25LB R407C (R-407C) Refrigerant Gas | 20 Cylinders

500 lb of charge, held as 20 separate 25 lb cylinders rather than in fewer large ones. A 25 lb cylinder is light enough to carry up to roof plant or into a ceiling void, and it is a size you can finish on a single job, so a part-used cylinder does not sit around holding a large remainder. Log each one as you open it and the running stock stays easy to count.

R-407C came in as the service answer to R-22 in direct-expansion air conditioning and medium-temperature commercial refrigeration: splits, rooftop packages, air-cooled chillers, cold rooms, display cases. It is a zeotropic HFC blend, chlorine-free, and it glides. Charge it as a liquid every time — cylinder inverted, or metered into the suction side with the compressor running. Weigh the charge in. Draw vapour off the top and you skew the mix and leave the wrong gas behind.

Read pressures off the correct column: dew point for superheat, bubble point for subcooling. Retrofit work wants polyolester oil, because mineral oil will not return through the system, and head pressure sits noticeably above R-22, so look at the condenser and any pressure controls before you commit. R-22 itself is an HCFC on the way out, so a charge this size suits plant you intend to keep running. Store cylinders upright, strapped, and out of the heat.