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Old 05-05-2014, 11:37 PM   #1
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1966 17' Caravel
Klamath Falls , Oregon
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Three way fridge problematic??

A few posts back I was asking about the virtues of having a three way fridge as opposed to having a two way model. What I learned was that a two way that ran on propane and 110v is all you really need. I am totally ok with that and thought that is all I really need and I should go ahead and get one. Then my little pea brain said to me, "What is the harm in buying a three way, It will only afford me yet one more option and how can that be bad?" I subsequently spoke to a fellow who said that a friend of his had one and it gave him nothing but grief. Do you think that it was an isolated incident or are they inherently problematic?
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Old 05-05-2014, 11:47 PM   #2
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I have no practical experience but I do know that the "third way" is 12 volt. That translates to "drain my batteries". I happen to have solar and an inverter which CAN keep the batteries charged up IF the sun shines and the panel is getting full sun. The other potential plus would be that the reefer could run without open propane tanks when traveling. The tow vehicle's battery charging system would run it. In my immediate neighborhood, there are several bridges and tunnels where we have to stop for inspection of the propane bottles - which must be turned off. So 12 volt might be handy for me. Of course a bag of ice, or some dry ice is simple and cheap.

OTOH, more complexity is one more thing to break. As for the actual running problems with a 3 way, I'll let people who've had one respond.

Paula
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Old 05-06-2014, 01:10 AM   #3
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The heating element on the 12 volt side of the 3 way is generally in the range of 240 watts or it takes 20 amps at 12 volts. That is a lot. However the 120 volt heater is usually about 300 watts so you can see that in hot weather, the 12 volt element is not going to do as good a job at cooling as the 120 volt element would because of it's lower output.

There is some additional complexity in control, but not all that much.

The main issue, again, is how much power the 12 volt element takes. It is hard to get 20 amps through the tow vehicle to trailer charge connection (typical is 5 to 10 amps) and the remainder has to come from the trailer's battery, which will not last long with that load. And the load is pretty constant in hot weather, unlike your home compressor type refrigerator which cycles on and off. In hot weather, your RV refrigerator stays on virtually full time.

I have had several 3 way refrigerators in trailers, and find them to be a solution looking for a problem to solve. Understand, like all opinions voiced here, this is mine. About 90% of my travels are with the refrigerator on propane, as I almost exclusively boondock and don't have power available to even use the 120 volt side of the refrigerator.
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Old 05-06-2014, 08:32 AM   #4
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I have had several three way refrigerators in the past and haven't had any trouble with any of them. I have used the 12 volt while traveling, the 120 volt to pre cool the box and while hooked up to shore power in a campground. I use the propane for boondocking and sometimes for traveling. I have found that the biggest enemy of any RV refrigerator is the installation by the factory especially the ones with the double side vents. These units will work efficiently on all three forms of heat source if they are installed with plenty of free flowing air circulation to remove the heat buildup from the top of the unit. Some of the more recent installations that I have seen are a joke including my present A$. The top edge of the upper vent is actually lower than the top of the fridge compartment. I guess nobody told them that hot air rises. There is a fan installed that has to run almost constantly in warmer weather to keep the top of the compartment cooled. I can not believe that the manufacturer actually approved this type of installation. Suffice it to say that two way or three way any of these units properly installed with adequate ventilation should give you many years of trouble free service.
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Old 05-06-2014, 08:40 AM   #5
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The 12 volt mode in our B190's fridge wasn't good for much - maintain temperature at most... on a good day. If we needed to run the fridge, we'd often also need the rooftop A/C, so we'd have the generator running anyway, and would just run the fridge off the generator too (there was enough overhead capacity in the generator to do that).

It's possible our 12 volt mode wasn't working correctly, and the B190's fridge has a lot going against it in terms of staying cool on the road, being that it sits right above the rear axle. In other words, your mileage and experience may vary.

But as mentioned the 12 volt mode does draw some power. In the motorhome, it was wired so that it only came on when the engine was running.

Our trailer's fridge doesn't have a 12 volt mode and we haven't missed it.
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Old 05-06-2014, 01:39 PM   #6
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Quote:
Originally Posted by Stefandmissy View Post
"What is the harm in buying a three way, It will only afford me yet one more option and how can that be bad?" I subsequently spoke to a fellow who said that a friend of his had one and it gave him nothing but grief. Do you think that it was an isolated incident or are they inherently problematic?
3 way fridges are just 2 way fridges with an extra heating element and the controls for it. No difference in reliability. The disadvantages are:
1) purchase price, typically $100-$200 more
2) complexity of installation, since heavy cable has to be run to the batteries for the 12v section unless it is already present.

Quote:
Originally Posted by idroba View Post
The heating element on the 12 volt side of the 3 way is generally in the range of 240 watts or it takes 20 amps at 12 volts. That is a lot. However the 120 volt heater is usually about 300 watts so you can see that in hot weather, the 12 volt element is not going to do as good a job at cooling as the 120 volt element would because of it's lower output.
In general the 12v and 120v elements are designed to have the same wattage under actual operating conditions. How many watts this is will vary depending on the size of the fridge. The larger 8 cf and up fridges would have elements approaching 300 watts while smaller fridges typical of the OP's situation will have 100-150 watts.

The actual watts is proportional to the square of the voltage, so a 10% voltage change will lead to a 20% change (approximately) in wattage.

Usually 3 way fridges that don't cool well on 12v are adversely affected by undersized wiring or loose connections.

Quote:
I have had several 3 way refrigerators in trailers, and find them to be a solution looking for a problem to solve. Understand, like all opinions voiced here, this is mine. About 90% of my travels are with the refrigerator on propane, as I almost exclusively boondock and don't have power available to even use the 120 volt side of the refrigerator.
I agree. They have a place in boats, B vans, and truck campers, where a solid connection to the 12v supply from the alternator is more readily achieved and where there are more difficulties filling the propane tank.
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