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Old 17-03-2019, 10:34   #16
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keel cooled fridge and freezer on the hard

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Originally Posted by Anna Sail View Post

Using a fan as your heat exchanger is classic; it also uses 25% more energy than a pumped-water or keel cooled system. Sure, it's simpler to install, and usually less costly, but if energy conservation is important, as well as peace and quiet, little maintenance, and consistent performance in weather conditions from Maine to the Tropics, then the keel cooler is a better choice, in my humble opinion.


My fan draws .15 amp, I think. My system draws it seems somewhere between about 4 to 8 amps, depending on the speed the AEO is running the compressor.
Now I suck at math, so Iím not going to try to determine a percentage, but Iím pretty sure itís nowhere near 25%.
.15 amp is just not worth spending big $$ and adding a potential headache to save. Assuming a 50% duty cycle, I think that is less than 2 AH in a 24 hour period.


Water cooled house heat pumps were all the rage in the 70ís due to their theoretical energy savings and in the 70ís I guess electric prices must have shot up cause people were building underground houses and super insulating houses and Solar heating etc.
Or maybe it was just a Fad, but ground source heat pumps were the ticket.
Within a few years two things happened, air cooled became much more efficient due to much larger and better designed condensers, and the maintenance headache that a ground source heat pump was made them much less desirable.

Now if you find one, itís an anomaly.

If properly designed, an air cooled system is just as efficient.
Itís proper design, and not the particular parts that are in a system that determine efficiency and reliability.
So, Iím certain that there are inefficient and problematic air cooled systems out there, just as there are water cooled ones.

Just it seems that I have heard of far more catastrophic problems with water cooled, particularly keel cooled systems, it seems that they work, until they donít and when they donít itís often a catastrophic problem like stray current has eaten the keel cooler and or water has gotten into the gas system, wrecking the whole system etc.

To me, it seem that if you want water cooled, using the fresh water tank is just logical, it seems that no matter what it is you cool with seawater, itís a maintenance issue, engine, air conditioning etc.
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Old 17-03-2019, 18:17   #17
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Re: keel cooled fridge and freezer on the hard

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Originally Posted by Richard Kollmann View Post
A penalty of 5% not 25% more energy over water cooling is not worth discussing.
That's really up to the purchaser I would think.

For us, it was a big deal - it's our biggest consumer of power by far. Even our autopilot draws less. Being able to reduce our consumption by even 5% (and it was much larger) without having to dig out and redo our entire 32 year old 1" of fridge insulation was an important consideration. When that 5% is coupled with all the other energy saving methods we have done (better storage and better energy production) the system as a whole is much more balanced than it ever was.

You seem to hate keel coolers. Ours is so much better than our old air cooled unit because its located in the engine room where it gets hot and doesn't cool off for a very long time, especially on the hard. This was very hard on the air cooled system.

Even if I have to buy a brand new keel cooled condenser for $1000 every 5 years that's only $200 a year for a freezer so cold it makes clear ice - in the tropics. We won't because we have the air cooled option but for those that don't have it the air cooled add-on is only $325.
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Old 17-03-2019, 20:26   #18
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Re: keel cooled fridge and freezer on the hard

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Originally Posted by a64pilot View Post
Iíd counter that by saying heat wise itís equal to one half a person, so if you have a guest, they add as much heat as two fridges to the boat, or put the evaporator in the lazarette and dump the heat in there.
A computer fan is cheap and readily available, as compared to holes in the boat and metal in salt water.
Iíve just heard of real, expensive problems with keel coolers, like stray current corrosion
If you are struggling to stay cool in a small boat even the equivalent of half a person of added heat might appear significant.

My fridge rebuild is to include a condensing unit in the lazarette so I'll agree with you on that point.

The keel cooling condenser may or may not add corrosion concerns depending on how it is implemented.

I notice where boat aircon is used it's mostly water cooled. This would suggest that if you want to move a lot of BTUs water cooling is superior in the marine environment for some reason.

I notice one of the condensing units Ozepete's employer markets has both air and water cooling in the same heat exchanger. It appears that it would be only a matter of switching from one to the other whilst running and watching the compressor current draw and the refrigerant output temperature to arrive at a valid comparison.
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Old 18-03-2019, 11:05   #19
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Re: keel cooled fridge and freezer on the hard

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That's really up to the purchaser I would think.

For us, it was a big deal - it's our biggest consumer of power by far. Even our autopilot draws less. Being able to reduce our consumption by even 5% (and it was much larger) without having to dig out and redo our entire 32 year old 1" of fridge insulation was an important consideration. When that 5% is coupled with all the other energy saving methods we have done (better storage and better energy production) the system as a whole is much more balanced than it ever was.

You seem to hate keel coolers. Ours is so much better than our old air cooled unit because its located in the engine room where it gets hot and doesn't cool off for a very long time, especially on the hard. This was very hard on the air cooled system.

Even if I have to buy a brand new keel cooled condenser for $1000 every 5 years that's only $200 a year for a freezer so cold it makes clear ice - in the tropics. We won't because we have the air cooled option but for those that don't have it the air cooled add-on is only $325.
I do not hate Keel cooler systems nor do I know of anyone who dislikes them. Even one of the followers of this forum who was forced to scrape his Frigoboat system do to compressor over heat problems seems to prefer the old keel cooler system over the other air/water cooled unit he has operated the last few years.

There are generally advantages and disadvantages with every ice box conversion refrigeration as well as all boats are not configured to accommodate refrigeration the same. If you are satisfied with the system you have that is all that is important.

If we were to post a thread asking for the worst ice box or hated conversion refrigeration, answers would be 25 like all available systems to one hate for a system even if they did not own it.
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Old 19-03-2019, 05:39   #20
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Re: keel cooled fridge and freezer on the hard

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If you are struggling to stay cool in a small boat even the equivalent of half a person of added heat might appear significant.



My fridge rebuild is to include a condensing unit in the lazarette so I'll agree with you on that point.



The keel cooling condenser may or may not add corrosion concerns depending on how it is implemented.



I notice where boat aircon is used it's mostly water cooled. This would suggest that if you want to move a lot of BTUs water cooling is superior in the marine environment for some reason.



I notice one of the condensing units Ozepete's employer markets has both air and water cooling in the same heat exchanger. It appears that it would be only a matter of switching from one to the other whilst running and watching the compressor current draw and the refrigerant output temperature to arrive at a valid comparison.


Couple of observations.
Marine air conditioning is water cooled due to packaging concerns, one little water exit is a whole lot easier to fit than say a 9 sq Ft air cooled condenser, think window unit for example. However anyone who has ever had a Marine air conditioning system, knows that 90% of the maintenance required on the system has to do with the water part.

I think Peteís dual water/air system uses the fresh water tank as a heat sink and does not therefore have holes in the boat and corrosive salt water in the system. However I donít have one, so I could be wrong.
I also believe Pete is the owner of the company.

I do dislike keel systems myself, cause I believe them to be unnecessary and are problematic, they donít deliver on their promise of greater efficiency, but do bring other problems or issue.
I have maintained complex systems for a living for decades.
I love KISS, but I changed it up, I say if itís simple, but works, itís not stupid.
There are many, many systems that are unnecessarily complex, often the marketing dept loves complex because they can claim all kinds of advantages and why their product is superior and better designed, cause itís so complex.
However the day eventually comes to where it has to be maintained, and that day is when simple systems, put together with readily available off the shelf parts are worth their weight in gold.
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Old 19-03-2019, 11:20   #21
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Re: keel cooled fridge and freezer on the hard

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Originally Posted by a64pilot View Post
Couple of observations.
Marine air conditioning is water cooled due to packaging concerns, one little water exit is a whole lot easier to fit than say a 9 sq Ft air cooled condenser, think window unit for example. However anyone who has ever had a Marine air conditioning system, knows that 90% of the maintenance required on the system has to do with the water part.

And a few coils around the compressor is a whole lot more compact, easier to place and install and does not than a large set of fins and tubes exposed to the outside environment. However, if you can achieve the amount of heat transfer with the thousands of BTU transferal required by an aircon the relatively small demands of a 12V fridge or freezer should be easy to achieve even in the tropics where water temperatures are relatively high.

I think Peteís dual water/air system uses the fresh water tank as a heat sink and does not therefore have holes in the boat and corrosive salt water in the system. However I donít have one, so I could be wrong.
I also believe Pete is the owner of the company.

The point of the Ozepete air/water cooled condenser reference was that a simple comparison of the relative efficiencies could be carried out with the flick of a switch.

I have been watching Ozepetes development of boat refrigeration on the internet for years and have come to the opinion that he puts a lot of thought into the design of his systems and is not afraid to innovate.


I do dislike keel systems myself, cause I believe them to be unnecessary and are problematic, they donít deliver on their promise of greater efficiency, but do bring other problems or issue.

I suspect many of the maintenance problems are caused by the use of unsuitable materials after all many of us have and trust bronze through hulls on our boats and the quality ones appear to have very long life spans.

I have maintained complex systems for a living for decades.
I love KISS, but I changed it up, I say if itís simple, but works, itís not stupid.
There are many, many systems that are unnecessarily complex, often the marketing dept loves complex because they can claim all kinds of advantages and why their product is superior and better designed, cause itís so complex.
However the day eventually comes to where it has to be maintained, and that day is when simple systems, put together with readily available off the shelf parts are worth their weight in gold.
There is nothing simpler than running refrigerant through a metal conduit exposed to cool water. No pumps, no electric fans, no wiring, no switching and no batteries to store electricity.
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