An Evaluation of Improper Refrigerant Charge on the Performance of a Split System Air Conditioner with a Thermal Expansion Valve

Abstract

The effect of the improper charging on steady state and cyclic performance (capacity, EER, power consumption, SEER, and coefficient of degradation) of a residential air conditioner which utilized a thermal expansion valve was investigated. This study was the continuation of ESL/CON/88-1 performed by Mohsen Farzad and Dennis O'Neal. A fully charged condition was established as a base case. The full charge was obtained by charging the unit to the subcooling specified by the manufacturer for a specific indoor and outdoor temperatures. Once the full charge was determined, the unit was subjected to 40%, 30%, 20%, 15%, 10%, and 5% undercharging and 5%, 10%, 15%, and 20% overcharging of refrigerant by mass. The fully charged tests were compared to those for under and overcharging. The performance of the unit was evaluated as a function of charge as well as at four outdoor room temperatures (82°F, 90°F, 95°F, and 100°F). As the outdoor temperature increased, the total capacity and EER dropped. The maximum total capacity, EER, and SEER were found at 10% undercharging (12 6 oz). The capacity and efficiency (EER and SEER) of the unit were found to be less sensitive to under/overcharging than the unit with a capillary tube expansion previously studied. Other data such as refrigerant flow rate, sensible heat ratio, superheat and subcooling were also presented.