AHRTI Issues First Low-GWP Alternative Refrigerants Report

Residential and commercial ‘worst-case scenarios’ included in A2L research

ARLINGTON, Va. — The Air-Conditioning, Heating, and Refrigeration Technology Institute (AHRTI), the research arm of the Air-Conditioning, Heating, and Refrigeration Institute (AHRI), has released the first research report as part of its ongoing testing of flammable A2L refrigerants, many of which are identified as possible replacements to the high-global-warming-potential (GWP) hydrofluorocarbons (HFCs) scheduled to be phased down under the Montreal Protocol.

The report, Benchmarking Risk by Whole Room Scale Leaks and Ignitions Testing of A2L Refrigerants, was developed following testing at UL, which began in June 2016. The objective was to conduct refrigerant leak and ignition testing under real-world conditions to develop data and insight into the risk associated with the use of A2L refrigerants, which have a low-GWP but are mildly flammable. Room scale tests were performed for commercial and residential scenarios, including a packaged terminal air conditioner in a motel room, a rooftop unit in a commercial kitchen, a walk-in cooler, a reach-in refrigerator in a convenience store, a split HVAC unit in a utility closet and with servicing error, and a split HVAC unit with hermetic electrical pass-through terminal failure. A copy of the report is available here.

“The ongoing global effort to phase down the use of high GWP refrigerants requires this vital research, which will help us update relevant codes and standards so that appropriate, climate-friendly alternatives can be safely used in air conditioning and refrigeration equipment” said Karim Amrane, AHRI's senior vice president, regulatory and research.

“The testing was designed to create relatively low-probability events to evaluate if the ignition spread or had the potential to spread if ignition took place,” said Amrane added. “This means that more refrigerant was leaked into the space during these tests than what is proposed by the standard. In other words, a worst-case scenario.”

The ARTI project monitoring subcommittee (PMS) said, in part:

“One decision made initially was to always use ignition sources that were thought to have sufficient energy to cause ignition if a flammable mixture reached the ignition source. The reason for this was that the PMS was interested in learning about the severity of post-ignition events, if ignitions did occur. Likewise, ignition sources were placed in locations where we judged combustible mixtures were most likely to occur. Because of the way we approached these experiments, some relatively low probability events were forced to occur and we have learned some things that were not previously known to us.”

“The PMS feels that follow-up research projects will be needed to enable us to provide the best guidance to the developers of HVACR safety standards and building codes. Future work should include reviewing irregular test results, and potentially include updating risk assessments to better quantify both the probability of occurrence and severity of any ignition events, with a more thorough evaluation of the probabilistic distribution of real world ignition sources in terms of ignition energy, quantity, spatial location throughout the room, and activation frequency [and] the probabilistic distribution of different refrigerant release scenarios, across a range of leak rates and total refrigerant charge released.”

The research and testing program is part of a $5.2 million commitment on the part of AHRI, ASHRAE, U.S. Department of Energy, and the California Air Resources Board to further test in real-world settings low-GWP, but mildly flammable or flammable, refrigerants. Further testing is planned as part of this effort and results will be released when they are available.

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