Results of a 20-month performance monitoring project on a groundwater source heat pump system installed in a 12,500 ft² (1,161 m²) office building are reviewed. The open-loop groundwater source heat pump system serves as the central plant for a 14-zone, internal water,loop heat pump system.

Intensive monitoring of the open-loop groundwater central plant during phase 1 of the project showed a heating mode seasonal performance factor of 2. Results for phase 1 cooling mode showed a seasonal average COP of 37 (EER 127). These cooling results are superior when compared to alternative cooling systems such as a spray cooler or cooling tower, typically used as the central plant.

A second water source heat pump was added during Phase 2. Results for phase 2 heating mode show that a seasonal performance factor of 3.0 was obtained for the improved central plant. The second water source heat pump replaced a backup electric water heater previously used for the second stage of heating.

Results of economic analysis show a simple ,payback of two to three years when this open-loop water source heat pump system is compared to a conventional central plant consisting of an electric boiler and cooling tower. The system does not have a payback when compared to oil or gas systems at current prices. The second heat pump added in phase 2 has a 0.8 year payback period compared to the phase I system.

The authors conclude that an open-loop groundwater heat pump system as a central plant is competitive with all-electric systems in small commercial buildings.

Units: Dual