Drop-in performance of the low-GWP alternative refrigerants R452B and R454B in an R410A liquid-to-water heat pump

•R452B and R454B drop-in tests are performed in an R410A liquid-to-water heat pump.•The heat pump uses a variable speed compressor and an electronic expansion valve.•Refrigerant sweeps are performed and the optimum refrigerant charges are identified.•R452B and R454B show up to 8% heating powers lower than R410A.•COP values for R452B and R454B are similar to those of R410A. R410A is a widely used refrigerant in residential liquid-to-water heat pumps. Variable speed compressors and electronic expansion valves are known to increase the heat pump performance and are becoming a common option in high efficiency heat pumps. Additionally, in order to minimize the system dimensions and the refrigerant charge, many domestic heat pumps are produced without liquid receivers. These systems are said to be critically charged as the refrigerant charge has a direct impact on the system performance. Even though refrigerant R410A does not contribute to the depletion of the ozone layer it has a Global Warming Potential (GWP) of 1924, so its impact on global warming is significant. For this reason, various lower-GWP alternatives to R410A have been proposed in recent years. Two of them are R452B and R454B with GWP values of 675 and 466, respectively. This paper presents an experimental study of the drop-in performance of refrigerants R452B and R454B in an R410A liquid-to-water heat pump. Experimental results for the three refrigerants are presented for the heating mode of operation at two different water temperatures in the condenser and different compressor speeds. The effect of the refrigerant charge for each case is also studied in order to identify its impact on the heat pump performance. An optimum charge that maximized the system COP could be determined for each refrigerant. This optimum charge is lower for the alternative refrigerants and it is slightly affected by the test condition and compressor speed. When compared with R410A, the lower-GWP alternatives present higher discharge temperatures, lower heating and compression powers, and similar COPs.