13 tips for better CDU specs in liquid-cooled systems

With the growing density of computing power, liquid cooling is becoming the standard for modern data centers. The central element of such systems is the Coolant Distribution Unit (CDU), and the stability of the entire IT infrastructure depends on its correct selection. An improperly chosen specification can lead to insufficient performance, failures, and significant financial losses.

To help you avoid common mistakes, we have adapted key recommendations from the engineers at Stulz, a global leader in data center cooling solutions. These tips will help you formulate precise technical requirements and select a CDU that perfectly suits your needs.

Step 1: Project and Environmental Requirements

This stage lays the foundation for the future cooling system.

• Define the fluid requirements. Specify the desired type of coolant (e.g., purified deionized water or propylene glycol), as well as the operating temperature and pressure range. This is a key parameter for Stulz CyberCool solutions.
• Consider the environmental conditions. Where will the CDU be installed? Specify the maximum room temperature and humidity, as well as the altitude above sea level, as this affects cooling efficiency.
• Analyze the water source. Describe the characteristics of the facility water circuit, including its temperature, maximum pressure, and available flow rate. This will allow for the selection of a CDU with the appropriate heat exchanger.
• Assess the electrical infrastructure. Specify the available voltage, phase, and frequency for powering the CDU. This ensures full compatibility of the equipment with your electrical grid.

Step 2: Technical Specifications and Performance

Accurate technical data is the key to the system's effective operation.

• Specify the required cooling capacity. This is the most critical parameter. Determine the total heat load (in kW) that the system must dissipate.
• Determine the desired fluid temperature. What fluid temperature should be supplied to the IT equipment? This directly affects server performance.
• Calculate the required flow rate. Specify how many liters per minute (LPM) the system must pump for effective heat removal from the components.
• Choose the pump type. Do you need redundancy (N+1)? Stulz solutions offer configurations with redundant pumps for maximum fault tolerance.
• Specify the communication interfaces. Determine how the CDU will integrate into your monitoring system (BMS/DCIM)—via Modbus, BACnet, or SNMP protocols.

A properly configured CDU is not just a component, but a guarantee of the stability and longevity of your data center.

Step 3: Additional Options and Reliability

Modern CDUs are more than just pumps and heat exchangers.

• Leak detection system. Specify if you need a built-in monitoring system for immediate notification of any fluid leaks.
• Water treatment kit. For systems using deionized water, special cartridges help maintain its quality and protect the equipment.
• Flexible hoses. Determine the required length and diameter of the hoses for connecting to the IT racks.
• Control options. Consider installing additional pressure sensors, flow meters, and buffer tanks to optimize system operation.