used in a vehicle that moves around a lot, where there is an engine alternator running that can keep up with this demand.
 
Gas is a gas burner. 110 volt option is a 110 volt heating element. 12 volt option is a 12 volt heating element.

Assuming you are not familiar with the 12 volt heating option, the 12 volt heating element is great while travelling on the road. It will maintain cabinet temps but offers little recovery if the fridge is expected to cool down.

12 volts is also used as the control circuit for all modes.

Earlier RVs had the 3 way fridge as a standard option. It is very useful but the manufacturers decided to save some costs by doing away with it. I have had two 3 way fridges prior to my current 2 way only because thats what the builder put in my current unit.

The 3 way is much better but requires  12 volt wiring modification to accomodate the 12 volt heating element.

 
2-way vs 3-way is very little different.  The cooling system is identical in every way except for the heat source used to drive the absorption cooling process.  In either case, there is a boiler that has multiple heaters under/around it; a 3-way adds a 12vdc heater to the LP gas and 120vac heaters of the 2-way.  That gives you a 3rd option for operating the fridge.

Your wording suggests you may have a misconception about what "2-way" means.  Both 2-way & 3-ways fridges use 12v DC power to operate the controller circuit board and open the gas valve when needed.  The standard 2-way fridge has 120vac and LP gas as its boiler heating source, while a 3-way has 120vac, LP gas plus 12vdc heaters for the boiler.

NOTE:  The 12v heater requires a lot of DC amps to provide enough heat to drive the cooling process, too much to operate for very long on battery power.  If you have 120vac shore power available, it makes more sense to use that. If not, LP gas is a reliable and efficient heater.  There aren't many situations where a 12v heater would be both preferred and practical. For that reason, 3-way fridges are not often used in RVs.
 
Our little Winnabego has a 3 way fridge. I never use the battery option. When traveling it?s on gas and when parked with shore power it?s on AC. It will run the battery down in a few hours if left in DC mode.
 
I had a small three way refrigerator in my Alaskan camper.  I wired the alternator output on the truck with two diodes.  One went to the refrigerator and the other to the truck battery.  Thus the only time the refrigerator run was when the truck alternator was running. Thus no drain on the battery.  But required a large wire from the diode to the refrigerator.  Because it was an onboard camper no 7way connector needed.

This worked very well for me as running a refrigerator on gas is something I still will not do with my 5th wheel.

The 12 DC worked good on the small refrigerator the Alaskan had but I suspect the larger refrigerators in today's 5th wheels and Motor homes will require too much power from the 12 volt system to work well.
 
lavarock1210 said:
I had a small three way refrigerator in my Alaskan camper.  I wired the alternator output on the truck with two diodes.  One went to the refrigerator and the other to the truck battery.  Thus the only time the refrigerator run was when the truck alternator was running. Thus no drain on the battery.  But required a large wire from the diode to the refrigerator.  Because it was an onboard camper no 7way connector needed.

This worked very well for me as running a refrigerator on gas is something I still will not do with my 5th wheel.

The 12 DC worked good on the small refrigerator the Alaskan had but I suspect the larger refrigerators in today's 5th wheels and Motor homes will require too much power from the 12 volt system to work well.
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Why won?t you run your fridge on gas?  My problem wasn?t the truck battery draining but the RV battery would drain in a few hours when the fridge was on DC power. Now if I am driving and pulling the TT there is no problem with the TT battery. But I still use the propane because if I used the battery for the fridge and stopped for any length of time my TT battery would deplete.
 
Gas is not always dependable while travelling. This depends on a few things but gas flames are sensitive to air currents both at the intake and the output. Some of the older campers would have constant flame issues when travelling. I had great success back in the 80s using the 12 volt 3 way. I dont recall it using 400 watts. I think it was in the 10-15 amp range which is about equal to a power window maybe a little less. I used it only during travel and knew I had back up if a gas problem came up and had no ac. Its a good option and offers additional flexibility. I wish I had the Lavarock design because I do remember occasionally forgetting to switch over when the driving was over. If I remember correctly, the 12 volt option was not on a thermostat. It ran endlessly by design. It always maintained my cabinet temps while travelling. I suspect the standard option of 3-way fridges was discontinued mostly because rv owners did not manage the usage very well and it was cheaper just to discontinue. Its a worthwhile option if used correctly.
 
I dont recall it using 400 watts. I think it was in the 10-15 amp range which is about equal to a power window maybe a little less.
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It's not 400 watts.  The size of the 12v heater varies with the size of the fridge, but 12v mode isn't offered on larger fridges that would need a 400+ watt heater.  The heater for a 6 cu ft fridge would be only about 300W. A smaller one is less, typically 180W- 240w.  That would draw 15A-20A from the batteries or alternator.  Some small fridge models draw as little as 11A.
 
I helped a friend troubleshoot his newly installed 600 watt solar system in his 32 foot Class A, because he said it wasn't fully charging his four house batteries while boondocking - even in good sunlight. He had LED lights and an LP fridge, so 600 watts should have been more than enough solar.

When we looked at his battery monitor, it showed a charge rate of 2 amps in the middle of the day. When we switched off the solar panels, it showed a discharge rate of 32 amps. The only things that were on were some small parasitic loads, one LED light and the LP fridge. I assumed it was running on propane, but after narrowing the problem down to the fridge, he told me it was running on battery power, to save propane.

That fridge was consuming 30+ amps on battery power - more than three times the DC current our 22cf residential fridge (plus inverter) consumes on battery power. I convinced him to run it off propane.

Kev
 
?he told me it was running on battery power, to save propane.?

The fridge consumes a negligible amount of propane. On the other hand the fridge will drain my battery in just a few hours.
 
There are 1-2-3 way Fridges. Properly called "Absorption cooling units"
1: propane
2: Shore power (120vac)
3: battery power and lots of it (12 volt at like 20 amps, will take batteries down FAST)

There are also 2-way (Gas/Electric) and 2-way Electric-12/120) These are really something but also rare  Your 3 way is not one.

There is but one cooling unit but 3 heat sources.

Absorption cooling is powered by heat.  You boil a mixture of stuff. it goes through tubes and is cooled in the heat exchange up top. when it re-combines it is "endothermic" (Absorbs heat), hence the name absorption cooling unit.

The propane burner.. Not much bigger than an oven's pilot light
AN electric elememt 350-400 watts at 120 volt
Or about 150-200 watts at 12 volt

I would not use that last option.

But the heat sources are simply stacked in the "Stack" (right side as you look at it from teh rear. usually a round tube about 3-4")

Now the one I have beside me (12/120 volt) that's a compressor unit but it's also expensive.
 
Isaac-1 said:
I think you are confused a bit here, a 2 way refrigerator runs on Propane or AC shore power, though it does also require DC battery power to run the control board
Click to expand...
YES, I was confused. But having read through these responses I feel like I've now gone through RV fridge 101.
I will definitely not be wasting any $$$ on upgrading to a 3-Way but instead replacing the old 2-way with a newer more efficient one. So now goes the task of comparing and picking one out.
Thank you all for your responses. (Respectful Bow while leaving room)
 
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