Freezer/Refrigerator converter - opinions?

[HKBB]

Hi, all! New to the boards, and in the design stages (planning on a Benroy or Rimple), and noticed that electrical power is an issue. Was thinking about chest-style mini-fridges, but couldn't find anything within my planned power limits.

I found this idea, (http://mtbest.net/freezer-to-fridge-thermostat.html) (technical specs on it here http://mtbest.net/chest_fridge.pdf ) and thought it sounded very do-able. Problem is, it's set up for a 240v freezer/fridge. I sent an email to the guy who developed it, asking if it was possible to do this with a household chest-fridge. Haven't heard back yet, but thought I'd post it here to get opinions.

Any electrical engineers or technicians out there?

[Rock]

Just from looking at the website, I believe all that this is is an add on thermostat that allows a freezer (with maybe an operating range of -10 F to 30 F) to run at refrigerator temps (30 F to 50F?)

I don't see that there would be any efficiency gain (and I am an electrical engineer.) Why not just buy a refrigerator and and use it?

If you're determined to run a freezer as a refrigerator, these add on thermostats are readily available domestically (in 120V.) Home brewers use them to control a chest freezer at refrigerator temps for fermentation and aging.

Your best possible solution, however, is simply to buy an Engel 12V fridge/freezer.

EDIT: I did scan the PDF - I see that he is advocating the use of a chest freezer mainly due to the fact the lid is on the top. Lots of threads here regarding this type of thing. The thermostat he is selling is available domestically as I mentioned. Be warned though that running a freezer like this can kill it. The reason is that the refrigeration system is designed to run at freezer temps. Running it at fridge temps will "short cycle" the compressor and burn it out. I killed a freezer like this (homebrewing.)

And once again - buy and Engel and be done

Eric

[mikeschn]

Hi Lena,

Welcome to the forum.

Are you planning on camping rustic, or on a campground. You can usually get electric on the campground.

If you are planning on camping rustic, then a cooler filled with ice is probably a better bet, unless you want to spend really big bucks on a 2way or a 3 way gas asorbation fridge.

Our local RV store had a 1.7 cu ft. 3 way on clearance last week for $499. I was so tempted... but I passed on it. It seemed too small for us, and was the wrong color.

Mike...

[HKBB]

I'm not sure how much time we would be spending in campgrounds with electrical hookups. Some, I'm sure, but most of the time would be spent hunting, fishing, etc., mostly boondocking, and probably for 1-2 weeks at a time. An ice chest probably wouldn't cut it - I really don't have any interest in taking off every couple of days for more ice.

With that in mind, solar seemed the way to go, but I'm not so sure we'd be able to get enough power that way to recharge the battery/batteries. Maybe I'm just not understanding how much battery capacity would be needed to reasonably ensure a refrigerator working for a two week period, with at least 7 of those days being sunny, without access to 'shore power'.

Hmmm.... maybe I'll have to take another look at that. I've never used solar power before, and may have my numbers wrong.

And thanks for the warning about the thermostat. I guess if I want a chest-type refrigerator on the cheap, I could always just take the compressor out, turn the thing on it's back (careful to provide air flow), and reinstall the compressor right-side up.

[mikeschn]

A small norcold...
http://www.advrv.com/norcold.htm

might be the way to go...

Mike...

[Rock]

Lots to consider. If you want to boondock for 2 weeks and not worry about it, then as Mike suggested a "3-way" (12V DC, 120V AC, Propane) powered absorption fridge is the way to go. Others will have to chime in on how much propane you would typically use in a week.

I have this freezer here: http://www.bigfrogmountain.com/Engel%2045.htm 12V DC, 120V AC. It has a compressor like the fridge in your kitchen, but is designed from the get go to be super efficient.

Here is power consumption data vs. fridge temp vs. outside temp. http://www.bigfrogmountain.com/images/MT45F%20curve.jpg It's a little hard to read. For example, at 35C ambient (95 F) and 5 C internal temp (41 F) this fridge will consume 1.14 amp-hour per hour, or a total of 27.3 amp-hours a day.

Here's some info regarding some cheap Harbor Freight solar cells I have: http://tnttt.com/viewtopic.php?t=30521 Two of these kits should put out 5.5 amps at 14.4 volts in good sunlight.

So for my Engel fridge and 90 watts of Harbor Freight solar power, I figure I can boondock for an unlimited time as long as I get say 4-5 hours of good sunlight a day on average.

To go this route there's no cheap way to do it. I think all included you're looking at least $1000 including solar, fridge, batteries, charge controller, etc.) Hope this is not too confusing.

Eric

[HKBB]

Well, that makes things a LOT clearer. Thanks, Eric!

I'll take a look at those items you suggested. I knew up-front investment in power was going to be expensive, and adding in the cost of building the camper... well, the "accessories" won't do me much good without the camper to put them in first!

I'll take a look at my TD plans, and just build for future "accessories", and add them as time and finances permit. Good info though - at least I'll know what to initially build for so I'm not trying to make structural changes in the future!

Thanks!