MCCs are MVPs in preserving business function, employee comfort, and operational safety. Learn why they deserve your attention.

Key Takeaways:

  • MCCs are essential to many businesses
  • They contain many components
  • They also have a very specific purpose
  • Installing these devices correctly is important

“MCC” (motor control center) is one of those neat technical terms that has everything you need to know in the title. Try telling someone there’s an Arrhenius in their spurious-free photodiodes and see where it gets you. MCC is clear as can be. They’re dedicated to motors – controlling them, actually – and are centrally located and key to the performance of essential systems.

We oversimplified somewhat by saying MCC tells you everything you need to know. They’re a bit more complicated, but they won’t be after this introductory guide. We’ll explain what makes them so central and how proper installation and maintenance keep your motors running.

MCCs are crucial for multiple motor management

You may have yet to ponder how many motors your business uses. Your HVAC system, for example, couldn’t run without them, and the bigger your building is, the more electrically powered motors are required to keep the HVAC going. In fact, every process in your business that needs a pump or fan to function relies on motors, meaning you could have hundreds of them working simultaneously.

It makes no sense to have the controls for all those different motors scattered everywhere. Your MCC is thus the nerve center where all motors are monitored. If your business has a general control or operations room, odds are that’s where the MCC will be situated in the form of one or more component cabinets.

Basic types of MCC

MCCs can be manually operated, or they can function semi- or fully automatically. The first type requires someone to make necessary changes or turn motor functions on and off as required. This isn’t so great, though, if your systems need to stop on a dime – more to come on that.

Semi-automatic MCCs are somewhere in the middle and incorporate system sensors alongside manual controls. Fully automatic designs include a control circuit that makes motor adjustments without the need for human intervention (unless the MCC breaks down, that is).

Some standard components and MCC functions

The specific design of each MCC varies depending on what it has to control and what it needs to be protected against. Generally speaking, all MCCs are either low voltage or maximum voltage.

Low voltage MCCs manage current from the low 200s to 600 volts, sometimes up to 1,000 kilovolts. Maximum voltage MCCs handle loads in the thousands of volts (up to 15,000 kilovolts in some cases). MCCs usually contain the following core components:

  • Busbars: These horizontally and vertically positioned bars send power directly to the electrical components and can help to cut down on unnecessary wiring and cables. Problems with MCCs can often be traced back here.
  • Indicator lamps: The dashboard warning lights of an MCC. These help operators and maintenance teams locate problems and check power levels more easily.
  • Transformers: Two kinds of transformers are at work in your MCC. Current transformers help with measuring current and protecting systems. Control (sometimes called “potential”) transformers help lower the operating voltage for some components that don’t run at the same high voltage as the busbar.
  • Circuit breakers: These are used on the load side to isolate power and provide protection against short circuits caused by excessive loads and heavy electrical flow. Also called MCBs (miniature circuit breakers) and MCCBs (molded case circuit breakers).
  • Overload relay: Helps keep the MCC cool when it starts to overheat due to overworked machinery. Overload relays can disconnect motors from an overloaded power source to protect that component and its connected systems from damage.
  • Magnetic contactors and timers: Contactors start and stop each motor and can be used to control them remotely. Timers often function in tandem with magnetic contactors to automatically set activation/deactivation cycles for motors.

One of an MCC’s many jobs is ensuring motors start working slowly before ramping up to the necessary rotation that prevents unnecessary wear and tear. MCCs often contain variable frequency drives to moderate motor speed.

MCCs are also vital in ensuring processes stop suddenly during emergencies to prevent harm to people or machinery. They can also reverse the rotation of machinery, which is necessary for some operational settings. 

What professional MCC installation, upgrade, or repair looks like

Whether you’re adding a brand new MCC or upgrading an existing one, there are some universal concerns for power pros to consider. The first is knowing if your building runs on AC or DC, a factor that can affect voltage and frequency considerations. The next is defining where “central” should be.

The size of your business will dictate the size of your MCC, which will require a room big enough to house it comfortably. MCCs are fairly modular in their design, meaning units can (and sometimes must) be expanded over time. This is another space consideration if you’re aiming to upscale your organization.

The room your MCC unit resides in must be carefully temperature controlled. MCCs can produce a lot of heat and contain components highly sensitive to local conditions, so review our previous blog for some transferable tips. The room will dictate whether underground or overhead cabling would be best for the MCC, with the electrical contractor reviewing which size of cables are necessary for your site’s load demands.

Electricians must also ensure that the MCC can provide start/stop functions on a reliable timer or on demand in an emergency. Sometimes, your existing motors must be resized to cope with new load demands or repositioned if they’re exposed to debris, liquids, or elemental damage.

We can’t forget how important it is to fix the correct IP (ingress protection) rating for the MCC. This measurement decides how well shielded units and circuits will be from intrusion by dust, debris, or liquids.

Contact the power pros at Universal Electrical Services with any questions

The UES team brings decades of electrical experience to multiple industries throughout Florida. From full installations of electrical systems to emergency callouts, we’re here to help your business stay powered up while running safely and smoothly. Just contact us for a free quote or answers to any electrical questions!