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Old 07-24-2013, 07:46 AM   #11
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Average dorm sized refrigerator needs 33 watts when active.
Remember cool down time could be 6 hours of constant active time.
And if you put all warm beverages in fridge after cool down it may take another 4-5 hours to recoup.

I bet lou could do the math for us

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Old 07-24-2013, 08:31 AM   #12
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33 watts? Are you serious?
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Old 07-24-2013, 08:36 AM   #13
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Quote:
Originally Posted by herk7769 View Post
33 watts? Are you serious?
https://www.google.com/url?sa=t&sour...WaNnQ58SFqUIxA

Seems odd now that I think about it.
That's like less then a half an amp right?

I confused watts with amps.
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Old 07-24-2013, 09:13 AM   #14
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The following is my opinion

That post says 33 watts. At 120 volts that means it draws less amps than a 40 watt light bulb when running the compressor.

33 watts at 120 volts is 0.275 amps to run a fridge compressor. Sounds too good to be true. It may be very optimistic.

However,

I found this college level test question:

1. Many college students have a mini fridge in their dorm room. A standard mini fridge costs roughly $100, uses about 100 watts of electricity, and can be expected to last for 5 years. The refrigerator is plugged into an electrical socket 24 hours a day, but is usually running only about 12 hours a day. Assume that electricity costs $0.10/kWh.

(a) Calculate the lifetime monetary cost of owning and operating the refrigerator. (2 points)

[100 watts X $0.10/kWh X 12 hrs/day X 1 kW/1,000W X 365 days/year x 5 years] + $100 initial cost = $319 lifetime cost


So assuming 100 watts to be provided by the battery driving an inverter:

100/12 volts = 8.33 amps of battery power while running for 1/2 the day or 12 hours.

If the only thing running off the battery (no lights, radio, etc) is the fridge and the inverter, then 8.33 (plus some inverter loss) times 12 hours is 100 amp hours.

A typical Marine Group 27 battery can deliver 100 amp hours provided the constant draw is 5 amps. At 8.5 amps, the capacity to deliver amps drops to 85 AH from that same battery.

So in my estimation this scenario would deplete a Group 27 Marine battery in approximately 1 day (less if you used the battery for anything else - more if the fridge is shaded and runs less often). You would need to recharge the battery by some method every day by running off the generator for some significant number of hours each day (while charging - which could take 3-4 hours). You would also need a very good battery monitor system to make sure the battery did not deplete below 50% capacity to avoid plate damage.

So, to sum up. A minimum of 2 100 AH 12 volt batteries (to make sure you never discharged them below 50% each day) and a generator to recharge them for the next day.
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Old 07-24-2013, 09:28 AM   #15
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And there u have it.
Thanks lou.
33 watts sounded optimistic to me to.

Sooooooooo tonight I'm going to turn my complete distribution panel down and then fire up the outside fridge and see how many amps it pulls.

To the op.

I'll post my findings later today.
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Old 07-24-2013, 01:55 PM   #16
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I have the exact same fridge as the ones they put in the outside kitchens. I can tell you they don`t like heat! mine will cut out with the thermal limiting switch when temps get near 100 deg. hasn`t burned up, but I can see it shutting down till the cooling unit cools off.
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Old 07-24-2013, 02:36 PM   #17
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Quote:
Originally Posted by Dodge Guy View Post
I have the exact same fridge as the ones they put in the outside kitchens. I can tell you they don`t like heat! mine will cut out with the thermal limiting switch when temps get near 100 deg. hasn`t burned up, but I can see it shutting down till the cooling unit cools off.
Mines sits with door to outside kitchen closed for days without overheating.
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Old 07-24-2013, 03:48 PM   #18
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Our last trailer had an outside kitchen with a dorm fridge. We used it for holding bottled water, pop, and sometimes beer. Basically we stored anything that would be nice to have cold in it, and treated it like an ice box. I found that if I put the bottles of water in our home freezer just before we left, that they would keep thing cold for quite a few days without power, and definitely on travel days between hookups. We ran that refrigerator for 3 years without any problems and it was in an enclosed space.

Our new rig has the same type of dorm fridge and it is under the inside kitchen counter, so the heat it outputs goes into the rig, but it does have a larger volume of air to interact with (the entire inside volume), so its effect is next to nothing. I have thought about plugging it into the inverter socket that our electric fridge is plugged into. I just want to do a power consumption test (much as Lou is doing) to be sure the faster battery drain is worth the extra storage capacity.

Just for comparison, the electric fridge in our rig uses either 0, 11, 14 or 17 amps of 12v DC and it is a 18 cubic foot Refrigerator/Freezer with an ice maker. The different consumption rates had me puzzled, but it seems change based on the compressor, fan, and I think the ice maker motor/solenoid use. The duty cycle of course depends on how often it gets opened and how much ice is being made.

I have seen people put in a second gas fired fridge if they were primarily dry campers. Some of the bigger houseboats have two 12 cu. ft. gas fired refrigerators for the same reason.
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Old 07-24-2013, 06:07 PM   #19
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Outside fridge has been running for 10 minutes at 1 amp.
Just an fyi.
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Old 07-24-2013, 11:35 PM   #20
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Since I have the 160 watt solar panel, how would this come into play with charging the batteries?


1 amp = ?? Watts?
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