An air-to-air split-system residential heat pump of nominal 2 3/4-ton (9.7-kW) capacity was instrumented and tested in the laboratory. The coefficient of performance, system capacity, and component efficiencies were measured during steady-state and frosting-defrosting conditions in the heating mode (1) to gain better understanding of the physical processes that affect the performance of the test heat pump and (2) to quantify the frosting and defrosting losses. Cumulative frosting and defrosting loss coefficients were calculated, from which empirical frosting and defrosting algorithms were developed for modeling of frosting and defrosting losses. Seasonal analyses indicate that the test heat pump with tube-and-wavy-fin outdoor coil had 1% to 5% energy loss due to frosting and demand defrosting accounted for only an additional 1% to 3% yearly energy loss. Demand defrost control can reduce yearly frosting-defrosting losses by 5% to 10% over 90- and 45-minute time-temperature controls.

Units: Dual