Cold Plate / Thermoelectric?

[wolfenzee]

In an earlier thread I mentioned I was biulding an ice box and asked about insulation....people were very helpful there. Ice box I am building will be able to use block ice and thermoelectric or cold plate.....I am upgrading my electrical system to 2 deep cycle marine and 1 8D for cabin power and two deep cycle marine for dedicated engine, this should be able to handle a fridge. I don't want to (and can't afford) a pre-made fridge. I am making my own ice box, top loading, about 3cf...if that. How do I make a cold plate fridge.

[Pblais]

I don't want to (and can't afford) a pre-made fridge. I am making my own ice box, top loading, about 3cf...if that. How do I make a cold plate fridge.

OK, you really want 3 inches of closed cell foam insulation. More is not worse. If you want 3 cf then you need to add the room for the ice. I get about 3 cf with my 6 cf fridge using ice. My old fridge died and I use ice for this summer until I get the new fridge installed (soon). Ice sucks! When you start out right you can go 4 days maybe. The next round drops to 3 days. More insulation is always better, but don't forget the room the ice takes. A drain for the melt water is best advised too.

Freeze everything that can be frozen before you leave and get an extra day free. Forget cold beer and drink rum. I like single malt or wine.

The cold plate is what I prefer but this time around I won't because the plate is too big for the fridge setup. Cold plate buffers the opening and closing of a fridge and works well if you want a freezer too. The spill over can work a dual system well when the day time temps are over 90 F.

With ice you can forget frozen food after one day. We just completed a 10 day trip on ice. The good news is the battery bank never went below 95%. You just can't need that much power when you don't have a fridge. I spent a fair amount on ice though. Long term - ice sucks unless you can add 20 pounds every other day (or more). The other option is don't use it. I was a mountaineer for 30 years and we never ever carried ice - went went where there was some instead! Coffee was enough of a starting battery. I don't do that any more but we still carry coffee. That only takes propane! One of those lasts a way long time.

[Evan]

Thermoelectric cooling is not very effective because it is limited to about 40F below ambient. On a very hot day (say 90F) you fridge is only going to be 50F. That is too hot for very effective refrigeration.

On my last boat I used 4" foam all round a small (say 2 cubic foot) icebox. 40 lbs of ice would last a week in Mexico.

On my current boat I am using mostly 6" foam with a small 2.7 cu ft. old fridge liner + an "icebox conversion unit" from NovaKool. I have to keep it on the highest temperature setting or it will freeze the contents.

[wolfenzee]

The space I have figured for the ice box does not include the space for the ice, it will drop in behind the food from the counter, so I don't have to take everything out each time I put in ice....I have that space figured in and the melt from the ice will drain into a sump (with a trap that will keep cold air from draining too) as my galley sink is below the water line it will drain into the same sump with a foot pump (also used for salt water rinse) will pump out the sump. I have got the amount of insulation figured in. I have sailed alot with just ice and lived on this boat fro two years with no refrigeration, just a cooler in the cockpit, but would also like to build this ice box to be able to have electric cooling as well as block ice.....any suggestions on cooling.

[clockwork orange]

There was a thread on here a while ago about stirling cycle coolers which sounded interesting,it would be interesting to get some feedback from folks who have experience with them. I have been thinking of building something similar to what you are, using block ice remotely mounted and capturing the melt water for drinking.
Steve.

[witzgall]

Peltier coolers (thermoelectric) are way to inefficient to use on a boat, unless you are running the engine 24x7.

Chris

[gbanker]

if i was to "build" my refrigeration i would be tempted to build an insulated "ice box" with 4 - 6" of insulation such that an Engle or similar unit could be dropped in. simple to build, cheap to buy the refrigerator/freezer and easy to fix (replace) when the unit fails. we have several friends who have gone this route with good results.

[cantxsailor]

Bite the bullet and buy the ENGEL. They are as close to a bulletproof piece of equipment as I have ever used. Mine (mt35f) has been running for 2 years non stop and will keep my beer at 32F when the ambient is over 95F. Max draw is 2.7amps(when set to hard freeze) so my solar/wind generators can handle it with ease. Same physical size as a 40qt ice box and will run off either 12vdc or 110vac both plugged in at the same time so if 110v goes out 12v kicks in and the other way. Ice is nice in a drink but a waste of time(for me) for keeping food cold and messy too. Mold is a constant companion of most ice boxes. Maybe however the worst thing is in most places it's expensive.

I have also seen very few DIY systems that work well enough for my taste(ie cheap)...........m

[wolfenzee]

Originally Posted by gbanker

if i was to "build" my refrigeration i would be tempted to build an insulated "ice box" with 4 - 6" of insulation such that an Engle or similar unit could be dropped in. simple to build, cheap to buy the refrigerator/freezer and easy to fix (replace) when the unit fails. we have several friends who have gone this route with good results.

What do you consider "cheap"? I already plan in at least 4" in the "thin spots" and to fill the gaps where there is waste space. This will be both ice and "powered" fridge...I am not trying to make my own ice.....just keep things a little cooler than and more convenient than the bilge. Because of my cabin lay out this will have to be top loading 18"x18"x18" for food section is the largest I can realistically fit (with 4"+) insulation on sides, top, and front, because I can't get back there the back will just fill in gall the spaces.

[mesquaukee]

Check out the do it yourself 12 volt systems such as Nova Kool at www.southerncalmarine.com/product_info.php/cPath/24_47/products_id/112 It’s about $900. It's the least expensive system I know of. I had a Nova Kool for 4 years in the tropics before I built a larger more efficient system.
This page gives you an idea about energy use www.boatelectric.com/novalt200-rt6%20&%20lt200.htm
There are a bunch of other do it yourself systems that are larger and more expensive.. All of them come pre-charged with quick disconnect fittings.
12 volt cold holdover plate systems are expensive and use considerably more energy than the above type of systems. The reason is very simple. The evaporator pressure has to be much lower to freeze the solution in the cold plates. This translates into longer run times for the same amount of heat moved.
Cold holdover plate systems which run off the engine are horribly expensive. They are great if you run your engine 2 or so hours a day for other reasons than cooling your fridge.

Have fun, Tom

[SURV69]

I use a Coleman 40 quart pelzier cooler and I like my milk . . . cold.

I have not been dissatisfied with my milk's "coldness", on 90+ degree days in northern Ohio.

Just my $0.02 worth

[Pblais]

I have not been dissatisfied with my milk's "coldness",

You would probably like 38 degrees F but you may have only 45. If you are not getting below 40 degrees then it won't keep food fresh very long.

[wolfenzee]

The idea of a pelzier based system seems the most logical for me, my ice box will be heavily insulated, have a section for block ice and I have cooling fans/heatsinks originally designed for computer harddrives but also used for ice boxes. Taking the "guts" of a lightly insulated pelzier cooler, adding more insulation and cooling power and suplementing that with ocasional ice (also the ice box is against the hull below the waterline).
In my galley refit I have gutted the entire galley all the way down to the inner hull (1/4" ceiling on top of 2" ribs, with 1" hull).

[Paul Elliott]

Look at the efficiency of the Peltier units (Watts in / BTU out), and the practical temperature differential. It isn't all that encouraging, especially when using an air-cooled system.

I have seen a system (Swedish?) that used a thermally-conductive interface between the Peltier cooler and a through-hull water heatsink, and the numbers were slightly better, but still not very exciting.

[wolfenzee]

my ice box will be built for ice with the ability to have electric added to it when I figure out what I am going to do, even if I *had* $900 to put into an refrigeration system (plus all the add-on costs) I would put the money somewhere else. I have lived on the boat 2 years with only a small cooler in the cockpit, which was more of a place to put stuff and rarely even had ice. The space I need to keep cold is fairly small, very heavily insulated and I don't need it land-lubber cold.