The schematic shows a kitchen refrigeration system that contains a heat exchanger with related pumps and controls used to pre-heat domestic hot water to a maximum temperature of 30°C. The system utilizes either a once-through potable cold water supply or back-up condenser water loop to cool the refrigeration compressors. The potable water supply and normally-closed chilled water supply combine and cool the compressors. The compressor-heated water can either be allowed to drain away to the municipal sewer or returned to the condensers for additional cooling when the cold water supply alone cannot meet the load. The heat exchanger for domestic hot water pre-heating straddles the combined potable and chilled water supply piping and the chilled water return piping. Pumps were added on both sides of the heat exchanger that ensure the counter-flow of compressor-heated water and the supply for the pre-heating of domestic hot water. To maintain the refrigeration loop within an acceptable temperature range, whenever the cooling loop exceeds 29°C a temperature sensor causes a solenoid-controlled valve on the drain to open, allowing the warmed potable water to drain away to the sewer, shuts off the 2 pumps related to the heat recovery system, and the cooling system reverts to its pre-retrofit operation.