Abstract: A reverse cycle defrost or water defrost type ice-maker refrigeration system includes a programmable controller which initiates a freezing cycle in which water is pumped for application to the chilled surface of an evaporator for freezing. All water that fails to be frozen absorbs minerals from the frozen water and is returned to the sump. The programmable controller terminates replenishment of water removed from the sump substantially prior to completion of the freezing cycle so that the sump level falls and the mineral content of water in the sump increases substantially. The ice is harvested at the end of the freezing cycle by hot refrigerant gas from the compressor directed to the evaporator or warm water while the sump is being drained and subsequently refilled prior to the initiation of a subsequent cycle of operation. The operation is energy efficient since water is saved and a reduced amount of water is used and a reduced amount of previously refrigerated water is disposed of by drainage of the sump.