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

Abstract

The effect of the improper charging on the performance (capacity, EER, power consumption, SEER, and coefficient of degradation) of a residential air conditioner during the steady state (wet and dry coils) and cycling operation was investigated. The fully charged condition was established as a base case. A full charge was obtained charging the unit to the superheat specified by the manufacturer's charging chart for specific set of indoor and outdoor temperatures. Once the full charge was determined, the unit was subjected to 20%, 15%, 10%, and 5% under and overcharging of refrigerant (by mass). The fully charged tests were compared to 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 investigation of improper charging showed that the total capacity, EER, and SEER were more sensitive to undercharging than overcharging conditions. A 20% undercharge resulted in a 21% reduction in SEER while a 20% overcharge produced a 11% reduction in SEER. Other data such as refrigerant flow rate, sensible heat ratio, superheat and subcooling are also presented.