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Old 01-08-2014, 08:32 PM   #1
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Help me Im Freezing, Marine Air System

I have a 1981 Litton Trawler. Brand new to boating. Only had the boat two months and been a great rollercoaster but I DONT DO COLD. I have a Marine Air System Model C16H. I noticed a few days ago that the overboard discharge was getting weaker and not as noisy. It finally stopped flowing ang as expected the heat did too. I troubleshot the pick up pump to be good, no known blockage in the line. the problem is that the coils are freezing, not allowing water to flow thus not making heat?? I thawed the unit with a space heater and ran it with some success. I was able to achieve a 90deg air output while supplying 90 deg heat directly accross the coils....defeats the purpose. The AC pump is working but still have not got it to discharge overboard the way it used to. If I take the space heater off the unit it drops almost instantly and just freezes solid? The outdoor temp is 17-30 and the water is about 50. Please help I see the $$$ flying away by running space heaters.
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Old 01-08-2014, 08:37 PM   #2
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Not sure if this will help, but I circulated de-scaler through my coils in the fall. Used the little pump from an old shower sump, my starting battery booster box, and used a 5-gallon bucket to circulate it through the coils only.

Though, it sounds to me like you have a blockage of some kind. If thats the case, my de-scaler rig would be useless. Sorry.
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Old 01-08-2014, 08:48 PM   #3
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It sounds like you have reverse cycle units. They produce heat by taking the heat from the 50 degree water. When it exits your above waterline thru hull fitting it is considerably colder than 50 degrees. At 17 to 22 degrees outside temperature, it is probably freezing at the outlet. Can you place a heater close to where the thru hull fitting inside the boat is? That may clear the log jam. Running the pump with no circulation could possibly damage the pump.
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Old 01-08-2014, 08:52 PM   #4
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Possibly a reversing valve stuck? Find it and give a tap with a wrench or hammer. Don't beat it just tap.
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Old 01-08-2014, 08:58 PM   #5
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Sorry just re read your post and saw the flow problem and not the lack of heat. My bad
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Old 01-08-2014, 09:04 PM   #6
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Just had a thought of something to try. You may want to go to a hardware store and get some heat tape for pipes. Wrap it around the whole exit piping. That should help more than a heater.
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Old 01-08-2014, 09:21 PM   #7
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I do not think it is the AC unit, as the pump is moving water. With a heater on the coils you are getting heat. The water output is not flowing, so I would start at the thru-hull, check the strainer, and then disconnect the hose to the AC unit and check the flow of water reaching it. If that all shows good, can you connect a hose from the AC water pump, direct to the output hose of the AC unit to bypass the AC unit and have water flow through the discharge.
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Old 01-09-2014, 06:50 AM   #8
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My research shows that home heat pumps just reverse back to the air conditioning mode for a tiny bit "auto defrost" the coils...

You can try this and it also helps to keep your reversing valve from sticking.

Also I think there may be another issue that is beyond the "normal frosting up". You might have a bit of an air flow problem...make sure your space has plenty of air flow and the fins are all clean, if you aren't in the higher fan modes, try those.

Finally....while more rare...and I'm not positive but you might have a refrigerant charge issue...if all else fails...call yhe manufacturer to see if there's anything else you can do and then get the exact specs for your setup and situation if and when you do get a AC guy out there.
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Old 01-09-2014, 06:54 AM   #9
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Thanks for all the info. While the space heater is blowing directly accross the coils everything works fine. Once I remove the heater it slowly starts to loose water flow as well as no longer make heat. My hunch is that the blockage is ice building up inside the coils? Does the unit have a defrost mode? Or is it just too darn cold outside? The unit is under my aft deck just forward of the swim step so it does get pretty fold back there.
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Old 01-09-2014, 06:59 AM   #10
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It shouldn't freeze up with water temp at 50 and air temps at 30...maybe air temps in the teens but even then it takes a wee bit to freeze moving water. Any others right around you using reverse cycle and having issues?

Call Marine Air today...they have good tech support from what I have been told.
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Old 01-09-2014, 07:00 AM   #11
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Still not a bad Maintenance tip. Thanks. I also read along the way that you can put bromine tablets in our sea strainer to reduce growth.
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Old 01-09-2014, 07:04 AM   #12
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No one else seems to be having issues which is why im leaning toward some kind of defrost issue. I agree that water flowing at 8.5 gpm should not be able to freeze.I plan to call Marine Air when they open. If they cant help I may do the heat tape idea and possibly get a water heater blanket.
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Old 01-09-2014, 07:25 AM   #13
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Look up what a TX (expansion valve) is and learn how to adjust it .

Sounds like yours was monkeyed with.
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Old 01-09-2014, 07:53 AM   #14
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Gee, I'd be looking at the raw water flow and associated blockaged. You have already identified the raw water flow as being reduced even when you first start the system, and presumably before it has any chance to freeze up. I'll bet you have scale and other accumulated congestion in the raw water loop causing reduced flow. With reduced flow, the water that does get through is trying to provide all the heat that the system wants, and it's dropping the water temp too much. As the water starts to freeze, the problem just accelerates.

I'd get some barnacle buster and give your raw water loop a real good flush. I'll bet that fixes the problem.
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Old 01-09-2014, 08:02 AM   #15
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If it even has one ... probably not. Few small direct expansion marine air conditioning units use a TXV. Most are capillary tube units.
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Old 01-09-2014, 08:17 AM   #16
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Whats the raw water overboard temp?
Anyone know what the normal raw water temp delta is on a heat pump in heat mode. If its 20 - 25 F it could be freezing. I have the same unit and have run it at 40F water temps with no problem but it was in thwe 30s outside. Too bad mines winterized. I would run some test data.
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Old 01-09-2014, 08:18 AM   #17
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Greetings,
Mr. 81. No-one else seems to have suggested this but could your coolant (Freon) charge be low? Seems to be about the time you should call in a HVAC tech.
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Old 01-09-2014, 11:02 AM   #18
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Ok so i thawed out the coils with a space heater then I created a closed loop and started with a 5 gallon bucket full of descaler solution and the bucket had 70 deg water in it. I primed the pump and had awesome flow and minimal "junk" came out. I let it run in the start mode for about 30 minutes and got it clean. Then I flipped it into heat mode and it was working great until..... I obviously drew all the heat out of the bucket and again lost flow to what I'm thinking is freezing in the coil? So does the reversing valve kick in anti natively to defrost the system and is that what is bad? Guess I'll thaw it back out and see if I can go into cool mode.
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Old 01-09-2014, 11:29 AM   #19
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Did I miss it or did you try the pump only - hooking up a line to discharge overboard while pulling from the normal pickup point. It sounds to me the pump doesn't like cold water and resultant shrinkage around necessary close tolerance requirement places that have been worn down over the years.

My reverse cycle units worked while anchored in Glacier Bay with water temps around 42F.
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Old 01-09-2014, 11:51 AM   #20
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Yes. If I run the pump only and not the condenser then I have great flow for as long as I have it running. Once I flip it into heat mode and the condenser kicks on its only a matter of about 30 minutes before I no longer have flow. I talked with Marine Air Directly and they are stumped as well. He still swears there is a blockage in the line.
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