The compressor drive motor is controlled using a frequency converter. The evaporators are in individual insulated compartments. In the first compartment the temperature is regulated using an intake pressure controller and thermostat (mechanical regulation), in the second compartment using a case controller (electronic regulation). The cooling capacity of the system with 2 separate evaporators can be changed by adjusting the speed of the open compressor. In both cooling compartments a cooling load can be generated using an electrical heater. Fans ensure even temperature distribution. A bypass capacity regulator is installed in the refrigerant circuit that connects the high and low pressure sides of the compressor. The signals provided by these sensors are also used by the case controller. The system is equipped with temperature sensors at all relevant measuring points.