The adoption of low GWP A2L refrigerants for commercial refrigeration must deliver on safety, energy consumption and cost effectiveness in comparison to other low GWP solutions. R-454A and R-454C are HFO based refrigerants, both are blends of HFC-32 and HFO-1234yf. In an operating store, the R-454A (GWP 238) system is claimed to deliver efficiency improvements over natural alternatives with leakage rates below 4% for new systems at a lower cost to the industry-leading technologies. The R-454A system uses a conservative approach for the risks of the A2L refrigerant, with a technical working group designing the systems to meet the A3 (highly flammable) safety standard. The medium temperature system is under 40 kW in capacity and below the 54 kg charge limit required by European Standard EN 378, with the low temperature system having about 15 kW capacity and 11 kg refrigerant charge. One aim was to create an A2L design standard over time so that any lower flammability refrigerant could be used.
R-454C (GWP 148) was selected for a trial new convenience store installation, to maintain the advantages of R-404A, including ease of installation and maintenance, cost efficiency, safety, and energy efficiency, while using a low GWP refrigerant. A team with the required expertise from across the refrigeration industry focused on meeting long-term sustainability and GWP requirements of the F-Gas regulation and complying with necessary requirements and standards (EN378) for A2L refrigerants. The aim is to use very low GWP refrigerant without sacrificing energy efficiency or overall system performance. Any increase in indirect emissions from increased power consumption would greatly reduce any net gain from lowering the refrigerant GWP.
Separately, the final report “Experimental Study on the Consequences of Full-scale Ignition Events Involving the A2L Refrigerant R-454C” has been published by the Air-Conditioning, Heating and Refrigeration Technology Institute (AHRTI). The project evaluated how refrigerant disperses in a room under various room-scale release conditions and the post-ignition consequences of the R-454C releases, which were compared to similar tests performed with the A3 refrigerant R-290. Overall, the tests showed that ignition consequences for R-454C were minor under quiescent (still) and low-humidity conditions. Equivalent R-290 ignition events were much more severe.
Explanatory Note: Over the lifetime of RACHP equipment, the use of energy (usually electricity) represents most of the lifecycle cost – typically more than 70%, with initial capital cost being around 20% and maintenance 10%. The use of electricity is typically the source of 70% to 95% of total CO2 emissions. The use of lower GWP refrigerants only makes sense if the energy efficiency is equal to or better than the efficiency of the higher GWP fluid being replaced (reference). Compared to a R-404A system with eg 30% of the total emissions due to refrigerant, a comparable low GWP refrigerant system (GWP <300) would reduce emissions due to refrigerant to about 3%, without taking into account any improved refrigerant containment for a new system. See 2019 September newsletter In Brief item for a table showing RTOC classifications of refrigerant GWPs.
Reference: Selecting Refrigerants during the global phase-down of HFCs, Ray Gluckman, IIR International Conference on the Application of HFO Refrigerants, Birmingham, UK 2-5 September 2018, Paper ID 1172 DOI:10.18462/iir.hfo.2018.1172
Source for study on ignition of R-454C