Coolant distribution units (CDUs)

What it is

A CDU moves heat from the IT-side loop (TCS) to the facility water system (FWS) through a plate heat exchanger. It controls supply temperature and flow, keeps the TCS above the dew point, filters the coolant and raises alarms on leaks, pressure or flow. Liquid-to-air units reject heat to room air instead and suit sites without facility water.

Form factors

In-rack units sit inside an IT rack and typically cover tens to low hundreds of kW. In-row units sit in the row and in 2026 commonly span about 0.6 to 2.5 MW. Facility or skid units sit in a gallery or plant room and are marketed from about 2.5 MW to beyond 8 MW per unit. Examples with published figures: Vertiv CoolChip CDU 70 to 2300 kW, Rittal CDU In-Row 1,000 kW at 4 K approach, DCX 8 MW FDU at 2 °C approach.

Why ratings are hard to compare

A capacity figure means little without approach temperature difference (ATD), flow per kW, fluid (water, PG25) and supply temperatures. The same Eaton ROL2300 is rated 2,300 kW at 8 °C approach and 1,150 kW at 4 °C. LiquidStack's CDU-1MW reaches 1,350 kW at 1.15 lpm/kW but 1,004 kW at 1.50 lpm/kW. Always normalise to the same ATD and lpm/kW.

Sourcing considerations

Check redundancy (N+1 pumps, 2N filters, dual power feeds), filtration grade (25 or 50 micron, side-stream 0.2 micron options), wetted materials and fluid compatibility, controls protocols (Redfish, Modbus, BACnet, SNMP), group control for many units, harmonics of pump drives, service access, factory test load, local service coverage and lead time. The Open Compute Project publishes the Project Deschutes facility specification as an open reference for CDU requirements.

Prototype vs shipping

Many 2025 to 2026 CDUs are announced before they ship. Examples in our records: Trane LiquidStack CDU 2.X is on pre-order with shipments from Q2 2027. nVent lists CX121 and CZ61/CZ62 on a 'coming in 2026' page. Supplier records mark each product family as prototype, announced, orderable or shipping, and unknown status stays unknown.

Questions to ask suppliers

• State capacity at a defined ATD, TCS flow per kW, fluid and FWS/TCS supply temperatures
• Pump redundancy and whether pumps and filters are hot-swappable
• Filtration grade on TCS and FWS sides
• Wetted materials list and approved coolants
• Control protocols and group control limits
• Electrical supply options, dual feed, harmonic mitigation
• Factory acceptance test load and witness options
• Commissioning, flushing and fluid sampling responsibility
• Local service presence and spares stock in the project country
• Lead time and current shipping status

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