How much propane does fridge use? - Fiberglass RV


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Old 07-07-2011, 08:58 AM   #1
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How much propane does fridge use?

I'm interested in the idea of a solar fridge. To get calculations started I need to know about how much power the fridge uses. Can anyone give a rough estimate of how long a fridge would run on a single full tank (20 lbs propane)?

Poking around tells me about two weeks or a million seconds. That translates to about 450 watts, which seems high.
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Old 07-07-2011, 09:35 AM   #2
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I'm interested in the idea of a solar fridge. To get calculations started I need to know about how much power the fridge uses. Can anyone give a rough estimate of how long a fridge would run on a single full tank (20 lbs propane)?

Poking around tells me about two weeks or a million seconds. That translates to about 450 watts, which seems high.
When I dry camp, I go through a propane bottle every 7-10 days on the fridge and hot water heater. I use those exchange tanks you see at home depot, etc.
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Old 07-07-2011, 12:17 PM   #3
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I'd have to guess multiple weeks if used only for the refrigerator, can't say for sure because I use the stove and furnace too. Wanted to point out that those exchange tanks aren't the full 20 lbs, they're something like 16lbs of propane the last time I exchanged at Lowes (blue rhino tanks)
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Old 07-07-2011, 01:05 PM   #4
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I'd have to guess multiple weeks if used only for the refrigerator, can't say for sure because I use the stove and furnace too. Wanted to point out that those exchange tanks aren't the full 20 lbs, they're something like 16lbs of propane the last time I exchanged at Lowes (blue rhino tanks)
I fill them up at my RV Repair shop, so they are definitely at least 20 LBS.

I usually turn off my H20 Heater in the AM as I am leaving for the day. And turn it on in the PM so that I have hot water for washing dishes, my hands, etc.

In winter when I use the H20 Heater, propane heater, and fridge, one tank lasts 7-8 days. So I think you can go at least a week with the fridge alone. Also, I have a full size fridge and freezer.

Hopes this helps.
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Old 07-07-2011, 03:38 PM   #5
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Propane use doesn't correlate well to the electrical demand, especially since many don't have true thermostatic control. Condenser fridges are not very efficient to begin with. Is your fridge condenser or compressor or semiconductor based? Your use is also going to depend on the temperature difference you're trying to overcome. Say 40F in the fridge to 80F or more outside. I think my condenser fridge uses about 100 watts on 110V to maintain a 30F drop on average, but the size of the fridge, how well insulated and how frequently opened are factors, too. If you are electrical only, you might steer clear of condenser (ammonia) fridges.

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Old 07-07-2011, 04:25 PM   #6
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Something like this chart may be of help. Generator Sizing Chart - Find the model that works for you.

The manufacturer of your present fridge and the solar fridge you're thinking to buy may be of help.

Good post Matt, food for my brain.
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Old 07-07-2011, 05:25 PM   #7
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You really have not given enough detail of what you wish to do. When you say solar fridge I am not sure what you mean. If you wish to run a fridge on solar for example why worry about propane when electrical specs are available for both ammonia (electrical/propane) and freon (danfoss) RV fridges. Please elaborate. Raz
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Old 07-07-2011, 07:17 PM   #8
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Last summer I left my fridge on 24/7, (I really liked having cold beer at my summer "camp"). Went through a 20# tank about every six weeks. This is with a 33 year old Dometic.
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Old 07-07-2011, 09:50 PM   #9
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Thanks to those of you that answered my question. I wasn't very specific because I am just trying to get an order of magnitude guess on the power required for the absorption fridge. In my case, I happen to have a very small one but I am interested in the problem in general. With Scott's numbers that averages out to be about 125 watts.

Sorry for not being clear but I was only asking how long propane lasts, not questions about my particular setup. Some of you thought I was thinking about PV but that would be pretty silly. You'd lose about 80% of the energy before you got started. Rather, I was thinking of taking the light from the sun and converting it directly to heat. If you could focus the rays from a significant area and shine them directly on the heating element you might do OK.

The average solar flux near me is something less than 1000 watts/m^2. To get a couple of hundred watts in good sunshine would require a mirror or lens about half a meter by half a meter. Not impossible, but not easy in a trailer that moves around. Take a lens or mirror from an old telescope and you would only be able to power the fridge in the middle of the day, in the desert.

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Last summer I left my fridge on 24/7, (I really liked having cold beer at my summer "camp"). Went through a 20# tank about every six weeks. This is with a 33 year old Dometic.
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Old 07-12-2011, 12:06 AM   #10
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Quote:
Originally Posted by biw314 View Post
Thanks to those of you that answered my question. I wasn't very specific because I am just trying to get an order of magnitude guess on the power required for the absorption fridge. In my case, I happen to have a very small one but I am interested in the problem in general. With Scott's numbers that averages out to be about 125 watts.

Sorry for not being clear but I was only asking how long propane lasts, not questions about my particular setup. Some of you thought I was thinking about PV but that would be pretty silly. You'd lose about 80% of the energy before you got started. Rather, I was thinking of taking the light from the sun and converting it directly to heat. If you could focus the rays from a significant area and shine them directly on the heating element you might do OK.

The average solar flux near me is something less than 1000 watts/m^2. To get a couple of hundred watts in good sunshine would require a mirror or lens about half a meter by half a meter. Not impossible, but not easy in a trailer that moves around. Take a lens or mirror from an old telescope and you would only be able to power the fridge in the middle of the day, in the desert.
I like your way of thinking. It's outside the box and that's why the responses were what they were, inside the box. Keep it up. Hopefully you'll invent a better way.
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Old 07-13-2011, 05:04 PM   #11
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I agree. Using anecdotal propane usage to calculate the power consumption of an absorption refrigerator instead of the manufacturers DC heating element voltage and current ratings is indeed thinking outside of the box.
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