Changing The Refrigerant on an Engine Driven Boat Refrigerator
I am working on a Grunert engine driven boat refrigeration system. This system uses a Sanden wobble plate compressor identical to those used on car air conditioners, and originally operated on R-12. For some unknown reason, the screen on the oil orifice in the suction accumulator plugged and almost all of the mineral oil in the system became trapped in the accumulator tank. I have flushed the entire system and installed a new accumulator and a suction filter dryer. The compressor seems to be in good condition.
Since all of the old oil is out of the system, I thought this would be a good opportunity to replace the mineral oil with PAG or POE oil and run the system on R-134a refrigerant. I corresponded (Email) with the manufacturer (now Dometic) but cannot get an answer from them on the refrigerant change. Sanden Compressors endorses the change and provides a retrofit guide. In my experience, the R-12 TEV and the low and high pressure switches work with R-134a.
Does anyone see a problem with this refrigerant change?
I'm positive some pei ple will say that's not the right thing to do but I have converted a r12 system to r 134a and had good luck I du d have to adjust the TEV a bit and you may or may not be able to adjust yours. Hot Shot is another option
Sanden may have more specific guidelines for marine applications, but here's what they say about mobile retrofits:
It appears to be much like what I did when I converted my 1989 Chevy van some years ago. Flush, replace o-rings, add PAG oil, etc....
The main issue is the oil. PAG is not so hydroscopic as POE and it's designed for mobile applications. Use what the manufacturer recommends.
Since you're water-cooled, the condenser should be adequate and the pressure controls and expansion device will work the same with R134A.
Fresco are you working on a small craft or a larger commercial vessel system? I ask only because of service concerns while underway, I only used R134a on commercial vessel conversions due to high numbers of line set leaks caused by random objects coming loose in bilges or mechanical areas, seen lots of leaks like that over the years. Bottom line is the engineer can top off an r134a system in an emergency situation, while a hotshot leak is going to require an entire system evac if the leak doesn't take out the compressor from lack of oil circulation.
If you develop a leak with a system charged with hotshot there's a real possibility of the refrigerant blend fractionizing and not carrying oil back to the compressor. You all know the rest of the story when that happens.
You will see better overall system performance with hotshot conversions and it's especially well suited to low rpm use's in trawler and sail auxiliary applications.
I suppose you would classify this as a small craft: a 45 ft Sailboat. The system has had DuPont Isceon MP49+ blend in it when it had the mineral oil and there was no more R-12. By the way MP49+ is 75% R-134a.
Yep, I agree that falls well within the realm of small craft / private vessel and you should do fine using the 134a. For what it's worth we did several sail conversions for a bareboat charter company using an identical plate system to what your working on, I thought that was a better option for them as you never know who's running the boat and what they might cram in the bilges.
The first year alone when we made those conversions I recall a couple line set's being damaged, one was smacked by a portable bbq grill someone stuffed in the engine room and the other was caused by rebellious scuba tanks someone let run loose between the stringers taking out the braze on the suction line connection.
FWIW, both of those compressors survived the leak.