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Protecting your sensitive electronic equipment requires housing it in enclosures that can provide the best protection against all potential hazards. NEMA ratings provide you the confidence that a particular enclosure delivers you the level of protection it promises. Two of the most commonly used NEMA-rated enclosures for outdoor applications are NEMA 3 and NEMA 4 enclosures.
What Is NEMA?
The National Electrical Manufacturers Association (NEMA) provides the industry standards for the reliability and safety of all electronic equipment, including enclosures and medical imaging equipment. NEMA is the largest electrical manufacturer organization in the United States, and it does not perform product testing but rather sets the criteria for performance under certain environmental conditions.
Types of NEMA Enclosures
Polycase HD-22F NEMA 3r Polycarbonate Enclosure
Sensitive electronic equipment, made to serve industrial uses, can only remain functional when protected from the potential hazards in its environment; likewise, it protects people, animals, property and the environment from damage caused by the exposure of that electronic equipment to the elements.
Enclosures are made to protect people from accidentally touching the active electrical components inside. They are also designed to keep your valuable equipment, such as junction boxes, from being potentially tampered with or stolen.
However, to protect your equipment from all potential risks, you need an enclosure capable of withstanding your application‘s environmental conditions.
Some enclosures are made of high-quality plastic, polycarbonate, aluminum, or steel. They may be hinged, lockable, or come with or without knockouts. They may or may not be waterproof, corrosion-resistant to agents like gasoline or acetylene, weather-resistant, or resistant to oil and chemical seepage and splash; they might offer any manner of other protections from common threats to parts and to people. Knowing which characteristics you need and finding the enclosure that best meets those needs are where NEMA ratings come in.
What Are NEMA Ratings?
NEMA ratings help you ensure that you can protect your electronics from impact, water damage, and other threats from hazards like high-mess spraying, temporary submersion, and hazardous weather. Note that NEMA ratings do not refer to construction details of an enclosure, just its capacity to withstand certain potential threats and hazards.
NEMA testing methods and performance criteria are among the guidelines that entities like Underwriters Laboratories (UL) use to investigate and list electrical enclosures. An enclosure carrying an authorized UL label is guaranteed to have been properly tested and to have passed the tests required to meet the corresponding standard.
The official, definitive source for NEMA ratings is the NEMA 250- Enclosures for Electrical Equipment.
Find out more about NEMA-rated enclosures with one of our experts
The NEMA rating system is similar to the European IP rating system, and each NEMA rating has its IP equivalent. NEMA 3-rated enclosures in America are rated IP 64 in Europe, while NEMA 4-rated enclosures in America are rated IP 66 in Europe.
How Are NEMA Ratings Determined?
The NEMA rating system ensures a material’s ability to withstand certain threats from chemical, liquid, and solid sources.
Liquid threats include:
- Light splashes
- Hose down and splashes
- Temporary submersion
- Prolonged submersion
- Rain, snow, and sleet
- Ice
Solid threats include:
- Incidental contact
- Falling dirt
- Circulating dust
- Settling airborne dust
- Windblown dust
Chemical threats include:
- Oil and coolant seepage
- Oil and coolant splashes
- Corrosion
How Is a NEMA 3 Rating Determined?
Enclosures are subjected to several tests to determine whether they meet NEMA 3 standards, as follows:
- A specifically sized rod is used to attempt to penetrate the enclosure’s interior.
- The tops and sides are sprayed with water at a water pressure of approximately 5 psi; the industry intended to simulate sleet or rain under 5 mph wind conditions. For the enclosure to pass this test, the interior must remain dry.
- An ice test ensures the enclosure does not get penetrated and that ice formation does not make the enclosure less effective or usable.
- Dust and direct tests ensure fallen and windblown dust and dirt cannot penetrate the enclosure.
In addition, all enclosures meant for outdoor applications are subjected to tests to ensure their materials offer the products inside adequate UV protection.
How to Know Which NEMA-Rated Enclosure Is Right for You?
To decide which NEMA-rated enclosure is best for you, you need to know your product’s final application. You also need to know the answer to the question: what does NEMA 3 mean vs. what does NEMA 4 mean? That way, you can best figure out the right enclosures for your application and the degree of protection it requires.
ZH-100802 NEMA 4X Hinged Junction Box
Common misconceptions about NEMA ratings are:
- The higher the number of ratings, the greater the protection it provides.
- The higher-numbered ratings include all the tests from the lower ratings, which may be the bases in some instances but it is not necessarily the case across the board.
- All NEMA-rated enclosures are dust-proof and waterproof.
When you need an electronic enclosure for outdoor applications, two to consider are NEMA 3 and NEMA 4 enclosures.
Choose the right NEMA enclosure for your application
What Does NEMA 3 Mean?
Made for both indoor and outdoor applications, enclosures with a NEMA 3 rating are weather-resistant. This means they protect the components they contain from:
- Fallen and windblown dirt and dust
- Sleet, snow, rain, and other weather hazards
- Damaged caused by ice formation
NEMA 3 enclosures provide the same protection as NEMA 1 enclosures. This means no fingers or other objects alike can be used to access the interior from the exterior. NEMA 3 enclosures can come with a variety of latching and locking mechanisms.
Types of NEMA 3 Ratings
There is more than one type of NEMA 3 rating, each with a slightly different meaning. These include:
NEMA 3R Enclosures
A NEMA 3R enclosure has not passed the dust test because it is not required to comply with the dust standard. It may or may not have a dust gasket. This depends on whether or not the application requires it to prevent rain ingress.
On the bottom of a NEMA 3 enclosure is a small drain hole that permits ventilation and allows any water entering the enclosure to disperse quickly.
NEMA 3S Enclosures
The products in a NEMA 3S enclosure can function even when encased in ice. This test is usually performed on the NEMA 3S products themselves in addition to the enclosure.
NEMA 3X Enclosures
Any NEMA rating with an ‘X’ included means the enclosure also protects the products inside from corrosion. A common application for this particular type of enclosure may be for use near salt water.
NEMA 3RX Enclosures
A NEMA 3RX enclosure provides products with protection from corrosion but not from dust because the products require the former but not the latter.
NEMA 3SX Enclosures
A NEMA 3SX enclosure provides products with protection from corrosion, and external mechanisms on it can operate even when laden with ice.
What Does NEMA 4 Mean?
Like NEMA 3-rated enclosures, NEMA 4 enclosures must also be weather resistant. Beyond that, however, NEMA 4 enclosures are held to stricter requirements than NEMA 3 enclosures.
Designed more for rigorous outdoor applications, materials on all NEMA 4 enclosures must have UV protection from degradation. NEMA 4 enclosures may come with custom cutouts, pre-punched holes, insulation, lift-off hinges, locks, or latches.
How Is a NEMA 4 Rating Determined?
For an enclosure to obtain a NEMA 4 rating, it must meet all the same requirements that a NEMA 3 enclosure must meet. In addition, it must be able to withstand being sprayed with water from a hose with a 1-inch nozzle at a pressure of at least 65 gpm for five minutes from a distance of at least 10 feet away. For an enclosure to pass NEMA 4 rating test, it must allow no water to penetrate.
Types of NEMA 4 Ratings
Unlike the NEMA 3 rating system, NEMA 4 ratings have just one subgroup: NEMA 4X. Like the ‘X’ on some NEMA 3 subgroups, the ‘X‘ means the enclosure is resistant to corrosion.
NEMA 3 vs. NEMA 4 Enclosures
Enclosures with a NEMA 4 rating generally offer a greater degree of protection than those with a NEMA 3 rating, making NEMA 4 more suitable for certain outdoor applications, such as when harsh weather is a consistent factor. Note, however, that NEMA 3 enclosures are required to handle ice formation, but NEMA 4 enclosures are not. That said, some NEMA 4 enclosures are tested to withstand ice formation, even though it’s not required for the rating.
NEMA 4 enclosures are also well-suited for industries requiring thorough, regular cleaning, like those in which the products they contain require hosing down. The medical and food industries are good examples of useful applications for NEMA 4 enclosures.
Some NEMA 3 enclosures, however, can be a more economical choice for purely indoor applications. As for their common outdoor applications, the construction and transportation industries often use NEMA 3 enclosures, and you’ll often see this type used on shipping and loading docks.
Both NEMA 3 and NEMA 4 enclosures may be available with custom powder coating and silk screening.
Other NEMA Ratings
While NEMA 3 and NEMA 4 rated enclosures are among the most commonly used, there are other ratings of enclosures, including:
- NEMA 1 - Offers some indoor protection against some amounts of falling dirt
- NEMA 2 - Offers some indoor protection against falling dirt and some falling water
- NEMA 5 - Offers some indoor protection against non-corrosive, dripping liquids and settling fibers and dust
- NEMA 6 - Offers both indoor and outdoor protection from external ice formation damage, hosed water, and water entry during periodic, temporary submersion to a certain depth
- NEMA 7, 8, and 9 - These are certified for use in certain Class I and or Class II areas with dangerous conditions as defined in the National Electrical Code (NEC) and other National Fire Protection Association (NFPA) standards
- NEMA 10 - Complies with Mine Safety and Health Administration (MSHA) standards
- NEMA 11 - Made for general use, providing protection against corrosion from gases and liquids and meeting tests for drip and corrosion resistance
- NEMA 12 - Constructed with no knockouts and offers some protection from falling dirt, non-corrosive liquids, dripping liquids, and circulating fibers and dust
- NEMA 12K - Offers the same degree of protection as NEMA 12 enclosures except constructed with knockouts
- NEMA 13 - Offers some indoor protection against oil, dust, non-corrosive coolants, and spraying water
NEMA types 1, 2, 5, 12/12K, and 13 are rated for indoor use; NEMA types 3 and its subgroups 4/4X and 6/6P are rated for both indoor and outdoor use.
NEMA 3 vs. NEMA 4 Enclosures: Which Is Right For You?
NEMA 3 enclosures and NEMA 4 enclosures offer electrical components that protect against a variety of outdoor threats. You can have the peace of mind of knowing your products are safe by finding the enclosure that provides the exact protection you need without having to pay more than necessary.
Contact the Experts on Electronic Enclosures
Polycase is one of the premier electronic enclosure manufacturers, with more than 65 years of consistent service. We provide enclosures for everyday use. We can be your single-source supplier for all your needs, with in-house engineers operating precision technologies like CNC printing and machining to create customized solutions at competitive prices. To discuss how Polycase can serve your enclosure needs, call toll-free at 1-800-248-1233 or email us by using the contact form on our website.
You can also speak with a Polycase rep over live chat during business hours (between 8 a.m. and 5 p.m. EST Monday through Friday) from the same contact page linked above.
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