Power distribution FAQs

Power distribution is a critical part of any IT or facility infrastructure, facilitated through power distribution units (PDUs). These devices take the power conditioned by your uninterruptible power supply (UPS) and deliver it to your IT equipment. PDUs help manage and even control energy consumption, whether in smaller environments or large-scale data centers. By ensuring efficient power delivery, PDUs contribute to reduced operating costs and increased system reliability. Whether you're equipping a few racks or an entire data center, selecting the right PDU is essential to building an effective power infrastructure.

One of the key factors in choosing a PDU is understanding the type of power it handles—namely, whether it’s single-phase or three-phase. The number of phases a PDU supports refers to the electrical phases it receives and distributes. Single-phase PDUs are commonly used in environments with lower power demands, such as small to medium-sized businesses, schools and office buildings. In contrast, three-phase PDUs are designed for high-capacity power distribution and are ideal for large power consumers like colocation data centers and hospitals. These facilities require large volumes of electricity, and three-phase power provides the most efficient means of delivery.

Understanding your specific environment and power requirements—along with the differences between single-phase and three-phase options—will help you select the ideal PDU solution for your power distribution needs.

Deploying both a cabinet/floor-standing PDU and a rack mount PDU together offers a comprehensive power management solution that enhances efficiency, reliability, and scalability in data centers and other high-power environments. This combination allows for optimized power distribution, ensuring that high-capacity power from the floor-standing PDU is efficiently delivered to multiple racks while the rack-mount PDU provides localized power management within each rack. This setup prevents overloading circuits and improves power allocation across critical infrastructure.

One major benefit of using both types is redundancy and reliability. If one PDU encounters an issue, the other can serve as a backup, reducing the risk of downtime. Additionally, having multiple power sources allows for better load balancing, which prevents overheating and power disruptions. Another advantage is scalability and flexibility—floor-standing PDUs support high-power loads and can accommodate future growth, while rack-mount PDUs allow IT teams to configure power distribution at the rack level, making it easier to adapt to changing equipment needs.

Cable management is also significantly improved when both PDUs are used together. The floor-standing PDU supplies power to multiple racks, reducing the need for excessive cabling across the facility, while rack-mounted PDUs organize and distribute power efficiently within each rack. Furthermore, deploying both types enables enhanced monitoring and control, as many modern PDUs offer remote power management features, allowing IT teams to track power usage and optimize efficiency at both the room and rack levels.

Ultimately, using a floor-standing and rack-mount PDU together ensures a robust and efficient power distribution system. This setup enhances redundancy, scalability, organization, and monitoring capabilities, making it ideal for mission-critical IT infrastructure where uptime and power efficiency are top priorities.

Rack mount and floor-standing PDUs serve different roles in power distribution, making them suitable for distinct environments based on size, power needs, and infrastructure.

Rack-mount PDUs are ideal for data centers and server rooms where multiple servers, networking equipment, and storage devices require reliable power distribution within a single rack. They are also well-suited for enterprise IT and telecom closets, efficiently managing power in small to medium-sized IT rooms. Additionally, edge computing sites  and remote locations benefit from rack mount PDUs, as they provide stable power distribution and remote monitoring capabilities. Industrial and lab environments also utilize them for powering multiple devices within equipment racks. These PDUs are space-efficient, offering precise power allocation and advanced features like remote monitoring and outlet-level control.

On the other hand, floor-standing PDUs are best suited for large data centers and high-density power applications where centralized power distribution is needed across multiple racks. They are commonly used in manufacturing and industrial facilities to support heavy machinery and industrial IT systems with continuous high-power demands. Broadcast and media production studios rely on floor-standing PDUs to power extensive audio, video, and broadcasting equipment, while universities and research institutions integrate them into high-performance computing clusters and large-scale research labs. These PDUs handle high-power loads, provide centralized distribution, and support redundant power configurations for mission-critical operations.

Choosing between a rack mount and a floor-standing PDU depends on the specific needs of the environment. If localized power distribution within a rack is required, a rack mount PDU is the best choice. For high-power, centralized distribution across multiple racks, a floor-standing PDU is more suitable. In large-scale IT environments, deploying both ensures optimal redundancy and efficiency, balancing power loads and improving overall system reliability.

What is the difference between a UPS and a PDU?

An Uninterruptible Power Supply (UPS) provides battery backup to IT equipment and other electronics during power outages. A UPS also filters incoming power and provides surge protection.

A Power Distribution Unit (PDU) distributes the power from the UPS or other AC source, such as a wall outlet or generator, to multiple devices. It does not generate or condition power on its own.

What is the difference between a PDU and a rack-mount power strip or surge protector?

PDUs, power strips and surge protectors all provide multiple outlets. What a PDU adds is support for robust distribution of reliable network power for multiple servers, networking hardware, telecom equipment and other IT devices. A PDU will distribute the available amperage evenly and efficiently among all outlets so that all connected equipment receives the best available power to maintain operation. PDUs can also provide higher maximum load capacities than power strips. Basic 120V PDUs are available from Eaton that can provide up to 3.8kW of power, much more than even the typical industrial power strip can handle.

Depending the type of PDU, you also get options for input current monitoring, remote monitoring and control, secure access and environmental monitoring.

Note that most PDUs do not provide surge protection because a PDU installed in a rack is typically connected to a UPS system. The UPS protects connected equipment from power surges and line noise interference. For Eaton PDUs with premium Isobar® surge protection built in, see our selection.

What is the difference between a power distribution unit and a power distribution center or cabinet?

A power distribution cabinet, also known as a power distribution center, is electrical equipment that provides supply and redistribution of electrical energy, protection of electrical power lines and protection of the overload and short circuit currents. See Eaton solutions for power distribution centers.

What is the best power supply for a rack?

A Power Distribution Unit (PDU) is designed for the specific purpose of powering multiple devices in a server rack or enclosure. A PDU distributes the available amperage evenly and efficiently among all outlets so that all connected servers, networking hardware, telecom equipment and other devices receive the best available power to maintain operation. PDUs are available in a variety of styles that provide everything from basic power distribution to enhanced remote power management.

How do you use a hot-swap PDU?

The dual input and manual bypass features of the PDU enable UPS system maintenance–from battery replacement to complete power module exchange–without powering down connected mission-critical equipment and hiring costly service specialists. Here are the basics of using a hot-swap PDU:

1. Plug the primary input of the hot-swap PDU into an on-line UPS system.
2. Plug the secondary input into utility power, i.e. a wall outlet.
3. If the UPS needs to be taken offline for maintenance, repair or replacement, use the manual transfer switch to move the connected load to the secondary input. When the UPS is restored, switch the PDU back to the primary input.

For further reading, refer to our hot-swap technology page.

How does a PDU help monitor conditions in the rack, network closet or data center?

A monitored or switched PDU has a network interface that can be used to receive information communicated from environmental sensors connected to the PDU, helping personnel ensure optimum operating conditions. The sensors monitor ambient temperature and humidity, as well as contact closure status of alarm, security and telecom products.

Where do you mount a PDU in a server rack or enclosure?

PDUs can be mounted inside your server rack wherever you need a source of power for your equipment. You can mount them vertically along the side rails or in the back of the enclosure, or horizontally within the rack, in the same space as a server. Vertical mounting can save rack space and can utilize both the right and left side of the enclosure, while providing more outlet receptacles per unit. Horizontal mounting will take up “U” space.  You can also mount PDUs so that the power cords exit the enclosure at the top or bottom.  PDU installation options are completely based on your preference, space requirements and the number of outlets required. Mapping out how you will set up your rack space before buying the equipment can save you time and money.

How does a Eaton PDU technology enhance power efficiency?

Eaton provides a variety of PDU solutions designed to help users monitor power usage—boosting power efficiency, lowering costs, maintaining uptime, and enhancing performance. Discover our energy-efficient options like the Rack PDU G4 to learn more.

What are best practices for maintaining and troubleshooting a PDU & does Eaton provide technical support? 

If in need of troubleshooting support, please refer to the Eaton PDU Network module secure configuration guideline document for general deployment, configuration and troubleshooting information.

And for additional, step-by-step assistance, please reach out to your Eaton service representative.

What warranty options does Eaton offer for its PDUs?

Eaton offers 3-year warranties for your PDU product lines, read more.  

*For more PDU FAQs, click here

Automatic transfer switch – An automatic transfer switch (ATS) is a PDU that provides power redundancy to IT equipment to prevent shutdowns when the primary power source fails or requires maintenance. Acting as a go-between for power sources and traditional PDUs, an ATS will automatically switch from the primary power source – either utility power or a UPS – to a secondary source, such as a UPS, in approximately 10 mili-seconds when it detects a power disturbance. This means that IT equipment stays protected from damaging power fluctuations and continues operating as normal.

Similar to an ATS, a maintenance bypass is another way to build in redundancy without incurring the cost of deploying a fully redundant system.  To learn more about how to design your backup power system to avoid unnecessary shutdowns, consider these maintenance bypass installation best practices or look at the automatic transfer switch diagrams in this brochure.

Branch circuit monitoring – Branch circuit monitoring is the most in-depth level of monitoring available on a floorstanding power distribution unit.

Knowing how power is being used is important in any IT environment, but in a large data center that requires a floorstanding three-phase power distribution unit, it is critical to the health and efficiency of the whole system. In floorstanding, or cabinet power distribution units, there are three options available for monitoring: no monitoring, basic system-wide monitoring or premium branch circuit monitoring.

In most installations, cabinet PDUs feed power into rackmount PDUs, which means it is possible to forego monitoring on the cabinet PDU because the rackmount PDUs will monitor the amount of power they are receiving from the cabinet and where it is going.

System-wide monitoring allows a user to see how much power is moving into the whole cabinet PDU and how much is being transferred out, which is a good indication of the efficiency of the PDU. Once again, when paired with rackmount PDUs with power monitoring, you can get an accurate picture of how power is being used.

For some applications, though, simply accurate is not good enough. That is when deploying a three-phase power distribution unit with premium branch circuit monitoring is preferable. This level of monitoring allows customers to get data on each breaker’s power demand on an individual circuit level. With this level of monitoring, customers can be confident that they know everything about the health of their entire IT environment.