During this process it is automatically ensured that the compressors are evenly loaded. A cooling load can be applied to the evaporator in the system using a heater in a closed brine circuit. This compound system is controlled via a regulator so that individual compressors can be switched in, depending on the performance required. Using the compound controller it is also possible to compare the energies during individual and combined operation, as the power consumption of the compressors in operation can be read on the controller. The measurement of all relevant process parameters with electronic sensors allows the data to be acquired by a PC. A data acquisition card and analysis software is included. All measured data can be simultaneously read on the system so operation is also possible without a PC. The system requires a supply of three phase mains electricity.