Data centers are aging, and operators are continually seeking new ways to reduce Total Cost of Ownership (TCO), either by optimization or by complete equipment upgrades. One method of improving TCO through upgrades is to address Mean-Time-To-Repair (MTTR) and reduce equipment footprints by replacing power distribution equipment with front accessibility.

To fulfill market needs, OEMs are leveraging customer feedback and designing a new generation of power distribution equipment to optimize a data center’s grey/white space. One next-generation example of engineering is fully front-accessible Static Transfer Switches (STS).  But be careful, not all front-accessible STSs are the same.

While some OEMs market their offerings as “front-accessible,” for many activities, side access is invariably required. A true front-accessible STS needs to offer:

  • Proper footprint (if too small, it’s hard to service)
  • Simplified installation, e.g.. how conduit is landed
  • Operational and service convenience and ease-of-use
  • Enhanced safety measures

These new STSs are created with extensive input from end-users, as well as engineering consultants and contractors. They helped OEM product managers and engineers learn that users were willing to give up certain, infrequently used features such as pull-out drawers, to facilitate a design with true front access. It was also imperative to think of the design in three dimensions, and optimize the use of every cubic inch.

Front access could be improved by a design approach that combined functions into fewer parts, for example, bracing and mounting using the same part. And speed-to-market could be optimized by using a scalable design, such as varying only those design elements that help to reduce the footprint and cost.

Leveraging the aforementioned lessons, a new, innovative design was created that includes:

  • True Front-access for installation, service/maintenance, IR (infrared) scanning, and arc flash compartmentalization
  • An STS Contractor board designed with its own compartment so the contractor setting up communications, doesn’t need to access the area where power cables are landed.
  • An isolated logic board that eliminates the need to power down the STS to conduct service and maintenance
  • Decreasing the frequent need for opening STS doors – for example, when accessing the touch screen or redundant operator interface

In addition, the new innovative design provides access from front to back, allowing customers to reach the Operator Interface, Board, Controls, SCR and Molded Case I/O Compartments, as well as Power Connections.

With this new design, data center operations personnel will have to suit-up to work on STSs less frequently than with most Static Transfer Switches in the market today.

In summary, with insight from engineering and end-users, an OEM provider such as Power Distribution Inc., has the knowledge and foresight to design the market’s first True Front Access STS.  The product balances the needs of data center architects and designers, installation contractors, operations managers, and service personnel. Most importantly, it has minimized the customer’s TCO.

The design innovation, however, could not have been achieved without prior success in designing next-generation PDU, RPP, and overhead Busway products.


Isaac Folk, Engineer IV; Evan Owen, Global Product Manager, STS, PDU, Magnetics; Greg Schlueter, Senior Principal Engineer and Engineering Manager; and Anand Krishna, VP Business Development for Power Distribution, Inc. (PDI), the leading supplier of power distribution and monitoring solutions for data centers, contributed to this article.