Adler-Barbour R-134a Conversion Success

[K7MX]

I recently successfully converted my elderly Cold Machine refrigeration system from R-12 to R-134a and it was a lot easier and way more successful than some "experts" that I consulted said it would be. My old compressor had died, I wanted to learn somethig about refrigeration, so I figured I had nothing to lose so set out on this project. On Craigslist I found someone selling a nearly new Danfoss BD-50 compressor along with a controller very reasonably. This compressor is a direct replacement for the original R-12 one so mechanically it was very simple. I used a propane torch and copper tubing cutter along with typical plumbing procedures to accomplish the removal and re-installation of the copper lines. Make sure you clean up the copper fittings well with steel wool and use flux on the solder joints. After installing Schrader valves on both the low-pressure and high-pressure lines, and replacing the dryer, it was a simple matter of going to Wal-Mart and buying an automotive can of R-134a with a fill valve and pressure gauge attached. Once fully assembled, I attached the refrigerant can to the low-pressure side, powered on the Cold Machine and added refrigerant a little at a time. Keep an eye on the pressure on the fill gauge and keep adding refrigerant until the pressure is in the green (normal) band on the gauge. Pretty quickly the evaporator inside the cooler began to frost over and things were looking good. I can report that even here in SW Floriida at the peak of summer I am getting a 61 degree F. differential from the cabin temp. to inside the icebox (100 degrees in the cabin and 39 in the box). My 1985 Hunter 31 has about 5 cubic foot inside the box and the evaporator is freezing ice cubes very well. The retrofittted system draws 5 amps peak from my batteries...I expect this to go down as the ambient temps go down in a few months and the compressor's duty cycle drops. All in all this was a pretty easy project and was a lot less expensive than a total replacement, and I got to learn something about refrigeration in the process. Contact me if you need any more info at k7mx@comcast.net. Good luck!!

 

[bobtigar]

you dont talk about vacating the system so you could add the refrigerant. Bob

 

[sailaway78]

I knew a guy

Several years ago, before R12 was phased out, I knew a guy who installed after marked AC in cars. He did not even own a vacum pump. What he did was blow two or three cans of freon through the system, then charge it up. Always worked.

 

[bobtigar]

Re: I knew a guy

Blowing 134a thru an r12 system will remove most lingering remnants of the 12, but you still have to vacuum the pressure down to remove air and create a vacuum. Other wise the air in the system blocks circulation of the refrigerant. Then there is the matter of changing the oil in the pump. I believe that there is residue of 12 in the oil and that can cause corrosion. Bob

 

[packman]

Sweeping

Sweeping the system was commonly done 20 years ago and will blow out most air, moisture, and contaminants. On the other hand, it's not the proper way to do it EPA wise and will tend to leave moisture behind in odd pockets. The thing I might be concerned about is using regular solder on the high press side, I'm no expert, but I always use silver solder and an oxy/acetyline torch, possibly MAPP gas will get hot enough. I'd hate for a hot soak or a really hot day to pop my fittings. Just my opinion

 

[kloudie1]

Yes, "sweeping" the system was OK for car AC where ya have a lot of horsepower to drive the compressor, but in a battery powered compressor in a refrigeration system, a little air in the system increases the power draw of the compressor because of the higher condensing temperature/pressure that air causes. Sweeping works better than it sounds like it might because the system is really a long tube with a restriction in it.. Think about a coiled hose full of smoke.. You can blow through it to remove the smoke but there will always be a little left in it; same with sweeping the coils with refrigerant.. Not an optimal way to handle it.(diffusion). Back in the old days, there were valves on the top of the compressors that you could manipulate to use the compressor as a crude vacuum pump.. again, not optimal but if ya swept the system and then did that, you could get a pretty good result. The real problem (mechanically) with 134a in a R-12 system is that it is a hydrocarbon. It is a solvent for the old mineral oils that used to be used in the R-12 systems. It would decrease the lubricity enough to fail the compressor bearings and valves.. The oil that is used with 134 is a synthetic that is not affected by the refrigerant. The newer versions of that oil are also OK with R-12. Most of the "conversion kits" that were sold had an oil viscosity modifier included to combat the effects of the solvent on the old oil.
Like PackMan says, normal solder is not really strong enough to handle the vibration and jostling from marine use on a refrigeration system, so it is not used by any of the manufacturers. Silver solder is the one to use..

 

[K7MX]

Sorry...I forgot to include the part about pulling a vacuum on the system. I borrowed a friends pump and pulled a negative pressure for about 30 minutes before backfilling with R-134a. I haven't had any problems with using regular lead-tin solder on the fittings. It's been several months now of constant use and no indications of leaks and still holding about 60 degrees F differential temperature.
Don