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Old 14-04-2009, 20:27   #1
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CruisAir System Freezing Up on Heat Cycle

I have a 2009 Beneteau with two CruisAir air conditioning/heating systems. My problem is they are freezing up in the heat cycle. The sea water temperature is around 55 degrees. I cleaned the intake strainer. Both units definitely have water flowing through them and out the through hull. They will not give me more than 60 degrees Fahrenheit. The salon unit is getting a thick layer of ice on the compressor unit. Air is flowing out of the vents at full speed. Help!

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Old 15-04-2009, 05:33   #2
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If your particular unit doesn’t have an automatic Defrost Cycle, you’ll have to manually set it to Air-Conditioning mode, until the evaporator defrosts.

Or ask CruiseAir.

Dometic Corporation, Environmental Division
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Old 17-04-2009, 02:45   #3
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Just a little discussion on how the system works during the heat mode. When operating as an air conditioner, the system is pretty straightforward: The heat generated during compression is transfered to the sea water in the condenser, and heat is absorbed by the refrigerant from the air passing through the air handler.

During the heat mode, however the reversing valve turns everything around: The heat generated during compression is transfered to the air in the air handler, warming the compartment. This heat transfer also condenses the refrigerant, so what used to be the evaporator during air conditioning, is now the condenser. The condensed refrigerant is immediately expanded in the capillary tube at the air handler, and returns to the "condensing unit" in the engine room as a rapidly cooling mixture of liquid and gas (although the unit is called a condensing unit, no condensing occurs there when in the heat mode). In order for the system to absorb heat from the sea water in the coiled heat exchanger above the compressor, the refrigerant must be colder than the sea water. And, since the refrigerant travels on the outside of the coaxial sea water tube, it is also absorbing heat from the air surrounding it.

In your case, the refrigerant is not only colder than the 55 degree sea water, but colder than 32 degrees F, hence the formation of ice. Generally, the only variable available to increase the heating in the air handler (if the fins in the air handler are free of dust) is changing the amount of refrigerant in the system. If you add refrigerant to the system, you increase the pressure at the compressor discharge (the head pressure) and therefore increase the temperature at which it condenses in the air handler.

Since your system is both an air conditioner and a heat pump, and since you do not want to have to change the amount of refrigerant in the system each time you shift from one to the other, it is best to use the charts provided by the manufacurer to put the right amount of refrigerant into the unit. Although there are charts for charging the system in both the heat mode and the cooling mode, the most accurate one to use is the cooling mode chart with the unit operating as an air conditioner and using the suction pressure.

I had no idea, when I started this reply, that it would run this long, but I hope it was helpful.
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Old 17-04-2009, 04:31   #4
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What Mayball is saying is have your refrigerent level checked by an A/C guy.
Steve
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Old 17-04-2009, 08:57   #5
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Moe,
I tried to email you yesterday to help out, but didn't get a response, so I figured I'd make an account on here to see if I can be of assistance. It would be better to know exactly what model units you have to see exactly what's going on. I don't think Beneteau goes much bigger than a 16,000 BTU unit so I can give you some general information.

In the heat cycle it's normal for the units to frost periodically, but not completely ice up, especially when the water is only 55 degrees. It could be a charge issue, but I kind of doubt it being that it's two units doing the same thing. Beneteau uses self contained units, so they shouldn't have to charge them on install. Those units have a specifice weigh in charge from the factory. Checking the charge, or putting gauges on the unit should be a last resort.

I would have to say that the units are not getting enough water flow. Checking to see if water is discharging overboard, only means that they're getting water, but not how much. A general rule of thumb we use on a 16,000 unit, is simple. Take the outlet water hose off the each unit, and place a 5 gallon bucket there. If you can fill up that 5 gallon bucket, then the unit should be getting enough water flow, and then you can move on to checking the charge. We recommend about 500 gallons per hour, per ton of BTU's. In your case on a 16, you should probably only need about 300, making that 5 gallons a minute.

If you have any questions, please email me at jacob.prince@dometicusa.com

Tx.
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Old 17-04-2009, 09:14   #6
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Sorry, I forgot to say that it should fill up that bucket w/in a minute.
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Old 20-04-2009, 15:34   #7
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Found the problem with Air Conditioner/Heaters freezing up!

Hello Fellow Sailors:

I isolated the problem with the help of an air conditioning repair person supplied by my boat dealer, Winters Sailing. Both of my units, on my new Beneteau, had globs of Silicone jammed in the "Condensing Coil". The repair person tried his best to unclog the units but to no avail. I hooked up an air compressor to a 1/8" stiff poly propeline line about 6 foot long. I slowly and carefully fed it into the condensing coil through the water intake line until I hit the clog. I then gave it about 100 PSI and kept moving it in and out until the silicone broke up and it went through the system. I suspect the silicone was used on the clear rubber intake hose somewhere between the intake and the units.

Heat Finally!

Thanks to everyone who helped me.

Big Moe
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Old 06-05-2015, 12:26   #8
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Re: CruisAir System Freezing Up on Heat Cycle

Thanks for these posts. I'm dealing with similar issue.

I have three Cruisair units fed by one Dometic pump. While in Heat mode the two units I had on iced up. I turned everything off and left it to defrost for a day.

Lake Michigan water temp was only 40 degrees, so maybe that caused things to freeze. But also, my Dometic pump intake filter was clogged with seaweed, so maybe that caused the condenser to ice up?

Lastly, NauticalAir has suggested an electric heat add-on for my STQ16 unit. Which I'll probably do.

So my questions is what caused the freezing 1) water temp 2) cloged intake filter? 3) combination?

Thanks - pics attached in pdf.

Joe Rickard, Chicago Montrose Harbor
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File Type: pdf CruisAirDometic_Frozen.pdf (197.1 KB, 72 views)
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Old 07-05-2015, 07:04   #9
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Re: CruisAir System Freezing Up on Heat Cycle

3 units on 1 pump doesn't sound right but then I don't know what size pump you have. However 40d water temperature is low and probably the large part of the problem. A heat pump extracts heat from the sea water to get things toasty. Along with that you got to have enough flow to keep things from freezing up once that heat is removed so the clogged filter didn't help either. Low flow and Low temps = ice cubes on the units.


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Lagoon 410 S2E
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