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This paper is based on findings resulting from ASHRAE Research Project RP-1641.

The presence of unsaturated fluorocarbon contaminantsin the refrigerants used in HVAC&R systems may result in reactionproducts that could potentially cause problems in systemperformance or reliability. Since 2007, the 40 ppm limit forunsaturated halogenated contaminants in new and reclaimedrefrigerants set by the Air-Conditioning, Heating, and RefrigerationInstitute (AHRI) in AHRI Standard 700 (AHRI 2015)has proven to be more restrictive to reclaimers, recyclers, andHVAC&R system providers than previously thought. In addition,compounds such as hydrofluoroolefins (HFOs) have beentested as low global warming potential (GWP) alternativerefrigerants and shown to have acceptable stability in someapplications. So, it may not be appropriate to classify all unsaturatedcompounds as unstable and blanket them under thesame restrictive limit.

ASHRAE RP-1641 (Rohatgi and Clark 2015) aims atdetermining the effects of halogenated unsaturated contaminantspresent in refrigerants on the stability of refrigerant/lubricant systems and recommends a concentration limitspecific to the unsaturated contaminant below which therefrigerant/lubricant system is thermally stable. Based on aliterature search and review, the following refrigerant/lubricantmixtures with their corresponding contaminants wereselected for a stability study in sealed-tube tests:

  • R-134a (1,1,1,2-Tetrafluoroethane)/Polyolester (POE) withR-1130 (1,1-Dichloroethylene), R-1130(E) (Trans-1,2-Dichloroethylene), R-1131 (1-Chloro-2-fluoroethylene),and R-1234yf (2,3,3,3-Tetrafluoropropene)
  • R-1234yf/POE with R-1225ye(Z) ((Z)-1,2,3,3,3-Pentafluoropropene),R-1233xf (2-Chloro-3,3,3-trifluoropropene),and R-1243zf (2,3,3-Trifluoropropene)
  • R-123 (2,2-Dichloro-1,1,1-trifluoroethane)/mineral oilwith R-1122 (2-Chloro-1,1-difluoroethylene), R-1123(1,1,2-Trifluoroethylene) and R-1131

Based on criteria such as visual changes, total acidnumbers (TANs), organic anions, and dissolved metal concentrationsafter aging, it was concluded that the R-134a/POEsystem was as stable as the control (without contaminant)when the concentration of its contaminants was less than1000 ppm. The R-1234yf/POE system was stable when itscontaminants were less than 5000 ppm, while the R-123/mineral oil system was stable when its contaminants were lessthan 30,000 ppm. These maximum concentration limits werebased, however, on sealed-tube stability tests and would needto be balanced against other safety concerns, such as toxicity,flammability, and handling and recycling practices.

Citation: 2016 Annual Conference, St. Louis, MO, Transactions 2016, Vol 122 pt. 2