Application of Safety Factors When Setting Charges Limits for A2L Flammable Refrigerants (LB-17-C046)

Today’s societal demands to control climate change are forcing HVAC&R equipment designers to consider new lower GWP refrigerants, some of which are slightly flammable under certain conditions. This paper supports setting a safety factor as low as 2 to 1 (50% of LFL) when setting the charges limits for A2L flammable refrigerants depending on the HVACR products application refrigerant charge and application height. Computational fluid dynamic (CFD) analysis was performed to support the justification of setting the safety factor. Numerous fast leak scenarios, 4 min leaks, were evaluated at various heights, room areas and refrigerant charge sizes. Maximum refrigerant charges for a large number of ASHRAE 34 classified refrigerants will be summarized for comparison purposes at various LFL endpoints.