NEMA 4X Specifications

NEMA enclosure ratings are among the most commonly used tools for identifying and evaluating the protective characteristics of an electrical enclosure. Ratings such as the NEMA 4X specifications provide key information to enclosure buyers—but they’re only useful if the buyer understands the rating thoroughly.

In this article, we’ll take a detailed point-by-point look at one of the most common NEMA standards: NEMA 4X specifications. First, let’s look at the definition. Then, we’ll break each line down into simple terms that will help clarify what buyers can expect from a NEMA 4X enclosure.

NEMA 4X Specifications: The Basics

Here’s the official definition of a NEMA 4X enclosure, according to the National Electrical Manufacturers Association website:

“Enclosures constructed for either indoor or outdoor use to provide a degree of protection to personnel against access to hazardous parts; to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (windblown dust); to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (rain, sleet, snow, splashing water, and hose directed water); that provides an additional level of protection against corrosion; and that will be undamaged by the external formation of ice on the enclosure.”

That’s a lot of information to process, so let’s pull the definition apart line by line.

“Enclosures constructed for either indoor or outdoor use”

This means that a NEMA 4X enclosure will meet a generally accepted minimum standard for both indoor and outdoor use. The specifics of what the enclosure protects against are enumerated in the rest of the definition, but in general, indoor/outdoor enclosures (such as NEMA 4X enclosures and NEMA 6P enclosures) are designed to meet more stringent standards than indoor-only enclosures.

“To provide a degree of protection to personnel against access to hazardous parts”

This is a basic feature that nearly every type of electronics enclosure offers. It can be all too easy to damage or destroy components with a few careless movements, so a NEMA 4X enclosure provides a barrier that helps prevent personnel from accidentally touching or engaging device components.

“To provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (windblown dust)”

Windblown dust can be a serious problem for devices in outdoor enclosures, particularly those in dry climates and sandy soil conditions. A NEMA 4X rating certifies that an enclosure is designed to protect against the ingress of windblown dust, usually through the inclusion of a weatherproof gasket.

“To provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (rain, sleet, snow, splashing water, and hose directed water)”

Ingress by even a small amount of water can be devastating to an electronic device. That’s why NEMA 4X specifications require the use of a waterproof gasket that is able to prevent many different types of water ingress. Pay special attention to the protection against hose-directed water, as many lower NEMA ratings protect against splashing and dripping, but not pressurized droplets from a hose.

“That provides an additional level of protection against corrosion”

Corrosion protection is one of the most important features of the NEMA 4X standard and is the difference between NEMA 4 vs. NEMA 4X. NEMA 4X enclosures are created from materials that are resistant to corrosion or have corrosion-resistant coatings and can include stainless steel enclosures, polycarbonate enclosures or aluminum enclosures.

The corrosion resistance is a major reason why you’ll often find NEMA 4X enclosures, like the Polycase SA Series, used for marine applications (although enclosures subject to submersion need a NEMA 6 rating or NEMA 6P rating). Environments where harsh chemicals are frequently used may also require NEMA 4X enclosures.

“And that will be undamaged by the external formation of ice on the enclosure”

When ice forms on the outside of an enclosure, it can leak water into an enclosure that’s not sufficiently protected. The gasket in a NEMA 4X enclosure is designed to prevent this damage from external ice formation.

UL Certification for NEMA 4X Enclosures

Finally, it’s important to note that NEMA itself does not issue rating certifications. NEMA 4X specifications should be verified by an independent authority such as Underwriters Laboratories (UL). All Polycase enclosures are UL-tested and certified for their NEMA ratings so that our customers can be confident in our products’ standards of design and quality.

Polycase SA-30 NEMA 4X Stainless Steel Enclosure

Polycase is an industry leader in NEMA-rated electrical enclosures. We offer a full range of NEMA 4X enclosures, including polycarbonate enclosures, aluminum enclosures and stainless steel enclosures. For more information on Polycase enclosures and their NEMA ratings, see our in-depth NEMA ratings guide or contact our enclosure experts.