A cooling system (100, 150, 200, 300) comprising: a first pump module configured to control a first pump (110, 180, 210, 313) to pump a first cooling fluid through a first cooling circuit (104, 154, 204, 304); a first condenser fan module configured to control a first condenser fan (122, 192, 224, 334) to transfer air across a first condenser (118, 188, 218, 314) of the first cooling circuit (104, 154, 204, 304); and at least one control module (102, 152, 202, 309, 350) configured to, while operating in a pumped refrigerant economizer mode or a mixed mode, determine a requested call for cooling percentage, characterised in that the first pump module is configured to activate the first pump (110, 180, 210, 313) if the requested call for cooling percentage is greater than or equal to a first predetermined call for cooling percentage, and the first condenser fan module is configured to (i) if the requested call for cooling percentage is greater than or equal to the first predetermined call for cooling percentage, at least one of activate the first condenser fan (122, 192, 224, 334) or operate the first condenser fan (122, 192, 224, 334) at least at a first minimum speed, and (ii) based on the requested call for cooling percentage, adjust a speed of the first condenser fan (122, 192, 224, 334) between the first minimum speed and a first maximum permitted speed to provide the requested call for cooling percentage. a first pump module configured to control a first pump (110, 180, 210, 313) to pump a first cooling fluid through a first cooling circuit (104, 154, 204, 304); a first condenser fan module configured to control a first condenser fan (122, 192, 224, 334) to transfer air across a first condenser (118, 188, 218, 314) of the first cooling circuit (104, 154, 204, 304); and at least one control module (102, 152, 202, 309, 350) configured to, while operating in a pumped refrigerant economizer mode or a mixed mode, determine a requested call for cooling percentage, characterised in that the first pump module is configured to activate the first pump (110, 180, 210, 313) if the requested call for cooling percentage is greater than or equal to a first predetermined call for cooling percentage, and the first condenser fan module is configured to (i) if the requested call for cooling percentage is greater than or equal to the first predetermined call for cooling percentage, at least one of activate the first condenser fan (122, 192, 224, 334) or operate the first condenser fan (122, 192, 224, 334) at least at a first minimum speed, and (ii) based on the requested call for cooling percentage, adjust a speed of the first condenser fan (122, 192, 224, 334) between the first minimum speed and a first maximum permitted speed to provide the requested call for cooling percentage. the first pump module is configured to activate the first pump (110, 180, 210, 313) if the requested call for cooling percentage is greater than or equal to a first predetermined call for cooling percentage, and the first condenser fan module is configured to (i) if the requested call for cooling percentage is greater than or equal to the first predetermined call for cooling percentage, at least one of activate the first condenser fan (122, 192, 224, 334) or operate the first condenser fan (122, 192, 224, 334) at least at a first minimum speed, and (ii) based on the requested call for cooling percentage, adjust a speed of the first condenser fan (122, 192, 224, 334) between the first minimum speed and a first maximum permitted speed to provide the requested call for cooling percentage.