Coolant Distribution Units (CDUs) for Liquid Cooling
A coolant distribution unit is the heart of a liquid-cooled AI hall. It isolates a clean, filtered "technical" loop for the server cold plates from the facility water, pumps and controls the coolant, and sets the flow and temperature the GPUs need. Modern liquid-to-liquid CDUs reject up to 1.3 MW per unit.
What it is
A coolant distribution unit (CDU) sits between the facility cooling loop and the direct-to-chip cold plates. Inside a liquid-to-liquid (L2L) CDU, a heat exchanger transfers heat from the secondary loop (the clean technical water that touches the servers) to the primary loop (facility water going to the chiller), while keeping the two fluids separate. This lets you run treated, filtered, corrosion-controlled coolant through delicate cold plates regardless of facility water quality.
The CDU also owns the hydraulics and controls: redundant pumps (typically N+1), variable-speed control to hold a target supply temperature and flow rate, filtration, and instrumentation for leak detection and monitoring. Sizing is by heat load — a 1.3 MW liquid-to-liquid unit serves a cluster of high-density racks — and units are provisioned with N+1 headroom so one pump or one CDU can fail without dropping the racks it feeds.
When you need it
Any direct-to-chip liquid cooling deployment needs a CDU. It is the piece that makes cold plates safe and controllable at facility scale.
- Any direct-to-chip liquid cooling build — the CDU isolates and controls the cold-plate loop.
- Rack clusters above ~40 kW/rack where cold plates need clean, temperature-controlled coolant.
- GB200 / GB300 NVL72 halls, sized so total rack heat is matched by CDU capacity with N+1 headroom.
- Poor or unknown facility water quality — the L2L design keeps corrosive facility water off the cold plates.
- Redundancy targets (N+1 / 2N) that require pump and unit failover without losing the racks.
Quick facts & specs
Vertiv · Vertiv CDU 1.3 MW
| Type | Liquid-to-liquid CDU |
|---|---|
| Cooling capacity | 1,300 kW |
| Loops | Primary + secondary |
| Pump redundancy | N+1 |
| Approach temp | ≤ 3°C |
| Install | In-row, floor-mounted |
AI Rack Cooling Calculator
Size cooling capacity and heat rejection per rack, get an air-vs-liquid recommendation and CDU sizing.
Source it
Add the equipment to your quote list — pricing, availability and lead times are confirmed after you ask, usually within a business day.
Rear-Door Heat Exchanger
passive rear-door · up to 40 kW/rack
From $7,400 / unit
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Frequently asked
What is a coolant distribution unit (CDU)?
A coolant distribution unit is the pumping and heat-exchange hub of a liquid-cooled data center. It isolates a clean technical water loop for the server cold plates from the facility water, controls the coolant’s flow rate and temperature, and provides filtration, redundant pumps and leak detection. A liquid-to-liquid CDU can reject up to 1.3 MW.
How do I size a CDU for my racks?
Size by heat load: the CDU capacity must match the total rack IT load it serves, with N+1 headroom so a pump or unit can fail without dropping the racks. As a planning rule, one 1.3 MW liquid-to-liquid CDU serves a cluster of high-density direct-to-chip racks. Our AI rack cooling calculator estimates the CDU count for your load.
Liquid-to-liquid vs liquid-to-air CDU — which do I need?
A liquid-to-liquid (L2L) CDU rejects heat to a facility water loop (chiller or dry cooler) and scales to the megawatt loads of an AI hall — the standard for direct-to-chip at scale. Liquid-to-air CDUs reject to room air and suit smaller or retrofit deployments without facility water. Most AI training halls use L2L units.
Why does a CDU isolate two loops?
The secondary (technical) loop that touches the cold plates needs treated, filtered, corrosion-controlled coolant to protect the fine channels in the plates. Facility water is often not clean enough. The CDU’s heat exchanger transfers heat between the loops while keeping the fluids separate, so cold-plate coolant stays clean regardless of facility water quality.