It is part of the HSI training system for refrigeration and air conditioning technology. In combination with the base unit the operational model of a domestic refrigerator is created. The model is plugged onto the base unit, secured using fasteners and connected with refrigerant hoses to become a complete refrigeration circuit. It consists of a refrigeration chamber with a heater as cooling load, evaporator, fan and various expansion elements. The fan supports the achievement of an even temperature distribution in the chamber. A cooling load can additionally be simulated with the heater. Solenoid valves enable the operation of the system with capillary tube or with expansion valve. All components are clearly arranged on a panel. The operation of individual system components, here the temperature control, fan, heater, compressor and solenoid valves, takes place via the software. The software offers the option to simulate faults.