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 delivery: the best options, the most efficient choices, the latest and greatest voltages, etc. Oftentimes, 3-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, 3-phase voltage allows utilities to deliver more power over smaller, less expensive wires. If 3-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 3-phase voltage is 208V power as a feed to the rack. A 3-phase voltage is 120V phase to neutral, and phase to phase voltage of 208V (see 3-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, neutral, and ground to the rack with, for example, an L21-20 or another type of amperage and plug style, offers several options to help ensure quick and easy upgrades down the road.


3-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 3-Phase Voltage


So what does this all mean for you?


If you’re a co-lo data center, offering equipment, space and bandwidth for rental, 3-phase voltage delivers the ability to support a wide range of customers.


If your co-lo data center is attemptingto 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, 3-phase voltage allows you to be all 120V today – but, by using a 3-phase outlet and a L21-20P, you can upgrade or add 208V with a simple PDU change. Because this switch can be made quickly, you’ll increase your speed to redeploy, upgrade and MAC work.

Belden has a wide range of PDUs and power strips to support any of your data center’s 3-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:

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

For more information about Belden’s PDUs, visit our 3 Phase PDUs page.