Annual performance, Partial load, Standard
Because of the moderate climate of Japan, most of the air conditioners (A/Cs) used are split-type A/Cs and can provide both heating and cooling during the year. Therefore, the coefficient of performance (COP) and the annual performance factor (APF) are used as criteria to evaluate the annual average performance of A/Cs; these criteria are established on the basis of Japanese Industrial Standards (JIS). The JIS-based performance rating method is easy and useful but does not take into account the intermittently driven mode of the compressor. In practice, A/Cs are mainly operated under partial load conditions, which are often 30%–50% of the full load. In this study, partial load tests were conducted for three different room air conditioners, and the measured APFs were compared to those calculated using the JIS-based calculation method. Because the inverter-driven compressors, which are widely used in A/C systems, are driven intermittently when the load is small and show low COP, the measured APFs were found to be much lower than those calculated using the JIS-based method when taking into account the intermittently driven mode. It is suggested that the JIS be revised by considering the performance deterioration at low load conditions.