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Old 28-02-2012, 07:35   #1
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Keel cooled or Air Cooled Compressor for Tropics

I need to decide on wether go with a keel cooler or just air cooled for my fridge. I hear people raving about the keel coolers but am not thrilled about putting another hole in my boat nor the prospect of losing my fridge if we are on the hard. Im pretty much resolved to go air cooled.

Fridge in question will be 6-7 cubic feet. BD 35 compressor with a flat plate evaporator. Well insulated and will operate solely as a fridge no freezer. Boat will be full time live aboard primarily located in the tropics.

I guess Im wondering about any significant improvements from a keel cooler when water temp and air temps are likely to be pretty much the same?
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Old 28-02-2012, 07:47   #2
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Re: Keel cooled or Air cooled compressor for Tropics

NONE only more complication and things to go wrong
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Old 28-02-2012, 07:54   #3
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Re: Keel cooled or Air cooled compressor for Tropics

I know this test is biased, but it does make sense.

Keel Cooler Test

In my humble opinion, the best deal is an air cooled condenser with a water loop as a backup for those really hot days. When our fridge stuffs it, my ideal replacement will be an air/water cooled condenser with a thermostat on the seawater pump, that way the pump will only come on if the air for the condenser exceeds a predetermined temperature.
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Old 28-02-2012, 08:56   #4
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Re: Keel cooled or Air cooled compressor for Tropics

Our refrig/freezer (separate) are both water cooled. There's no contest here - you dump that heat into the water instead of into your boat. Water is WAY more efficient at cooling than air.
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Old 28-02-2012, 09:13   #5
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Re: Keel cooled or Air cooled compressor for Tropics

I have an air cooled Danfoss BD 35 compressor aboard and it works great (and has for over 10 years now). Also have an air cooled BD-50 driven system in the house - ditto.

A good fan set-up to dissipate heat is important. Finding a way to vent this outside can of course be a challenge on some installations.

Water cooling is more efficient simply because water dissipates heat way faster than air, but air cooled works just fine.
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Old 28-02-2012, 09:14   #6
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Re: Keel cooled or Air cooled compressor for Tropics

Don't know how well this works, but thought it was a cool idea. The heat exchanger is water cooled and is contained in a though hull.

Fisheries - Product Detail
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Old 28-02-2012, 09:16   #7
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Re: Keel cooled or Air cooled compressor for Tropics

Quote:
Originally Posted by bstreep View Post
Our refrig/freezer (separate) are both water cooled. There's no contest here - you dump that heat into the water instead of into your boat. Water is WAY more efficient at cooling than air.
Water is definitely a more efficient medium for heat transfer however, water also requires significantly more energy to circulate. I went through this process looking for the most energy efficient refrigeration system I could find. According to both Richard Kollman and Nigel Calder, 12V air-cooled compressor systems are fine for smaller, well insulated fridge boxes - even in the tropics.

That being said, when I designed my 4.6 cu.ft. fridge box, I talked to the owner at Sea Frost about whether to go with the BD35 or the BD50. He said I was right on the dividing line and that either compressor would probably work fine. He did say the energy usage would be just about the same regardless of compressor. I took him at his word, especially considering the price difference between the two units was negligible.

Just a thought - might want to consider a BD50 unit. It will cost marginally more but will have the reserve capacity for cold tropical beer on really hot tropical days...
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Old 28-02-2012, 09:37   #8
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Re: Keel cooled or Air cooled compressor for Tropics

we run the water cooling for our 200liter fridge and freezer through the fresh water tanks works great,no corrosion issues,works on the hard as well,600 liter tanks and keeps the water nice and fresh
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Old 28-02-2012, 10:29   #9
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Re: Keel cooled or Air Cooled Compressor for Tropics

Yeah sorry meant to say BD50 not 35. It is not a big challenge for me to route intake air from the bilges and exhaust air out through a vent to the cockpit on this boat so if I go air cooled I wont have the system dumping the hot air inside the cabin. I thought about sticking a keel kooler in a water tank but my boat is set up with 4 water tanks and the only one in decent proximity to the ice box is not likely to always have water in it. I also dont really like the idea of cutting a hole in a water tank and am not sure I like the idea of circulating my potable water through a fridge condensor. Of course YMMV.
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Old 28-02-2012, 10:47   #10
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Re: Keel cooled or Air Cooled Compressor for Tropics

A keel cooled unit (the kind without a pump) is very simple and reliable. One problem in the tropics is the heat from an air cooled unit either goes into your cabin, or if in the engine room your compressor works harder from the engine heat surrounding it. Not a huge deal either way I suppose. My friend's used a small water cooled unit throughout the SO Pac with no issues at all. The thing was tiny without all that air cooled crap.
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