Compressor manufacturer Bitzer has approved the hydrofluoroolefin (HFO) refrigerants R-1234yf and R-1234ze(E) for its CSH and CSW screw compressors. The two alternatives to R-134a have a global warming potential (GWP) of less than 10. The HFO/hydrofluorocarbon (HFC) blends R-513A and R-450A, with GWPs of about 600 each, are also approved for the CSH and CSW series.

According to Bitzer, the volumetric refrigerating capacity and pressure levels of R-1234yf are comparable with those of R-134a, while the capacity figures and pressure levels of R-1234ze(E) are around 20 to 25 percent lower. Bitzer said it subjected the R-1234yf and R-1234ze(E) refrigerants to intensive testing, and the compressors performed well with both in all of the tests and laboratory experiments. The tested compressors achieved nearly identical isentropic efficiency values with R-1234yf and R-1234ze(E) as with R-134a. Due to differences in the thermodynamic properties, the COP measurement results were in some cases slightly lower.

Both of the HFOs are suitable for air conditioning and medium temperature applications as well as for heat pumps, Bitzer said.

According to Bitzer, there’s a degree of uncertainty regarding flammability. In safety data sheets, R-1234ze(E) is listed as nonflammable, though this only applies to transport and storage. When used as a refrigerant, a higher reference temperature of 140°F is applied in flammability tests. At this temperature, R-1234ze(E) is flammable, and both it and R-1234yf are assigned to the A2L safety group. HFO/HFC blends such as R-513A and R-450A, on the other hand, are nonflammable and therefore classified in the A1 safety group.

Alter evaluating all of the results, Bitzer announced approval of the HFO refrigerants R-1234yf and R-1234ze(E) and the HFO/HFC blends R-513 and R-450A for its CSH and CSW compact screw compressors. According to Bitzer, these products can be operated with the standard ester oil charge with HFO refrigerants in the documented applications.