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Old 07-27-2016, 06:54 AM   #1
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how cool does your old cruisair split system get?

Mine may be low on refrigerant. I have a sight glass and can see some bubbles. I last added refrigerant about 5 years ago myself. Mine is a 16K BTU water cooled marine unit. Has split, so large evap in main cabin, and small evaporator in lower cabin.


I have been using during this heat wave. When it is 100 outside, inside temp I can get to mid 80's with a vent discharge air temp of 65*F

When the outside cools down into the upper 80's, the vent discharge temp can drop to 53*F. Boat will get to the 70's.

If the sun goes down, boat cools off well. But with the sun on full bore heat, boat does not cool well. My Bimini top is off the boat. Boat is a 37 foot Egg Harbor sedan cruiser with upper and lower cabin.

Yesterday, unit was drawing 13.3 amps.
Later, when sun went down, amp usage went to 12.5 amps.
I figure that is due to higher system pressure when it is real hot, causing the compressor to draw more amps.
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Old 07-27-2016, 07:55 AM   #2
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Your A/C sounds like it is working just right. Discharge air should be 15-20 degrees cooler than return air. And yes amperage draw will be highest during high outside temps and drop a bit when it cools off outside and the compressor discharge pressure drops as you note.


A 16,000 btu/hr unit will struggle to keep the temps down on a hot, sunny day. Consider adding a shade awning. That made a huge difference on a 43' sailboat. It dropped mid day inside temps from the low 80s to the mid 70s.


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Old 07-27-2016, 10:20 AM   #3
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Our 16k btu Cruisaire will only get inside temp down to low to mid 70's when it's 85 outside. All our windows have phifertex covering them during summer.
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Old 07-27-2016, 10:38 AM   #4
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15-20 t/d at the cooling coil, not downstream at the outlets.
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Old 07-27-2016, 10:48 AM   #5
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Our 16k btu Cruisaire will only get inside temp down to low to mid 70's when it's 85 outside. .
Same here but it's tolerable.
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Old 07-27-2016, 11:24 AM   #6
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During this heat wave. When I get to the boat early afternoon, the interior thermometer reads about 106*F !
I suppose similar to a car sitting in the sun. It will take hours to cool the boat down.

I have been working on the inside reconfiguring the fridge space since new fridge is bigger. It is really tough to work in that kind of heat. Been thinking go very late like after 5PM and work into the night hours.
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Old 07-27-2016, 11:28 AM   #7
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Quote:
Originally Posted by sdowney717 View Post

I have been using during this heat wave. When it is 100 outside, inside temp I can get to mid 80's with a vent discharge air temp of 65*F

When the outside cools down into the upper 80's, the vent discharge temp can drop to 53*F. Boat will get to the 70's.

If the sun goes down, boat cools off well. But with the sun on full bore heat, boat does not cool well. .
Quote:
Originally Posted by djmarchand View Post
Your A/C sounds like it is working just right.
Sounds exactly how mine is operating in this heat. We're in the same area. 12K BTU AC in my 28ft boat is marginal in this 100 degree weather..
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Old 07-27-2016, 12:09 PM   #8
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While the temp delta seems in the ballpark, your unit might benefit from some freon if you are seeing consistent bubbles in the sight glass.
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Old 07-27-2016, 12:28 PM   #9
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Sounds just fine to me. I have 2 16BTU units...one is brand new. I do have more interior space than you do. It can get down into the upper 70s in Texas heat with 90 degree water. One thing I have done that helps tremendously is to put a small high RPM fan right in front of one of the larger vent outlets. That alone knocks an additional 3-5 degrees off just by moving that air around. Coincidently, that outlet is near the aft stateroom entrance. I can point it out into the salon during the day and then down into the stateroom at night. It get downright COLD back there at night!!!
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Old 07-27-2016, 12:29 PM   #10
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Very hard to compare BTUs between 2 boats. Too many variables....concentrate on the delta between room temp or return air and discharge.

On many boats the discharge is only a couple feet at most from the unit, and on the big units with large discharge vents the temps are close enough to be useable. If not, check at the unit fan.

Just like a car, the discharge temps should be in the low 50s...just checked mine.....

16K unit in saloon, 48 degree discharge, 75 degree room temp, 86 degree and high humidity outside.
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Old 07-27-2016, 01:01 PM   #11
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Our boat has charcoal colored carpeting on the flybridge and on the sundeck (which has a hardtop). Soaks up a lot of heat on a sunny day, so I spray those deck areas down with a hose. Swamp cooler effect makes a huge difference for the AC performance. Also keep the insulated curtains drawn on the sunny side.
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Old 07-27-2016, 01:04 PM   #12
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Sounds right. I have the same unit in a somewhat more voluminous Krogen Manatee 36. Results you reported almost identical.
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Old 07-27-2016, 02:28 PM   #13
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It sounds like normal operation. The bubbles in the sight glass are refrigerant flashing off too soon because it has not been properly subcooled in the condenser, Likely because the intake water temp is very high today. I would not worry about it.
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Old 07-27-2016, 02:51 PM   #14
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It sounds like normal operation. The bubbles in the sight glass are refrigerant flashing off too soon because it has not been properly subcooled in the condenser, Likely because the intake water temp is very high today. I would not worry about it.
Decades ago when installed by a prior owner, the installer did not use the right size suction line going from the split to the compressor. They used 3/8 tubing, and stretched it and it barely fit the suction fitting on the unit. So of course, someday it broke on me, dumped the entire charge when I had to move it slightly.

I researched and found out the suction line should have been 1/2 inch, so I switched out the tubing to half inch on the run from the split to the compressor, and redid all the flare couplings. That was maybe 5 years ago. I put in a sight glass on the output at the unit, and installed a nice Sporlan filter-drier in the suction line after the heat pump valve going into the compressor. Since the original install was done 1970, I found out looking at compressor it was replaced early 90's. I figure the filter-drier was a lot better than the cigar shaped drier - sieve .

I was told that having a smaller suction line than recommended on a heat pump affects the heat more than the AC.

My feeling is it has lost a little charge over 5 years after I did all that work on it. I may retighten the flares and put in a little more refrigerant, I have of course gauges, vacuum pump, etc.. and little bit of experience.

I did note years ago, the copper tubing for the forward evaporator ran thru the bilge area and had some corrosion on the copper. So I smeared a whole lot of sealant on them (actually polyurethane construction adhesive) wrapping them with fiberglass tape. The little high pressure line had worse corrosion than the suction line, and I figured if the line was really bad, under the high pressure, it would have had an obvious leak, and it did not, so did not change the tubing.
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