Document Type


Publication Date

January 1982


The thermal behavior of a 5-ton groundwater heat pump and the wood-frame house in which it is installed (located in Logan, Utah, latitude 44°49’; elevation 4775 ft.) were investigated during two 30 day peak use periods, the first in late summer and the second in mid-winter. Continuous measurements were taken of indoor and outdoor temperatures, groundwater temperatures, supply and return air temperatures, gallons of groundwater cycled, and Btu rejected or absorbed. These measurements were used for 1) determining the instantaneous heat gains and/or heat losses of the house by conduction and infiltration of both periods studied and 2) computing the average coefficient of performance of the heat pump for both periods. Heat gains from solar radiation through the fenestrations were computed from radiation data obtained from a local meteorologist. The total heat gains and losses (by conduction, infiltration, solar radiation, and internal sources) for each test period, along with the heat removed or added to the living space by the heat pump, were integrated by computer calculation over each of the 30-day test periods. For the summer cooling test period the calculated heat gain exceeded heat loss by 14.6 percent. During the winter heating test period the heat loss exceeded heat gain by only 0.90 percent. Solar radiation during both periods made a significant contribution to the total heat gains. While the output of the heat pump was 19.9 and 7.2 percent lower than the manufacture’s rating for cooling and heating, respectively, the overall average coefficients of performance were 2.92 and 4.13 for the same respective periods. These efficiencies make the system more economical than conventional heating and cooling systems presently in use in the Logan area.