Cooling performance improvement of a horizontal ground coupled heat pump

Performance of the horizontal-coil ground-coupled heat pump system for the summers of 1983 and 1984 is described. The overall coefficients of performance (COP) were 1.80 (1983) and 2.41 (1984) while the overall cooling seasonal performance factor (SPF) was 1.11 (1983) and 1.43 (1984) with the system located within the conditioned space. If the system was outside the conditioned space, an SPF of 1.31 (1983) and 1.76 (1984) should be realized. In both years, the systems were identical with the exception that prior to the 1984 cooling season, the ground coil was excavated and a new one of identical length was installed using sand as a backfill material. Although the 1984 SPF was 29% higher than that measured in 1983, the improvement cannot be totally attributed to the backfill material. During the summer of 1983, 30% more cooling degree days were in current than in 1984. A decrease in runtime (as a result of lower ambient temperatures) would also increase the performance factor.