Bitzer points out that the two HFO alternatives to R134a have GWPs of under ten, and the non-flammable HFO/HFC blends GWPs of about 600.
The volumetric refrigerating capacity and pressure levels of R1234yf are described as comparable with those of R134a, while the capacity figures and pressure levels of R1234ze(E) are around 20 to 25% lower.
Bitzer says it subjected R1234yf and R1234ze(E) 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 R1234yf and R1234ze(E) as with R134a. Due to differences in the thermodynamic properties, Bitzer says the COP measurement results are in some cases slightly lower.
The German compressor manufacturer maintains that both of the HFOs are suitable for air conditioning and medium temperature applications, in particular, as well as for heat pumps.
Bitzer has also tried to unravel some of the uncertainty regarding flammability. In a statement, the company says, “In safety data sheets, R1234ze(E) is listed as nonflammable, though this only applies to transport and storage. When used as a refrigerant, a higher reference temperature of 60°C is applied in flammability tests. At this temperature, R1234ze(E) is flammable and therefore assigned to the A2L safety group, just like R1234yf. For this reason, a risk assessment in accordance with the ATEX Directive is required for systems with both refrigerants – with potential consequences in the system design.”
As R513A and R450A are nonflammable, using them requires nothing more than a conventional risk assessment in accordance with the Machinery Directive.
All the refrigerants mentioned can be operated with the standard ester oil charge (Y-model).