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Power distribution FAQs

Power distribution is a key component to any IT environment. Whether yours is a small deployment or a data center housing hundreds of racks full of IT equipment, understanding your environment and power needs allows you to begin making the right choices about your power distribution equipment. 

What is power distribution?

Power distribution is facilitated through different pieces of equipment that take the power conditioned by your uninterruptible power supply (UPS) and send it to your IT equipment. Power distribution solutions can manage and even control energy consumption in smaller environments as well as large data center applications. Distributing power efficiently results in reduced operating costs and increased reliability.

Whether you need integrated power distribution within a few racks or power throughout your data center, there are many solutions to consider when building out your power infrastructure. Understanding your environment and power needs allows you to begin right-sizing your distribution equipment.

Single-phase PDU vs three-phase PDU

The phases of a PDU, such as a single-phase PDU  or a three-phase PDU, describe the number of electrical phases that a PDU receives and transmits. Three-phase power is used by large power consumers, such as colocation data centers and hospitals, because that is the most efficient way to transport the large volumes of electricity required for those facilities. Single-phase power is used by smaller power consumers, such as small and medium businesses, schools and most office buildings.

Cabinet PDU vs rackmount PDU

Power distribution units come in two form factors: floor standing or cabinet PDU s and rackmount PDUs.

A floor standing PDU, or a cabinet PDU, is a large, three-phase power distribution unit that comes enclosed in its own cabinet. These PDUs are often used in large data centers for raised and non-raised floor applications to take incoming power and distribute it to an individual rack or groups of racks. A PDU can optimize utilization and availability down to the branch circuit level as well as address specific needs for isolation, voltage transformation, harmonic reduction, and voltage regulations. Cabinet-based PDUs should have monitoring capabilities as well. Because floor standing PDUs are most often found in large data centers, they are usually deployed in conjunction with managed rack PDUs that are placed in each server rack or enclosure.

Rack PDUs are used to effectively distribute power to racks where multiple outlets are necessary. Beyond the capabilities of a power strip, a rack PDU offers a range of intelligent features to help control the power distributed to IT devices. Rack PDUs are used in all types of environment sizes and come in a variety of plug and outlet configurations, including 120 and 200-240 volts. Whether it’s the only distribution unit or part of a whole distribution strategy, PDUs are a vital connection point and allow you to protect your entire IT investment.

Which type of rack PDU is right for you?

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 is 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.

What functionality can I get from my rackmount PDU?

Rackmount PDUs offer a variety of capabilities to fulfill the needs of your IT environment. From the streamlined and cost-effective rack PDUs favored by cryptomining companies to the outlet-level billing grade accuracy needed by colocation data centers and even the fully configurable PDUs that enterprise data centers rely on, Eaton has a rackmount PDU to meet the particular challenges of your business.

To find out which PDU has the features that are most valuable to you, read the full breakdown of functions available in Eaton’s power distribution units for server racks.

Find the right rack PDU for your IT needs

Select the function, plugs and receptacles, and form factor, among other things.

What is an 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. Working with traditional PDUs, 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.

What is 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 that 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 of 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.  

Want to learn even more about power distribution units?