R-407c is a mixture of hydrofluorocarbons used as a refrigerant. It is a zeotropic blend of difluoromethane (R-32), pentafluoroethane (R-125), and 1,1,1,2-tetrafluoroethane (R-134a). Difluoromethane serves to provide the heat capacity, pentafluoroethane decreases flammability, tetrafluoroethane reduces pressure. R-407c cylinders are colored burnt orange.
This refrigerant is intended as a replacement for R-22. R-22 production will be phased out by 2020 as per the Montreal protocol.
It is not recommended to drop R-407c into R-22 systems on top of the existing charge in cases of low refrigerant levels. A licensed professional should be contracted to completely remove the R-22 and as much of the mineral oil as possible. In the case of compressor change-outs, replacement compressors are already manufactured with POE (polyolester) oil and are therefore more compatible with R-407c than returning the recovered R-22. The recovered R-22 can be sent to a facility for disposal.