The fastest way to choose a data center liquid cooling pump for your CDU is to follow a four-step decision path — flow rate, head, voltage, then model — instead of ordering the largest pump that fits the manifold. For rack-level CDUs that path usually lands on a 24 V brushless DC pump, stepping up to 48 V on OCP and AI racks; for facility-level CDUs it lands on a 380 V AC multistage pump. The target is the pump whose duty point matches your heat load and loop pressure drop, not the one with the biggest nameplate. This guide walks that path from rack heat load to a specific model number.

The Decision Path at a Glance

Do the steps in order. Flow and head define the duty point; voltage defines which pumps are even eligible; the model is the last choice, not the first.

Step 1: Convert the Heat Load Into a Required Flow Rate

Liquid cooling removes heat by raising the coolant temperature as it circulates, so the flow you need follows from the heat you must remove and the temperature rise you allow:

Flow rate = Heat load ÷ (coolant density × specific heat × ΔT)

As a planning figure, a 20 kW rack with a 10 °C temperature rise needs roughly 28–30 L/min of water-based coolant. Size from the worst-case rack heat load — the sum of GPU TDPs plus overhead — not the average. Allow an 8–12 °C ΔT at the rack CDU: a wider ΔT cuts flow but raises return temperatures, which the facility heat-rejection plant must handle. If your CDU feeds two racks, sum both loads before choosing.

Step 2: Sum the Loop's Pressure Drop Into Required Head

Head is the pressure energy the pump adds to push coolant through every restriction in the loop, and it is the most underestimated number in CDU pump selection. Count each element:

Cold plates: high-performance plates add roughly 3–8 m of pressure drop each.

Quick disconnects and manifolds: typically 1–3 m on a rack loop.

CDU internals: filter, heat exchanger, and control valve add several meters.

Pipe runs and fittings: small, but never zero.

A rack loop commonly totals 8–20 m of dynamic head before margin. Add 10–20% for fouling and filter loading. This is why the P4552 (11 m of head) suits simple, low-drop loops, while the P6092 (27 m of head) is the common choice for high-drop or dual-rack CDUs.

Step 3: Lock the Voltage to the Rack Architecture

Voltage follows the rack, not the pump. Legacy and edge nodes run 12 V; most current racks run 24 V; OCP-style 48 V architectures are spreading quickly because they cut distribution losses at a given power. On the facility side, 380 V three-phase is standard. Choose the voltage band first, then the duty point inside it.

Step 4: Match the Model to the Duty Point

Pick the smallest model whose curve covers both your flow and head at the operating point, then confirm its rated power fits the CDU's electrical budget. For redundancy, plan N+1 pumping so one unit can carry the loop during maintenance or a fault.

FAQ

Q: What is the first thing to size for a CDU pump?

A: Required flow rate, derived from the worst-case rack heat load and your design ΔT. Head and voltage are sized next, and the model is chosen last.

Q: Rack-level or facility-level — which pump class do I need?

A: Rack-level CDUs use brushless DC pumps measured in L/min (12 V–48 V). Facility-level CDUs and distribution use 380 V AC multistage pumps measured in m³/h.

Q: How much head should I budget for a rack CDU loop?

A: Sum the cold plates, quick disconnects, manifold, CDU internals, and pipe runs — typically 8–20 m — then add 10–20% margin for fouling and filter loading.

Q: Can I oversize the pump "just to be safe"?

A: Avoid it. An oversized pump runs away from its best-efficiency point, wastes energy, and hurts the PUE gains liquid cooling is meant to deliver. Size to the duty point.

Q: How do I confirm a pump fits my CDU design?

A: Send the heat load, target ΔT, and loop pressure-drop estimate to the pump supplier. CDU pump selection is a design collaboration, not a catalogue pick.

Data Center Liquid Cooling Pumps from Shenpeng Technology

Shenpeng Technology builds both pump classes that go into CDUs: rack-level brushless DC pumps such as the P4552 (24 V, 11 L/min, 11 m, 28 W), the P6092 (24 V, 25 L/min, 27 m, 88 W), and the P609248I04 (48 V, 30 L/min, 20 m, 100 W), plus the 380 V SP8/20-0.8 (15–30 m, 3–15 m³/h, 800 W) for facility-level units. Contact our engineering team with your heat load, target ΔT, and loop layout — we will confirm the duty point and recommend the right data center liquid cooling pump for your CDU.