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Old 18-05-2017, 06:57   #1
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Keel Cooled Air Conditioning

Is there a reason why keel cooled air conditioning systems are not more popular? I see boats constantly struggling with keeping their water cooled Air conditioners clean of debris.

Heat Exchangers & Keel Coolers for heat dissipation - HVAC, Marine Engines, Generators, Gear Boxes
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Old 18-05-2017, 08:07   #2
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Re: Keel Cooled Air Conditioning

I can't see having a water cooled air conditioner at all. I went to a box store and got a 5000 btu window unit for under $100 and use it. I have an inverter that will handle it although I usually run my Honda for it to save the batteries. It fits in the hatch way and I'll set it on deck with an old piece of sail over it to direct the flow down into the cabin. When it goes bad it makes a nice anchor and I buy a new one.
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Old 18-05-2017, 08:25   #3
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Re: Keel Cooled Air Conditioning

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Originally Posted by zboss View Post
Is there a reason why keel cooled air conditioning systems are not more popular? I see boats constantly struggling with keeping their water cooled Air conditioners clean of debris.

Heat Exchangers & Keel Coolers for heat dissipation - HVAC, Marine Engines, Generators, Gear Boxes

Keel coolers work best when moving , they don't work well standing still .

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Old 18-05-2017, 08:43   #4
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Re: Keel Cooled Air Conditioning

A few issues:
- There are up front costs that need to be factored in. Particularly for sailing vessels, the keel has other design considerations. It can be done but there are trade offs. Much simpler and cheaper to punch a couple holes in the hull and install thru hulls.
- Your average new boat buyer doesn't think about system maintenance.
- All things being equal, keel coolers are not as efficient as fiberglass is not a great heat conductor.

I get your point but I would rather see an air cooled design. A window unit not so much as it become difficult to mount and keep the air vents sealed in rough weather but the portable units that use 4-5" diameter air hoses could be easily closed off for rough weather (most cruising boats don't use the air/con anyway when away from the dock) but would eliminate clogged thru hull issues.
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Old 18-05-2017, 09:01   #5
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Re: Keel Cooled Air Conditioning

I tried this with disastrous results. I tried to use a Honda 2 kW portable generator to run a 6000 BTU window unit but the starting current required was too great and the Honda went into convulsions, finally vibrating itself overboard. Have you experienced any problems when first starting your window type air conditioner either with the invertor or portable generator?
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Old 18-05-2017, 10:09   #6
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Re: Keel Cooled Air Conditioning

Absolutely, it would be possible. However, extremely unpractical.

The current keel-cooled refrigeration systems, such as Frigoboat, use a keel cooler that is about 5" x 10" (going from memory) to serve a Danfoss BD 35 or 50 compressor. These compressors are capable of, say 300 -600 btuh, depending on several variables, using this keel cooler.

A 12,000 btuh AC unit would then theoretically require a keel cooler of approximately 20-40 times larger (likely even more since efficiency decreases when scaling up). Perhaps something along the lines of 20" x 50" up to 36" x 58" or more. This would be a sizeable device hanging from your hull.

Due to the different duty cycle of an AC unit as opposed to refrigeration duty, the keel cooler would have to be increased even further as the ability to condense the hot gas refrigerant would deteriorate as the keel cooler warmed up, as well as the adjacent water warming due to the heat of rejection.

On the other hand, some large slow-moving motor vessels do utilize a keel cooler for engine operation. These are a different application, though appear to be beneficial for boats such as large trawlers for engine cooling.

Interesting idea though.
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Old 18-05-2017, 10:54   #7
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Re: Keel Cooled Air Conditioning

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I tried this with disastrous results. I tried to use a Honda 2 kW portable generator to run a 6000 BTU window unit but the starting current required was too great and the Honda went into convulsions, finally vibrating itself overboard. Have you experienced any problems when first starting your window type air conditioner either with the invertor or portable generator?
That's odd, I have a Yamaha 2400 and it runs the 15k btu unit on my RV or the 12k btu portable on the boat. Both are functionally the same as a window unit only larger (neither has a soft start function).

A little 6k btu unit shouldn't be a problem. Do the Honda's still have the eco mode (my Yamaha doesn't have this)? I've heard people say you have to turn that off if you want to start a heavy load with the Hondas.

As far as leaving it on the edge of the boat unsecured...well...
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Old 19-05-2017, 09:34   #8
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Re: Keel Cooled Air Conditioning

The GoneWithTheWynns folks have a nice description of an A/C setup.

Off Grid Solar Powered RV Air Conditioning - Is it Possible? - Gone With The Wynns

The big missing piece of information is the Soft Start product that they link to. They have a very nice site for information on RVing and have moved on a catamaran in the last year.

Bob
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Old 19-05-2017, 12:45   #9
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Re: Keel Cooled Air Conditioning

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Originally Posted by gliderbobo View Post
The GoneWithTheWynns folks have a nice description of an A/C setup.

Off Grid Solar Powered RV Air Conditioning - Is it Possible? - Gone With The Wynns

The big missing piece of information is the Soft Start product that they link to. They have a very nice site for information on RVing and have moved on a catamaran in the last year.

Bob
It's not so much a desire to run the A/C off grid but instead have a system that doesn't require pumping water into the boat for cooling, thus removing the maintenance issues so common with those types of installations.
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Old 19-05-2017, 13:22   #10
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Re: Keel Cooled Air Conditioning

Water cooled less capital investment, at least equal efficiency and as I understand it, more reliable. Cleaning the coolant strainer every few weeks is not much of a burden. Also water temperature does not matter (in the Keys the ocean can go to the mid 80's.
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Old 19-05-2017, 13:39   #11
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Re: Keel Cooled Air Conditioning

Workboats use keel coolers for their mains and generators all the time. Very efficient and with a heck of a lot more heat to dispose of than an a/c unit. But that underwater radiator adds a lot of drag, not something you would want to put on a sailboat. A steel hull has a lot of potential for using the skin as a radiator so that could work.
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Old 19-05-2017, 13:51   #12
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Re: Keel Cooled Air Conditioning

I don't know who is "struggling". keel cooling would work fine but is more complicated maybe? Ditto for engine keel cooling. a simple water pump and one hole in the hull is all that is needed without keel cooling...
Don't most keel coolers have a water circulating pump anyway? The engine does on a engine cooler, but for an ac unit... you'd need a pump right?
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Old 20-05-2017, 12:54   #13
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Re: Keel Cooled Air Conditioning

I'm still waiting for a keel battery. Flooded lead acid. Why not? Then no more problems with where to store those big and heavy batteries...and I can dump my diesel and go electric.
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Old 20-05-2017, 14:22   #14
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Re: Keel Cooled Air Conditioning

Heat extraction, which is what a/c really is, is totally efficiency degree dependent on difference between ambient air, and water temp.
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Old 20-05-2017, 14:25   #15
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Re: Keel Cooled Air Conditioning

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I tried this with disastrous results. I tried to use a Honda 2 kW portable generator to run a 6000 BTU window unit but the starting current required was too great and the Honda went into convulsions, finally vibrating itself overboard. Have you experienced any problems when first starting your window type air conditioner either with the invertor or portable generator?
So the honda committed suicide?
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