Piecing together an A/C system

I've always started with 1 can for a dry system (add oil to compressor first, measure it), whether R-12, R-134A, or Duracool. That gives some cooling, but usually see ~25 psig low-side w/ compressor running on an 80 F day. I then add another full can, stopping before I read 50 psig, though usually hits ~40 psig which is perfect. R-134A cans in CA have a spring-loaded output valve, requiring a special adapter. That is so you don't vent any excess the atmosphere. You return the can for a $10 refund and the parts store sends it off to recover any excess refrigerant left in the can.

Once I added Duracool but still had left over, so did an experiment. Web geniuses claim it is "explosive", so I poured some liquid on the cement and lit it. No explosion, it just burned slowly like a candle flame. It can only burn as fast as it vaporizes (also true for candle wax). I even blew it out and let my little girl have fun lighting the "water". Didn't surprise me since, unlike these web geniuses, I took two graduate engineering courses in combustion. Indeed, you'd swear the 6 oz can is empty (compared to 12 oz R-134A can). You should be more afraid to carry a newspaper in the cabin. If it does leak, you know it from that sulfurous "natural gas" smell (mercapton added). How common is a refrigerant leak into the cabin anyway? Duracool paid for an engineering study that calculated even if the full charge instantly leaked into the cabin, it wouldn't form a combustible mixture with the air inside.