DATA CENTER COOLING

A system for cooling air in a data center includes a data center having electronic equipment in operation, a cooling water source, and a plurality of on-floor cooling units. The cooling water source is configured to retain at maximum capacity a total amount of water. Each on-floor cooling unit is configured to cool air heated by a portion of the electronic equipment in the data center using water from the cooling water source. The total amount of water is insufficient to maintain a leaving air temperature of each on-floor cooling unit below an inside setpoint when a temperature outside of the data center is above a predetermined external temperature.