A ground-coil heat pump (GCHP) system with six shallow-well U-tubes of unequal depth was installed at the test site in Knoxville, TN. The system was operated for one cooling and one heating season. During that time, the cooling seasonal performance factor (SPF) was 1.75 and the heating SPF was 2.85. An annual performance factor (APF) of 2.39 was achieved, compared to 2.10-2.17 for an air- source heat-pump (ASHP) in an identical house. Hourly integrated peak demands for the GCHP system were 3 .3 kW for winter and 3.8 kW for summer. Peaks for the ASHP were 9.1 kW and 3.7 kW, respectively.

The GCHP system was also subjected to two weeks of continuous tests and five days of cyclic tests. An equivalent radius approach was adopted to analyze the experimental results. It was found that the equivalent radii for the wells were not equal. However, the average equivalent radius for the six wells was found to be about 1.3 times the coil radius, which is very close to the multiplier, the square root of 2, used by others.

Units: Dual