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.

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.

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.

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.

hey thanks everyone. I figured my best approach is a professional but wanted to make sure.

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.

Excellent point. Thanks!

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.

never heard propane being a substitute for R-12 and -22. thanks for recommendations!

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.

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 ????

JESSEDIVER49 said:

never heard propane being a substitute for R-12 and -22. thanks for recommendations!

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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.

>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.

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.

JESSEDIVER49 said:

never heard propane being a substitute for R-12 and -22. thanks for recommendations!

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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.

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.

Edelweiss said:

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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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.

I generally use phosphoric acid for cleaning the raw water side, but moronic acid works to. Be carefull mixing it.

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.

kulas44 said:

I generally use phosphoric acid for cleaning the raw water side, but moronic acid works to. Be carefull mixing it.

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I can think of a lot of other uses for moronic acid...

They use it in Washington

Capthead said:

They use it in Washington

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Yes, I believe it dissolves anything sensible it comes into contact with.

We could start a new thread on the uses of moronic acid. I have used it on occasion, unbeknownst to me at the time. But after further investigation it became obvious that it was the major ingredient in the mix. It mixes well with alcohol.

To get the temperature right for a freezer propane usually requires about 10-20% butane mixed with it.

Installing a sight glass is a fine idea , but on a boat spend the extra $2. and use an armored sight glass , a built on cover covers the glass area when not being observed.

You might save yourself a little money by finding the leak for the refrigeration mechanic. Always wear eye protection, liquid refrigerants can blind you, best leak detector is a bottle of Mr. Bubble and a small paint brush.
Good Luck
Bill

AC supply companies have a goo paint on product that stays together for micro leaks that blow up like a balloon over an hour or 2 that will also tell the tail. I usta be a bubble chaser for the pressurized cable systems with the the phone company and we mostly used soap like mr bubbles...he is right about the bubbles. Putting red dye In the system will also work. Another method, there is oil in there, clean everything with lacquer thinner, acetone..very clean then a day or 2 later or whatever spray it all with aerosol foot power and see what sticks...

Look for the name plate on the unit and see what the refrig type is,.Also amp draw.See what the comp is at when running,and if there is any temperature at the lines. If the suction is cool and discharge is warm then you may still have some refrigerant in the system.Does the cold plate get cold?You can get gauges at a auto part store or harbor freight,but to get the right refrigerant requires a license .R.12is very $$$$$ and R22 is only available with a license here in Florida. You can look for the leak at the flare nuts or any connection were oil is present with soapy water. I would also suspect that the leak was known to the past owner.

Moronic acid is used on politicians.

Lots of funnies with the moronic acid - going back to initial post I made. Update on my old cold plate unit (in '84 GB 42): had a very slow leak at the valve where you charge the unit. Rest of system ok, but all refrigerant had leaked it. Fixed the valve and recharged the system. So far so good almost 2 weeks later.

Glad you found the leak. Our system is 28 years old ('86 GB) and going strong.