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Old 20-04-2008, 17:18   #1
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Using regular everyday fridge/freezer

So as I've begun seriously planning out my galley I have gone back to something I've wondered over and over again.

When it comes down to refrigeration is it worth buying all the super expensive and tiny marine units, or could I just use standard store-bought appliances?

I want to have both a chest freezer and a small refrigerator in my boat.

You can buy a 5 cubic foot chest freezer with a fairly small footprint for between $150-250. The only difference in them seems to be in thickness of the cabinets and I would imagine energy efficiency. Likewise I can buy a very nice and fairly efficient refrigerator (3.5-4 cf) for between $150-500 depending on how nice it is and the shape of it.

Now I know how I eat and live, and I use my fridge for things that are either left over for a few days, for dairy stuff that doesn't stay in there for long, for fruits and vegetables, and for drinks. Those things don't require a super cool environment. I do eat a lot of meat dishes and tend to make big meals divvie them up and freeze them.

So I'm thinking one of these under counter fridges and a chest freezer is the perfect set up for me. Plus I lived in Europe with a similar system minus the freezer and never had a prob.


Either way, I would imagine that these household units are on their own less energy efficient than custom marine apps. They do use compressors, which use electricity. They would also require me to run A/C power for them (unless I can figure out how to convert them to DC).

But, I would think I should be able to add a further layer of hardcore insulation around these units as part of the install and make them a bit more energy efficient on the cheap. Plus, the more you keep in a fridge or freezer the less it has to operate (even if you're just freezing ice).


So, what the whole point of this post is, when you look at the initial cost of between $300-700 for full installation versus the added expense over time of using a bit more electricity, is it worthwhile to go with these units over somethign designed for a boat?
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Old 20-04-2008, 18:11   #2
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Depends on where you want to cruise... it might be hard to get the insulaton factor up there if you are in the tropics.

Also, I have read about people taking chest freezers and just putting a different thermostat in to use them as super-efficient top-loading refrigerators. Because it's a freezer, it's already insulated like crazy and when you bring the temp down to 34-40degF, you have a very efficient refrigerator.

Sorry... I don't have a link, but it's not so hard to switch out a thermostat.

You'd just have to buy a super-efficient one. A lot of people who live off grid and use wind/solar on land do this.

Also, the added electricity would add up on an "off the shelf" fridge - especially if you used something like a generator to power it and had to buy a new generator all the time.
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Old 20-04-2008, 20:50   #3
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I'm hoping to keep everything on wind and solar. It's one of my project goals -- to make the whole thing sort of energy-equal. At the same time, I know I'll spend most of my time in the tropics, so I have to figure cooling and refrigeration into that equation. I saw some info on propane refrigeration. Interesting option, but doesn't mention anything about efficiency. There is also a solar option that runs the same way -- basically heating coils (with sun or flame) to initiate the cooling process. I'm guessing though that the simplest system would just be to use simple appliances with a good solar/wind system and either a propane or diesel backup generator.
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Old 20-04-2008, 23:26   #4
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Its really a drag to have to keep running your gen set or your main engine because your refer is constantly dragging your battery voltage down.

Drew, its all about efficiency. Marine refrigeration has to be more efficient because all you have is the power you bring with you to sea. Your obviously not tied into the grid where you have virtually limitless power.

Other than insulation, the other efficiency factor is dual power. Much marine refrigeration can run off the onboard DC system or AC. When you are underway, the most efficient way of keeping the beers icy cool is from the boats DC system. In port, if and when you have AC available from shore power, it will make the most sense to keep your fresh lobster cool with AC.

There is also the factor of building a unit that can survive a marine environment....which typically means more resistant to salt air and movement.

So what do you get?...a refrigeration unit that seems like a ripoff compared to a terrestrial based refrigerator but if you take all of what a marine refrigeration unit needs to be then its not such a bad deal.
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Old 21-04-2008, 01:26   #5
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Fridge

Have had propane always leary flames on boats.Propame units very pricy % use ammonia as coolant which is corrosive.The two I had did not last lonf.They also worked on ac.Withac refers converting dc to ac you expend energy just to invers(2nd law thermodynamics).Need to ck price for inverter capable of producing current required.
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Old 21-04-2008, 01:57   #6
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I have three cooling units on board.
One is an upright 3 way fridge/freezer. It draws 17A continuous on DC so we never run it on DC. I imagine the AC will be similar power consumption, so we only use AC when on shore power and Gas when out. It uses 330grams of LPG/24hrs. It has a small Freezer box and the rest is Fridge. The unit was really expensive when I bought it and from what I know now, I would never have bought it if I new it then.
The next one is a fridge, although it gets close to freezing, but not quite. This one is a 12VDC Danfoss Compressor and a fan forced cooler unit in a built in cool box. It draws about 5-6A but cycles, so is not drawing that amount all the time. I have found it to be very economical. The compressor is mounted down under the floor in a dry bilge area, so it is reasonably cool down there. And completely silent.
The third was a bit of a "I wonder" kind of thought. We needed extra Freezer space badly. I had a space, but it would mean it had to be upright. So seeing as a sale was on, I bought a cheapy made in China SST upright Freezer to fit into the space. It is Mains AC only and yes we have an inverter. It worked quite well, but every time I opened the door, I felt the cold air drop out onto the floor around my feet. I knew this was wasting energy. So I had an idea. I had a cool box already built under a Bunk. I pulled that out and in the space, I dropped the freezer in lying on it's back. Before I lay it on its back, I removed the Compressor and kept that upright. Then lowered the Freezer and Comp into the space. The comp sits outside the Freezer and upright. The freezer on its back. The first minor hickup I found was the insulation on the back of the Freezer was not very thick and now the cold was "dropping" through the back(now floor) of the freezer. So I got some Polystyrene and glued it to the back. At the same time I made a mistake and glued the stuff around the sides as well. I then found the sides got terribly hot. Duh! of course the evaporators are built into the sides to get rid of the heat. So I now have exposed sides to let the heat escape. The unit has been working flawlessly for about three years now. I am thrilled with how it performs. It cost me a grand total of NZ$199.00 The other fridge retails at around NZ$1100.00 and the big upright Fridge/Frzr cost a wopping NZ$2500. If the Freezer fails, I will do the same again without hesitation.
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Old 21-04-2008, 05:06   #7
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Quote:
Originally Posted by drew.ward View Post
I'm hoping to keep everything on wind and solar. It's one of my project goals -- to make the whole thing sort of energy-equal. At the same time, I know I'll spend most of my time in the tropics, so I have to figure cooling and refrigeration into that equation. I saw some info on propane refrigeration. Interesting option, but doesn't mention anything about efficiency. There is also a solar option that runs the same way -- basically heating coils (with sun or flame) to initiate the cooling process. I'm guessing though that the simplest system would just be to use simple appliances with a good solar/wind system and either a propane or diesel backup generator.
Yup... trying to run everything on solar and wind usually means you have to have everything as efficient as possible. You can scrap the idea of inexpensive components in your electrical system.

You should go through the excercise of doing a "power budget" and tallying up every bit of power you use all day, finding out what your solar and wind will *really* put out in actual conditions you plan to be in, and then add a fudge factor in. There are quite a few threads on here discussing power budgets. I have to get underway now, or I would add some more...
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Old 21-04-2008, 07:38   #8
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Thanks for all the info guys.

I'll do some more research. This is going to sound like a dumb question, but how warm does the inside of a boat generally get?

I'm in New Orleans and will be mostly between here and Mexico, so the air is generally warm and we certainly have the sun.

I was really planning on redoing the layout of the boat for as much natural ventilation as possible with using a/c at night if needed but if the inside of the boat is going to always be a huge microwave during the day I'd suppose I'l have to rethink this.

I like the custom freezer idea, and have actually been considering that. One issue I keep wondering is if there is a cheaper (energy and parts) setup than a compressor.

I like the idea of fewer moving parts, and simplicity is always nice.
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Old 01-05-2008, 04:56   #9
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other types of cooling

Drew, be sure to read the thread on"Coleman Stirling Power Coolers" in this same section for some other ideas.
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Old 01-05-2008, 05:11   #10
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Originally Posted by drew.ward View Post
... how warm does the inside of a boat generally get?
I'm in New Orleans and will be mostly between here and Mexico, so the air is generally warm and we certainly have the sun...
In the sub-tropics, assume that the inside temperature will be between 1 to 3 degrees warmer than the outside ambient temperature, except when cooking or entertaining larger groups of people (inside), at which times it could go even higher.
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