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Marine A/C and refrigeration

2K views 8 replies 7 participants last post by  Minnewaska 
#1 ·
Time to learn this stuff more than the basics I know now. What recommendations are there for the best book on really learning this stuff....uh, cold. :)

Also, what tools should I have and where should I get them? The 110v ac electric work, I have down. Its the pressure gauges, compressed gases, etc that have evaded me so far.

Early this season, I had the yard's HVAC contractor come to clean my a/c units and check pressures. He calls and says I need an entirely new unit in the aft cabin, as the reversing valve was stuck. That made no sense, as I had already used it for both heat and a/c this year and it was the most effective unit on the boat. I told him not to do anything but to meet me on Saturday with his gauges. Sure enough, when he checked with me there, the unit worked 100%. That would have been $4k down the toilet. It has continued to work well all year.

Now, my fridge is acting up and I don't trust this guy. It's cold one day, and fully defrosted and dripping the next. I replaced the thermostat, but that didn't help. Suspect a switch on the compressor, but just don't know enough about this.
 
#3 ·
If you Google "marine refrigeration and air conditioning" my book will pop up as the first listing : ).

Marine Refrigeration and Air-Conditioning: James Harbach: 9780870335655: Amazon.com: Books@@AMEPARAM@@http://ecx.images-amazon.com/images/I/41FTCN9VBJL.@@AMEPARAM@@41FTCN9VBJL

But I would not recommend it for what you want. It's an engineering level text for use at the maritime academies and for practicing professionals. You want a technical level book. There's lots of those. Don't be limited to those that say "marine". Refrigeration is refrigeration.
 
#4 ·
Harbor freight has all the tools you need. The frig should be 134a (most likely) available at any auto parts store. If you need refrigerant though, you have a leak, and it must be repaired first. You need certificate to handle any other refrigerant. Most prebuilt frigs don't have service ports either and you need to install a piercing valve.
A meter and your fingers will tell you whar a unit is doing. Could be a fan is starting and running sometimes and not others, then compressor goes out on high head or thermal. Or several other things, all of which a meter or observation will tell you.
I only charge $50 an hour plus travel expenses!;-)
 
#5 ·
Minne, you would need to find out how your refrig ssytem is set up. In theory the thermostat turns the compressor on/off, but there are probably also high/low pressure switches thta can turn the compressor off for safety, and possibly an overheat switch in the compressor as well, i.e. multiple safety devices can shut the compressor, so the "switch" may simply be doing what some other system is telling it to do.

If you know where all the safeties are, you can probably test each one with a DMM, but the real test will require you to check the gas pressure in the system and that's going to mean a gauge set, assuming there are ports in the system to simply hook up guages. (In some, you have to tap in ports.)

So there's a limited amount you can do, but you still may want to look for a refrigeration tech, who can deal with the gas side of things. Ain't rocket science, plenty of flowcharts to troubleshooting out there, just that the tools (gauges & gas & EPA license) are often an inconvenient expense.
 
#7 ·
I doubt you need to worry about EPA certs, unless your boat is before 1996 or so when they went to 134 gas. Biggest issues will be putting in ports, and hooking up the gauges. Never understood why they would not put in ports, but I guess the couple of cents saved on the fittings got someone a raise. I have not messed with marine ac/refrigeration but have done home and auto and as said above it is not rocket science. It is really about balance, too much or too little gas can have big affects.

In the old days we would just add a can of R12 and see if that made it cold, I am sure that method burned out a bunch of compressors.
 
#8 ·
I fought a problem with my Frigoboat air cooled fridge for over a year. It started out as stopping working. By turning it off for a few hours it would then run for months. It eventually got worse. I spoke with refrigeration guys and didn't like their solutions or explanations. I finally diagnosed it myself (debris in the system), changed the evaporator, added a filter/dryer and topped it off with 134a. Got a gauge set at an auto parts store, adapters for the compressor (Frigoboat uses R134 connectors?) and $500 later it works. Not a cheap fix but that is why it took me so long to finally fix it. I wanted to be sure that was the problem. If you find someone that knows these small systems then I would trust them more.

Gene
 
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