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Old 20-09-2016, 14:57   #1
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Fresh Water Cooling For Fridge

A post earlier this year gave me an idea about 'upgrading' the fridge cooling system on my boat. The DB 50 was cooled by a coil thru which sea water was circulated. I switched it over to fresh water.

The compressor is in the engine room, along with a 85 gal diesel tank and a water tank of similar size right beside it. By replumbing the cooling coil I now use the water tank to cool the refrigerant. The freshwater exits the tank at the bottom, circulates thru the coil and is pumped back into the tank thru the top. I use the breather for the tank for the return.

This summer was the test as we cruised north of Desolation Sound for three weeks. The system worked flawlessly. I checked the temperature of the fresh water tank a few times each day and found the temperature was generally only about 2 degrees centigrade higher than the diesel tank next to it. This temperature varies according to how much motoring we do. At anchor or while sailing it was around 23 degrees, and after a few hours of motoring it would reach around 37 degrees (about the same temperature as the engine room). I didn't keep track of how often the compressor cycled on and off, but I really didn't notice a difference.

Advantages:
-Two seacocks no longer needed, with all the advantages that entails-No need for the sea strainer, always a pain in the butt to clean and maintain.
-I now turn on the reefer a day before embarking on a cruise, ensuring it is nice and cold when we load it without me worrying about seacocks left open when away from the boat.
-The system seems to run more efficiently, no hard data.
-Fresh water less corrosive on the whole system than sea water.

Disadvantages:
-85 gallons less fresh water. The other tank holds around 130 gallons so this was not a problem on a three week cruise - partly because we carry bottled fresh water for drinking.
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Old 20-09-2016, 15:21   #2
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Re: Fresh Water Cooling For Fridge

It should have no effect on the quality of the water, it should still be fit to drink. All your doing is dumping a little heat into it is all.


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Old 20-09-2016, 15:28   #3
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Re: Fresh Water Cooling For Fridge

I would worry about the efficiency of 37 degree water to remove enough heat from the fridge.
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Old 20-09-2016, 15:32   #4
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Re: Fresh Water Cooling For Fridge

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Originally Posted by a64pilot View Post
It should have no effect on the quality of the water, it should still be fit to drink. All your doing is dumping a little heat into it is all.


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As I just started using the fresh water to circulate thru the coil without somehow cleaning the coil and hoses that had circulated the sea water for many years I isolated the tank. I may drain the system and refill with "fresh" fresh water and start using again.
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Old 20-09-2016, 15:35   #5
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Re: Fresh Water Cooling For Fridge

Quote:
Originally Posted by Tingum View Post
I would worry about the efficiency of 37 degree water to remove enough heat from the fridge.
I did, but believe that a 3 week test in the summer should be a pretty good indicator that the system is workable.
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Old 20-09-2016, 15:50   #6
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Re: Fresh Water Cooling For Fridge

The australian ozefridge has had this system for many years. It is very effective (and long lasting).

If you have any concerns about the water deteriorating in the tubing its a simple matter to run the water as a closed system with a small header tank.At some point in the line you introduce a length of copper pipe and put that into your water tank thus converting it into a heat exchanger.

worked for me.
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Old 20-09-2016, 15:54   #7
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Re: Fresh Water Cooling For Fridge

Thanks qwert, great suggestion
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Old 21-09-2016, 10:16   #8
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Re: Fresh Water Cooling For Fridge

85 gallons of water can hold a lot of heat. If you start using that tank as a source of fresh water the ability to hold heat will obviously go down as you draw down the tank. If you run that tank down too far then you'll also loose cooling for your fridge.
You could use a higher outlet on the tank for fresh water use insuring there will always be some water in the tank to cool the fridge.
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Old 21-09-2016, 10:24   #9
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Fresh Water Cooling For Fridge

Been using the 45 gallon fresh water tank to cool the cold plate fridge compressor for 25 years. It's worked without a flaw in the cooling side. No blocked sea water filter, no corrosion. The tanks are in the keel touching the hull. So seawater temp is the same as the fresh water temp

BTW We have been sailing in the tropics for the past 11 years. Water temp is in the 80's


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Old 21-09-2016, 10:45   #10
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Re: Fresh Water Cooling For Fridge

Comon guys, really? just air cool these damn
things . It works just fine . No pumps to worry about . We have gone around and around in this forum about water cooling VS air cooling . But if I had to have it, I guess your idea will work but as it has been stated, what happens when you empty the tank ?

I hope you have a water maker or are always close to a fresh water supply .

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Old 21-09-2016, 11:17   #11
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Re: Fresh Water Cooling For Fridge

Yes fresh water is best, recommended by Indel Webasto after the problems I had, three pumps and other parts, mostly because of dirty water (Baltimore) and yes cleaning the filters ( I added two see through) every week is no fun.
IW uses fresh water pumps for their system, why????, Shurflo pump manufacturer recommended salt water pumps and that has helped. I have one connected to a 10 gal. fresh water tank which I set up near the pump, but that's 50lb. of water, the other two pumps are on the through hull fitting. I have moved the boat out of Baltimore and that has helped tremendously
I would like to connect all three pumps to the main water tanks but they are up front of the salon, the pumps are aft by the motors, it's a long run, too long for the pumps to draw I think.......bad design in the system, ok for clean ocean but we don't always cruise in clean water.
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Old 21-09-2016, 12:20   #12
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Fresh Water Cooling For Fridge

Quote:
Originally Posted by typhoon View Post
Comon guys, really? just air cool these damn
things . It works just fine . No pumps to worry about . We have gone around and around in this forum about water cooling VS air cooling . But if I had to have it, I guess your idea will work but as it has been stated, what happens when you empty the tank ?

I hope you have a water maker or are always close to a fresh water supply .

Regards

Yep the next fridge will be air cooled but hopefully that won't need to be addressed for a number of years. We have used a 5 gallon jug for cooling many years ago while hauled out in Queensland doing the bottom. Worked just fine. No we are a long way from any fresh water source. We do have a wm and two water tanks of 45 gals each.

We use a low flow Flojet pump to circulate the water. The total run is about 20' with a 5' lift



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Old 22-09-2016, 07:51   #13
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Re: Fresh Water Cooling For Fridge

Quote:
Originally Posted by chouliha View Post
Yep the next fridge will be air cooled but hopefully that won't need to be addressed for a number of years. We have used a 5 gallon jug for cooling many years ago while hauled out in Queensland doing the bottom. Worked just fine. No we are a long way from any fresh water source. We do have a wm and two water tanks of 45 gals each.

We use a low flow Flojet pump to circulate the water. The total run is about 20' with a 5' lift



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Just looked at your blog , beautiful boat. Enjoy your adventures .

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Old 22-09-2016, 08:00   #14
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Re: Fresh Water Cooling For Fridge

With sea water, you have an unlimited amount of cooling water at whatever temperature the sea water happens to be. Using fresh water in a closed system, where does the heat go? It goes into the fresh water of course but as you continue to transfer heat from the refrigerator to the water, the water temperature rises. Then what?

You need a way to cool the fresh water. Perhaps a heat exchanger with sea water running through the other side? But wait - now you are back to cooling with sea water but you've just made it more complicated and you're using more energy for pumping cooling water.

Nothing is free. I would think the original system was the best and certainly the least complicated.

Well air cooled is less complicated but perhaps not as efficient.
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Old 22-09-2016, 08:16   #15
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Fresh Water Cooling For Fridge

Your not dumping in much heat at all, on average about what a 30W light bulb would make. The heat dissipates into the environment especially if the tank is in contact with the hull. I'd be surprised if there is a more than 1 or 2 degree change before equilibrium.
But I have never measured it. If I had a water cooled fridge I would do it, I have heard of more than one super cold machine that salt water corroded through ruining the machine
Air cooled if fine 99% of all house heat pumps and refrigerators are air cooled, there would be more water cooled if it were much more efficient


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