A cooling system has both pumped refrigerant economization and direct expansion cooling. When outside air temperature is low enough that pumped refrigerant economization can provide enough cooling to satisfy cooling demand, only pumped refrigerant economization cooling is used to provide cooling. When outside air temperature is low enough that pumped refrigerant economization can provide some but not all of the cooling needed to satisfy cooling demand, the pumped refrigerant economization is operated at one hundred percent capacity and the direct expansion cooling is operated at a capacity to provide any supplemental cooling that is needed. If the outside air temperature is high enough that pumped refrigerant economization cannot provide any cooling, then only direct expansion cooling is used to provide cooling.