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Old 26-11-2006, 10:40   #1
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Thoughts on 'Marine' Refrigeration

Has anyone had experience taking a small inexpensive refrigerator such as those sold for college dorms at places like Best Buy, taking them apart and "making" a refrigeration system for their boat. I have given much thought to this "marine" refrigeration problem. The bottom line is that every marine system seems to use the same type of compressor and essentially the same parts used to refrigerate these small refrigerators.

If you can put a danfoss compressor into a $150-$200 small refrigerator why should we have to pay 8 times that and in many cases much more to refrigerate the same space in a boat? Of corse the manufacturers will claim that their systems are "Marinized". But what exactly does that mean and what standards are there for these units. I would submit that this is done better by some Mfg's than others. Conformally coating a PC board does not a marine system make!

I realize that there are issues of piping and connections but these are done all the time in larger systems with regularity, in large boats, commercial kitchens and air conditioners! As for the piping, in most larger cities there is a commercial hose, piping and refrigeration wholesaler who has many of the parts needed for such an installation.

I think the big issue for most of us in tackling this project is the lack of knowledge about refrigeration. This could be overcome with an online course or one at a local junior college.

I am convinced after much research and thinking on this subject that we boaters ar being taken to the cleaners for refrigeration units by companies that are honest and do add value to the various parts they assemble, but are essentially selling us early 20th century technology cobbled together and called "marine" refrigeration.

What are your thoughts? Ideas? Experience?
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Old 26-11-2006, 15:32   #2
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Your problem will not be with the compressor or any of the mechanical components. The problem lies in the fact these "dorm fridges" (or any land fridge for that matter) will not be properly insulated from a marine perspective. It will be highly inefficient. These refrigerators are made to be plugged in all the time and will not stay cold. They will hog all of your power and leave you with warm food and dead batteries.

If you are talking about sitting at a dock 100% of the time, that is a different story. However, you can't use one for cruising.

Now... if you could improve the insulation of one of these boxes, they might just do the trick without a lot of modification (except you may have to do something with the condenser to be sure it gets cool enough and doesn't add too much to ambient cabin heat).
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Old 26-11-2006, 15:39   #3
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PS: You can learn a lot about refrigeration by purchasing this book, or vising this website:

http://www.kollmann-marine.com
http://www.bluewaterweb.com/Nautical...59&TopicID=115

I'm not associated with him in any way, but was able to get a used marine refrigerator with quite a few problems up and running well with that book.
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Old 26-11-2006, 15:43   #4
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I had similar plans and actually wanted to refoam and skin a large 300l fridge / freezer, but was told that they have plumbing embedded in the foam and damage would occur while pulling it off.

If you were carefull and picked at it you'd think it would work and then put 100mm foam all round.

mmmmmmmmm cold beer and Ice in the rum.

This crowd does domestic with danfoss BD80, still has skinny foam though.

http://www.solazone.com.au/fridges.htm
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Old 26-11-2006, 17:09   #5
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I think some of you have misunderstood me. I did not mean to use the refrigerator as is, but rather as I said in my post, take it apart and use it's component parts to make your own reefer system. This of course assumes that you have an area like an existing ice box that can be insulated for the purpose. This would give you the compressor and cold plate at about $200 then you would need some additional tubing, connections and a motor and controller.

Alan Perry
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Old 26-11-2006, 17:48   #6
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Your question is a good one. THe main difference between marine refer units and land refer units is that marine units are designed to work off level. I do not know enough about refridgeration to tell you how this is done, but it is the main issue in using a cheap compressor. Even some marine units claim a functional limit to off level operation. Norcold, for instance, provides refer units that will work anywhere, and their compressors will work off level for extended periods of time, but a few units do qualify that they can not handle over a certain degree of heel for long periods. The ability of some of the smaller units to pump enough for the cold plate you want is also an issue. A course in refridgeration would probably answer all of those questions.
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Old 26-11-2006, 19:17   #7
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Quote:
They will hog all of your power and leave you with warm food and dead batteries.
Sean sums it up pretty well. There isn't much inside one of these wanna be fridges that could be used for anything usefull unless there were a few cold ones inside before you started. Wanting something that isn't something else is not heading in the right direction. The thermostat might be usefull but you can buy them cheaper than $200.
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Old 26-11-2006, 21:06   #8
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Iv'e heard of people using houshold freezers as fridges - better insulation, and only a thermostat recalibration needed to make them operate at fridge temperatures. In fact there are claims that these are extremely efficient.
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Old 27-11-2006, 04:23   #9
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You wil find them on trawlers. They are running large engines and can make more power than they can use. They also tend to be plugged in more. Given the units all need to be connected to an inverter the whole time al the power you use costs you dearly in DC -> AC conversion. I only know one person using a "dorm fridge" and they use it at the dock and use ice at sea.
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Old 28-11-2006, 22:16   #10
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[quote=cat man do]I had similar plans and actually wanted to refoam and skin a large 300l fridge / freezer, but was told that they have plumbing embedded in the foam and damage would occur while pulling it off.

If you were carefull and picked at it you'd think it would work and then put 100mm foam all round.

mmmmmmmmm cold beer and Ice in the rum.

--------------------

A few months ago, I did exactly that. At a garage sale down the street, I acquired (for free) an RV 110v/12v refrigerator with a tiny freezer at the top. I completely gutted it and built a freezer for the boat. (I already have a small refrigerator, but for cruising it wasn't big enough.) The insulation in the new box consists of pink rigid foam from the local building supply store. I built a box lined on the inside with some vinyl sheeting, and covered it with 3" of foam all around and 4 1/2" on the bottom. The top has a hinged lid with 2" of foam. The whole thing is covered on the outside with thin guage aluminum left over from the original refrigerator. The box was built for a space on the boat under a deck hatch at the helm, so the boat dimensions dictated the result, and the exterior looks mattered not in the least. The compressor and condenser were mounted on the outside in the same manner as originally. Inside dimensions are estimated at 1 1/4 cu ft. By readjusting the stop on the thermostat I can get a 50% duty cycle run time and 12 degrees box temp. When running, it draws slightly less than 5 amps @ 12 volts. Wife is happy, ergo, I'm happy.

BTW I own a trimaran, so the heeling thing is not an issue, but during the construction I was curious about that so I tried running the compressor on the garage floor in different orientations. It had to get almost 90 degrees off it's original orientation to start to lose its effectiveness. (It started to cavitate.) I tried fore and aft as well as side to side tilting.

Steve B.
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Old 29-11-2006, 01:51   #11
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you can actually do this but instead of a bar fridge you get the little freezers as these have sufficient insulation to make a half decent fridge
sean
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Old 29-11-2006, 03:28   #12
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Making ice is expensive. Probably the best method for the cruiser who is away from the dock is a cold plate system but it will suck a bunch of amps or require engine run time. Not sure if you can get enough amps from solar and wind to run a fridge/freezer combo. We use dual voltage so it was simply easier to install a generator. I hate to run the propulsion engine to simply make ice or charge batteries unless we are underway.

If you want to build your own, these guys have all the parts.

http://www.rparts.com
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Old 28-12-2006, 11:26   #13
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Not a good idea. I did the same thing on my boat for a few months as the boat was just tied to the dock. The thing died on me when I went out sailing one day with a fresh breeze and lots of motion below. I suspect that the angle of heel combined with the motion killed the compressor.
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Old 09-03-2010, 01:40   #14
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Most of the small refers use about 4 amps @ 110 Volts, Is that about 40 amps at 12 volts? A 50 danfoss maxed out uses about 6 or 7 amps I think. Big deal on my little bitty batteries. Set me stright Gordy
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Old 09-03-2010, 01:41   #15
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6 or 7 amps 12 volt
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