Abstract: A system includes one or more modular hot aisle cooling units (MHACUs) disposed in a data hall, each MHACU configured to cool one or more servers in the data hall. The system also includes a fluid cooler configured to receive the heated fluid from the one or more MHACUs, cool the heated fluid into cooled fluid, and output the cooled fluid. The system also includes a fluid supply line configured to convey the cooled fluid to the one or more MHACUs in order to cool heated air inside the data hall. The system also includes a pump package configured to control a flow of the heated fluid and the cooled fluid. The fluid cooler, the one or more MHACUs, and the pump package form a single fluid loop.