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Old 06-01-2015, 04:25 PM   #1
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AC Problem

Well, I'm at a crossroads with my Marine Air spilt system (Heat and cool). I have the 3 knob manual controls (2) and two air handlers. One air handler in the forward V birth area and another in the salon. Had the system recharged with R22 and ran it for 24 hrs. Clean both coils but only keeps the boat at around 78 degrees at night. Air coming out of salon duct measures 68 degrees (with a lazer gun) and 72 degrees in birth area. Temp of air going into the evaporators is 78 degrees. Compressor never shuts down. AC tech says the pressure was a little high when he was charging the system. Thought it might be dirt in the system blocking freon exchange.??? Don't know how old the system is. Anyway, how do I identify the BTU rating on the condenser. Label gone or painted over. Thinking I would change out the condensing unit first before tackling the evaporators. Or should I just scrap the whole thing and replace everything. Kind of at a quandary right now. I'm going down to the boat this weekend and run some cleaner through the water cooling system. Maybe it is scaled up and not transferring heat the way it should. Sea water strainer is clean and I have a good stream of water exiting the boat. Maybe, I'm overlooking something. Any ideas?
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Old 06-01-2015, 04:54 PM   #2
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Should have more temperature drop across the evaporators. Need some pressure readings to diagnose the problem. Most likely compressor is not providing enough suction. With split system you are at the mercy of HVAC guy with special tools. I would replace the system with two self contained units. re-route some power and water and be free of the special tool requirement. Freon/compresser problem, remove the unit and send it to shop for repair. comes back tested and ready to reinstall.
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Old 06-01-2015, 07:25 PM   #3
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I have never dealt with Marine Air so don't know how their tech support is, some companies have good folks who will really try to help, it might be worth giving them a call. Strange, I had AC problems last week too but simple, a relay was bad easy and cheap to fix.
Good luck!
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Old 06-02-2015, 06:42 AM   #4
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What's the difference in intake and outlet water temp? I would eliminate the easy (cheap) stuff first before calling in a tech. Vinegar in the raw water side would be a start.

Do you have frost on the condenser when operating?
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Old 06-02-2015, 03:13 PM   #5
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no frost-I did measure the temp on the raw water inlet and outlet but for the life of me I can remember what it was. I think it was 5 degrees difference. I'll clean the raw water system and see what happens.
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Old 06-02-2015, 04:38 PM   #6
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You could call marineairr. I called them last fall and discussed my cooling issues. They helped me out to narrow it down. There is a small valve on your saltwater pump. It is supposed to be throttled to provide a certain amount of GPH to cool.

Strange thing about fluid dynamics, there is actually a 'too fast' rate that slows heat transfer down in heat exchangers. Find out what the "gallon per minute" rate is, either by your manual, or calling marinairr. then use a gallon jug over the side and time how long it takes to fill a gallon of water. Make sure the flow rate is correct.
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Old 06-02-2015, 05:18 PM   #7
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Don't waste time with vinegar. Use a stronger acid.

You should be seeing outlet air temps in the mid 50s to low 60s.

How hot are the compressors running? Can you put your hand on them for a short time? Is the Freon return line cold/cool right up to where it goes into the compressor?

I doubt it has anything to do with the flow rate of the pump if the system worked well in the past and the pumps the same.

Flush the raw water system properly first and then check the pressures. High pressure is indicative of poor water flow/heat exchange. If your tech did not catch this find a new one.

Are the units getting their return air directly from the rooms they are trying to cool? Or a more indirect path that could allow them to pull warm/hot air from some where else?
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Old 06-02-2015, 06:20 PM   #8
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Capt. Bill, what would be a good acid to use?
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Old 06-02-2015, 07:12 PM   #9
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Take a five gallon bucket put a 3/4 ,5/8 thru hull fitting in the side near bottom . Put intake hose on pump to nipple and discharge hose in the bucket and let pump circulate cleaner thru for an hour or so . You can get a rescaled from a marine store or engine supp layer. Put gauges on before and check head pressure before and after. No gauges then temp of coil or water. Was the system out of freon or just needed a shot? Did he do a evacuation of the system? Could be air in system if he added gas. If out then you need to find the leak,start at the flare nuts or any area that might look oily or rusty causing a leak. You can use soapy water to locate a leak. Temp coming out of the vent should be about 15 to 18 degree different from air temp going in. If all else fails call your guy back and say its not working right.
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Old 06-02-2015, 07:57 PM   #10
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The tech added 2 lbs of R22-didn't evacuate. Checked for leaks and found none. Did find, whenever he attached his gauges, that whoever charged it last (I think in Sept) they hadn't shut off the high pressure valve and it was leaking slightly around the cap for inlet port. I can keep my hand on the compressor for a while-warm not hot-pressure line is cool not cold-return line is warm not hot. The return air comes from the room being cooled.
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Old 06-15-2015, 09:08 AM   #11
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Got back to the boat and chemically cleaned the water cooling tubes on the condenser. Water flow did increase a little. Water outgoing was 5 degrees warmer leaving the unit. Unit still not cooling enough. Incoming air was 75 degrees and outcoming was 67 degrees, High pressure line was cold and suction line was cool. Compressor was 65 degrees. I did find a label under the electric cover. It is a 16000 BTU unit. Guess I'll call the technician and set up another appointment. Only thing I can think of is the unit my be airlocked somewhere.
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Old 06-15-2015, 09:24 AM   #12
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High pressure line should be hot, low pressure should be cold and sweating. How old is the unit?
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Old 06-15-2015, 09:54 AM   #13
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You are low on gas again.. Find that leak,look for oil around any joint,connection . Use a soapy mixture a round the subjected area. Check top of access valves at unit. Have tech evacuate system ,see if vacuum is loss. Find that leak.
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Old 06-16-2015, 09:42 AM   #14
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Tech coming out this week after jury duty. Hope he makes it before Friday.
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Old 06-16-2015, 10:11 AM   #15
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Lafayette, La is the wrong place to be with semi functional AC....good luck!
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Old 06-16-2015, 10:28 AM   #16
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that is why I got rid of split systems and bought smaller self contained units.


a couple screws to loosen, a few hose clamps, umplug a couple wires and off to the nearest inexpensive but AVAILABLE AC&R guy...even if a couple hour drive.


saves time and money.


then again I just found out my genius son is also doing all his own AC&R work so maybe I was premature....
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Old 06-16-2015, 10:33 AM   #17
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Quote:
Originally Posted by what_barnacles View Post
Capt. Bill, what would be a good acid to use?
TRAC Barnacle Buster, Rydlime, phosphoric or diluted muratic acid. You could even use CLR Clear.
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Old 06-16-2015, 12:51 PM   #18
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Quote:
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Lafayette, La is the wrong place to be with semi functional AC....good luck!
Ain't that the truth!!!
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Old 06-16-2015, 02:33 PM   #19
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I just happen to have a drop in replacement unit sitting in my locker (minus the oil capacitor). If you need it you know where I am LOL
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Old 06-16-2015, 05:07 PM   #20
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Dimer2
I might take you up on that. I'll see what the tech says. I need to visit you anyway, so I'll have an excuse to trawler west. Plus, I owe you for a battery and a set of jumpers.LOL My crew is anxious to take another trip. Hey, I might find some more gems in your locker.hehe
Did you decide to keep the new boat??
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