From Installation Manual -  The Calorex ‘Propac’ range of air/water heat pumps are designed for swimmingpool heating and consists of 2 models. Heat pumps in this manual aredesigned to heat pool water and spas within the range of 10°C to 40°C.Standard units are suitable for outdoor pools operating in ambient temperaturesabove 10ºC.The water heat exchanger is a full flow type, manufactured fromtitanium tube, which is a highly corrosion resistant material. The heat pumpsare suitable for use in fresh water and salt water pools. The heat pumps arefitted with rotary compressors which are known for quiet running. With thesefeatures the heat pump is designed to have a long, trouble free life