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Open Roads Forum  >  Tech Issues

 > Dorm Fridge

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Strabb

Holland MI

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Posted: 07/05/10 05:29pm Link  |  Print  |  Notify Moderator

We have a 92 prowler fiver and the fridge croaked. With it being an old trailer I did not want to spend the money so I went with a dorm fridge in the old opening,plugged into the existing outlet that the dometic was plugged into. Will this work through my 12 volt system as is or do I need to insatll an inverter. It works great on the shore power which is what we will have 99 percent of the time. Just wondering about the 12 volt. Thanks


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Golden_HVAC

Fulltime, CA, USA

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Posted: 07/05/10 05:46pm Link  |  Print  |  Notify Moderator

Hi,

If you get some blue ice, then you can run the refrigerator about 8 hours and leave it off for 8 that you are traveling, the blue ice packs will keep the inside below 40F.

Or you can get a set of 4 golf cart batteries, a $500 pure sine wave inverter, and then be able to run the refrigerator for the hours that you are between campgrounds. I would stic with the blue ice.

The lower cost inverters are called Modified Sine wave. They can be much less expensive, but also will not provide the torque required to run the refrigerator motor. A 1,000 watt MSW inverter is only about $85 - 100, but will quickly burn up the compressor motor.

Remember the old campers? I had one. It had a ice box, and was built in the 60's. The tray in the middle drained the ice water to the ground, and I could buy a block of 20 pounds of ice. It was plenty to keep the refrigerator cold for about 4 days. But I could not take along ice cream.

With your refrigeraror, you can take along ice cream, as long as you will be in a campground every 3 hours after leaving a place where you where last plugged into.

Good Luck,

Fred.

Gdetrailer

PA

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Posted: 07/05/10 05:54pm Link  |  Print  |  Notify Moderator

Dorm fridges (120V AC) type fridges can work but it depends on what type of camping you are planning to do as to how much battery and how you will go about recharging.

You WILL need an inverter since a dorm fridge will not directly run from 12V DC.

To size the inverter, you can take the name plate rating in amps and multiply by 10. In my case, 1.1A @120V AC = 11A of surge current at 120V (1320W), this was the absolute minimum surge wattage the inverter must be able to supply.

Using my info above you would need at the minimum of 700W (1400W surge) inverter. I opted to go bigger, 1250W inverter with surge of 2500W.

I normally only overnight so I used only one pair of 6V GC batteries (connected in series to get 12V) which gives me plenty of capacity to overnight. If you are planning to boondock (no commercial power) then you would need to plan for at least one extra pair of GC batts and a generator to recharge the batteries.

You can take a look at my rebuild (which has a picture of my fridge)
HERE

And for much more detailed info (including my power/inverter/fridge setup you can view that HERE

(Hopefully both links are working, I had to find a new online storage since my old one suddenly is gone with no trace.)

Note that I used a Appartment size (10 cu ft) fridge, it is much better insulated than the smaller Dorm(1-4 cu ft) so it runs less (which saves on batteries).

Good luck with your trailer!

Strabb

Holland MI

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Posted: 07/05/10 07:47pm Link  |  Print  |  Notify Moderator

Definitly going with the ice packs we have a freezer full already I put them in my lunch box. Thanks for the help

gmachine

Marion,IN & Chuluota,FL, USA

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Posted: 07/05/10 08:12pm Link  |  Print  |  Notify Moderator

Probably not necessary to purchase a Pure Sinewave inverter. Have run 4 different AC frdiges on Modified Square Wave inverters and have had NO probs.


Bering MD23(Cummins ISB)w/60" flattop Kenworth sleeper & 2005 Excel 35MKO Limited, 2006 Scion XA.

wa8yxm

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Posted: 07/05/10 08:35pm Link  |  Print  |  Notify Moderator

Dorm fridge is 120 vac only.. LIkes true sine wave and may need as much as 1,000 watts to fire it up.. (only about 100 to run it but starting takes way more power) 450 watts likely will not power it up.. I tried.


Home is where I park it.
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gmachine

Marion,IN & Chuluota,FL, USA

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Posted: 07/06/10 07:31pm Link  |  Print  |  Notify Moderator

Granted, 450W is insufficient to start any of the high efficiency fridges, in my experience. Mine have all taken approx. 6.5A to start on 120V shore power. This has been the case from 2.7 cubic ft. to our 19 cubic ft. built-in. They all seem to take the same(both start and run)but the larger ones run longer. We have two 2500W MSW inverters, so no start up probs.
Good Luck, Jim

cptdondo

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Posted: 07/06/10 07:59pm Link  |  Print  |  Notify Moderator

wa8yxm wrote:

Dorm fridge is 120 vac only.. LIkes true sine wave and may need as much as 1,000 watts to fire it up.. (only about 100 to run it but starting takes way more power) 450 watts likely will not power it up.. I tried.


Wonder if a hard start capacitor would work... They work for A/C compressors; why not fridge compressors?


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mchero

Concord, NH

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Posted: 07/06/10 08:20pm Link  |  Print  |  Notify Moderator

cptdondo wrote:

wa8yxm wrote:

Dorm fridge is 120 vac only.. LIkes true sine wave and may need as much as 1,000 watts to fire it up.. (only about 100 to run it but starting takes way more power) 450 watts likely will not power it up.. I tried.


Wonder if a hard start capacitor would work... They work for A/C compressors; why not fridge compressors?


Good question/thinking cptdondo!

gmachine

Marion,IN & Chuluota,FL, USA

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Posted: 07/08/10 07:50pm Link  |  Print  |  Notify Moderator

Start cap. o'size would probably work but why not get a larger inverter to start with, they're cheap and would allow other apps.? MSW's seem to run everything for us except a laser printer & Sunbeam electric blanket.
Jim
Oh, and a electronic control toaster that I s'canned.

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