A refrigeration system including at least one refrigeration circuit, the refrigeration circuit comprising: a compressor for compressing a refrigerant fluid in the refrigeration circuit; a first heat rejecting heat exchanger for receiving the compressed refrigerant fluid and exchanging heat between the compressed refrigerant fluid and a second fluid to increase the temperature of the second fluid; a second heat rejecting heat exchanger for receiving the compressed refrigerant fluid and exchanging heat with ambient air to cool the compressed refrigerant fluid; an expansion valve for expansion of the refrigerant fluid; a heat absorbing heat exchanger for heat exchange between the expanded refrigerant fluid and a third fluid to decrease the temperature of the third fluid; a heat recovery control valve for controlling flow of the compressed refrigerant fluid between the first heat rejecting heat exchanger and the second heat rejecting heat exchanger, with the valve having a variable opening; a plurality of sensors including one or more of a sensor for ambient air temperature, a sensor for temperature of the temperature controlled space, and sensors for obtaining temperature and/or pressure measurements within the refrigeration circuit; and a controller for control of the variable opening of the heat recovery control valve, wherein the controller is arranged to receive measurements from the plurality of sensors; and means for obtaining the temperature of the second fluid, said means comprising the plurality of sensors and the controller; characterised in that the controller is arranged to control the size of the variable opening based on the temperature of the second fluid after heat exchange with the refrigerant fluid, wherein the controller is arranged to control the size of the variable opening of the heat recovery control valve to ensure a required set-point temperature for the second fluid, with the degree of opening of the heat recovery control valve being reduced if the temperature of the second fluid is below the set-point temperature. a compressor for compressing a refrigerant fluid in the refrigeration circuit; a first heat rejecting heat exchanger for receiving the compressed refrigerant fluid and exchanging heat between the compressed refrigerant fluid and a second fluid to increase the temperature of the second fluid; a second heat rejecting heat exchanger for receiving the compressed refrigerant fluid and exchanging heat with ambient air to cool the compressed refrigerant fluid; an expansion valve for expansion of the refrigerant fluid; a heat absorbing heat exchanger for heat exchange between the expanded refrigerant fluid and a third fluid to decrease the temperature of the third fluid; a heat recovery control valve for controlling flow of the compressed refrigerant fluid between the first heat rejecting heat exchanger and the second heat rejecting heat exchanger, with the valve having a variable opening; a plurality of sensors including one or more of a sensor for ambient air temperature, a sensor for temperature of the temperature controlled space, and sensors for obtaining temperature and/or pressure measurements within the refrigeration circuit; and a controller for control of the variable opening of the heat recovery control valve, wherein the controller is arranged to receive measurements from the plurality of sensors; and means for obtaining the temperature of the second fluid, said means comprising the plurality of sensors and the controller; characterised in that the controller is arranged to control the size of the variable opening based on the temperature of the second fluid after heat exchange with the refrigerant fluid, wherein the controller is arranged to control the size of the variable opening of the heat recovery control valve to ensure a required set-point temperature for the second fluid, with the degree of opening of the heat recovery control valve being reduced if the temperature of the second fluid is below the set-point temperature.