Data Center

3-Phase Voltage for Data Center Agility

Mike Peterson

In the world of data centers, there’s a lot of talk about voltage and power deliverythe best options, the most efficient choices, the latest voltages, etc. Oftentimes, three-phase voltage is the power delivery method of choice.

As a combination of three single-phase circuits that deliver power so the load is the same at any point, three-phase voltage allows utilities to deliver more power over smaller, less expensive wires. If three-phase voltage is what you have to work with in your data center, there are ways to make the most of it.


3-Phase Voltage Offers Flexibility

Although other voltage options exist, the most common three-phase voltage is 208V power as a feed to the rack. A three-phase voltage is 120V phase to neutral and phase-to-phase voltage of 208V (see Three-Phase Power: Wye It Matters for more information). This indicates that line-to-line (L-L) voltage is 208VAC in a wye configuration; the line to neutral (L-N) voltage is 120VAC. This voltage provides necessary flexibility in your data center.


Using a power distribution system that supplies all three phases (e.g., neutral, ground-to-rack & L21-20 or other type of amperage & plug style) offers several options to help ensure quick and easy upgrades down the road.


Three-phase voltage also allows you to have 120V or 208V outlets; you can mix and match types in a single PDU (power distribution unit) or have one voltage cover the entire strip.


Implications of Three-Phase Voltage & What It Means for You

Image of goldfish jumping from small to larger fish bowl

If you’re a co-location data center, offering equipment, space and bandwidth for rental, three-phase voltage delivers the ability to support a wide range of customers.


If your co-lo data center is attempting to standardize parts, you may not need 120V or 208V (or both) in a rack. If you choose three PDUs and select an outlet with an L21-20 receptacle for the PDU to plug into, the only thing that needs to be done if the voltage changes is to change the PDU—not rewire. This translates to no scheduled downtime and the elimination of hazardous hot or live electrical work by electricians.


If you want to futureproof your data center, three-phase voltage enables 120V today and using a three-phase outlet with L21-20P allows for upgrades or adding 208V with a simple PDU change. Because this switch can be made quickly, speed to re-deploy, upgrade or perform MAC work will increase. 

Belden has a wide range of PDUs and power strips to support any of your data center’s three-phase voltage needs, from a variety of input voltage and amperages and outlet combinations to monitoring and management capabilities.


A few hints as you explore Belden’s PDU options:

  • L6-XX—“L” refers to locking & “6” indicates 208V, two hots and a ground.
  • L21-XX—“L” refers to “locking” & “21” indicates 3 phases, three hots, a neutral & ground. The presence of a neutral wire means the PDU can be 120V or 208V (or both).

For more information about Belden’s PDUs, visit  Three-Phase PDUs page.