keel cooled refrigeration...need your input

[4sandybutts]

I m considering putting a keel cooled refrigeration system on my Catalina 30. Can you nice salties give me any info on your experience with these units vs traditional units? Thanks.

[Typhoon]

Lots of reasons to stay away from a Keel cooled system . Many are troublesome. There are many many threads on this forum that describe one reason or another to avoid such a system . Mind you, I am biased because Im a vendor, so don't believe me, do your research . Always compare the pros and the cons , also read very carefully the efficiency of all systems , and what comes standard and what you have to pay extra for . Whats involved in installing the system , another thru hull !!!###@@##



A blog post from my site .

Avoid These 5 Refrigeration System Problems

Regards John.

[Cheechako]

I'm not sure it's worth the trouble. Frankly , I'm not sure using anything other than a simple air cooled unit is.... after owning many. I found no discernable difference in charge time from water cooled to air cooled.
By "keel cooled" I assume you mean installing heat exchange tubes thru the hull and under the hull.

[Terra Nova]

The most efficient system I ever installed was a keel-cooled Frigoboat system that could be operated as either a fridge or freezer.

[zboss]

I'm very pleased with my bronze sinter Frigoboat keel and/or air cooled system vs. my air cooled only Adler Barbour. We reduced our energy consumption by nearly half. Some of this is simply due to newer technology but a lot of it is due to the keel cooler.

We normally run with only the keel cooler but in very hot tropics we can turn on the air cooler to maintaining cooling capacity.

The keel cooler is very useful outside the tropics or in the winter when the water isn't very warm; it does best in areas where there is at least some current or tidal flow. In tropical areas that have very little tidal or current flow, like in many protected marinas, it does not help as much and uses on our upper end of energy consumption. This is why we went with the keel cooler and the extra air cooled option.

We only added a few inches of extra insulation in the bottom of our fridge and freezer and now we have about a 4 cu.ft. freezer and a 4 cu. ft. fridge (about) and use 40 Ah in winter and 60ish in summer. The fridge has about 1" of 30 year old insulation otherwise.

[senormechanico]

Another vote for keel cooled system.
I installed a Vitrifrigio with a BD35 in my Dragonfly.
It's extremely quiet and with my Clean A Hull ultrasonic hull system, I never get any growth on the keel cooler at all.
It's mounted about a foot below the surface, so I can reach it from a dinghy for inspection.

[Anna Sail]

Originally Posted by ColdEh Marine

Lots of reasons to stay away from a Keel cooled system . Many are troublesome. There are many many threads on this forum that describe one reason or another to avoid such a system . Mind you, I am biased because Im a vendor, so don't believe me, do your research . Always compare the pros and the cons , also read very carefully the efficiency of all systems , and what comes standard and what you have to pay extra for . Whats involved in installing the system , another thru hull

John, I'm disappointed to hear you join the small group of technicians/sales people dissing the Keel-Cooler, usually from lack of understanding or the wish to sell their product instead.

It's a fact: water is a better heat-exchanger than air. Keel Coolers (a generic term) have been used for decades on the large commerical fishing boats, for example. Eliminates the need for a pump and the extra power needed to run it. Frigoboat simply makes that technology available on a much smaller scale for the ice boxes found on pleasure boats, over 40,000 of them world-wide. That's a rather large number of happy/repeat customers for a product you call "troublesome".

[Typhoon]

Originally Posted by Anna Sail

John, I'm disappointed to hear you join the small group of technicians/sales people dissing the Keel-Cooler, usually from lack of understanding or the wish to sell their product instead.

It's a fact: water is a better heat-exchanger than air. Keel Coolers (a generic term) have been used for decades on the large commerical fishing boats, for example. Eliminates the need for a pump and the extra power needed to run it. Frigoboat simply makes that technology available on a much smaller scale for the ice boxes found on pleasure boats, over 40,000 of them world-wide. That's a rather large number of happy/repeat customers for a product you call "troublesome".

Again, all I can say, is do your own research , no marketing hype . On a personal note . I would not install a keel cooler on my own boat.

Regards John

[skipmac]

Here's my take after reading every article, manual and online discussion for a couple of years before buying an air cooled unit.

Keel Cooler

Pros
- very quiet in operation
- in very hot climates might be slightly more efficient that an air cooled unit.
- Claims that putting the heat into the outside water keeps the boat interior cooler. This is not my experience with an air cooled unit and I did a several day test taking temps in various parts of the boat to confirm.

Cons
- The freon lines run to the cooler and if for some reason the lines corrode you expose the freon lines to salt water which will immediately kill the compressor. Read a number of previous threads on this issue.
- The difference in efficiency seems to be minor or in cooler climates or cooler seasons there is no benefit at all.
- Unless you have a dual cooled unit you can't use the fridge on the hard.


Air cooled

Pros
- simple, less expensive, easier install
- works in or out of the water
- less risk of compressor damage in a failure.

Cons
- there is some noise from the fan
- might use slightly more power in a very hot climate.

I have a well insulated 9-10 cu ft box with 1.5-2 cu ft of that a freezer. In FL in mid summer, daily temps over 90 I used less than 50 amp hours/day. Winter about half that.

There is no doubt that water is a more efficient heat transfer medium that air however, Richard Kollman who literally wrote the book on marine refrigeration has posted some technical discussions on this issue on this forum that point out some problems with water cooling. To be honest I didn't quite grasp the details but something to do with too much cooling causing a temp or pressure difference that was not good for the system. A forum search should turn this up if you want to read the details.

[redsky49]

Self-installed unit, circa 2005. Heavy use in tropical as well as temperate waters. Two minor issues. Outstanding efficiency. Quiet operation. Good, though not great, manufacturer support.
Would absolutely purchase again. Currently in Florida. Typically runs at low speed for about 35-40 ah/day in these demanding conditions - warm water and hot air temperatures.
Listen to what actual users have to report.
My unit is a Frigoboat keel cooler.

[Typhoon]

Ah usage is always a direct indication of box insulation . How vapour and pressure work together is a bit complicated and a steep learning curve but a system that is reliant on maintaining condensing temperatures, must do just that, to be efficient . We use a TXV so not as reliant on condensing temperatures .

Regards John

[Russ]

Go Frigoboat Keel Cooler Version. GREAT! Fast, Cold, NO noise!!!!!!!!!!

[KRMS]

I agree with Skipmac but my conclusion was to go with keel cooled. I did the installation myself with the Frigoboat system. It had prefilled refrigerant lines and was very easy to do. We have ended up up with a large freezer box within the original fridge and with better wire baskets have lost no fridge space.

It's been in for 3 years and has been great. The lack of noise is a real selling point for us.

[Terra Nova]

Originally Posted by skipmac

...
Air cooled

Cons
- there is some noise from the fan
- might use slightly more power in a very hot climate...

Add:

Heats the inside of your boat.

[skipmac]

Originally Posted by Terra Nova

Add:

Heats the inside of your boat.

If you read my full post, I tested that issue and did not find that to be a problem. In theory this would seem to make sense and certainly the heat from the fridge must be going into the inside of the boat. Real world test however, proved to my satisfaction that the amount of heating is not significant.

My compressor is installed in a closed space under the floor of the main cabin. When this question came up previously I ran the following test in my boat.

I closed or covered all the holes and vents from that space and for additional insulation of the space put a carpet on the cabin sole over where the compressor is installed. Put a thermometer under the floor in the compressor space where any heat buildup would occur and one in the main cabin above. Ran the fridge for a couple of days with the hatches open in the main cabin so the cabin would be at ambient to compare to the temp in the compressor space.

It's been a while since I did the test so don't remember the exact numbers but the difference in the temp under the floor vs in the open, ventilated cabin above was insignificant.