The effect of improper refrigerant charging on the performance of an air conditioner with capillary tube expansion

Abstract

Air conditioners currently account for approximately 15% of the energy use in the U.S. residential sector. One of the more popular residential air conditioners is the split system. The outdoor subsystem (condenser and compressor) of a split-system unit is typically precharged with refrigerant at the factory. In the field, a technician has the responsibility of both installing the unit and assuring the proper refrigerant charge of the system. The objective of this investigation was to quantify the effect of improper refrigerant charge on the steady-state and seasonal performance of a residual split-system air conditioner. A literature review was conducted, an experimental setup constructed, and data were collected and analyzed. A 10.6 kW capacity split-system air conditioner with capillary tube expansion was used in the experiments. The charge in the system was systematically varied to determine its effect on system variables such as capacity, power consumption, coefficient of performance and seasonal coefficient of performance. The degradation in performance for each of the variables was generally greater for under-charging than for overcharging. Results indicated that undercharging by as little as 5% can cause as much as a 6.1% drop in seasonal coefficient of performance.