Calibration method of refrigerant saturation temperature in a refrigeration system, a controller for applying such a method and a cooling machine

A method of determining a refrigerant or a composition of refrigerants in a refrigeration system comprising an expansion valve, an evaporator, one or more evaporator fans, a condenser, one or more condenser fans, one or more temperature sensors for measuring at least a suction temperature, one or more pressure sensors for measuring at least a suction pressure, a compressor, and a controller for controlling the refrigeration system, the controller comprising a memory, the expansion valve, the evaporator and the compressor being fluidly interconnected in a refrigerant path having refrigerant flowing therein, and wherein said suction temperature and said suction pressure are measured in the refrigerant path between the evaporator and the compressor, the method comprising the steps of:

• a) running a test run and reading out values from two or more of the sensors;
• b) determining a composition by the result of step a;
• and
• c) adjusting the refrigeration system in relation to the composition determined by step b, wherein the method further comprises the additional steps of:
• bringing a saturated temperature and the suction temperature to a stable state, in which a difference between the saturated temperature and the suction temperature exhibits a temperature change with respect to time of less than 0.1° C./min, by increasing an opening degree of the expansion valve and/or reducing a speed of the one or more evaporator fans;
• operating the system for a period of time of between 10 seconds and 10 minutes;
• storing values from the one or more pressure sensors and the one or more temperature sensors in the controller memory;
• and
• bringing back the opening degree of the expansion valve and/or the speed of the one or more evaporator fans to normal operation.