Insights on Ensuring Compliance with UL Standards for MCCs

Motor control center (MCC) builders and consumers rely on standards, particularly UL 845, to ensure panel safety and operation. Below you will find information and suggestions to help you better comprehend the essential aspects of those standards.

Building panels that comply with strict and confusing UL standards is not an easy task. Just because some technical aspects match between UL standards, doesn’t mean conflicts will not exist so one needs comprehensive knowledge to ensure panel safety during a build.

Reviewing test plans with a primary UL contact is recommended to avoid having to reevaluate the project UL requirements later.

More Than Ratings

Choosing a specific UL rated component is only one aspect of a safe panel build. One must also consider the panel volume to prevent an explosion from breaker offgassing. Breaker cable entries should also be evaluated for bracing or bending requirements, directions for which may often be located in installation guides.

Savvy MCC project engineers will insist on testing every application because of the common bus connecting all sections of the MCC. Panels with enclosed components also require additional testing.

At the end of the day, UL ratings alone do not guarantee a safe build. Panel volume, bracing requirements, component spacing among others must always be considered and not ignored due to design limitations, as tempting as that may be. Appropriate testing may add delays and additional costs to any build but those costs are likely far less than the potential risks.

UL-Recognized vs UL-Listed

A “Listed” item stands on its own, given that the manufacturer’s instructions regarding mounting, space, volume and temperature guidelines are followed. Breakers that are Listed are often utilized as branch circuit protectors in mains or feeders.

Some components, such as terminal blocks, are "Recognized," which means they must be tested with specific cables to guarantee they do not rip out.

Product classifications and standards are subject to change over the years. One example of this are variable frequency drives, which used to be Listed (UL 508C). That was 10 years ago; today, VFDs must be designated as “suitable for use” with the breaker.

Constructing MCCs

Compliance with UL standards is deceivingly straightforward and the details can be burdensome. The UL designations do not stand alone in the building of a safe MCC. Keeping the above points in mind, will assist panel builders in achieving compliance.

For assistance with your build, contact our knowledgeable team to assist you in selecting the appropriate components or allow us to build your MCC in-house. Shop ABB Low Voltage online.