Is it time to move past MCC's?

First, a little background. In 1937 Westinghouse began manufacturing the 11-300 Motor Control Center, a group mounted starter assembly connected using a pluggable horizontal bus. In the early 50's the big 3 auto manufacturers were looking for solutions to help quickly revamp production lines to meet each new model year. Motor control centers allowed for easy replacement and rearrangement of starters as production needs changed.

Dynamic auto manufacturers benefited from the interchangeability and standardization that MCC's offered. Over the next 2 decades GE, Schneider, Allen Bradley, and others began offering their own lineup of plug and play motor control centers. In this halcyon age dominated by across the line and inside the delta starters MCC's rule and their use spread far and wide. There is no better way to manage a few dozen NEMA starters.

Flash forward. The days of the across the line starter are gone but MCC's are everywhere.  Variable frequency drives and other solid state products now dominate the industry.

MCC's show up in a wide range of applications, used as a panacea for every design. “FrankenMCC's”, cobbled together with components from half a dozen different manufacturers, heavily modified to accept products they were never designed for are being specified by engineers daily. Why anyone would feel the need to use VFD Manufacturer X, Transfer Switch Manufacturer Q, MCC Structure Manufacturer A, C or G, and a sprinkle in a few random control and automation components from manufacturers Z, Y, D, and R just for good measure is baffling. It defeats the whole intent of the MCC – interchangeability. By hacking and slashing the structures to accept the random brands requested you wind up with something that is essentially a very expensive, oversized control panel. At the end of the day the end user would be better served with a custom control panel.

VFD's with their cooling and spacing requirements are difficult to manage in a standard MCC section. Stacking VFD's with one mounted above the other on a back panel requires careful planning and heat management to avoid prematurely ending the life of a VFD. Building custom control panels for drives provides additional benefits:

  • Better environmental ratings. Custom drive panels can be easily designed to Nema 4(X). MCC's can be custom built for these types of applications but the cost is often prohibitive. This allows for VFD's to be positioned close to the motors they operate reducing the need for reactors and filtering.
  • Space optimization of the drive cabinet. Not having to deal with the rigid structure of MCC sections means that we can place the drives in an ideal arrangement to manage heat and use the available space. One recent example of a 6 drive package we budgeted: custom enclosure 60"x60"x16" (33 cubic ft), the same package as an MCC required 90"x90"x21" (98 cubic ft).

As electrical and controls professionals we have to acknowledge that additional building space required to house our equipment is one of the most costly elements of a project. Using space efficiently on a large project can result in millions in real savings.

MCC’s have their place. Arc flash hazards, projects that include large centralized E-Rooms, and medium voltage applications are all good reasons to choose an MCC lineup. But if your intent is to cram a bunch of low voltage drives and other miscellaneous hardware into an MCC, consider having a custom control panel built.


Leave a comment

Comments will be approved before showing up.