Frequently asked PDU questions

1. What does PDU stand for?

PDU stands for Power Distribution Unit. It is the heart of the power supply within a server rack or other IT installation. A PDU ensures that electrical power from the main supply is distributed in a controlled manner to all connected servers, switches, storage systems and other critical hardware.

In a data centre environment, a PDU is much more than just a power strip:

• Reliable power distribution: A PDU ensures that each device receives the correct voltage and current, without overloads or unnecessary losses.

• Continuity of IT services: By using PDUs with monitoring and switching capabilities, operators can prevent outages and respond more quickly when intervention is required.

• Intelligent energy management: Modern PDUs measure power consumption at rack, branch or outlet level. This provides data centre managers with the insights they need to plan capacity, improve energy efficiency and meet compliance requirements.

• Integration with IT infrastructure: Advanced PDUs communicate directly with DCIM and BMS systems, making energy data an integral part of overall data centre monitoring.

2. What is a PDU?

A PDU is a professional power distribution device specifically designed for use in data centers and server rooms. It distributes power efficiently and often includes additional features such as power monitoring and switching capabilities.

3. Why use a PDU?

PDUs provide a safe, efficient and organised way to distribute power within a server rack. They help manage energy consumption, optimise space and offer capabilities such as monitoring and switching.

In high-density racks running AI servers, HPC clusters or cloud infrastructure, power levels can quickly reach tens of kilowatts per rack. Without a reliable PDU, a power-related issue can lead to downtime, data loss and significant costs.

For this reason, a PDU has become an integral part of critical IT infrastructure:

• They ensure the safe distribution of high power loads.

• They enable remote switching, allowing servers to be powered on or off in a controlled manner.

• They provide data that can be used for capacity planning, predictive maintenance and energy reporting.

• They support sustainability and energy optimisation, which are increasingly important in modern data centres.

4. What is the difference between a power strip and a PDU?

A power strip is simply an extension lead with multiple sockets, while a PDU is designed for professional use in racks, offering options for monitoring, switching, and other advanced features.

5. What’s inside a PDU?

A PDU typically contains:

• An inlet (for power input)
• A series of outlets (for power output)
• Depending on the type, internal components for monitoring, switching, or surge protection.

6. What is a PDU inlet?

The PDU inlet is the connection point where power enters the PDU. This can be a fixed power cable or an inlet connector, such as a C14 or C20 connector.

7. What types of PDUs are there?

There are several types of PDUs, including:

• Basic: No monitoring
• Basic Plus: Upgradeable to monitoring
• Metered: Monitoring per phase and circuit breaker
• Monitored: Monitoring per phase, circuit breaker, and outlet
• Switched: Monitoring with switching capabilities per outlet
• Managed: Full monitoring and switching per outlet
• Inline Meter: Monitoring for existing PDUs

8. What does a metered PDU mean?

A metered PDU provides power monitoring at the level of phases and circuit breakers, helping manage energy consumption.

9. How does an intelligent PDU work?

An intelligent PDU (such as a Managed or Monitored PDU) has sensors and communication modules that enable real-time monitoring and management. Users can remotely check and control data such as power consumption, voltage, and current.

10. Do PDUs have circuit breakers?

Yes, many PDUs come with circuit breakers to protect connected equipment from overload.

11. What’s the difference between a UPS and a PDU?

• UPS (Uninterruptible Power Supply): Provides emergency power and protects against voltage spikes and power outages.
• PDU: Distributes power efficiently to multiple devices in a rack.

12. Do PDUs have surge protection?

Some PDUs offer surge protection, but this is not standard on every PDU. Be sure to check the device’s specifications.

13. How many PDUs do I need in a rack?

The number of required PDUs depends on the power consumption of your equipment, the desired redundancy, and the layout of your rack. In professional data centre environments, it is standard to install at least two PDUs per rack: one on the A feed and one on the B feed. This ensures power redundancy – if one path fails, your equipment continues running on the other feed.

In high-density or critical infrastructure racks, a C feed may also be used. In some cases, multiple PDUs per feed are installed to support both horizontal and vertical equipment distribution.

14. Where should I mount the PDU in the rack?

PDUs are typically mounted on the side or rear of a rack. This optimizes accessibility and saves space.

15. What does a rack PDU do?

A rack PDU distributes power to the equipment within a server rack. Depending on the type, it may also provide monitoring, switching, and remote management.

16. What is a floor PDU?

A floor PDU is a larger power distribution unit used to distribute power across multiple racks or zones within a data center.

17. What is the voltage of a PDU?

The voltage varies depending on the PDU type and region. In Europe, the standard voltage is 230V, but there are also PDUs for 400V or other voltages.

18. Which PDU do I need?

The choice depends on your needs:

• Basic: No monitoring. This type of PDU is ideal for simple applications where only power distribution is required, without the need for monitoring or additional features. It is suitable for small offices, non-critical IT systems, or equipment with predictable power consumption.
• Basic Plus: Upgradeable to energy monitoring. This PDU is suitable for situations where you don’t currently need monitoring but want the flexibility to add it later. It is useful in growing IT environments where future energy management may play a role.
• Metered: Energy monitoring per phase and circuit breaker. This PDU is necessary in environments where insight into total energy consumption is essential, such as medium-sized data centres or server rooms. It helps with capacity management and identifying peak loads.
• Monitored: Energy monitoring per phase, circuit breaker, and outlet. This type of PDU is suitable for data centres and IT environments where detailed insights into energy consumption per device are required. It is useful for detailed reporting, cost management, and energy-saving initiatives.
• Switched: Energy monitoring per phase and remote switching per outlet. This PDU is ideal for situations where you want to be able to restart or switch off equipment remotely. It is suitable for businesses with multiple locations or data centres where physical access is limited.
• Managed: Full energy monitoring and remote switching per outlet. This type of PDU is essential in high-performance data centres and critical IT environments. It provides maximum control over energy consumption and device management, improving operational efficiency and uptime.
• Inline Meter: Energy monitoring for existing PDUs without monitoring. This is an excellent option if you already have existing PDUs without energy monitoring but need insight into power usage. It is suitable for upgrading older racks or equipment with basic PDUs without replacing them entirely.

19. Is a PDU necessary?

Yes, especially in professional environments like data centers, where efficiency, safety, and monitoring are essential.

20. Who manufactures PDUs?

Many manufacturers produce PDUs, including us at Schleifenbauer. We offer customized PDU solutions tailored to the needs of our customers.

21. What does DCEM mean?

DCEM stands for Data Centre Energy Management. It is software that helps data centres gain insight into, analyse and optimise the energy consumption of IT equipment and infrastructure. DCEM software collects measurement data from sources such as PDUs and inline meters and translates this data into actionable information for energy management, cost control and compliance.

22. What is DCEM software and what is it used for in data centres?

DCEM software is energy management software for data centres. It is used to monitor real-time and historical energy data at rack, PDU, circuit or outlet level. Data centre operators use DCEM software to reduce energy waste, improve capacity planning, generate reports and comply with regulations such as energy audit requirements.

23. What is the difference between DCEM software and DCIM software?

DCIM (Data Centre Infrastructure Management) focuses on the entire data centre infrastructure, including space, cooling, assets and workflows.
DCEM (Data Centre Energy Management) software focuses specifically on energy and power management. DCEM is often simpler, faster to deploy and more scalable when energy insight and energy reporting are the primary requirements.

24. What data does DCEM software use?

DCEM software uses measurement data from sources including:

• Managed and monitored PDUs
• Inline meters
• Power measurements per input, branch and outlet
• Environmental or status sensors

This data is used for real-time monitoring, trend analysis, alarms and energy reporting per rack, customer or location.

25. Is DCEM software suitable for energy compliance and reporting?

Yes. DCEM software is widely used for energy compliance, audits and reporting. It helps data centres demonstrate energy consumption, efficiency and CO₂-related targets. DCEM supports reporting for both internal analysis and external compliance requirements, without the need for complex DCIM systems.