8 Common Electrical Enclosure Types and Practical Uses
At first glance, electrical enclosures may not seem all that important. However, these carefully engineered boxes play a vital role in protecting electronics in industries such as telecommunications, IT systems, utilities and the Internet of Things (IoT), among many others.
With our technology growing at such a fast pace, innovative electrical enclosures are more important than ever. Choosing the right electrical enclosure type can save not only lives, but billions of dollars in equipment and operating costs. After all, the elaborate networks of electrical conductors, connectors, receptacles and devices that make up today’s electrical systems require protection from the many environmental conditions that can harm them — and it’s the responsibility of device designers and electricians to select and use the correct electrical enclosures to protect them.
The challenge for design engineers is knowing which electrical enclosure is right for their unique application. Today, electrical enclosures, such as junction boxes, come in many different types which must be carefully considered before moving forward with electrical projects.
Which electrical enclosures are we referring to, exactly? In this post, we’ll discuss eight different types of electrical boxes that are commonly used in today’s high-tech world.
ELECTRICAL ENCLOSURE TYPES – NEMA RATINGS
When discussing the different “types” of electrical enclosures, most people are referring to the enclosure ratings as defined by the National Electrical Manufacturers Association (NEMA).
NEMA is the organization which defines the North American standards for electrical enclosures, which are referred to as the NEMA rating system. To improve the safety and reliability of their products, most manufacturers in the United States design their enclosures to meet these standards.
Purpose of NEMA Ratings
A NEMA enclosure is an enclosure that’s been designed to meet one or more specific NEMA ratings standards. NEMA ratings signify an electrical enclosure’s ability to withstand specific environments and hazards. This makes it much easier for engineers to choose an electrical enclosure with confidence in its ability to perform.
For example, a utility company housing their sensitive electrical equipment outdoors in a coastal environment may choose a NEMA 4X enclosure to protect against the weather, as well as corrosion caused by salt spray.
Below, we’ll discuss the most popular NEMA rated electrical enclosure types and the critical role they play to ensure product function and safety.
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NEMA 1 ELECTRICAL ENCLOSURES
NEMA Type 1 enclosures are designed for indoor purposes and offer the most basic level of protection of all NEMA rated enclosures. These enclosures offer a degree of protection against light dust, dirt and accidental contact with electrical equipment.
Despite their limited protection, NEMA 1 enclosures are commonly used in a variety of industries to house indoor electrical equipment, such as variable-frequency drives installed in standard indoor locations.
Enclosure Considerations
When installed in non-hazardous environments, NEMA Type 1 enclosures are a cost-effective solution to protect valuable electronics and prevent public access to dangerous electrical equipment. Still, those who are concerned about excess moisture in the atmosphere may want to consider a NEMA 2 enclosure which offers an additional layer of protection against light drops of water.
Another thing to keep in mind is the heat generated by the electrical equipment. In data centers and IT networking equipment, overheating caused by a high internal heat load can result in damaged electrical components and operational failure.
To prevent this type of disaster, design engineers often rely on venting accessories to allow for the passage of air through the enclosure. Additionally, manufacturers, such as Polycase, can make custom cutouts in their enclosures using CNC machining services to allow for dissipation of heat.
NEMA 3 ELECTRICAL ENCLOSURES
NEMA 3 enclosures are designed for both indoor and outdoor use. However, they are mostly used as outdoor electrical enclosures.
This is because NEMA 3 enclosures provide protection against falling dirt, rain, snow, sleet and external ice formation. While they may not be suitable for extreme weather conditions, these enclosures can function as outdoor electrical junction boxes to protect electrical wiring connections and cables.
Enclosure Considerations
Because Type 3 enclosures have the lowest rating for outdoor electrical enclosures, it’s important that engineers consider the exact location and material of their enclosure. For example, ABS plastic enclosures are known to warp in direct sunlight and can put electrical equipment at risk, so they’re thus recommended only for indoor use.
Polycarbonate enclosures are durable, cost-effective and UV-resistant. These qualities make them a much safer choice for outdoor environments in both commercial and industrial applications.
NEMA 4 ELECTRICAL ENCLOSURES
NEMA 4 enclosures offer greater protection against harsh weather conditions compared to NEMA 3R enclosures. Most importantly, they have watertight features which make them suitable for industrial applications, such as protecting outdoor electrical systems, wire splices, circuit breakers and mounted telecommunications equipment.
The difference between a NEMA 3R weatherproof enclosure and a NEMA 4 waterproof enclosure is significant. Unlike Type 3 and 3R, NEMA Type 4 enclosures offer a degree of protection against splashing and hose-directed water.
Another key difference between the two electrical enclosure types is the enclosure’s protective seal. Gaskets on a NEMA 4 enclosure ensure a watertight seal to prevent ingress of water.
Enclosure Considerations
In an era of constant connectivity, the need for electromagnetic (EMI) and radio frequency interference (RFI) shielding has steadily increased. With all the signals beaming in the air at one time, it’s important for design engineers to ensure their own device doesn’t cause interference, or get interfered with.
EMI/RFI shielded enclosures are widely used in the telecommunications industry. NEMA 4 aluminum enclosures offer a natural level of protection against interference and have vast benefits beyond EMI/RFI shielding. Read our guide to EMI shielding to learn more.
NEMA 4X ELECTRICAL ENCLOSURES
NEMA 4X offers the same level of protection as NEMA 4, but with greater protection against corrosion. As such, these weatherproof electrical boxes are often found in applications with excessive moisture, intense water spray and corrosive chemicals.
Corrosion is a common problem in electrical systems where excess moisture is present. NEMA 4X enclosures are watertight and can prevent condensation from damaging sensitive electrical components.
Enclosure Considerations
In some applications, it may be necessary to install wiring connectors, cables or conduits onsite. In such applications, enclosures with knockouts are key to providing onsite flexibility.
The Polycase SK Series plastic enclosures with knockouts make onsite cabling and wiring simple. The knockouts are easy to remove and require no additional equipment.
When electrical technicians need to make modifications onsite, electrical enclosures with knockouts can help save time and money. And with a NEMA 4X rating, these outdoor electrical boxes are engineered to protect against harsh weather conditions, including potential corrosion.
NEMA 6 ELECTRICAL ENCLOSURES
Designed for both indoor and outdoor use, NEMA 6 enclosures are used in applications in which occasional temporary submersion in water may be likely. These weatherproof boxes are found in a wide range of applications, including electric vehicles and maritime transportation.
With a NEMA 6 enclosure, design engineers have little to worry about. In addition to providing protection for accidental contact with electrical equipment, NEMA 6 enclosures offer protection against wet environments, falling dirt, external formation of ice and ingress of water when temporarily submerged.
Enclosure Considerations
You’ll often encounter NEMA 6 enclosures in applications where a designer requires an extremely durable surface mount electrical box. NEMA 6 enclosures are especially common in power plant and alternative energy applications. They come in a range of materials and sizes, from small, impact-resistant polycarbonate enclosures to larger steel structures.
NEMA TYPE 6P ELECTRICAL ENCLOSURES
NEMA 6P enclosures offer the same level of protection as NEMA 6 enclosures, but allow for prolonged submersion in water (hence, the “P” in 6P). It also adds another layer of protection against corrosion.
NEMA 6P enclosures are among the most durable electrical enclosure types on the market today. With their ability to withstand extreme environments, Type 6P waterproof enclosures are often used to house electrical instruments and devices in underground mines and remote caves.
They’re also used to protect electrical devices in offshore environments, which can be highly corrosive. Chemical cleaners can also cause corrosion, making NEMA 6P enclosures necessary for the safe protection of electrical equipment.
Enclosure Considerations
Aluminum is a commonly used material for NEMA 6P enclosures due to its many attractive qualities. The world's most abundant metal — aluminum — is lightweight, rugged and corrosion-resistant.
However, polycarbonate NEMA 6P enclosures are also popular. Today’s polycarbonate materials are extremely resilient, and with high-quality manufacturing processes, they’re competitive in performance with aluminum enclosures.
Because of their corrosion resistance, aluminum and polycarbonate enclosures are often preferable to stainless steel enclosures, which are easily damaged by corrosion, in marine environments. This is because salt spray is highly corrosive and can pose a serious threat to electrical equipment.
NEMA 7 ELECTRICAL ENCLOSURES
NEMA Type 7 enclosures are built for indoor hazardous locations classified as Class 1, Division 1, Groups A, B, C or D, which are defined in NFPA 70. These hazardous classifications include atmospheres containing inflammable gases in the air which may cause internal explosions.
Explosion-proof enclosures, such as NEMA 7 enclosures, are designed to contain explosions without causing external damage. Explosions are not uncommon in chemical plants and oil and gas facilities.
Enclosure Considerations
NEMA 7 enclosures are typically made with diecast aluminum or stainless steel. While they aren’t as common as NEMA 4X enclosures, they are becoming more popular with the rise of the Internet of Things (IoT).
With IoT systems being placed in hazardous environments (oilfields, warehouses, etc.), NEMA 7 enclosures are being used to protect equipment from dust, dirt, water and potential explosions caused by combustible gases.
NEMA 12 ELECTRICAL ENCLOSURES
NEMA 12 enclosures are used for indoor applications and provide protection against water drips, falling dirt, dust and non-corrosive liquids. Despite their high number, NEMA 12 enclosures are a step above NEMA 1 and 2 when it comes to protection, but still less protective than outdoor electrical enclosure types like NEMA 4X and NEMA 6P.
As you probably know, dust isn’t good for electrical equipment. When other materials get mixed into the dust, it can make dust combustible and prone to explosion. NEMA 12 enclosures are designed to protect against the ingress of dust and dirt to keep electrical equipment, such as automation equipment, running smoothly. They also protect against ingress from dripping and splashing water.
Enclosure Considerations
NEMA 12 enclosures are generally used in machining, manufacturing and industrial applications. They often have gasketed seals to prevent dust, fibers and water from entering.
If knockouts are important to you, consider a NEMA 12K enclosure instead. The knockouts are the only difference between the two enclosures.
ELECTRICAL ENCLOSURE MATERIAL TYPES
In addition to NEMA ratings, electrical housings also come in different materials which can significantly impact their function and performance. The following are some of the most common base materials used to manufacture enclosures:
Polycarbonate Plastic
Polycarbonate plastic enclosures are generally less expensive than metal enclosures and have excellent impact resistance. Polycarbonate is also incredibly versatile and suitable for a wide range of indoor and outdoor applications. It’s a favorable alternative to other non-metallic enclosure materials like PVC due to its balance of cost and durability.
Because of their relatively low cost, polycarbonate enclosures are commonly used in desktop electronics and electrical instruments associated with the IT industry. They’re also a common choice for electrical applications that use non-metallic cable, although it’s possible to use them with metallic cable as well so long as a properly installed ground wire is present.
ABS Plastic
Acrylonitrile butadiene styrene (ABS) is another popular material for indoor plastic electrical boxes. ABS is typically one of the most affordable enclosure material options, and even if it doesn’t offer the same durability that polycarbonate does, it’s still a durable material with excellent resistance to impacts and heat. Thus, it’s one of the most popular types of electrical boxes for indoor applications that require basic protection.
Aluminum
Aluminum enclosures are more expensive compared to plastic enclosures. However, they offer some key benefits of their own.
Aluminum is extremely durable, suitable for both indoor and outdoor boxes, and able to withstand high temperatures. Additionally, aluminum alloys are highly resistant to corrosion and offer natural EMI/RFI shielding to prevent interference. Metal enclosure materials like aluminum are also important for applications that use metal conduit or metal sheathed cable, since a metal enclosure is usually needed to ground the conduit.
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Stainless Steel
Like most enclosure materials, there are advantages and disadvantages to stainless steel enclosures. Although stainless steel is fire-resistant and functions well in wet environments, it is a heavy material generally more expensive compared to other enclosure materials. However, its extreme durability and attractive appearance continue to make it a popular material for metal boxes and, like aluminum, it can provide grounding for metal conduit and metal sheathed cable.
Carbon Steel
Carbon steel enclosures are strong and cost-effective. However, they are highly susceptible to corrosion and shouldn’t be used in coastal regions where salt in the air can easily wear down the enclosure, unless they have a protective powder coating applied.
FINAL THOUGHTS
With the rise of technological advances, we’re starting to place electrical equipment in a variety of nontraditional environments. To ensure proper protection of electrical components, choosing the right electrical enclosure for the application at hand is critical.
At Polycase, we offer a vast range of electrical enclosure types engineered to meet the needs of virtually any application. From waterproof enclosures in polycarbonate plastic to diecast aluminum enclosures with NEMA 4X ratings, we have the ideal enclosure solution for both indoor and outdoor environments. Our enclosures are UL Listed for dependable performance, and we offer fast and easy customization options for creating custom cutouts and printing on many of our enclosure models.
Explore Polycase’s full selection of NEMA enclosures here to see everything we have to offer. Need assistance? Call us at 1-800-248-1233 or reach out online. Our friendly staff is always happy to help!