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Old 04-21-2006, 03:48 PM   #11
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There is a dude named Steve that sells reconditioned propane/electric fridges in the 8.5 cubic foot range for 400 to 500 bucks with a 3 year warranty. I bought one from him. I think he even joined this board. My question is does it have to be enclosed between walls to be sturdy and to keep from tipping over?

Tim
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Old 04-22-2006, 11:20 AM   #12
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I've got to head to work so I have to keep this short...

4 amp/hr is not a particularly effecient model of refrigerator.

Jason nailed it...watts is watts.

Somewhere on the unit (and usually in the manual) there *has* to be the load rating for the applicance; in other words, how much power it draws while running. This is manadated in regulations so it has to be there somewhere (and must be on a plate/sticker on the unit).

Find out what it draws when it's running on AC power; multilply amps times volatge and you have watts. Takes those watts and divide by 12 (close enough) and you know what the load in amps is on the DC side.

Then...depending on where you live you can guess as to how long the refrigerator will run each day (based on air temp, how often you open and close the thing, insulation around it, etc). If you decide that's 50% of the time (12 hours per day) and you're pulling 4 amps when it's running then you need 48 amps from your batteries to support the refrigerator each day. To do that you should have a 137 amp-hour battery; probably a group 31 deep cycle would get the job done in a pinch.

Obviously if the unit only runs 30% of the time (about 7 hours) you'd only need 28 amp hours and that only needs an 80 amp-hour battery (about a group 27).

Most high efficiency units now use the Danfoss compressors; the smaller refers typically the model 35 (there are others on the market now). They'll pull as little as 2.5 to 3 amps on the DC side. They're used in the Norcold DE series which has no propane system. They also don't require the unit to be level; usually only within 35 degrees or so (it's only the absorption model refers that have to be level, or nearly so). They aren't inexpensive but neither are the high efficiency home units based on the same compressors.

Late...gotta go!
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Old 04-24-2006, 11:11 AM   #13
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Quote:
Originally Posted by SeanF
Let me just say...the way 'fridge manufacturers provide their model's kwh/year is almost useless. What they need to tell is how many watts the compressor uses while running.

It makes calculating power usage nearly impossible. Wonder why they do that?

Now back to the math frenzy already in progress.
if you're looking at the fridge in person, there is almost always a tag that tells either the amps @ 120 volts, or the wattage of the unit. This little tidbit doesn't really help if you're looking at them online though....The amount of current on the label does not reflect how many watts are required for startup either. A compressor can take 2 or 3 times the normal operating current during startup.
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Old 04-25-2006, 11:55 AM   #14
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Thanks for the info on the tagw. I looked at a bar size danby fridge and it uses 80 watts or 1.2 amps AC power. I then looked an apartment sized fridge with exposed coils on the rear and it used about 130 watts or 1.8 amps. Not a whole lot of difference. However after looking at brands like Norcold, nova kool and the prices that go with them I have decided that a power savings of .8 amps ac is not worth the extra $$. I think I can get it to run pretty consistently if I add extra insulation and keep the fridge low (under counter) and out of direct sunlight. I have seen a few used in the local paper for under $50. So we'll see how it works out.

Thanks for the info all!

-Richard
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Old 04-26-2006, 10:19 AM   #15
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Quote:
Originally Posted by captainkf
Thanks for the info on the tagw. I looked at a bar size danby fridge and it uses 80 watts or 1.2 amps AC power. I then looked an apartment sized fridge with exposed coils on the rear and it used about 130 watts or 1.8 amps. Not a whole lot of difference. However after looking at brands like Norcold, nova kool and the prices that go with them I have decided that a power savings of .8 amps ac is not worth the extra $$. I think I can get it to run pretty consistently if I add extra insulation and keep the fridge low (under counter) and out of direct sunlight. I have seen a few used in the local paper for under $50. So we'll see how it works out.

Thanks for the info all!

-Richard
It doesn't make any difference what they draw on the AC side if you're connected to shorepower (at least not this small difference). But if you're running on an inverter small changes add up...

The 80-watt unit needs a whopping 7 amps DC to run (about 5 hours on a Group 31 deep cycle battery) and the 130-watt unit will draw almost 12 amps; with the same Group 31 battery the larger unit can go about 3 hours. [This is calculated with inverter efficiency factored in and drawing the battery down to it's 50% level (after which damage occurs).]

So the change in wattage affects the DC side of the situation to a very large degree...in fact, in this case it represents a 74% increase in electrical usage (the 80-watt unit vs the 130-watt unit).

It may still work out just fine; this information is just so you know going in what to expect.
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Old 04-26-2006, 12:42 PM   #16
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that is quite a bit of juice, however I just can't shell out over $900 for a 2.7 cuft norcold or Nova Kool. They're much more efficient, true. But I am planning on at least 6 6volt tgo8 batteries which should keep some juice flowing for a bit, that and a bit of solar. I know it's not optimal, however I think it should work.

Worst case scenario I pull it out, use it as a "recreational beverage" cooler on my deck and throw a three way in down the road. I'll run gas lines and power just in case.

Thanks for all the info everyone!

-Richard
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Old 04-26-2006, 02:04 PM   #17
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[quote="lapeer20m
NO!, that's not correct.. watts are watts no matter what the voltage. An appliance that requires 120 watts @ 12 volts, still requires 120 watts at 120 volts. It will however take 10 times as many amps to run a device at 12 volts (rather than 120.) [/quote]

DOH! I did it again. That's right, of course.
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Old 04-26-2006, 03:05 PM   #18
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The sticker on the back of my little dorm fridge says:

115V AC 60HZ ...... 1.25 amp

According to lapeer20m, that means my fridge requires 143.75 watts

143.75 watts @ 12 volts = 14.3 amps

So basically the refrigerator that I own may be too much of a drain on the batteries to use with an invertor, but shouldn't be too much of a drag when plugged into a campground receptacle or powered by a generator.

I am a professional firefighter and a Bluegrass musician... and this electrical stuff is new to me. Thanks for sharing the knowledge.
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Old 04-27-2006, 12:18 PM   #19
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A chick firefighter....now that's hott! lol

I have been a paid on call firefighter for quite a few years, until recently. I work as a full time paramedic now.

do women firefighters tend to be pyro's like most male FF's?

as an example: I have a 30 foot flame thrower
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Old 04-27-2006, 01:34 PM   #20
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I am not a female, and I'm not a pyro. I have been fighting fire for 18 years, and If I never saw anything else on fire (besides a campfire) that'd be fine by me.
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