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Can Self-contained Air Conditioner Install Under Waterline?

Discussion in 'HVAC' started by etang789, Jun 4, 2020.

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  1. etang789

    etang789 Member

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    Wondering is it ok to install self-contained Air Conditioner under waterline? Meaning the AC unit will be below or same level the seawater pump.

    I currently have Split Gas type AC through out the Bertram 42 but the one in the master bedroom isn't working anymore, thinking to change to self-contained AC seems more efficient which would be mounted under the bed.
    Last edited: Jun 5, 2020
  2. Capt Ralph

    Capt Ralph Senior Member

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    I'm not sure the condensing tubes are rated for below the water line installations.
    Electrolysis or galvanic erosion may eat up the solder connects.
    Between compressor cycles, water will not drain from or siphon out of the condensing tubes. This could lead to advanced fouling in these tubes.

    I would recommend not.
  3. Capt J

    Capt J Senior Member

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    I believe you can, but not certain. But, what I do know is on the Sunseekers that I manage the sea water discharge is below the water line and the units stay completely full of water whether they're running or not. One unit is under the water line on one of the yachts.
  4. etang789

    etang789 Member

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    Yes this is my guess as well. Is there a way to route the water hoses or add some sort of accessories to fix this? Or simply pay more and buy split gas type...
  5. cleanslate

    cleanslate Senior Member

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    Check with the various manufacturers . Call them direct and get a tech / designer on the phone. See what they say.
    I would think you could put a loop in one or both lines , above the water line to help drain the line a little bit , helping with the electrolysis issue.
    And you should have a loop in the lines , above the water line in the discharge line and keep the through hull above the water line for safty . Not sure of the standard height above the waterline it should be.
    Perhaps you can elevate the unit just enough so it will drain overboard.
  6. Pascal

    Pascal Senior Member

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    Condensate is easy to handle with a small sump

    I m not sure i are the issue with having sea water in the tubes at all time. In some places, it s not unusual for air cons to run most of the time. Also boats with multiple condensing units or chillers and single pump, chances are you re always going to have at least once unit running with the pump sending water to all of them

    are you guys saying that galvanic corrosion is worst with sitting water vs flowing ? I don’t see how that would make a difference

    as to the tubes not being able to handle the pressure from being under the water line... maybe. But I doubt it will be low enough for it to be an issue.

    Is it ideal? Maybe not but I doubt it will be a problem. A bigger issue is don you want a compressor under your bed? I don’t.
  7. Capt Ralph

    Capt Ralph Senior Member

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    What has failed on the split system?
    I made a mistake in one of my forward cabins with a all-in-one unit under the bed, replacing a split system.
    It sux.
  8. Capt Ralph

    Capt Ralph Senior Member

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    Not sure. Just it may be an issue and needs to be considered.
    Yep..
  9. BRyachts

    BRyachts Member

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    I don't see what the issue is. Static water pressure is only 1/2 psi/ft. Any leak that may form from corrosion/erosion will show up much earlier when the system is pressurized from the pump, than failure/flooding from static non-use.
    If still concerned you could always add vented loops above the water line to the in/out feeds.
    As with any proper operation, if leaving the vessel for extended period you should close the sea inlet.
  10. mapism

    mapism Senior Member

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    By split gas type, do you mean centralized unit(s) with gas compressors for cooling fresh water, which in turn circulates throughout the boat into several fan coils to cool the interiors?
    If so, that is actually a system in many ways superior to self-contained units, and personally I would rather swap self contained for split units, than the other way round.
    BTW, even if self contained units are now much more silent than in the past, you might regret fitting one right under your bed...

    Anyhow, back to your question, I can't be positive about self-contained units, but pretty sure it's not a problem to fit split units under the w/line.
    As CaptJ told, that's the typical installation in most European boats, including the submerged discharge.

    That said, along the lines of better safe than sorry, I made one small modification to the very same system on my own boat, with a valve that allows me to select whether to feed the compressor unit with seawater (when it's running normally) or with freshwater (for flushing).
    This way, whenever I know that I'm not using the AC for some time, I can leave nothing but fresh water in my remote units (fan coils are already working with circulating fresh water anyway).
    You might consider doing the same also with a self-contained unit, I suppose.
    After all, when you think about it, whether the unit is above or below the w/line is irrelevant while it is being used.
    And by being able to easily flush it with fresh water, you aren't risking anything when not used, either.
    Feel free to ask for more details, if this wasn't clear enough.
  11. Pascal

    Pascal Senior Member

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    Split gas AC is just that. Refrigerant gas circulate between the con sensors located in ER and the evaporator / Air handlers installed in living spaces. Benefits are no compressor noise in living spaces and no long raw water lines thruout the boat or fewer hull penetration.

    completely different from chiller water systems

    split gas are typically found on mid size boats (45/70) although nowadays chillers are found on increasingly smaller boats

    personally I would never want raw water discharge underwater. Not only it adds an extra hull penetration but it also makes it impossible to eye ball water flow which is Often the first indication of air con trouble
  12. BRyachts

    BRyachts Member

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    Agreed there. I also like to see the discharge brought back to the same general location as the inlet. This makes it very easy to separate the piping (usually hoses) from the thru hulls for easy recirculation of cleaning media, (muriatic, Barnacle Buster etc).
  13. mapism

    mapism Senior Member

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    Interesting.
    All European boats I can think of are either equipped with self contained units, usually up to 40 feet or so, or chiller(s)+fan coils above that.

    Anyway, u/w discharge is always through skin fittings along the boat sides, just below the w/l.
    On top of granting a very silent discharge, which is the main purpose, that also makes the water flow as easy to check as if it were above the w/l.
  14. Capt J

    Capt J Senior Member

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    Larger, Sunseeker uses Self Contained up to 70' that I know of 66' Manhattan etc, Princess uses split gas on the 55' and 62'. The underwater discharge isn't as easy to check, when it's above the water you can see the exact amount of flow, when it's 2-4" under the water it's really hard to see.
    Last edited: Jun 5, 2020
  15. mapism

    mapism Senior Member

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    Which models? I'm not very familiar with Predators, but I've seen chillers even in their smaller Manhattans, already back in the days of the old 44, and including the latest 52. Up to the 80 Yacht, obviously with multiple chiller units.
    But I'm aware that their boats are specced differently from the Med compared to northern Europe, where some boats are also equipped with diesel heating, which is unheard of in the Med.
    So, if you tell me that they have self contained units in the US, I take your word for it.
    Maybe it also has to see with the equipment available for 120V/60hz, I'm not sure.
    But I'm a bit surprised to hear of such choice, which can only be cost driven.
    Acceptable in the PNW maybe, but FL certainly ain't cooler than the Med.

    Ref. how accurately you can check the water flow of submerged discharge, well, I guess it depends on which marinas you are used to.
    In mine, if I drop a coin overboard, I can see it on the the seabed 15 to 20 feet under, possibly near a sea star.
    I assure you that I can tell if the discharge flow is fine even while walking along the dock...! :)
    Which means from quite far away, mind: I'm talking of a dock where the boat is moored stern to, not alongside.

    PS: aside from self-contained vs. separate chillers, did you ever come across any European boat in the US equipped with the split gas system that we were debating? Just curious.
    Last edited: Jun 5, 2020
  16. Capt J

    Capt J Senior Member

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    The new(ish) F 55' and F 62' Princesses have a split gas system, I have managed 1 and 2 (62's) of those. A new 52' Manhattan and 66' Manhattan I've been managing both have self contained units and the "tropical a/c option" they do a good job of cooling. So does a 2007 62' Predator I manage. The 66' Manhattan does have 9 self contained units (including the crew). I don't like chillers on boats under 75', they need constant babysitting as they're always losing a little chilled water somewhere, they use a lot of electricity when the chiller cycles on, and it cycles a lot if the boat is just being kept at the marina in 78F in summer time when it's 90F outside. The chiller systems just seem to always need more watching over. It's been a long while since I've dealt with a new Azimut but believe they too use self contained units at 66' and under but may be mistaken. I like the self contained units, the only problem is I don't see more than 10 years out of them, but aside from having the sea water lines cleaned and air filters cleaned, they're maintenance free their entire life......
  17. Pascal

    Pascal Senior Member

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    I love chillers. One the best upgrade I did to my ole 53 was installing chillers 3 years ago. Never had an issue with them. I have two chillers and 5 air handlers. I can run the whole boat on one in mild / cloudy weather or at night...

    On the 2009 84 footer I run we have two chillers as well. Same thing in cloudy weather I run just one. Been four years now and they re trouble free. No maintenance. Well except for cruisair crappy quality that forced us to replace 4 air handler and one chiller so far...They have frequency drive so they ramp up smoothly. The smaller chillers on my boat don’t have frequency drive but the start up surge is minimal.

    i would never go back to splits or self contained. The total redundancy offers such piece of mind.
  18. mapism

    mapism Senior Member

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    Well, my experience with chillers is just about the opposite compared to to what CJ reports, and much closer if not identical to Pascal's.
    My boat has a double chillers unit in the stern lazarette, which I can barely hear cycling if I'm sitting in the cockpit in total silence, and even then I must pay attention to it.
    Anywhere onboard, it's impossible to hear the compressors, also when both are running.
    The 7 air handlers are also very quiet, particularly at low speed, as they always run after reaching the desired temp.
    I think it wouldn't take long for me to throw a self-containing unit overboard, should I have one under my bed.
    And all my boating mates, bar none, could confirm the same experience, with several different boats ranging from 40 to 80+ feet.
    Besides, the system I'm talking about is 16 years old, with all its original parts, and zero leaks anywhere.
    Built by Condaria, which used to be market leader in Europe, till they were bought by Dometic some years ago.
    But if their lineup of chillers, which used to go up to 400+kW/1.5 million BTU (and it's not a typo!) was maintained and is still equally reliable nowadays, I honestly don't know.

    Anyway, that's all rather irrelevant, for the OP.
    If his system still works fine except in the master cabin, where it can't be fixed for whatever reason, a self contained unit is certainly the more cost effective option - as long as he can live with the noise...
    Last edited: Jun 5, 2020
  19. Capt J

    Capt J Senior Member

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    I've dealt with chillers on many different brands of yacht.......there were always coolant leaks somewhere....always.....and there are always hoses sweating somewhere...........I've had to replace the insulation on the hoses on many of them, even if just small areas because they were sweating, then always have to add water to them monthly or perhaps sooner......most of them I've seen, run rubber hose throughout the boat, then use cheap breeze hose clamps that either lose tension or corrode, put insulation that's only 1/2" so it's easier to route through the boat and should have 1" and it ends up condensating all over after a few years. The other thing is you can only do heat OR air conditioning for the entire boat. Well, what happens if it's 70F outside and some people want their staterooms 78F and the others 65F. For 75' and over they're the way to go, but on the smaller boats I don't like them. Develop a coolant leak or circulation pump go bad, you lose all A/C throughout the boat, regardless of how many chillers you have. With individual units it's only the sea water pump you have to worry about. With chillers both the sea water side and coolant side can cause a loss of total A/C or Heat and you only have HEAT OR A/C not both. I've had failures on both the coolant side and the sea water side with chilled water systems.

    But we've all gone down a rabbit hole here. To the OP, just call Dometic and ask them. but I see no reason why a self contained cannot be mounted below the water line.
  20. mapism

    mapism Senior Member

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    Blimey CJ, you must ask your clients to choose better boats and/or to maintain them better, methink! :D