There’s one thing the HVACR industry is certain of — the future of refrigerants is uncertain. Given the current rate of regulatory changes, refrigerant life expectancy can sometimes seem like a flash in the pan; here today, gone tomorrow.
Historically, three hydrofluorocarbon (HFC) refrigerants covered a broad range of air-conditioning and refrigeration applications: R-134a, R-404A (or R-507A), and R-410A. These products have been targeted by regulations because of their higher Global Warming Potentials (GWPs). Instead, regulatory efforts have focused on moving toward lower GWP alternatives, where practical.
R-1234yf and R-1234ze are hydrofluoroolefins (HFOs), or very low GWP synthetic refrigerants. While these molecules are viable solutions for certain system types, they are unable to widely replace HFCs. This is due to the fact that they do not have the capacity of higher pressure refrigerants, and are themselves mildly flammable (A2L safety rating). However, blending HFOs with HFCs creates lower GWP alternatives that may be used in current equipment with a relatively modest level of system redesign.
Blending HFOs with HFCs creates lower GWP alternatives that may be used in current equipment with a relatively modest level of system redesign.
R-134a has the lowest GWP of the primary HFCs. R-450A and R-513A are nonflammable R-134a/HFO blends that have been approved by EPA under its Significant New Alternatives Policy (SNAP) program. While not truly low GWP, they represent a marked decrease in GWP from R-134a and have similar properties. This makes them well suited as replacements/retrofits for many R-134a applications in the short term. In the US, EPA’s Rule 20 will render R-134a unacceptable in new light-duty motor vehicle AC systems come Model Year 2021. R-1234yf is the preferred alternative. In new chillers, R-1234ze is used to replace R-134a. These products will see wider usage in the future.
Because R-404A has the highest GWP of the main HFCs, many new systems (e.g., supermarkets) have shifted to R-407A or R-407F over the last several years. These HFC blends have GWPs 50 percent lower than R-404A. R-448A and R-449A HFC/HFO blends, which have been recently approved by SNAP, are even lower GWP (less than 1/3 of R-404A) options; however, these blends can’t replace R-404A everywhere, as they have higher discharge temperatures and glides. For applications that require a closer match to R-404A, such as transport refrigeration, R-452A has been developed. While its GWP is mid-range, it is an effective operational R-404A clone.
HFCs will continue to be used for a while, particularly for system servicing. We expect to see the use of mildly flammable refrigerants become more common and other HFC/HFO blends emerge. Natural refrigerants, such as hydrocarbons and CO2, will see broader usage as they also continue to replace HFCs.
R-410A is the most challenging of the HFCs to replace, as there are no nonflammable R-410A-like alternatives. R-32, the lower GWP half of R-410A, is a mildly flammable option with noticeably higher discharge temperatures. Blends of R-32 and other HFCs/HFOs (e.g., R-452B) seek to improve upon R-32’s shortcomings and are gaining traction.
It’s important, though, to note that HFCs will continue to be used for a while, particularly for system servicing. We expect to see the use of mildly flammable refrigerants become more common and other HFC/HFO blends emerge. Natural refrigerants, such as hydrocarbons and CO2, will see broader usage as they also continue to replace HFCs.
As our industry continues its drive toward environmentally sustainable lower GWP refrigerant solutions, the only thing that’s certain is that more uncertainty will arise.
Stephen Spletzer is senior technical support engineer for Danfoss, and a frequent guest speaker at HVACR industry events.