Performance of an air to air heat pump in a temperate climate

The performance of a commercial air-air heat pump installed in an occupied house in New Zealand is reported. The data cover operation both before and after the heat pump was extensively modified to improve the efficiency and reliability. The consequences of the non-optimal refrigerant charge and capillary in the original unit are illustrated and the advantages of installing a suction accumulator, crank-case heater and other improvements described. The results also show the sensitivity of the operating time to changes in the heating capacity and the difficulty in sizing a heat pump for normal residential use.