Reports on the performance of two water-to-air heat pumps that were designed primarily for southern installations. The design details are presented in an accompanying paper (Kavanaugh 1991). One unit is optimised for cooling efficiency with condenser entering-water temperatures in the 75 deg F to 85 deg F (24 deg C to 29 deg C) range. It has water-heating capabilities using either refrigerants superheat or dedicated (full condensation) capacity. A similar unit was designed and built with air-to-refrigerant (indoor) coil bypass when the heat pump is using the full capacity of the compressor to heat water. Test results indicate significant improvements in cooling efficiencies over currently available water-to-air heat pumps. The highest certified water-to-air heat pump with a reciprocating compressor had an EER of 12.5 Btu/Wh (COP = 3.7) (ARI 1988) when this project was initiated. At the ARI rating conditions, the heat pump optimised for cooling efficiency operated with an EER of 14.7 Btu/Wh (COP = 4.3). Actual efficiency improvements were slightly better, since the test units have low water-side friction losses. The heating efficiencies are comparable to the best units in the certified rating programme. The second unit has slightly lower efficiency, as expected. However, the testing of the unit indicates bypassing the indoor coil in the dedicated water-heating mode may be unnecessary if a suction accumulator is used. Preliminary estimates indicate an additional 20% improvement in both cooling and heating efficiency is possible with scroll compressors and improved heat exchanger, fan, and pump designs. Units recently introduced by manufacturers indicate that this estimate has been partially realised.

KEYWORDS: testing, water air heat pumps, cooling, efficiency, soil heat pumps, performance, water heating, reciprocating compressors, heating, heat pumps.