[crane]

I've been working on a retro-fitted water cooler recently...took the plunge and finally evacuated the little .5 HP compressor and chopped off the evaporator coil to try some experimentation with different configurations. First thing i did was solder on a service port at the process tube on the compressor... i figured I would try my luck at pulling a vacuum and recharging before I went too far with evaporator mods. I forgot my 3CFM 2 stage vac pump at work,so i was limited to using my little hand vacuum pump(don't laugh) to pull a vacuum. Moisture wasn't a concern as it was only open a few minutes.
I pumped like hell and got it down to -25 and shot the gas to it and it started happily and cooled just fine...seems to me the little hermetic compressors are pretty tolerant of under/overcharge as i was able to fine tune the cooling by adjusting the R134a amount. It holds a whopping 1.75 oz.
I then decided that since the evac/charge scenario was simple enough... i would cut out the original evap and try some alternate configurations. My first evap replacement was a coil of 3/8 copper with the cap tube soldered in one end and the suction tube soldered on the other end of the coil. I then did the hand vac deal and recharged again... Once again it fired right up and made a big chunk of ice on the coils. I used some old plumbers solder I had lying around forever.. can't even read the type on the roll its so old. It seemed to hold pressure fine and i wasn't a bit concerned about something popping loose under pressure.
I wasn't too happy with the size of the evap coil I had made, so once again...chop chop and this time I made a coil out of 10 foot of 1/4" copper tube and soldered it in place,using the same crap solder i used before. Only difference was i bought a little container of tinning flux from Ho' Depot and that stuff is the cats ass for soldering copper. I will look at the bottle when i get home this weekend and post the brand and type.
To sum it up.. i wouldn't concern myself with brazing anything on the phase change system...just use a good flux and plumbing solder and have at it.
My results from playing around with my chiller were really quite good... it makes zero degree celsius water and and I had my chip down to 8 degrees celsius. But without any condensation proofing and insulation, I didn't run it but a little while as it was sweating terrible.
Next step,this weekend coming up is to remember to take home my HVAC vacuum pump... and also i'm going to replace my evap with a modded water block , insulate everything and make it a direct die phase change system.
One thing you may want to think about is the block orientation... of course the center would be where you put your cap tube, but where does that leave the outlet or suction tube? At the top? If its at the bottom,gravity is going to make the refrigerant leave the block quicker than if it was at the top of the block... But I guess with a maze type block it is going to go where it has to go... out the suction tube. Running the suction at the top would allow the block to be flooded with cold refrigerant,which is a good thing. I will be using a modified Z4 (cringe) water block I bought years ago... replacing the aluminum top with a copper top including fittings to solder on the cap tube and suction lines. I used a simple brass cap with a hole drilled in it for a place to put the cap tube.
Edit to add: Are you sure that the refrigerant oil travels throught the system on a hermetic type compressor? I don't think it does...Not like an automotive AC system where the oil is misicible and mixes with the refrigerant. I may very well be wrong, but I didn't see any evidence of oil inside of the piping on my system.
I beleive it stays in the crankcase for the most part.