NEMA vs. IEC: Understanding the Difference

NEMA or IEC - which organization’s markings should you be looking for 
when selecting electrical equipment, especially motor controllers? This 
can be a confusing decision for specifiers, especially as IEC components
 become more common in the U.S. market, and the correct answer likely 
will depend on the application in question. Eaton Corporation

Chuck Ross

NEMA or IEC - which organization’s markings should you be looking for when selecting electrical equipment, especially motor controllers? This can be a confusing decision for specifiers, especially as IEC components become more common in the U.S. market, and the correct answer likely will depend on the application in question.

It helps to understand the difference between these standards when making your evaluation. NEMA standards were developed by the National Electrical Manufacturers Association – “National,” in this case, referring to the United States, where NEMA standards predominate. IEC standards, on the other hand, are developed and overseen by the International Electrotechnical Commission, an organization headquartered in Geneva, Switzerland, and have been adopted in Europe, the United Kingdom and in many other areas of the globe.

Beyond these basics, NEMA standards are more likely to cover full assemblies rather than the individual components that are the focus of the IEC’s efforts. So, panel builders and other specifiers of motor controllers will generally find NEMA-style contactors already packaged into pre-assembled products. Because NEMA products are designed to apply to a broad range of motor applications, it’s easier to find fully-assembled off-the-shelf controls.

IEC contactors, however, are more often to be sold as application-specific components, even for motors that might be of the same size. So, for example, a motor subject to frequent start-stop operations might require a different IEC contactor than a motor that simply runs constantly. Because of this specificity, IEC controls are more likely to be sold to meet the very particular needs of original-equipment manufacturers and the products they are manufacturing.

These differences have implications for device dimensions, with NEMA-style devices potentially oversized to accommodate the added capacity their wide application range could require. Additionally, NEMA-rated products are more often designed for future maintenance and repair. IEC components, however, are more compact and are designed for easy replacement, rather than repair, in case of failure, and often simply snap into a DIN rail-type mounting system.


Photo courtesy of Eaton Corporation