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Old 09-07-2014, 05:28 PM   #1
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Marine Refrigeration

I have a '84 Grand Banks with a GRUNERT refrig system for my refrigerator and freezer boxes. Since buying the boat 10 mos ago, the system (an old one) has operated flawlessly. Last week it just stopped cooling yet compressor runs smooth as does the condenser fan. Electrically, all seem fine. Appears it's a low refrigerant problem and likely a leak.
QUESTION: can I add refrigerant myself or is this something that requires a marine refrigeration specialist. The Maintenance manual says for severe leak, unit needs to be pumped out using a vacuum pump. Any recommendations? Also, best way to check for leak. Manual says to look at fittings for an oily residue.
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Old 09-07-2014, 08:00 PM   #2
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For a start many of the old refrigerant R-11 and R-12 have been out of production for some time and may not be available. There are some alternative refrigerants to replace some of these. To charge the system if all the gas has been lost you do have to draw a vacuum on the system but if you have just lost a bit, refrigerant can be added, but this requires gauges to understand the suction and discharge pressures in order to add only the amount required to function properly. And, if you haven't searched for, found and repaired the leak this will be a waste of time. I don't often say this, because I am cheap, but likely the best advice I would recommend would be to have a professional look at the system. There are times when DIY just doesn't work IMHO.
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Old 09-07-2014, 08:17 PM   #3
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Allan's right. But if your feeling handy you could get some gauges and Nigil Calder 's book (http://tinyurl.com/ketqav8.) and at least trouble shoot it yourself.
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Old 09-07-2014, 08:19 PM   #4
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I would have a marine refrigeration person service your system. They can do a leak check on the entire system. For starters, you should have a little sight glass near the compressor (1/2 to 1-inch diameter). When the system is running look for air bubbles traveling past the sight glass. The presence of air indicates that you need additional coolant.

I think I spent less than $200 for a technician to service my Grunert system. Best money I ever spent on the boat.
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Old 09-07-2014, 08:35 PM   #5
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hey thanks everyone. I figured my best approach is a professional but wanted to make sure.
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Old 09-07-2014, 08:40 PM   #6
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my new mantra for air conditioning and refrigeration...

Is I have to be able to take it off the boat to ANY AC&R guy....and let him work on it on his bench....no more split systems.

Too many horror stories of "almost fixed" several times...bill $3000...nope.... bad unit...new install just another $3000 dollars. And a huge portion of that is travel time as many guys won't touch going to a boat.

If you live in an area of many good, boat AC&R guys...you are in boating heaven. They seem to be tougher to get, more expensive and way less adept at troubleshooting than the best diesel guys around.

That is until (if ever) I Take a few AC&R courses and learn to do it myself and get any necessary certs....may be the most valuable training I ever took.
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Old 09-07-2014, 08:42 PM   #7
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Excellent point. Thanks!
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Old 09-07-2014, 09:37 PM   #8
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Refridgeration aint rocket science. Get a few books. The best would be the classroom book used by every hvac school everywhere. Dont recall the name and would have to go find it but it covers everything. When you can grasp the basics its all easier afterwards. Your system is probably very simple. Just to iterate how simple it really is, most dont know that propane is a suitable replacement for R12 and R22, actually its a little better. The "knee jerk" reaction here is that its flammable, when in fact its been used in Europe for years. The ignorance surrounding refridgeration is astounding, like its magic or something. How will you get it repaired in places that dont use it ? Someone said "if you cant fix it it shouldnt be on the boat". Its easy to learn.
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Old 09-07-2014, 09:47 PM   #9
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never heard propane being a substitute for R-12 and -22. thanks for recommendations!
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Old 09-07-2014, 10:31 PM   #10
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There are laws here about refrigerant escaping, the ozone layer hole, that sort of thing. Any evacuation must be contained. USA probably has that too.
And here, like with lots of things, the newest refrigerant costs, like about $300 a kilo. It may be less now that we abolished the carbon tax.
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Old 09-07-2014, 10:33 PM   #11
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Not a reccomendation. Just saying its done, and not infrequently. I was trying to point out that most folks think its voodoo or black magic or the like when just a little study will get you enough knowledge to be better informed than most hvac guys. Case in point, my home A.C. is a 6 ton marine unit thats cooled with water from the indoor swimming pool (heats the pool). The compressor/condensor unit operates a 4 ton and a 2 ton air handler. I built it myself and its worked great for 5 years. Every AC tech here in Oklahoma thats looked at it says "that wont work" because they dont have a clue about refridgeration, dont even understand the basics. I know your smarter than that. To look at a device that obviously is working and say it wont work ????
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Old 09-08-2014, 12:48 AM   #12
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never heard propane being a substitute for R-12 and -22. thanks for recommendations!
Yes. . . Seen it used in a car AC unit and it worked great. But you still have to have the correct amount of compressor oil in the system as well.

That said I'm not sure I would want to use it in an enclosed space like a boat, remembering that most diesel powered boats don't have sealed explosive proof alternators and starters. A system leak of even a few oz of propane in the bilge might be a problem.
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Old 09-08-2014, 06:36 AM   #13
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>The presence of air indicates that you need additional coolant.<

What is seen in a sight glass is refrigerant that is in a vapor form , it has not been liquified. Not air.
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Old 09-08-2014, 09:21 AM   #14
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I always install a sight tube on any unit I build. Its a cheap and very usefull tool. I also install valves and a large dryer on the compressor/condensor unit that can be used to pull down the charge for storage/removal. I do have a recovery machine but its easier just to pull it down with the compressor and turn off the valves. Then pull a vacuum on the coil befor opening the valves. My vac unit is a small compressor from an old fridge, with a gauge and fittings brazed to it, cheap.
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Old 09-08-2014, 10:54 AM   #15
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never heard propane being a substitute for R-12 and -22. thanks for recommendations!
Oh yeah, and to find leaks you can use a small plumbers torch. Just flame paint all the fittings and copper tubes... Don't worry be happy. Hell nor heaven is half full....yet.. Be optimistic buy a harp, not a pitch fork.

I have been to air conditioning 101. By the time you screw with it chances are you are better off with a pro. Checking amp draw at the compressor can be handy, but beyond that, what with gauges, sniffers vac pumps, legal recycler pumps and so forth, why go through the aggravation, tool expense just to have to re learn it in a few years. I change filters, strainers, flush with barnacle buster or muanic using submersible pump and garbage can closed loop. Change March Pumps out like a pro...lots of practice on that one, but beyond that I pick up the phone.
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Old 09-08-2014, 10:59 AM   #16
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I have three cars and I always took them to AC guys. This year I bought the gauge and found anyone with a third grade education can do this so that included me too and I charged my own.

The wife's car had other issues and she took hers in, got snookered into paying 135 for an AC check up. All they did was see the freon was full and cleaned the condenser.

Harbor Freight sells everything you need. You'll only use it a few times in your life anyway so why pay more.
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Old 09-08-2014, 11:05 AM   #17
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Yes. . . Seen it used in a car AC unit and it worked great. But you still have to have the correct amount of compressor oil in the system as well.

That said I'm not sure I would want to use it in an enclosed space like a boat, remembering that most diesel powered boats don't have sealed explosive proof alternators and starters. A system leak of even a few oz of propane in the bilge might be a problem.
That is why it isn't exactly a best practice to use propane, and technicians have been burned when they service units so charged. It is also incompatible with mineral oil, which I gather is used in the compressors.
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Old 09-08-2014, 11:08 AM   #18
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I generally use phosphoric acid for cleaning the raw water side, but moronic acid works to. Be carefull mixing it.
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Old 09-08-2014, 11:13 AM   #19
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I dont condone the use of propane, but, it is compatible with the oil that is used in r12 and r22 units. It is not compatible with 134a oil.
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Old 09-08-2014, 11:17 AM   #20
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I generally use phosphoric acid for cleaning the raw water side, but moronic acid works to. Be carefull mixing it.
I can think of a lot of other uses for moronic acid...
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