Vertical PDUs vs. Horizontal PDUs: Comparing Rack and Rackmount PDUs

Data center managers have a lot of choices when it comes to power distribution units (PDUs). One option is the rackmount PDU — which, it turns out, is a different animal than the rack PDU.

It has to do with how the PDU is mounted and the unit's form factor. Also known as “vertical PDUs” or “0U PDUs”, ”Rack PDUs are mounted vertically in the “zero U” space in the back of the rack or cabinet. Best-in-class vertical PDUs have an ultra-low-profile design that provides easy access to IT equipment and increases airflow efficiency.

Rackmount PDUs are different. Also known as “horizontal PDUs,” They mount horizontally within the rack like other IT equipment. Typically, they are 19 inches wide, take up one or two rack spaces (1U or 2U), and have six to 16 outlets. Newer horizontal PDUs offer many of the same features as their vertical PDU cousins.

Generally, however, a vertical PDU is the better choice for the modern data center. Vertical PDUs provide more outlets, can handle greater heat loads, and have a more flexible, space-saving design.

Check out our past blogs for a refresher on what a PDU does, how PDUs work, and the different types of PDUs. This blog will focus on the benefits, drawbacks, and use cases of horizontal PDUs vs. vertical PDUs.

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Benefits and Drawbacks of Horizontal PDUs

Horizontal PDUs come in a wide variety of configurations. Basic 15A units have 125V receptacles with various plug options (PDU plug types), while 60A units are available for single-phase or three-phase power supplies (single-phase vs. 3-phase power). Switched horizontal PDUs allow administrators to turn individual outlets on and off. Metered units provide data on current, watts, voltage, power factor, and more. Network connectivity allows administrators to monitor and control the PDU remotely.

Horizontal PDUs can be a good choice for lower power loads or in conjunction with in-row UPS equipment. If there’s limited space in the back of the cabinet for cable management, it may make sense to install the PDU horizontally.

However, horizontal PDUs have a number of drawbacks:

  • They take up space that could otherwise be used for IT equipment. Anything that consumes rack space in today’s high-density data centers could create capacity management challenges.
  • Many horizontal PDUs are designed to operate at lower temperatures, which means they have to be cooled like IT equipment.
  • If the horizontal PDU fails, it will typically need to be removed and replaced, leading to unplanned downtime as the power supply is taken offline.

Older horizontal PDUs also require a separate network for connectivity. This increases networking equipment requirements and administrative overhead managing IP addresses.

Vertical PDUs Eliminate These Issues

Vertical PDUs eliminate these drawbacks:

  • They don’t take up any rack space, yet they provide as many as 60 outlets for IT equipment.
  • Low-profile designs leave plenty of room in the back of the cabinet for cable management and airflow.
  • Vertical PDUs are designed to withstand the higher temperatures caused by hot air exhaust at the back of the cabinet. Best-in-class units have branch-rated hydraulic-magnetic circuit breakers with an operating temperature of up to 140 degrees.
  • Hot-swappable components such as network management controllers mean that the vertical PDU can be repaired or upgraded without interrupting the power supply.

Today’s vertical PDUs can be daisy-chained for network connectivity so that one port and IP address are used across multiple units.

Enconnex Offers Rack PDUs for Every Use Case

Enconnex is your one-stop source for high-quality vertical and horizontal power distribution units. Our product line ranges from basic PDUs to smart PDUs, including input-metered, outlet-metered, and switched solutions (smart PDUs vs. basic PDUs). Our PDUs offer the highest levels of reliability and performance, making them suitable for use in the largest hyperscale data centers. They are also cost-efficient enough to meet any need and budget.

You can select from a wide range of options, including the number, type, and configuration of outlets, electrical specifications, and more. We are also getting ready to launch a new line of TAA-compliant, made-in-America basic PDUs. View our catalog to see all our PDUs for sale, and contact us to get the right PDU for your use case and to stay up to date on our latest offerings.

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Posted by Robert Faulkner on November 16, 2022

Robert Faulkner is the Vice President of Engineering and Operations at Enconnex. He comes from a strong background in product management with over 20 years in the IT industry. He currently holds an MSME and CDCD certification. He earned his MS degree in Mechanical Engineering at University of Nevada, Reno.

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