Reengineering an air conditioning unit to “marine” use. Purists should cover their e

[krush]

Since air is a better heat conductor than water and new marine units (24K BTU) are not what you wanted it probably works. Like bolting 3 outboards to the transom of a 36 foot inboard boat. I think there are other options but its your boat.

How do I conduct heat with air?

By the way, water is a much better absorber of heat than is air. The specific heat capacity of water is much larger than air- it both cools and heats better. Fifty degree water has a lot of heat energy in it, which is why water to air heat pumps work; fifty degree air has far less. None of this is a problem in FL where your aim is to get rid of heat, not keep it around.

50deg air and water both have the same amount of usable energy. The medium doesn't matter.

Water doesn't cool (or warm) "better" than air...it just takes less surface area to transfer the same amount of heat.

Edit: PS I think it's a great solution and implementation. Just watch corrosion on the coils and keep them clean.

[Boatsb]

Irish the idea is that water cooled systems are more efficient. Mostly because the temp of the water is more consistent and that the systems that use water move the heat out of the vessel more efficiently.


The central blower has been more comon in larger boats with ducting to the cabins. I just think the use of a 24k btu water cooled marine system would have been more effective but it seems like instalation was the issue.

[GJH]

I wish I'd taken a picture, but a clapped-out old 53MY came through here last year where the guy had jammed an apartment style window air conditioner into where one of his rear master SR port lights had been crudely cut out. Not a member of this forum, I suppose.

[Pascal]

Hi mario

Interesting project hope it works out in the long run. I had often wondered about using a roof top RV unit in the space under the helm...

Those living elsewhere don't realize that AC systems on most boats were not designed for south Florida... On the 53my/58yf you loose a lot by having one air handler low and the other one sEnding half its output to the galley were it does no good

On later boats Hatteras placed air handlers on the FB which helps but I wOnder how a compact unit would work as the water pump will have a hard time sending water 18' high.

What I did last year on my 53 is add a 5th system (10k btu) dedicated to the galley. This allows the full output of the forward salon AC to be used for salon making it nice and cool even in summer

The galley is now nice and cool as well and cold air spills forward in the how sr as well as act in companionway supplementing the stateroom ACs

In the ER in only took adding a shelf above the existing compressors.

Best money i spent on the boat!

[Angela]

From what I understand (and Mario, correct me if I misunderstood), the reason he went in this direction rather with a traditional marine unit was not an installation issue - sure, he could have just replaced what was in there that failed, right back in the same hole. It is my understanding that he wanted something that when it craps out, he can toss it and replace it for less than an AC tech's service call. So, when his AC goes bad next, the fix is less than $500, not $5,000 for a new marine system. Plus he has no seawater running to it, no water coils to clean, it's self-contained, etc. - just less of a maintenance item, and apparently it works much better than the marine unit he had. The rest - well it's the same stuff that I see in my marine evap/blower unit - copper, aluminum, electic fan motor. I wouldn't be the least bit surprised if his compressor is made by the same folks that make the ones for the marine units. This is just AC without the "boat" price tag. We all know how many digits the word "marine" or "boat" adds to the price of anything, even a PVC or nylon plumbing fitting.

I think Mario is starting to look at AC the way we have begun to see it - it's a disposable commodity on our boats. We want to give Mario's plan a shot for our pilothouse system which is currently broken. I don't need a unit nearly that big just to do my pilothouse, so the pig I'll have to wrestle through the cabinet doors will be much smaller.

[Boatsb]

Or duct the bridge ac and kill 2 birds

[Genesis]

I like it a lot.

Remember folks that these "window" AC units are used around the coast, where they get plenty of salt spray ingestion. Yeah, they eventually crap out, but they're cheap to replace. If you get five years out of this thing you're way, way ahead of the game.

[yachtsmanbill]

I never understood why bubba had to make it such a complicated system either... Especially these days with way higher EERs and quiet rotary compressors you barely here them run. Hell, even a member here has central heat (forced air) on his 58 TC... why not ad air to that?? ws



Maybe not the prettiest install but form does follow function...

[REBrueckner]

Mario....Interesting story and great photos....thanks.

I don't have an overall understanding yet of just how your efficiency improved...so
A few questions:

(1) "Also it is poorly designed in that the a/c cabinet is located at knee level and blows cold air up to the ceiling instead of from the ceiling down which is more efficient use of cold A/C."

Can you explain what this means??

(2) "..the unit that best fit our criteria for this redesign experiment was a LG 24,800btu Mod: LW2510ER window unit..."

What is the SEER for this unit? Any idea how it compared with the "marine" units you have? (see below) Usually the SEER is the single biggest element in determing operating costs.

(3) "...As an example, with the master room, guest room, forward salon and aft salon A/Cs operating I was pushing close to 50 amps. Now I’m drawing about 28 amps total!.."

This the new unit operating alone, at 24,800 BTU's, replacing both older marine units which totalled (14 +16) 30K BTU's???? So the new smaller unit does better than BOTH the old ones operating together!!!!???
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Calculation of old and new SEER; SEER = (BTU / h) ÷ W

If the old units were 30K BTU and used 50 amps at 120 volts, that's a SEER of ,

30,000/50 x 120 of 5!!!!....so any idea that these old marine units are efficient is a dream!!

New unit: 24,800/ 28 x 120 is 7.4....still pretty poor efficiency...???? but 50% better than the old units...

"I was just checking out window units at Home Depot...they are still all about 10.8 efficiency ...(but that might be EER, instead of SEER, where SEER = EER ÷ 0.9....
[A 24,800 BTU ac with 10.8 SEER would draw about 19 amps.]
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via Angela:
So, when his AC goes bad next, the fix is less than $500, not $5,000 for a new marine system.."

says it all!!!!! about first cost

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My home AC unit (220 volts, 3 tons = about 36K BTU) has a SEER of about 13...Apparently you can get them (for big additional $) up to a SEER of as high as 17!!!!! Anybody know why these bigger home units are SO much more efficient than room type??...

[MikeP]

"Water doesn't cool (or warm) "better" than air...it just takes less surface area to transfer the same amount of heat."

Cyanide and Aspirin can both kill you but it takes a lot more aspirin to do it. So I'd call cyanide a "better" poison, just like I'd call water "better" than air...