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Old 07-16-2016, 03:39 PM   #1
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Mini Split A/C Units

Surely this has been discussed but I can't find it.

I am thinking of heating/cooling the boat with one or (probably) two mini split units, compressor/condensor units mounted up top.

Advantages: MUCH cheaper and easier to install, maintain, repair. No thru-hulls, filters, etc. Very efficient (>20 SEER). Soft start and inverter compressor.

Disadvantages: exposure to salt spray. Noisier? Weight up top. Unattractive, unless I can hide them.

Is anybody using these things? Thoughts? No doubt I am overlooking much.

(Boat will be a power cat.)
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Old 07-16-2016, 04:40 PM   #2
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We just installed a 3zone in a city house, cheap?? Not even my wholesale pricing on the equipment can justify installing in a boat. Salt would really shorten the life of mini splits also Marine a/C units are made with heat exchangers that last quite long with salt water flowing through them.
Cost is really not cheaper,
Where to put the outdoor unit? Bolt to deck or roof? Again even on fresh water the unit would not last long
This basically what water to air units look like all in one ( self contained). Or split into 2.
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Old 07-16-2016, 05:17 PM   #3
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Lol, this is one of my favs. in a boat, the orange loop should be sea water in or out or circulating to and through 1 or more units. Just posting this just to lessen the mystery to non hvac types
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Old 07-17-2016, 06:52 AM   #4
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On many Euro boats the external units are simply bolted to the stern rail.

If sea spray bothered them , I am sure they would use a different location.

On a pleasure boat an outside mount and paint to match the area should be fine.

One huge advantage is HEAT production is 300% to 500% better than a heat wire , when it gets too cool for reverse cycle to function .

For a winter liveaboard that pays for electric , this could be critical.
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Old 07-17-2016, 11:03 AM   #5
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The op question got doing a bit more investigation Domestic offers water cooled condensers and remote pipe in evaporators. ( Larger boats). Essentially the same as mini splits but without the air cooled outdoor unit. http://www.dometic.com/USA/MS-11346-Marine/PG-12458-Air-Conditioning/PG-12490-Split-Gas-R417A-Air-Conditioning.

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Old 07-18-2016, 09:32 AM   #6
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The Dometic units seem to be the usual, the reverse cycle heat is removed from the sea water , which at 40F stops working.

It would stop anyway when the temp is cold enough to freeze the sea water.

The downside of most air reverse cycle setups is frost on the fins that then ice up , not allowing the system to function.

I have no idea how the mini splits do not fail in cold weather , but Germany , Switzerland , Norway all use them.
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Old 07-18-2016, 09:51 AM   #7
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Quote:
Originally Posted by FF View Post
The Dometic units seem to be the usual, the reverse cycle heat is removed from the sea water , which at 40F stops working.

It would stop anyway when the temp is cold enough to freeze the sea water.

The downside of most air reverse cycle setups is frost on the fins that then ice up , not allowing the system to function.

I have no idea how the mini splits do not fail in cold weather , but Germany , Switzerland , Norway all use them.
I will want some heating, but expect to stay south of <40 degrees F. I appreciate hearing about any and all concerns. My principal reasons for considering the mini splits with air-cooled compressors/condensors are initial cost, ease of maintenance and repair, and elimination of raw water cooling (fewer thru-hulls and associated pumps, filters and piping, and no raw water pump running when I'm not on the boat but need de-humidifying).
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Old 07-18-2016, 10:00 AM   #8
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Quote:
Originally Posted by FF View Post
The Dometic units seem to be the usual, the reverse cycle heat is removed from the sea water , which at 40F stops working.

It would stop anyway when the temp is cold enough to freeze the sea water.

The downside of most air reverse cycle setups is frost on the fins that then ice up , not allowing the system to function.

I have no idea how the mini splits do not fail in cold weather , but Germany , Switzerland , Norway all use them.
Heat pumps (rev cycle) in general are highly efficient to 17F Cold water is a prob if you only are concerned with marine applications. Larger boat systems could use modulating flow and condensing pressure controls of the refrigerant.

there are many other types that use use water even ice, Geothermal is one there are also Ice bank units. example.. a skating rink.

air source units (like mini spilts) get by the cold air problem with inverter tech. slowing down the rpm

if you want units on the rail or deck... it's your boat!
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Old 01-13-2017, 10:50 PM   #9
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I'm a fan of mini splits. Installed one in our bedroom so as not to run the central unit when not needed. IMHO though, Not ready for the water.

Be aware that units above 12000 btu or so require 220 power. Two, the inside unit (on our Mitsubishi, and I believe others) must be level. If it's not, condensate fails to enter the small drain tube, and spills indoors. Not promising on a rocking boat...

Next, the outdoor unit is noisy. So in addition to ugly on your deck, it's making its use quite untenable. Lastly, in a home, upper wall space for the 36" indoor air handler is plentiful. On a boat it's not, and using a ceiling mount version just brings you into installation issues.
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Old 01-14-2017, 03:08 AM   #10
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CottonTop, I realize this is an old thread now, but I thought I'd chime in (BTW - have you made a decision yet?).

I have seen mini-splits used extensively on boats (up to about 100ft) all over the middle east, asia and southeast asia - tugs, ferries, passenger boats, personal cruisers (dhows), etc. Yes they will eventually rust out but then you just toss the condenser in the trash and install a new one. Ratings are commonly SEER 22+ and many have HEPA filters built in. You have to get around the ugliness factor but many times I've seen stainless or aluminum expanded metal screens around them. Also, the evaporator (interior unit) can be installed in a ducted installation, commonly serving 2 or 3 rooms.

My 2000sf villa here has 7 units totaling 13+ tons. I certainly prefer central aircon like back in the States because of lower maintenance of a single unit, but I have to admit that these units are rather dependable considering that I am about 2 miles from the ocean, the humidity here is normally in the 45%-85% range, and the temperature that these units are working in (sitting in the sun on a concrete deck) is normally 150-160 degrees F (measured!).

A true marine unit is certainly a better solution for a boat, but if the mini-split serves your needs then go for it.
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