Compatibility of refrigerants and lubricants with motor materials under retrofit conditions

Abstract

Compatibility tests were conducted on motor materials to determine whether exposure to the original refrigerant/mineral oil would affect compatibility of the motor materials with the alternative refrigerant/lubricant after retrofit. The motor materials were exposed at elevated temperature to the original refrigerant and mineral oil for 500 hours, followed by exposure to the alternative refrigerant and lubricant for 500 hours. Motor materials exposed to the alternative refrigerant and lubricant (after an initial exposure to the original refrigerant and mineral oil) appeared to be compatible with the alternative refrigerant and lubricant. The only concern was delamination and blistering of the sheet insulation containing Nomex, especially after removal of absorbed refrigerant at high temperature. This was attributed to incompatibility of the adhesive and not to the Nomex itself. Embrittlement of the polyethylene terephthalate (PET) sheet and sleeving insulations was initially observed, but subsequent tests under extremely dry conditions showed that embrittlement of the PET materials was attributed to moisture present during the exposure.