Ammonia is a natural refrigerant which has been used continuously for more than 100 years. From almost any technical perspective, it is an attractive refrigerant, having good cycle efficiency, good heat transfer properties and low pressure drop compared to most other refrigerants. The volumetric refrigerating effect is also higher than for other fluids of the same vapor pressure. Applications are nowadays restricted almost exclusively to large industrial or commercial systems. We have previously demonstrated that ammonia is also a viable refrigerant for small systems (Palm 2008, Monfared and Palm 2011). In this paper we report on additional tests with a small capacity (7.2 kW) water to water heat pump for sanitary hot water production and space heating. Particularly, the losses in the compressor, electric motor and variable speed drive are investigated under full and part load conditions. New data for the general performance of the heat pump in terms of heat delivered at 60°C for sanitary hot water production and at 40°C for space heating, energy efficiency, etc. will also be reported.
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