A data center is configured using alternating rows of racks containing heat-generating electronic devices and air conditioners. Fluid, such as water or a refrigerant, for the air conditioners is supplied through pluming below a raised floor, such as those commonly found in current data centers. Attached to this plumbing are standard fluid couplings configured to couple to either air conditioners or liquid cooling units. These air conditioners and liquid cooling units use the same fluid so that they may share the plumbing. As data center migrates to liquid-cooled racks, a fraction of the air conditioners are replaced with liquid conditioning units in such a way that the data center contains both air-cooled and liquid-cooled racks without substantial reduction in efficiency of the air-cooling system. Since the air conditioners and liquid conditioning units use the same couplings and the same fluid, no infrastructure change is required.