R-12 and R-22 are totally different products. R-22 was used in most large
capacity air conditioning units...10, 20 30 ton and up chiller units. R-12
was the old stand by for most small refrigeration units and the automotive
industry till the Feds outlawed it's production and importation into the US
in '92 or '93. R-12 is the stuff THEY were most worried about. It is an
HCFC (hydrochloroflourocarbon), chlorine being the component which THEY
claim will damage the ozone. That is why it costs over 20.00 for a 12 oz
can. The only legal source for the stuff is what's recovered from the
field, and recycled back into "virgin state refrigerant". What do you
think they do with all that R-12 they charge you exuberant prices to
recover.
They let R-22 stay around a few more years because it didn't have the
chlorine. These substances, of which there are hundreds, are used as
refrigerants because they have the proper "pressure/temperature
relationship". In other words, when placed in a sealed unit or container
they have a precise and predictable pressure, dependant upon their
temperature, and vice/versa.
R-12 in a sealed bottle at a temperature of 81 degrees will have a pressure
of about 85 PSI. R-22 in a sealed container at 81 degrees will be 145 PSI.
Therefore they cannot be interchanged. They should never be
mixed or a completely different substance would be created which would have
a very different "pressure/temperature relationship"
R-134A is the supposedly ozone safe product to replace both. But realize
this: since R-12 and R-134A have a VERY similar "pressure/temperature
relationship", R-134A can be a drop in replacement for R-12. BUT, before
R-134A can replace R-22 the entire system pressure has to be redesigned
(different compressor.)
PS. for the environmentally friendly, the US Coast Guard and US Navy have
just about completely retrofitted every ship's refrigeration and air
conditioning systems with R-134A. It's a lot easier on the technician
cause
now we only have to maintain service equipment for one type of
refrigerant.....recovery machine, gauge manifold, etc, etc
Regards,
Earl F. Allen, Jr. MKC, USCG
