CDU (Coolant Distribution Unit)

A CDU (Coolant Distribution Unit) is the hardware module that separates a data center's facility water loop from the technology cooling loop, controlling the flow, pressure and temperature of coolant delivered to direct-to-chip cold plates or rear-door heat exchangers. In-row and in-rack CDUs typically handle 70 kW to roughly 2.5 MW of heat rejection, while larger sidecar and facility-level units from vendors such as Vertiv, Trane and nVent scale up to 8-14 MW to serve dense AI clusters where individual racks now often draw 30-50+ kW. CDUs use heat exchangers rather than direct mixing to isolate servers from facility-water contaminants while still allowing redundant N+1 pumping within the secondary loop. As liquid cooling scales alongside GPU rack density, CDU capacity and redundancy design have become a spec buyers check alongside PUE and kW-per-rack when evaluating AI-ready colocation space.