Agricultural products such as fruits, vegetables, grains etc. after harvesting and meats and fishes after butchery and catch must be kept at a specific temperature to preserve in the best condition for distribution to consumers. So, the refrigeration system must be equipped in every warehouse for the products to maintain a specific temperature inside a warehouse, and mainly sets of the evaporator and condensing units consist in the refrigeration system.

An Evaporator has a heat-exchanger and fan-motors in itself and is installed in the warehouse to supply cold air into a warehouse. It names an evaporator as liquid refrigerant from a condensing unit is evaporated in the heat exchanger.

A condensing unit has a compressor, a heat-exchanger, fan-motors, and other necessary accessories in itself and set outside a warehouse and pipe connected with the evaporator. It names a condensing unit as high pressurized gas refrigerant is condensed in the heat-exchanger and changed in liquid refrigerant.

Service parts are fan motors, and other accessories fitted in a condensing unit such as vessels, filter driers, sight glass, valves, etc. Those parts are needed for the system maintenance as the system working time goes on.