Performance of a Ground Source Heat Pump Coupled to Slinky™ Ground Heat Exchangers

A nominal four ton Ground Source Heat Pump (GSHP) system utilizing slinky™ ground heat exchangers was monitored in a residential structure. The system was instrumented to collect on-off time, loop inlet and outlet temperatures, air supply and return temperatures, outdoor air temperature, loop flow rate, electrical energy consumption, and undisturbed soil temperatures. Data were collected beginning November 9, 1993 through March 31, 1995. The performance of the ground loop is documented and analyzed relative to the IGSHPA loop design equation. The cost of operating the GSHP system and the domestic water heater are presented. System electrical demand, heating or cooling capacity, and COP or EER are calculated on a monthly basis. An early problem with heat pump performance was traced to reduction in system air flow caused by dirt accumulation in the air filter. The economics of using a desuperheater, to supplement domestic hot water needs, are analyzed during heating mode operation.