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NEMA Enclosure Ratings Explained

Electrical enclosures have different NEMA ratings and specifications. The primary objective of NEMA enclosure ratings is to provide a standard to ensure the safety, functionality and compatibility of electrical enclosure products across a wide range of manufacturers.

NEMA standards not only provide a framework for construction, but also include enclosure conditions for use in certain operating conditions and environments.

What is a NEMA-Rated Enclosure?

NEMA stands for the National Electrical Manufacturers Association, which has developed rating standards for electrical enclosure products.

Enclosures that are NEMA-rated simply mean that they have met NEMA’s rating standards to ensure the safety, functionality, and compatibility of the enclosure product.

The rating also helps provide the standards that help in defining the types of environments where the electrical enclosure can be used.

Also, NEMA ratings might indicate the enclosure’s ability against specific conditions (i.e. extreme temperatures, harsh environments, etc.).

NEMA ratings are typically applied only to fixed enclosures and are rarely applied to mobile enclosures.

NEMA, for example, have very strict testing requirements to check whether the enclosure can withstand corrosive materials, dust, external ice, oil immersion, and even water, among other materials.

While different NEMA ratings have different specifications, all of them have the same objective of keeping workers, electrical components, and property safe from damage or injury.

Why NEMA Ratings are Important?

If you use any kind of electrical enclosure, it’s recommended to check the enclosure’s NEMA rating before installing it. There are three important reasons for doing so:

  1. NEMA ratings help you ensure that the electrical enclosure product have proper compatibility with your environment/system, and has met the safety and functional standards
  2. It allows you to choose the right enclosure product that is suitable for your system and the environment in which the enclosure is going to be installed
  3. There are around 600 NEMA standards published in technical papers, which can help you understand more about electrical safety and functionalities, especially regarding enclosure products.

What are the NEMA Standards and NEMA Ratings?

The term “NEMA standards” and “NEMA rating” are often used interchangeably, but they are actually two different things.

NEMA Ratings

NEMA Standards actually refer to NEMA’s published technical whitepapers that at the moment have covered millions of products from NEMA members.

A NEMA Standard is in a nutshell, a paper that defines a product or process/procedure related to a product which might reference one or more of the following aspects of the product:

  • Nomenclature
  • Composition
  • Construction
  • Dimensions
  • Tolerances
  • Safety
  • Operating characteristics
  • Perf?ormance
  • Ratings
  • Testing
  • The service for which it is designed

Each NEMA Standard is identified by number and date, and you can easily search for a NEMA Standard related to a product on NEMA’s website.

Before purchasing an electrical enclosure from any vendor, be sure that it is rated for its intended use.

NEMA Ratings

NEMA ratings, on the other hand, refers to a rating system designed for electrical products to match a unique application and operating environment.

Using the right product with the right NEMA rating ensures you are using the right product for your application. It also guarantees the proper protection of your equipment, the workers operating in and around that equipment, and the property.

NEMA Ratings for Enclosures Explained

As discussed, there are actually many different NEMA ratings available, each defines different applications, environmental compatibilities, or other factors related to the product.

However, for enclosure products, there are six most common NEMA ratings used: 1, 3, 3R, 4, 4X, and 12

NEMA Rating Type – 1

Typical applications:

  • Indoor commercial applications like switches, utility boxes, junctions, and so on.
  • Used to provide a degree of protection of the equipment inside the enclosure against solid foreign objects like dust and debris.

Conditions for use: 

  • NEMA type-1 devices provide the least amount of enclosure protection, however, can adequately protect personnel against hazardous components.

NEMA Rating Type – 3

Typical applications:

  • Used for indoor and outdoor usage, providing a degree of protection to personnel against access to dangerous components.
  • Protects the equipment from falling dirt and dust, among other small solid objects.

Conditions for use: 

  • NEMA type-3 rating shows that the enclosure product is rain-resistant, dust-tight, and sleet-tight. The enclosure can also withstand an external formation of ice

NEMA Rating Type – 3R

Typical applications:

  • Used for indoor and outdoor usage, providing a degree of protection to personnel against access to dangerous components.
  • Also used in filtered fans, utility boxes, and meter cabinets among other applications.

Conditions for use: 

  • Enclosures are designed to be weatherproof and protected against rain, snow, windblown dust/debris, and ice formation on the external parts of the enclosure.

NEMA Rating Type – 4

Typical applications:

  • Used in industrial applications where enclosures could be subject to water contaminant.
  • Some examples ideally suited for NEMA Type-4 enclosures could be air-to-air heat exchangers or air conditioners due to the water particulate in the ambient temperature surrounding them.

Conditions for use: 

  • NEMA type-4 rating shows that the enclosure product is fully waterproof, and provide adequate protection against rain, sleet, ice formation, snow, and hose-directed/splashing water.
  • An enclosure with NEMA Type-4 rating must use a closed-loop cooling system so dust and debris won’t enter the unit.

NEMA Rating Type – 4X

Typical applications:

  • Similar to the applications for NEMA Type-4 enclosures. Type-4X enclosures offer additional protection against corrosion in wet locations because of their stainless-steel, plastic or aluminum construction.
  • With superior corrosion protection, enclosures with Type-4X rating are mostly found in marine applications, industrial food processing facilities, mining (oil and gas drilling), water treatment, and processing plants, among others.

Conditions for use: 

  • Suitable for indoor or outdoor use in harsh environments exposed to water or other liquid contaminants. This includes splashing and hose-directed water, rain and ice.

NEMA Rating Type – 12

Typical applications:

  • Enclosures with a Type-12 rating are designed to be dust-resistant for indoor use but not fully waterproof. They do not provide sufficient protection in extremely wet environments or washdown areas.

Conditions for use: 

  • An enclosure with a NEMA Type-12 provides sufficient protection against dust and oil particulate. They are used extensively in manufacturing facilities.

NEMA Ratings vs IP Ratings

NEMA ratings and IP ratings are two standards used to define the functionalities and capabilities of electrical enclosures, especially regarding how resistant they are to certain materials (water, ice, dust, debris, etc.).

Both NEMA and IP ratings define degrees of protection against these substances, but they use different parameters and testing methods to define their enclosure types, which are NEMA 250 and IEC standard 60529, respectively.

IP ratings are published by the International Electrotechnical Commission (IEC), which is a non-governmental standards agency based in Switzerland. IP actually stands for ‘International Protection’, but is commonly (and mistakenly) referred to as ‘Ingress Protection’, although it does fit the purpose.

There are actually a lot of different IP ratings, and the table below summarizes the various IP number designations:

However, for enclosures, the most commonly used ones are:

  • IP54: limited dust resistance, and protected against water spray (in any direction)
  • IP65: fully dust-tight, protected against high-pressure water projected from a nozzle
  • IP67: fully dust-tight, and protected against immersion between 15cm and 1-meter depth
  • IP68: fully dust-tight and fully waterproof (protected against immersion)

Another key difference is that NEMA ratings are more geared towards industrial applications and are primarily used in North America.

IP ratings, on the other hand, are more widely adopted in different countries all around the world.

Also, IP ratings only cover ingress protection of water and solid objects (dust), while NEMA ratings are more comprehensive and include protection standards against corrosion resistance, atmospheric gasses (i.e. gasoline), and others.

NEMA ratings also cover distinctions between hazardous and non-hazardous environments.

While there is not a direct correlation between NEMA and IP ratings, the table below covers cross-references between the commonly used IP and NEMA ratings.

You can use this table to help determine a NEMA rating that meets IP rating standards, and vice versa:

Conclusion

I hope we’ve done a sufficiently good job explaining NEMA Enclosure Ratings. It is extremely important to ensure that you are spec’ing the right electrical enclosure for the job. This will ensure longer life of your electrical equipment and machinery, as well as properly protect personnel and property.

If you found this article informative, you may be interested in some of our other articles here on the site.

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Fred Graham

Hi! Fred here, I am the founding member and site moderator here at PLCGurus.NET. I'd like to be the first to welcome you to the site. I have over 20 years in the Industrial Automation and Control Systems field. Be sure to Register Today!

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