Refrigeration system and a method for controlling such a refrigeration system

A method for controlling a refrigeration system, the refrigeration system comprising:

• a compressor for compressing a gaseous refrigerant, such that the temperature, pressure and boiling point thereof increases;
• a four-way valve controlling whether the refrigeration system is in a heating mode or a cooling mode;
• a condenser, in which the gaseous refrigerant from the compressor exchanges heat with a high temperature heat carrier, said heat exchange resulting in the refrigerant condensing;
• an expansion valve reducing the pressure of liquid refrigerant from the condenser, hence reducing the boiling point of the refrigerant;
• an evaporator, in which the low boiling point refrigerant exchanges heat with a low temperature heat carrier, such that the refrigerant vaporizes;
• a suction gas heat exchanger exchanging heat between high temperature liquid refrigerant from the condenser and low temperature gaseous refrigerant from the evaporator;
• and
• a balance valve arranged for controlling the amount of heat exchange between the high temperature liquid refrigerant and the low temperature gaseous refrigerant in the suction gas heat exchanger by directing a flow of high temperature liquid refrigerant from the condenser to the expansion valve without passing the suction gas heat exchanger;
• the method comprising:
• a) measuring a temperature of the high temperature liquid refrigerant;
• b) measuring a temperature of the low temperature gaseous refrigerant;
• c) calculating a temperature difference between the high temperature liquid refrigerant and the low temperature gaseous refrigerant;
• and
• d) controlling the balance valve to bypass the suction gas heat exchanger should the difference be less than a predetermined threshold value.