To evaluate the APF of an air conditioner according to GB 21455—2019

the performance parameters of low-temperature intermediate cooling conditions can be measured or converted

resulting in two different APF values using these two different methods in the same air conditioner. Considering the difference in results obtained by the different methods in the national standard

it is necessary to analyze the rationality of the difference and propose an improvement plan. Based on the definition formula of APF

this study presents the reason for the difference in the APF value determined by the test method and the conversion method at the low-temperature intermediate refrigeration condition. The test method given in the national standard causes a variation in energy efficiency under rated intermediate cooling conditions

contrary to the variation in the calculated APF value

which is not reasonable. One possible way to solve the problem of non-uniqueness of APF values is to change the method of obtaining the performance parameters of the low-temperature intermediate refrigeration operating condition stipulated in the national standard from "obtained by testing or conversion according to the rated intermediate refrigeration operating condition" to "obtained only by conversion according to the rated intermediate refrigeration operating condition."