Electrical Enclosure Standards

When you open the enclosure of any electrical device, nearly every part you’ll find inside is regulated by some kind of standard. Whether the standards are for transformers, switchgear, screens or the electrical enclosures themselves, strict adherence to these standards is critical for anyone who designs, engineers or builds electrical devices.

Electrical enclosures play a particularly important role in protecting electrical devices from environmental hazards of all kinds. In order to fulfill this role, an electrical enclosure needs to meet the right electrical enclosure standards. That’s why we have NEMA enclosure ratings, IP enclosure ratings and UL enclosure ratings. These are the electrical enclosure standards that provide common foundations for the practice of electrical enclosure manufacturing.

In this piece, we’ll provide a quick introduction to the various electrical enclosure standards that you’ll need to be familiar with when selecting an electrical enclosure. To get started, it’s useful to think about why it’s important to have a working knowledge of electrical enclosure standards.

Why Electrical Enclosure Standards Are Important

Why should you spend the time to familiarize yourself with electrical enclosure standards? Put simply, enclosure standards are a kind of shared language that helps professionals establish common benchmarks and requirements when dealing with technical information about electrical enclosures. These standards help device designers and engineers work more efficiently by aiding them in selecting the parts that will provide the performance they need.

Without knowledge of these common standards, it will be difficult to know that you’re choosing the right electrical enclosure for your needs. Words like “waterproof” or “weatherproof” can be frustratingly imprecise, leading to potential unpleasant surprises, such as learning that the enclosure that was billed as a waterproof electrical junction box is actually only water-resistant. Common standards create a reference framework that’s reasonably easy to understand.

Finally, depending on your industry, electrical enclosure standards may be a required element of regulatory compliance. Your electrical devices may need to meet certain IP, NEMA or UL standards to be sold in certain markets or used in certain regulated processes, so familiarize yourself with the relevant regulations.

Common Electrical Enclosure Standards

The most common electrical enclosure standards used in U.S. enclosure manufacturing are:

NEMA Ratings: The National Electrical Manufacturers Association (NEMA) rating scale rates an enclosure’s protective qualities against environmental hazards, such as solid ingress, liquid ingress and corrosion. It’s used mostly in the United States.
IP Ratings: The Ingress Protection (IP) rating scale rates an enclosure’s protective qualities against solid matter ingress and water ingress. It’s used both in the United States and around the world.
UL Ratings: Underwriters Laboratories (UL) provides standards that are similar to NEMA and IP ratings, but requires independent testing. UL has also established the UL 94 flame rating standard, a standard for rating an enclosure’s flame-resistant qualities.

These rating systems all have the same basic goal: to educate and inform the buyers of electrical enclosures about which models will meet their needs.

Limitations of Enclosure Standards

Electrical enclosure standards also have some common limitations. To understand how electrical enclosure standards should be applied, it’s important to understand what these standards don’t do.

One key caveat of enclosure standards is the fact that each standard relies on a group of specific tests. While this is necessary to make the standards consistent, it also means that they can’t account for every possible circumstance. Be sure to note the conditions under which the rating tests are performed, as they may differ from the conditions in your work environment.

More generally, electrical enclosure standards don’t account for differences between enclosures that stem from quality in manufacturing and design. For example, an enclosure standard usually can’t tell you whether an enclosure is made using high-quality materials, except inasmuch as it relates to the specific tests the enclosure undergoes. And the standard can’t tell you whether the enclosure’s design is functional or efficient—again, except to the degree that it satisfies or doesn’t satisfy a particular test.

Next, we’ll take a quick dive into each enclosure standard.

What Are NEMA Ratings?

The NEMA rating system is an electrical enclosure standard developed by the National Electrical Manufacturers Association. The NEMA rating scale uses alphanumeric ratings (sometimes only a number, and sometimes a number and a letter) as established in the NEMA 250 standard.

protective features of commonly used ratings

Here are some of the most commonly used NEMA enclosure ratings, in ascending order of protection. Note that each of these ratings also includes the protective features of lower-rated enclosures:

NEMA 12: Indoor enclosures rated to protect against access to hazardous parts, flying dust and light dripping and splashing water.
NEMA 3R: Outdoor weatherproof enclosures rated to protect against common outdoor conditions, such as rain and snow.
NEMA 4X: Outdoor weatherproof enclosures rated to protect against corrosion from marine environments, chemicals or other sources.
NEMA 6P: Outdoor weatherproof enclosures rated to protect against prolonged submersion in water.

It’s important to know that NEMA ratings are self-reported. That means that manufacturers aren’t required to submit proof of their device’s compliance with NEMA standards to any certifying authority. While most businesses make an honest effort to rate their products correctly, don’t forget that a NEMA rating isn’t an automatic guarantee of enclosure performance.

To learn more about NEMA ratings, be sure to read Polycase’s NEMA ratings guide.

What Are IP Ratings?

The Ingress Protection (IP) rating scale is based on the IEC 60529 international electrical standard. It uses a two-digit system to identify an enclosure’s level of protection, with higher numbers signifying more protection:

The first digit rates the enclosure’s protection against solid ingress on a scale from 0 to 6. Solid ingress can include accidental contact with body parts or tools, or it can refer to airborne dust, dirt, metal filings or other types of debris.
The second digit rates the enclosure’s protection against water ingress on a scale from 0 to 8. Water ingress can include dripping or splashing water, hose-directed water or even total submersion.

These are some of the most common IP enclosure ratings:

IP65: Rated for substantial protection against dust ingress and protection from water up to and including high-pressure jets.
IP66: Rated for complete protection against dust ingress and protection from water up to and including high-pressure jets.
IP67: Rated for complete protection against dust ingress and protection from immersion in up to one meter of water.
IP68: Rated for complete protection against dust ingress and protection from immersion in over one meter of water. This is the highest level of IP-rated protection available.

Note that when choosing an electrical enclosure with an IP68 rating, it’s important to note the manufacturer’s specifications for the specific depth for which the enclosure is designed.

Converting NEMA and IP Ratings

IP ratings can usually be converted into NEMA ratings fairly accurately, although the process may not always produce a perfect match in protective qualities. However, because some NEMA ratings provide more information than IP ratings can, converting NEMA ratings to IP ratings isn’t always possible.

For example, the NEMA 4X rating standard specifies that an enclosure has to provide a degree of protection against corrosion. Thus, the NEMA 4X rating has no IP rating counterpart because IP ratings don’t factor in resistance to corrosion.

If you’re ready to start converting IP ratings into NEMA ratings, see our IP to NEMA conversion guide. We offer a handy chart that makes it easy to convert IP ratings into NEMA ratings.

Polycase WC-21 polycarbonate enclosure, UL Listed to UL508-4x specifications

UL Ratings

UL (or Underwriters Laboratories) is the world’s foremost independent safety testing organization, and they issue many industrial and scientific safety standards that help make electrical and electronic devices safer. Even more importantly, they conduct rigorous testing on device components (such as enclosures) to ensure a high degree of confidence in component performance.

A UL rating can refer to several different types of electrical enclosure standards. Most of these standards are based on or harmonized with standards developed by other organizations, such as the IEC, NEMA or the NFPA. Thus, choosing a UL-rated enclosure is an important part of ensuring your enclosure is actually built to compliant specifications, rather than simply showing them on paper.

UL flame ratings are a particularly useful tool when evaluating electrical enclosures. The UL-94 flame rating scale measures how long it takes for a burning enclosure to extinguish itself, whether it will drip heated plastic and whether it will prevent the fire from exposing the enclosure’s contents.

Which Standards Does Your Enclosure Need to Follow?

Once you’re familiar with electrical enclosure standards, it’s time to apply your knowledge and decide which standards are appropriate for your electrical enclosures. Think about these questions:

In which countries or regions will the device be used and/or sold?
Which kinds of environmental conditions will the device be exposed to?
What is the function of your device?
Are there regulations that specify which set of standards the device must meet?
Do the best practices of your industry require the use of a specific set of standards?

Other considerations may affect your enclosure selection depending on your industry and device applications. Next up, we’ll discuss what some of those considerations are.

Other Requirements for Enclosure Selection

Electrical enclosure standards are only one part of the process of choosing an electrical enclosure. Other common requirements for electrical enclosure selection include:

Materials: Certain enclosure materials are better choices for certain applications. For example: Some materials, such as aluminum, feature natural radiofrequency shielding. That makes them an excellent choice for applications that require interference protection, but for others (such as devices that transmit Wi-Fi signals), they may not be an ideal choice.
Size: What dimensions (length, height and depth) will your enclosure require to hold all of its components safely? Pay attention to how much space is required for assembling and performing maintenance on the device, and see our guide to standard NEMA enclosure sizes to learn more about enclosure sizes that are commonly available.
Mounting and Facing: Where will your device be mounted, and which way will it face? This simple but important consideration is sometimes overlooked, and it can bring in other relevant factors such as junction box types and heat dissipation. Thus, make sure to examine your device’s requirements documentation to learn about how the device will be positioned when performing its everyday function.
Heat Management: Many electrical devices require heat dissipation solutions, such as heat sinks or venting. Make sure that your enclosure is large enough to accommodate necessary heat management components, and use our guide to calculating enclosure temperature rise for reference.
Customization: Your device may require an enclosure that’s been customized with cutouts, printing or other custom features. See Polycase’s options for enclosure customization to learn about how you can get the customized enclosures that you need–quickly and for an affordable price.

Electrical Enclosure Standards for Polycase Enclosures

At Polycase, we design our enclosures to meet a wide variety of electrical enclosure standards. Simultaneously, we recognize that high-performance enclosures need to go beyond simple compliance. These are some of the electrical enclosure models that demonstrate our dual commitment to standards compliance and to offering high-performance enclosures:

NEMA Rated Enclosures

Polycase offers a wide variety of NEMA rated enclosures, including models with popular ratings like NEMA 4X and NEMA 6P.

NEMA 4X Enclosures:

NEMA 6P Enclosures:

NEMA 12 Enclosures:

IP Rated Enclosures

Most of Polycase’s electrical enclosures also feature IP enclosure ratings, including widely used ratings such as IP66 and IP68.

IP65 Enclosures:

IP66 Enclosures:

IP68 Enclosures:

UL Rated Enclosures

Polycase’s enclosure ratings are always verified through independent testing by UL so that our customers can feel confident in the quality and compliance of our enclosures. Many of our enclosures also feature UL flame ratings to provide the additional flame resistance that our customers often require.

Polycase HD-44F polycarbonate enclosure, rated for compliance with NEMA 6P and IP68 standards

Polycase’s enclosure experts are always glad to provide help with navigating electrical enclosure standards. We can help you determine the enclosure standard that you need and then work with you to find the enclosure that meets that standard. Get started by calling us at 1-800-248-1233 or contact us online at any time.

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