We have begun a massive shift away from high-GWP HFC refrigerants. Many of the refrigerants that we are depending on for tomorrow’s HVACR systems are flammable (categorized as A3 refrigerants) or at least slightly so (A2L refrigerants). ASHRAE and others are revising their safety standards to allow these refrigerants to be practically used in the field and these standards will eventually be formalized in building and fire safety codes, nationwide. Clearly, the goals of these standards are to minimize refrigerant ignition risks, that is, if the refrigerant should leak, to keep them away from viable ignition sources and keep the concentration low, as not to approach a combustible mixture of refrigerant and air.
As these safety standards committees got into their work, questions arose: What are the risks for leaks and ignition? How does leaked refrigerant behave near a hot surface? How should maximum charge limits be determined? What installation and servicing guidelines will be needed?
To answer these and other questions, the Air-Conditioning, Heating and Refrigeration Institute (AHRI) gathered interested parties and together with the USDOE, ASHRAE and the California Air Resources Board, dedicated over $5 million for conducting flammable refrigerants research. AHRI’s research arm, the Air-Conditioning, Heating and Refrigeration Technology Institute (AHRTI), is carrying out this cooperative research, of a scale probably unprecedented in our industry. The program is guided by the AHRTI Flammable Refrigerants Subcommittee (FRS). The need is urgent: because of the regulatory imperative to phase down the use of HFCs, research results are needed in time to support the revisions of relevant safety standards.
Much of the research program looks at observing and modeling the flow of leaked refrigerant, to understand how it might form a flammable mixture. Other projects investigate the potential flammability risks and mitigations. Still others look at methods of leak detection and safe handling practices.
The early results from this work have shown that it is difficult to ignite pure refrigerants or refrigerant/oil mixtures on a hot plate, a fact important to efforts to mitigate flammable incidents, especially near furnaces.
Another project showed which common ignition sources within residences have enough energy to ignite a flammable mixture and which do not.
Work was conducted on testing and modeling the flow of A2L refrigerants in a variety of conditions and room geometries and now that work is being extended to A3 refrigerants.
All together, this body of research will inform future codes and standards so that new refrigerants can be applied safely.
AHRI is keeping stakeholders informed and releasing results in a number of fora. The reports of completed projects are available for the public at AHRI website (http://ahrinet.org/Resources/Research/Public-Sector-Research/Technical-Results). The most up-to-date information is on the AHRI website. Results are also discussed at ASHRAE’s national meetings and at technical conferences such as the Purdue Compressor and Refrigeration conferences.
The industry is devoting a great deal of financial and personnel resources to better understand the nature of refrigerant leaks and how to mitigate their effects. It’s a great example of how trade organizations, professional societies, corporations and government entities can come together to (relatively) quickly address a common concern.