R-409A is a zeotropic "service blend", its use being limited in time following the Montreal Protocol.
This HCFC has been developed to replace R-12 (CFC) for domestic, commercial and industrial applications.
It is preferable to use R-409A for fluid reconversions in order to eliminate R-12 and thus protect the stratosferic ozone layer
R-427A is a zeotropic HFC blend which has been designed to replace R-22 (HCFC) by conversion of existing systems or for use in new systems. It may be used in direct expansion refrigeration systems and air conditioning.