A cooling system including a primary cooling module supplying refrigerant to a circuit including a thermal load. A secondary cooling module provides a supplemental flow of refrigerant to the circuit upon detection of a deficiency of the primary cooling module. A valve is disposed between the primary: module and the circuit to prevent refrigerant flow between the primary cooling module in the circuit. The secondary cooling module transactions from a standby mode of operation to an online mode of operation and the primary cooling module is deactivated in response to detection of the deficiency of the primary cooling module.