The SP-unit is cooled directly by surrounding water. Because neither a fan or a pump is needed in order to remove the heat generated by the compressor, much less power is consumed and it remains remarkably quiet. It uses the natural pumping action that takes place from the SP-thru-hull to the sink in the pantry.
The Isotherm ASU system allows maximum cooling with minimum load on the batteries. It senses when surplus power from the engine alternator is available and increases the speed of the compressor, so that the cooling unit is cooled down quickly.