Effect of Return Air Leakage on Air Conditioner Performance in Hot/Humid Climates

Abstract

An experimental study was conducted to quantify the effect of return air leakage from hot/humid attic spaces on the performance of a residential air conditioner. Tests were conducted in psychrometric facilities where temperatures and humidities could be controlled closely. Return air leakage from hot attic spaces was simulated by assuming adiabatic mixing of the indoor air at normal conditions with the attic air at high temperatures. Effective capacity and Energy Efficiency Ratio both decreased with increased return air leakage. However, power consumption was relatively constant for all variables except outdoor temperature, which meant that for the same power consumption, the unit delivered much lower performance when there was return air leakage. The increase in sensible heat ratio (SHR) with increasing leakage showed one of the most detrimental effects of return air leakage on performance.