25LB R407C (R-407C) Refrigerant Gas

One 25 lb cylinder, R-407C. The blend came in as the service answer to R-22 in direct-expansion air conditioning and medium-temperature commercial refrigeration. US R-22 production has ended, so the work that still comes in on those systems is retrofit and repair. Zeotropic, no chlorine, nothing in it that attacks the ozone layer. It asks more of you than a single-component gas, and most of the trouble people have with it comes from treating it like one.

Charge liquid, always — cylinder inverted, or metered into the suction side with the compressor running. Vapour draw pulls the lighter component off first and leaves the wrong mix behind, in the cylinder and in the system. Weigh the charge in; pressure alone will not get you there. Glide means reading the right column of the chart: dew point for superheat, bubble point for subcooling.

After a leak, recover what is left, repair, evacuate, then weigh in a fresh charge rather than topping up a shifted mix. The blend wants polyolester oil; mineral oil will not circulate and return with it, so an R-22 retrofit is an oil job as much as a gas job. Head pressure sits somewhat higher than R-22, so check the condenser and satisfy yourself the controls will live with it.