PERFORMANCE OF GROUND SOURCE RESIDENTIAL HEAT PUMPS
This paper presents the results of two-year monitoring of two ground-to-floor residential heat pumps, typical of the Belgian market, used for space heating in single-family houses. Both systems are commontype vapor compression heat pumps and use ground as cold source, house floor as hot sink and R22 as refrigerant. Firstly, we present the measurement method to obtain daily COP values from instantaneous measurements on the refrigerant. Secondly, annual energy consumption, seasonal COP and costs are presented for a three-year (heat pump #1) and two-year period (heat pump #2). Seasonal COP values from 2.69 to 2.96 are obtained. Finally, daily COP values are correlated to evaporation and condensation temperatures, and the daily running time of the heat pump is correlated to the day-average outdoor temperature. Condensation temperatures, which vary from 35 to 38 °C, are well explained by the daily running time of the heat pump. Evaporation temperatures, which vary from -2 to -9 °C, are related to the ground temperatures in a complex way, depending on the heat transfer processes in the ground.