The SP unit is cooled directly by the surrounding water. No fans or pumps are required to remove the heat produced by the compressor, which means it consumes less battery power and operates remarkably quietly. The Isotherm SP unit uses the natural movement of the hull to draw heat down and out through a special fitting in the galley sink drain hose.
The Isotherm ASU system is preserves the maximum cooling capacity of the batteries. It detects when excess energy is supplied by the engine alternator and then increases the power of the compressor to generate cold more quickly in the refrigerated space.