The standards have to simply live for the control panel designers by providing the guidelines to which the products can be safely installed within their designs and panels. But sometimes these guidelines lead to confusion such as during a situation where two standards offer different guidelines for the same type of product.
This is what occurs in the industrial motor control devices that comply with standards from the National Electrical Manufacturers Association (NEMA) for the US or the International Electrotechnical Commission (IEC) for Europe and the rest of the world. This is not a new case as it dates back in the ’80s even though some of the customers are still confused about their differences, and they do not know when to use one vs the other. In this post, we will be discussing so as to clear up this confusion.
First of all, as mentioned earlier, NEMA is common for North American standards whereas the IEC devices are for Europe and the rest of the world. There are exceptions to heavy industries with American influence such as the oil fields in the Middle East where you can find NEMA controllers being commonly used
Second is that their difference is more technical in nature especially for tiny controllers that make up a large percentage of the majority of those sold which are the NEMA sizes 00, 0, 1, and 2.
Besides their different starts with the device configuration. The NEMA style contactors, as well as the starters, are normally purchased in fully assembled within casings. In case the customer or contractor is in need of a NEMA size 2 contactor, he/she will be able to pick one off the shelf from one of the many suppliers and he/she will be sure that it will suit the rated motor. The NEMA size unit consists of an extra reserve capacity inbuilt which allows the same size contactor to be used for many different applications.
When it comes to the IEC design contactors, they are sold much as components that can be installed within the panel. These are far more application-specific meaning that they are normally rated to be used in specific motors and for a specific purpose. In case you have two motors of the same size, but one of them will be turned off while the other will not, you are likely to use different sizes of IEC design contractors where each will be ideally designed for a specific purpose. The OEMs like that way as they can easily match contactors to the load than when it comes to the NEMA, which can help in saving space and money.
The NEMA design f contactors and starters normally allow for more maintenance, when it comes to specific parts that can be easily replaced if needed. With their inbuilt reserve capacity, they are also designed to be used for long life, typically around a million operations or a lot more than any motor starter.
When it comes to the IEC, their focus is on performance for the expected lifespan of the equipment which they control. As there are more modular in nature and component-based, it is easier to replace if there is any failed component as they normally slide into a DIN rail type mounting mechanism in the smaller sizes.
A common thing when it comes to all the products is that they are all required to be UL/CSA listed and should undergo UL testing which is the same for both the NEMA and the IEC design of products. This aims at assuring customers that neither of these products sacrifices anything from the safety point of view.
The selection remains within the customer’s point of view. In case you are looking for a simple device you can just pick off a chart and install it quickly, while being sure that it will last for the entire lifetime of the motor, then go for NEMA. In case you need a contractor that is more specific and is matched to the application as well as the equipment that you have in mind, thus saving panel space and money, the IEC is the best option for you.
But there might be other reasons that might lead you to choose one instead of the other. For example, Ford Motor Co. has dozens of final assembly plants all over the globe for its focus model. Despite the company being connected to the use of NEMA products, but its Michigan plants, when it came to the Focus model wanted it to have the same standard around the world so decided to use the IEC controllers in each plant.