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Standards are supposed to make life easier for control panel builders, by guiding the way to which products they can safely incorporate into their designs and panels. But sometimes they can also cause confusion, such as when two standards address the same type of product.
This is certainly the case with respect to industrial motor control devices that adhere to standards from either the National Electrical Manufacturers Association (NEMA) or the International Electrotechnical Commission (IEC) in Europe. While this is certainly not a new issue – it dates back to the late 1980s – I find customers are often still confused about the differences between NEMA- and IEC-compatible controllers, and when to use one vs. another. In this post, I hope to clear up at least some of the confusion.
First off, NEMA is pretty much a North American standard, whereas you’ll find IEC devices all over Europe and elsewhere in the world. Exceptions may be areas or industries with a heavy American influence, such as oil fields in the Middle East, where NEMA controllers are common.
Beyond that, the differences become more technical in nature, especially for the smaller controllers that make up the majority of those sold – NEMA sizes 00, 0, 1 and 2.
It begins with device configuration. NEMA style contactors and starters are generally purchased fully assembled in enclosures. If a customer or contractor needs a NEMA size 2 contactor, he can pick one off a shelf from any number of suppliers with confidence it will be suitable for an appropriately rated motor. The NEMA size system has extra “reserve” capacity built in, which is what enables the same size contactor to be applicable for a wide range of applications.
IEC style contactors, on the other hand, are sold more as components that are installed in a panel. And they are far more application-specific, meaning they’re rated to specific motors and purposes. If you’ve got two motors of the same size, but one will be turned off and on constantly and the other won’t, you’d likely use different sizes of IEC style contactors, each better suited for its specific purpose. OEMs like that approach because they can more closely match contactors to the load than with NEMA; that can save space and money.
NEMA style contactors and starters typically allow for more maintenance, with certain parts that can be easily replaced when necessary. And with their built-in reserve capacity, they’re also designed for long life, typically around 1 million operations – or way more than any motor starter would typically see in its lifetime.
With IEC, on the other hand, the focus is on performance for the expected life of the equipment under control. And given it’s more modular and component-based, it’s a simple matter to replace any failed component – they typically just snap into a DIN rail-type mounting system in the smaller sizes.
A common thread of all the products is they have to be UL / CSA listed and UL testing is the same for both NEMA And IEC style products. So customers can be assured that neither product sacrifices anything from a safety perspective.
In the end, it comes down to customer choice. If you want a simple device you can pick off a chart and install quickly, with the confidence that it’ll last for the life of the motor, then NEMA may be the way to go. If you’d prefer a contactor that’s more specifically matched to the application and equipment you have in mind, and may save panel space and cost less, IEC is likely for you.
Or perhaps there are other good reasons to go with one or another. Ford Motor Co., for example, has nearly a dozen final assembly plants around the world for its Focus model. Even though the company had always used NEMA products in its Michigan plants, for the Focus it wanted the same standard around the world, so decided to use only IEC controllers in every plant.
At Schneider Electric, we’re agnostic, because we sell both – including our NEMA Type S Starters and our IEC-compatible TeSys line is. But hopefully now you’re a little clearer on how to choose which one makes the most sense for you.