This article provides comprehensive information about NEMA enclosures. You will learn how NEMA enclosures are made, and their materials of construction as well as applications, advantages, and drawbacks.
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NEMA enclosures are boxes engineered to safeguard electrical components from environmental factors. Depending on the specific NEMA rating, devices housed within a NEMA enclosure are protected in the following ways:
| Indoor Non-Hazardous NEMA Enclosures | ||||||
|---|---|---|---|---|---|---|
| Specific Applications, Indoor Nonhazardous Locations | Type of Enclosure | |||||
| Provides a degree of protection against: | 1 | 2 | 3 | 11 | 12 | 13 |
| Incidental contact with enclosed equipment | X | X | X | X | X | X |
| Falling dust | X | X | X | X | X | X |
| Airborne dust, particles | X | X | X | |||
| Dripping noncorrosive liquid, light splash | X | X | X | X | ||
| Oil/coolant seepage | X | X | ||||
| Oil/coolant spray/splash | X | |||||
| Corrosive agents | X | |||||
In addition to safeguarding the enclosed equipment, NEMA enclosures also offer protection for personnel and property in the surrounding environment:
| Outdoor Non-Hazardous NEMA Enclosures | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Specific Applications, Indoor Nonhazardous Locations | Type of Enclosure | ||||||||||
| Provides a degree of protection against: | 3 | 3X | 3R* | 3RX* | 3S | 3SX | 4 | 4x | 6 | 6P | |
| Incidental contact with enclosed equipment | X | X | X | X | X | X | X | X | X | X | |
| Rain, Snow, and Sleet** | X | X | X | X | X | X | X | X | X | X | |
| Sleet** | X | X | |||||||||
| Windblown dust, lint, fiber, and flying | X | X | X | X | X | X | X | X | |||
| Hose down | X | X | X | X | |||||||
| Corrosive agents | X | X | X | X | X | ||||||
| Occasional temporary immersion | X | X | |||||||||
| Occasional prolonged immersion | X | ||||||||||
NEMA enclosure ratings are based on the NEMA 250 standard issued by the National Electrical Manufacturers Association (NEMA), an organization that develops standards to enhance the safety of electrical equipment for both end-users and manufacturers.
NEMA enclosure standards are voluntary and self-certified by the enclosure manufacturer, meaning that third-party certification is not required. The manufacturer commits to producing enclosures that meet these standards.
Given that you're relying on the supplier's claim that they have met or self-certified to NEMA enclosure standards, it's essential to purchase from a trusted, leading supplier.
An alternative is to opt for third-party testing and certification. Various testing organizations, such as Underwriters Laboratory, Intertek, and CSA, can certify that NEMA enclosures comply with NEMA standards.
A certified NEMA enclosure offers greater assurance compared to a non-certified one, especially for critical applications. In some cases, government, military, and other clients may require certification for the enclosures used in your design or equipment.
NEMA enclosures have a rating system that indicates the level of protection against the penetration of dust, liquids, or other substances, as well as the protection they provide for the electronics inside. NEMA has established rigorous testing and certification processes for each level of protection, and these enclosures often require specific types of gaskets to maintain a proper seal.
NEMA ratings specify the degree of protection an enclosure offers against the ingress of objects, particles, dirt, fine dust, water, water sprays or jets, and even water immersion. Hazardous locations are defined according to the National Fire Protection Association's NFPA 70®-2017, National Electrical Code®.
Additionally, NEMA ratings are categorized into three groups based on whether the enclosures are suitable for indoor use, outdoor use, corrosive environments, or hazardous locations:
All NEMA enclosure types are designed to protect personnel from incidental contact with the enclosed equipment, effectively safeguarding operators or users from the risk of electrocution.
NEMA enclosures are specifically intended for electrical equipment operating at 1000 volts or lower.
A NEMA 1 enclosure is intended for general-purpose indoor use only. As with all NEMA enclosures, it protects personnel from accidental contact with the enclosed equipment. Additionally, NEMA type 1 enclosures shield the enclosed equipment from falling dirt.
A NEMA 2 enclosure is drip-tight and offers the same protection as a NEMA Type 1 enclosure, with the added benefit of shielding enclosed devices from dripping and light splashing of non-corrosive liquids. Typically equipped with drip shields, NEMA 2 enclosures are used in environments where condensation is a concern, such as laundry rooms and areas around air conditioners, refrigerators, and other cooling equipment.
A NEMA 3 enclosure is weather-resistant and suitable for both indoor and outdoor use. It safeguards personnel against accidental contact with the enclosed equipment and protects devices from falling dirt, rain, sleet, snow, and windblown dust. Additionally, NEMA 3 enclosures are designed to withstand the effects of sleet or freezing rain, which can form an external ice layer without causing damage.
A NEMA 3X enclosure offers enhanced protection with added corrosive resistance compared to a NEMA 3 enclosure.
A NEMA 3R enclosure includes all the protective features of a NEMA Type 3 enclosure but does not provide protection against wind-blown dust.
A NEMA 3RX enclosure offers the same protection as a NEMA 3R enclosure but with added resistance to corrosive environments.
A NEMA 3S enclosure provides all the protective features of a NEMA 3 enclosure, with the added advantage that external mechanisms (handles, pushbuttons, etc.) remain operational even when covered with ice.
A NEMA 3SX enclosure includes the same benefits as a NEMA 3S enclosure but also offers additional resistance to corrosive environments.
A NEMA 4 enclosure is watertight and can be cleaned with a hose. Suitable for both indoor and outdoor use, NEMA 4 enclosures protect personnel from incidental contact with the enclosed equipment. They are designed to guard against falling dirt, rain, sleet, snow, windblown dust, splashing water, and hose-directed water. NEMA 4 enclosures are also resistant to damage from external ice formation.
A NEMA 4X enclosure offers all the protections of a NEMA 4 enclosure but includes additional resistance to corrosive environments.
A NEMA 5 enclosure is designed to be dust-tight and suitable for both indoor and outdoor use. These enclosures provide protection for personnel against accidental contact with the enclosed equipment. They also safeguard the enclosed equipment from falling dirt, settling airborne dust, lint, fibers, and flying debris, as well as from dripping and light splashing of non-corrosive liquids.
A NEMA 6 enclosure is submersible and suitable for both indoor and outdoor use. These enclosures protect personnel from accidental contact with the enclosed equipment. NEMA 6 enclosures guard against falling dirt and water ingress, including hose-directed spray and temporary submersion. They are also resistant to damage from drips, sleet, or freezing rain that may form an ice layer on the enclosure.
A NEMA 6P enclosure is designed to endure continuous submersion in water. In addition to this enhanced protection, it offers the same level of safeguarding as a NEMA 6 enclosure.
A NEMA 7 enclosure is designed for use in specific indoor hazardous locations and is also known as an indoor explosion-proof enclosure. Like all NEMA enclosures, it protects personnel from accidental contact with the enclosed equipment.
NEMA 7 enclosures are suitable for environments classified under Class I Groups A, B, C, and D according to the NFPA 70 standard of the National Electrical Code (NEC). These classifications include locations with flammable chemicals such as acetylene, hydrogen, manufactured gas, diethyl ether, ethylene, cyclopropane, gasoline, hexane, butane, naphtha, propane, acetone, toluene, and isoprene.
These enclosures are designed to contain any internal explosions and prevent them from causing external hazards or further explosions.
A NEMA 8 enclosure is designed for use in specific indoor or outdoor hazardous locations and is also known as an indoor or outdoor explosion-proof enclosure. Like all NEMA enclosures, it protects personnel from accidental contact with the enclosed equipment. These enclosures are suitable for hazardous environments classified as Class I Groups A, B, C, and D according to the NFPA 70 standard of the National Electrical Code (NEC). This includes locations with flammable chemicals such as acetylene, hydrogen, manufactured gas, diethyl ether, ethylene, cyclopropane, gasoline, hexane, butane, naphtha, propane, acetone, toluene, and isoprene.
NEMA 8 enclosures are engineered to contain internal explosions and prevent them from causing external hazards or further explosions.
NEMA 9 enclosures are designed to be dust-ignition proof and are suitable for specific indoor hazardous locations. Like all NEMA enclosures, they protect personnel from accidental contact with the enclosed equipment. NEMA 9 enclosures are intended for use in environments classified as Class II Groups E, F, and G according to the NFPA 70 standard of the National Electrical Code (NEC). This classification includes areas with combustible dusts such as metal dust, carbon black, coal dust, and coke dust. Unlike NEMA 8 enclosures, which immerse equipment in oil to prevent combustion, NEMA 9 enclosures are specifically designed to prevent the ignition of combustible dust through their robust construction and sealing methods.
A NEMA 10 enclosure is designed for use in specific hazardous locations within mining applications. Like all NEMA enclosures, it provides protection for personnel against accidental contact with the enclosed equipment. NEMA 10 enclosures comply with the Code of Federal Regulations 30 Part 18, as mandated by the Mine Safety and Health Administration (MSHA), ensuring they meet the stringent safety requirements for mining environments.
A NEMA 11 enclosure is designed for use in specific corrosive environments. These enclosures are drip-proof and provide protection for personnel against accidental contact with the enclosed equipment. Although the NEMA 11 rating may be considered obsolete or rare, it is still referenced by some suppliers. Enclosures with an "X" designation indicate added protection against corrosion.
NEMA 12 enclosures are designed for general-purpose indoor use and are constructed without knockouts. They offer a higher level of protection compared to NEMA 11 enclosures, providing enhanced durability and reliability for various indoor applications.
NEMA 12 enclosures protect personnel from incidental contact with the enclosed equipment. They safeguard enclosed equipment against the ingress of solids, objects, and particles, including falling dirt, airborne dust, lint, fibers, and flying debris. Additionally, NEMA 12 enclosures prevent the ingress of dripping water and light splashing of non-corrosive liquids, offering general-purpose protection.
NEMA 12K enclosures are general-purpose, indoor enclosures that come with knockouts. They offer all the protective features of a NEMA 12 enclosure while providing the added convenience of knockouts, which simplify the installation of electrical wiring and cables.
NEMA 13 enclosures are general-purpose, indoor enclosures equipped with knockouts. They offer the same protection as NEMA 12 enclosures, with the added benefit of safeguarding against splashing and spraying of oils, lubricants, heat treat oils, greases, metalworking fluids, and coolants.
Underwriters Laboratories (UL) has its own set of standards for enclosures applicable in the U.S. and Canada. UL ratings are used in the U.S., while c-UL ratings are specific to Canada. Unlike NEMA ratings, manufacturers cannot self-certify for UL or c-UL compliance.
Third-party certifying bodies, such as UL, Intertek, and CSA, provide listings that verify that NEMA enclosures meet additional UL or c-UL standards. These third-party certifications confirm adherence to safety requirements and enhance the quality of the enclosures.
Underwriters Laboratories' enclosure standards are:
The UL standards for enclosures are similar to the NEMA 250 standard but are limited in scope. Notably, they do not have equivalents for the NEMA Type 3X, 3RX, and 3SX designations.
To achieve a c-UL listing, enclosures must meet the applicable Canadian standards, including:
Intertek offers listings and marks for enclosure products, including ETL, c-ETL, and us-ETL. The ETL mark is recognized in both the U.S. and Canada. ETL stands for “Electrical Testing Labs,” which was founded in 1896 by Thomas Alva Edison.
The International Electrotechnical Commission (IEC) provides ingress protection (IP) ratings for enclosures. While NEMA-rated enclosures are more common in industrial applications in the U.S. and Canada, IP ratings are often used for consumer products like cameras and smartphones.
| IEC Ingress Protection (IP) Ratings | |||
|---|---|---|---|
| Ingress Protection (IP) Ratings per International Electrotechnical Commission (IEC) Strandard 60529 | |||
| 1sts IP Number | Particle or Solid Object Ingress Protection Type | 2nd IP Number | Liquid Ingress Protection Type |
| 0 | No Protection | 0 | No Protection |
| 1 | Objects over 50mm (2") | 1 | Vertical Falling Drops of Water |
| 2 | Objects over 12.5mm (0.5") | 2 | Spray up to 15° Vertical |
| 3 | Objects over 2.5mm (0.1") | 3 | Spray up to 60° Vertical |
| 4 | Objects over 1mm (0.04") | 4 | Light Spray from Any Direction |
| 5 | Limited Dust Ingress Protection | 5 | Light Jet Spray from Any Dirction |
| 6 | Total Dust Ingress Protection | 6 | Powerful Jets from Any Direction |
| 7 | Immersion Less Than 1m (3.28") | ||
| 8 | Immersion Greater 1m (3.28") | ||
| 9 | High Power Jets, High Temperature | ||
The IEC IP rating system is less comprehensive than the NEMA rating system for enclosures.
A specific NEMA rating may meet or exceed a corresponding IEC IP rating, but the systems are not directly equivalent.
IEC IP ratings focus solely on protection against dust, objects, and water ingress. In contrast, NEMA ratings also account for factors such as icing, corrosion resistance, oil and lubricant resistance, and specific construction details.
Additionally, NEMA ratings apply to fully assembled and installed enclosures, whereas IP ratings can apply to partially completed enclosure installations.
| Comparison of NEMA and IP Ratings | |
|---|---|
| NEMA Type Enclosure | IEC IP Closest Match |
| 1 | IP10 |
| 2 | IP11 |
| 3 | IP54 |
| 3R | IP14 |
| 3S | IP54 |
| 4 | IP66 |
| 4X | IP66 |
| 5 | IP52 |
| 6 | IP67 |
| 6P | IP68 |
| 12 | IP52 |
| 13 | IP54 |
What I find particularly interesting when comparing NEMA and IP rating systems is that the IP rating system lacks classifications for hazardous locations.
IECEx and ATEX ratings address hazardous locations with their respective certification systems. The IECEx certification system, established by the International Electrotechnical Commission, ensures international safety compliance for equipment and enclosures used in hazardous environments. It is based on the IEC 60079 standard for hazardous area enclosures.
ATEX certifications, on the other hand, are based on the European Union (EU) standards under the EU ATEX Directive. These certifications are applicable solely within the European Union and define the safety requirements for enclosures and equipment in hazardous areas with flammable liquids, vapors, gases, or combustible dust. ATEX certification covers electrical and mechanical equipment used on the surface, underground, and on fixed offshore installations.
In industrial environments, equipment like motors, induction heaters, electromagnets, RF transmitters, fluorescent lighting, halogen ballasts, arc welders, microwave ovens, RF generators, and other electrical devices can produce significant levels of electromagnetic or radio frequency interference (EMI or RFI).
EMI/RFI shielding is essential to prevent these emissions or signal leaks from affecting the equipment inside a shielded enclosure. It also protects sensitive instruments and electronics from external EMI/RFI interference.
Various standards and organizations offer schemes to designate or rate shielding for electromagnetic and radio frequency interference:
To shield electronics and electrical equipment from EMI and RFI, an electrically conductive or magnetic layer is required. Plastic enclosures need a metallic coating to provide shielding, while metal enclosures inherently offer protection. Ferromagnetic metals, such as carbon steel or 400 series ferritic stainless steel, can shield both magnetic and electrical fields.
However, EMI/RFI can still penetrate through gaskets on metal and metalized plastic enclosures. Shielding gaskets are used to maintain shielding effectiveness across seams or gaps in a shielded NEMA enclosure, such as between covers or doors and the enclosure. These gaskets can be made from metalized polymers (like silver-coated nylon), metal foil-polymers, conductive fabric-wrapped foam, wire mesh, stamped metals, or expanded metal.
The Telcordia GR-63 CORE Network Equipment Building Seismic Standard is commonly used to assess the suitability of NEMA enclosures for seismic applications. This standard divides the U.S. into zones based on varying earthquake risks, with Zone 4 (covering areas like California and Alaska) representing high risk, and Zone 0 (including states like Wisconsin and Florida) indicating low risk.
Data and communications equipment are particularly vulnerable to seismic disturbances, making the NEBS rating crucial for NEMA rack enclosures, NEMA rack cabinets, and open frame racks.
p>For markets outside the U.S., the International Building Code (IBC), formerly known as the Uniform Building Code (UBC), also addresses seismic standards, particularly in "High Seismic Areas." However, the IBC/UBC standards tend to be less stringent and more component-focused compared to the U.S. standard.
RoHS and REACH regulations restrict the use of specific toxic or hazardous substances in electrical and electronic equipment.
The Restriction of Hazardous Substances (RoHS) directive prohibits the use of the following ten materials and chemicals in electrical and electronic devices sold within the European Union:
The European Union’s REACH Directive applies to all materials, solvents, paints, chemicals, and other substances used in the manufacture of electrical and electronic equipment. The goal of REACH is to reduce exposure to carcinogens, mutagens, toxins, and other hazardous substances. Suppliers must provide information on the chemicals used, focusing on the health and safety impact of the supplied products.
In addition to the NEMA type number, NEMA enclosures can be classified in three ways:
Some enclosures are mounted to a machine or a wall in a factory, while other NEMA enclosures are freestanding or floor-mounted. The NEMA enclosure is engineered with the required mounting flanges, legs, mounting holes, or mounting brackets specific to the mounting location.
Mounting kits might be included with the NEMA enclosure or sold as an add-on option or accessory. These kits can include leg kits, pole mounting kits, pedestals and pedestal mounting kits, fastener kits, and mounting bracket kits.
Desktop NEMA enclosures are specifically designed to be mounted on workbenches, tables, and desktops. Analytical instruments often reside in these enclosures, allowing for chemical composition analysis while safeguarding the instrumentation electronics and detectors from the wet and corrosive environments typically found in industrial, R&D, and quality control laboratories.
DIN rail systems are widely utilized for mounting sensors, controllers, relays, switches, and other monitoring and control components. A DIN rail NEMA enclosure is engineered to be mounted on a DIN rail, offering protection to sensors, electronics, and electrical devices that are sensitive to environmental conditions in industrial settings. DIN refers to the German standards organization, which is the German equivalent of ANSI, the U.S. national standards body.
Drop over NEMA enclosures feature lifting eyes and an open bottom, designed to be lifted by the eyes and placed over larger electrical equipment that requires environmental protection. These enclosures are commonly used to safeguard motor control centers, drives, transformers, electrical metering units, and electrical distribution systems. Drop over enclosures can often be walk-in, ground, or pad-type enclosures.
Floor mount NEMA enclosures are similar to free-standing enclosures but are bolted or attached to the floor. They can be less deep compared to free-standing NEMA enclosures.
Typically, they employ unibody construction and are designed for stand-alone applications rather than integration into a machine or system. These enclosures can be heavy and often feature lifting eyes on the top to facilitate movement without damaging the sheet metal or internal components.
Floor-mounted enclosures usually include floor supports or legs, elevating them off the ground to provide easier cable access. Most have a wide back panel for mounting instruments, monitoring electronics, and industrial controls. The larger NEMA enclosures generally come with lifting eyes for straightforward placement or removal.
Free-standing NEMA enclosures rest directly on the floor and are not bolted or anchored. They are typically formed as a single monolithic or unibody structure, although modular options are available from some suppliers. These enclosures are commonly used in stand-alone applications.
Free-standing enclosures lack legs, floor supports, or floor support kits. They often feature a deeper base inside the enclosure door to prevent scraping against the floor. Their width and front-to-back depth are usually greater to enhance stability and prevent tipping.
These enclosures tend to be very heavy and frequently include lifting eyes on the top to facilitate movement without damaging the sheet metal or internal components.
Free-standing enclosures may have single or double front doors, with an optional rear door or removable rear panel. They generally include internal back and side panels for mounting various devices such as automation equipment, PLCs, drives, contactors, relays, controllers, IT equipment, or process instrumentation. Some models use DIN rails, 19” EIA rack rails, fixed frames, or swing-out frames for mounting devices.
Handheld NEMA enclosures, often integrated with pushbutton switches or joystick controllers, are used to activate devices such as winches, hydraulic presses, or robotic arms. These enclosures are smaller in size and typically have a rectangular or T-shaped design.
Ground or pad-mounted NEMA enclosures are large enclosures installed on a concrete pad, commonly used in outdoor applications. These enclosures typically feature an open bottom to allow wiring or cable feeds to come up through. They are designed to house industrial controls, motor drives, power distribution equipment, and transformers.
Pole-mounted NEMA enclosures are designed for installation on poles, such as those used for electrical distribution lines. These enclosures can house electrical, network, and communications equipment. Tower-mounted NEMA enclosures also fall into this category.
Pedestal-mounted NEMA enclosures are designed to be installed on a pedestal that is securely anchored to the floor. These enclosures are commonly used for operator interfaces and machine control. Cables run from the pedestal-mounted NEMA enclosure down through the pedestal, through a trough enclosure or protective jacket, and finally connect to the machine tool, press, or process equipment. It is important to distinguish between pedestal-mounted enclosures and pedestal enclosures; the former refers to enclosures mounted on a pedestal, while the latter is a type of outdoor enclosure used for utility applications.
Rack-mounted NEMA enclosures are designed to fit into standard 19-inch EIA racks or 24-inch racks. They may include integral or optional pull handles and rack mounting brackets for secure installation. Additionally, some rack-mounted NEMA enclosures can also be used as desktop enclosures, offering versatility in different setups.
Walk-in NEMA enclosures are extremely large enclosures, typically featuring one or two doors. They often have an open bottom but can also include a full floor. These enclosures are very heavy and generally equipped with lifting eyes for positioning over a concrete pad. They are designed to protect substantial equipment such as switchboards, switchgear, transformers, drives, industrial controls, and other power distribution systems that are too large for smaller pad-mounted enclosures or cabinets.
Wall-mounted NEMA enclosures are attached to a wall or vertical surface using molded or welded brackets for secure mounting. They may include 19-inch EIA rails or back panels for mounting automation components.
These enclosures are ideal for housing smaller electrical devices, instruments, and controllers, but they cannot accommodate as much equipment as floor-mounted or free-standing NEMA enclosures.
Wall-mounted enclosures come in two variations:
NEMA control panel enclosures safeguard various control panel components, including push button switches, monitoring devices, controllers, membrane switch panels, alarms, annunciators, indicator lights, tamper sensors, and other control equipment. Specialized NEMA control panels include:
NEMA battery enclosures are engineered to house standard battery sizes in diverse environments, including outdoor, marine, highway, and industrial settings. They are designed to withstand exposure to dust, snow, rain, and water, and can contain leaks from acid batteries. These enclosures are commonly used with solar power systems to store energy and provide power during the night.
Commercial NEMA enclosures are tailored for use in various commercial settings, including stadiums, theaters, retail stores, malls, and office building complexes. They are often used to house controls for elevators, escalators, HVAC systems, and electrical power systems.
Data center enclosures, IT and telecommunications cabinets, fiber optic termination boxes, and network boxes can be built using NEMA enclosures. These enclosures typically house patch panels, network switches, servers, and uninterruptible power supplies (UPS).
Console and console enclosures often feature an angled back front panel with two trapezoidal side panels. They can be mounted on the floor, pedestal, or desktop.
These enclosures are commonly used to protect controllers, instrumentation, and industrial computers that manage machinery or process equipment.
Types of console enclosures include pushbutton consolets, workstations, and operator consoles. Specialized versions, such as industrial computer enclosures and kiosk enclosures, are tailored for specific applications.
Electrical disconnect NEMA enclosures are designed to house disconnect switches, load break switches, and circuit breakers. These enclosures are essential for safely de-energizing electrical circuits before performing maintenance on equipment or electrical distribution systems.
Drive enclosures and motor control center enclosures house motor drives, inverters, and motor controllers, providing the necessary electrical power to manage the speed and operation of AC or DC motors. For larger installations, drop-over drive enclosures offer a protective solution.
NEMA enclosures designed for hazardous locations that contain volatile or combustible gases or substances are engineered to suppress internal explosions and prevent these explosions from causing external hazards.
NEMA enclosures are also used for hydraulic and pneumatic controls, managing the activation and deactivation of cylinders, hydraulic motors, and fluid power valves. These enclosures may house electropneumatic and electrohydraulic components, along with electrical switches and control panel indicator lights.
Additionally, NEMA enclosures are used to house pressurization and purging equipment and systems in process plants.
Industrial-grade NEMA enclosures are designed for use in manufacturing factories and process plant settings. Typically constructed from cold-rolled steel, galvanized steel, stainless steel, or aluminum, these enclosures are often made with heavier gauge thicknesses to ensure durability and robust protection.
NEMA instrument enclosures are designed to safeguard instrumentation such as monitors, analyzers, and data loggers used in factory settings. These instruments measure various parameters including temperature, pressure, humidity, flow, part count, force, and strain. While instrument enclosures are typically compact, larger versions are available to accommodate complex processes requiring extensive measurement and data logging.
Junction box NEMA enclosures are used to protect wiring connections, DIN rails, and terminal wiring within an electrical distribution system. They may also house switches, outlets, or receptacles. Junction boxes, also referred to as terminal boxes or utility boxes, provide a secure and organized way to manage electrical connections.
NEMA message board or display enclosures are designed to protect display screens mounted in overhead factory locations. These enclosures safeguard the screens that provide critical information to operators, technicians, and engineers about process conditions, productivity levels, and hazardous situations. Common applications include message boards for Vorne systems, which are housed in these protective enclosures.
Metering cabinets are designed to house transformers and electrical metering equipment, typically located outdoors and exposed to various weather conditions such as rain, snow, and ice. To ensure protection, these cabinets are equipped with NEMA-rated enclosures. They are also referred to as utility measurement cabinets.
Miniature NEMA cases are compact enclosures designed to house smaller components such as sensors, transducers, sensor transmitters, instruments, and printed circuit boards.
These cases are often integrated into or form part of a product design, serving as the housing for handheld instruments or monitors intended for operation in dusty, wet, or hazardous environments. A miniature NEMA case is essentially a scaled-down version of an instrument enclosure.
Enclosure designed to contain operator interface devices such as electronics, controls, pushbuttons, joysticks, switches, membrane switch panels, and displays.
Operator interface equipment enables an operator to monitor and control manufacturing machinery, process equipment, and other plant systems. Human-machine interface (HMI) devices are comparable products used for interacting with machines and processes.
Types of operator interface NEMA enclosures include console enclosures, pushbutton enclosures, PC enclosures, and handheld enclosures.
NEMA PC enclosures are designed to house and protect industrial computers, computer boards, monitors, keyboards, and peripherals. They are commonly used for process and machine control applications.
Pushbutton NEMA enclosures feature front panels with multiple holes designed to accommodate push button switches. Custom gaskets or seals are often required to ensure these openings are properly sealed.
NEMA rack enclosures are designed with 19-inch EIA rails to mount standard network and communications equipment, including servers, routers, UPS systems, network switches, and audio-video equipment. They are also used in cleanroom and laboratory environments.
Hygienic or sanitary NEMA enclosures are designed for use in industries such as food and beverage, pharmaceuticals, hospitals, dental, and medical device manufacturing, where washdown capabilities are crucial for maintaining clean and disinfected equipment. These enclosures are typically made from stainless steel and feature removable seals for thorough cleaning and disinfection. NEMA Type 4 or 4X watertight enclosures, which are suitable for washdown with high-pressure water, are often the best choice for these applications.
Solar energy NEMA enclosures are used to house components such as wiring, wiring terminals, and charge controllers. Batteries for solar energy systems are often housed in separate NEMA battery enclosures for added protection and organization.
Traffic control NEMA enclosures safeguard components used in rail, mass transit, and street signal systems, including timing clocks, lightning arrestors, circuit breakers, and disconnect switches. They ensure the protection of critical controls and equipment against environmental factors.
NEMA tamper and vandal-proof enclosures are designed with locks or lockable latches to deter tampering and unauthorized access. They may also include tamper sensors that detect when a control or security panel enclosure is opened without proper authorization, adding an extra layer of security.
NEMA wireways and wiring trough enclosures are used to organize and protect cables and wiring. They shield wiring runs from environmental hazards such as dirt, dust, oil, dripping water, rain, sleet, and snow.
Functioning similarly to ductwork for wires and cables, these enclosures come in various shapes and sizes. In addition to straight sections, they are available with several connectors and adapters, including:
Wireways can be regarded as a type of raceway or enclosed conduit. Wiring troughs typically come with two end caps or closed ends, whereas wireways have open flanged ends. Wiring troughs may feature knockouts along the sides or on the closed ends.
Wireways come in three distinct types:
Wireways and wiring troughs are also referred to as conduits, gutters, raceways, wiring ducts, and wire ducts.
Modular enclosures are typically designed with a frame to which the side, front, top, bottom, and back panels are attached. These external panels can be made from sheet metal, extrusions, or roll-formed parts. The frame is usually mounted to the floor with leveling feet or a base plinth.
This modular design provides enclosure manufacturers, system integrators, OEMs, and manufacturing facilities with greater flexibility to customize and adapt configurations for specific applications.
Modular enclosures are often used for IT equipment cabinets, featuring 19" EIA mounting rails for IT components. Internal side and back panels are utilized to mount various automation equipment, including monitors, relays, data acquisition units, and controllers.
Monolithic or unibody enclosures are constructed as a single solid structure, often made from formed sheets welded together, molded fiberglass, or die-cast aluminum. For larger enclosures, this construction type offers enhanced structural load support compared to modular or bolted assemblies. However, customization and modifications may be more challenging to implement compared to modular enclosures.
The level of protection and durability an enclosure provides is significantly influenced by its material composition. Enclosures are typically made from materials categorized as metals or polymers, including coated steel, galvanized steel, stainless steel, aluminum, fiberglass, and plastic.
Metals generally offer better conductivity for both heat and electricity compared to other materials. This electrical conductivity is advantageous for grounding the enclosure.
Metal enclosures can protect electronic and electrical devices from electrical and magnetic fields, as well as electromagnetic interference (EMI) and radio frequency interference (RFI). However, gaps in doors and openings for cables can still allow noise to penetrate.
Standard NEMA enclosure shapes include rectangular and square boxes, while less common shapes feature round boxes, T-shaped enclosures, and angled front boxes. T-shaped enclosures typically have a lower handle attached to a square or rectangular box.
Key components of an enclosure are the enclosure box, cover, bezel, legs or stand, and mounting hardware.
Steel, aluminum, stainless steel, and other metallic NEMA enclosures and their parts are commonly fabricated by bending, forming, drawing, roll forming, and stamping sheet metal into the desired shapes.
Aluminum sheet metal, due to its high ductility and formability, is particularly easy to work with when creating box or enclosure shapes. In addition to forming, aluminum enclosures can also be produced through die casting and extrusion processes.
Compared to steel, aluminum is softer and can be cut or machined more easily. Its softness allows even woodworking carbide saw blades to cut through it effectively.
Steel is a popular choice for forming enclosures due to its strength and malleability. As a commercial iron alloy containing carbon, steel comes in various grades. Low carbon steels like 1020 or 1010 are softer and easier to form, making them ideal for many applications. Compared to plastic, steel or stainless steel enclosures offer significantly higher impact resistance.
In a busy factory setting, heavy-walled coated steel or stainless steel enclosures are more durable and resistant to denting and impacts than aluminum or plastic enclosures. While a steel enclosure might sustain a dent from a forklift, a similar impact could shatter a fiberglass or plastic enclosure.
Steel lacks the inherent corrosion resistance found in plastics and stainless steels. Therefore, steel enclosures typically require additional protective coatings, such as electroplating, zinc galvanization, or powder coating. These coatings not only enhance durability but also offer the flexibility to match or provide colors for new product designs and older equipment refurbishments.
Stainless steel is preferred over standard steel in environments where corrosion resistance is crucial. It offers both chemical and corrosion resistance, and can handle relatively high-pressure conditions.
The most common grades for stainless steel enclosures are 304 and 316 austenitic stainless steels. Among these, 316 stainless steel provides superior resistance to pitting corrosion in chloride and saltwater environments. Additionally, 304L and 316L stainless steels are low carbon variants designed to maintain their corrosion resistance after welding.
In some applications, such as shielded NEMA cabinets for telecommunications and IT, 400 series ferritic stainless steels are used. These steels are magnetic and highly formable, though they are not as corrosion-resistant as the 300 series stainless steels.
Although stainless steel is more expensive than aluminum or standard steel, it is virtually maintenance-free. Unlike other metals, stainless steel does not require coatings that need to be stripped and reapplied. In fact, applying a coating to stainless steel can actually impair its corrosion resistance.
Aluminum, while generally more expensive than steel, offers several superior properties. Its lower density makes it lighter than steel or stainless steel, which can be advantageous for enclosures used in airplanes, spacecraft, or vehicles where weight reduction is critical.
Aluminum also boasts higher electrical and thermal conductivity compared to steel. This higher thermal conductivity can aid in managing heat dissipation from the joule heating of enclosed electrical or electronic components. To enhance heat removal, aluminum enclosures can be manufactured with extruded fins.
Although aluminum provides better oxidation resistance than steel, it still requires anodizing or protective coatings to withstand harsh environments such as ocean salt sprays or chemical plants.
A 316 stainless steel enclosure can cost nearly twice as much as a coated steel enclosure of the same size, making it a choice only for industrial environments where its superior corrosion resistance is necessary. In comparison, 304 stainless steel is about 50% more expensive than coated steel enclosures. Aluminum, while more costly per pound than steel, has a density of 2.7 g/cm³, which is only 34% of steel's density of 7.8 g/cm³. Consequently, aluminum typically carries a premium of about 20% over coated steel. These cost estimates are based on prices listed by a leading supplier.
Plastic or fiberglass NEMA enclosures are typically manufactured using various molding processes. Thermoplastic resin enclosures can be produced through injection molding, extrusion, and thermoforming, with common materials including PVC, ABS, and polycarbonate resins.
Plastics and fiberglass are easily machined to create cutouts or openings for wiring, switches, and operator interface controls.
The fiberglass fabrication process depends on the type of glass fiber used, such as short or long fibers, nonwoven glass mat, or woven fiberglass cloth.
Thermoset resin-based fiberglass enclosures can be made from sheet molding compounds (SMCs) or bulk molding compounds (BMCs), typically through compression or injection-compression molding. Reaction injection molding (RIM) is also used for molding thermoset resins, such as polyurethanes, into enclosures.
Resin transfer molding (RTM) is another method used for creating thermoset fiberglass enclosures. In this process, fiberglass mat or woven fabric is placed in a mold, and a thermoset resin mixed with a hardener or catalyst is then injected into the mold.
The SCRIMP (Seemann Composites Resin Infusion Molding Process) is an RTM method that uses vacuum pressure to pull liquid resin into a mold containing fiberglass reinforcement. SCRIMP is known for producing high-quality fiberglass parts with minimal VOC emissions.
Large custom enclosures or even industrial shelters are fabricated with manual lay-up molding. In the manual lay-up process, fiberglass cloth or nonwoven mats are laid into a mold. Thermosets are poured or sprayed onto the fiberglass. Rollers and squeegees are used to “wet out” the fiberglass or force the resin into the fibers, remove trapped air, and wipe away excess resin.
Pultrusion processes are utilized to create long channel shapes or ribs in larger sheets, which can be particularly useful for fabricating NEMA wireway enclosures. In this process, plastics are reinforced with long strands of fiberglass in a continuous, extrusion-like method, resulting in strong, durable shapes.
Plastic and fiberglass enclosures can be pigmented to match specific colors, whether for new product designs or refurbishing older equipment. Additionally, coatings can be applied to these enclosures to enhance their environmental resistance, improve UV stability and weatherability, and achieve specific colors suited to particular applications.
Polymer-based materials, such as plastic or fiberglass, are nonmetallic and exhibit a wide range of properties depending on the specific fillers, reinforcements, and additives used in their compounding formulations. These materials can be customized to meet specific performance requirements, making them versatile options for various applications. Common trade names for these polymer-based materials include Cycolac® (GE Plastics), Lustran® (Bayer), and Novodur® (Bayer).
Acrylonitrile-butadiene-styrene (ABS) is a durable, rigid, and cost-effective thermoplastic terpolymer known for its excellent chemical resistance and dimensional stability.
ABS achieves strong impact resistance through a “rubber toughened” structure, where small rubbery butadiene spheres are dispersed within a rigid plastic matrix. This impact-resistant ABS is commonly used in products like hard hats, automotive bumpers, and golf club heads.
Fiberglass or fiberglass reinforced plastic (FRP) is a robust, durable polymer that offers enhanced resistance to many caustics and higher temperatures compared to standard plastics. However, fiberglass is not completely resistant to environmental degradation. Over time, fiberglass enclosures may experience yellowing, discoloration, gloss reduction, fiberglass bloom, and blistering.
Fiberglass generally exhibits less shrinkage during molding and offers better dimensional stability compared to certain molded plastics.
As a composite material, fiberglass consists of reinforcing glass fibers embedded within a plastic matrix. The glass fibers used can be short or long strands, a nonwoven glass mat, or a woven fiberglass cloth.
The most commonly used thermoset resins for fiberglass include polyester and epoxy.
Polycarbonate (PC) is an amorphous material known for its outstanding impact strength, clarity, and optical properties. Some common brand names for polycarbonate include Caliber® (Dow), Lexan® (SABIC), Makrofol®, and Makrolon® (Bayer). Clear polycarbonate windows boast 200 times the impact strength of glass windows.
Polycarbonate is exceptionally tough and possesses excellent mechanical properties, making it suitable for molding with tight tolerances. However, it can be vulnerable to attack by solvents and certain chemicals. The weatherability of polycarbonate is generally moderate, but it can be improved with the addition of UV inhibitors and protective coatings.
Polypropylene is a thermoplastic known for its exceptional resistance to many chemicals, making it a popular choice for chemical laboratory bottles and labware. Due to its chemical resistance and durability, polypropylene is often used to fabricate enclosure covers, bezels, small junction boxes, and handheld enclosures.
Polystyrene is a low-cost thermoplastic that is generally more brittle compared to tougher polymers like polycarbonate or polyamides (Nylon). Despite its brittleness, polystyrene is often used to fabricate enclosure covers, bezels, small junction boxes, and handheld enclosures due to its affordability.
Polystyrene is a low-cost thermoplastic that is generally more brittle compared to tougher polymers like polycarbonate or polyamides (Nylon). Despite its brittleness, polystyrene is often used to fabricate enclosure covers, bezels, small junction boxes, and handheld enclosures due to its affordability.
Enclosure components are typically assembled and joined using fasteners, welds, or, less commonly, adhesives. An enclosure that is fastened together is referred to as a modular enclosure. Modular enclosures offer greater flexibility for customization by allowing the mixing and matching of different modular components.
Fasteners enable disassembly for repairs or part replacements; however, they can become loose due to vibration or movement commonly found in industrial environments. Additional sealing washers might be necessary to meet specific NEMA or IP ratings.
Welded enclosures, on the other hand, are more secure against loosening during operation. Welds provide a leak-tight seal, which can eliminate the need for extra seals, gaskets, or sealants in a NEMA enclosure.
A monolithic or unibody enclosure is made from a single, solid piece of material, whether through aluminum die casting, plastic injection molding, or welding of formed sheet metal. While repair or replacement of damaged components in a welded assembly can be more challenging, monolithic or unibody enclosures tend to be sturdier and have fewer gasketed gaps, reducing the chance of ingress.
Although a NEMA enclosure might appear as a basic metal or plastic box, each enclosure can be customized with specific panel cutouts, coatings, and accessory parts. Customizing metal NEMA enclosures generally requires less tooling investment compared to plastic NEMA enclosures, which is an important factor to consider in the overall cost and customization process.
Specialized custom coatings and printing can be applied to NEMA enclosures to enhance their appearance and functionality for specific designs and applications.
Openings must be created in NEMA enclosures to provide electrical power and facilitate data transmission for housed devices. Data signals need to be routed to and from electronic devices, monitors, process controllers, data acquisition modules, and other components inside the enclosure.
Power cabling from motor drives, contactors, transformers, and relays must pass through the enclosure walls to connect with motors, heaters, pumps, machine tools, lasers, or other equipment being monitored and controlled.
The configurations of these openings can vary widely, depending on the specific requirements of the application:
NEMA enclosures feature doors and covers designed to work with seals or gaskets to prevent the ingress of dust, water, and other contaminants. Leading manufacturers offer a variety of covers and doors to meet diverse needs:
The gaskets and seals used in a NEMA enclosure play a crucial role in ensuring protection against water, oil, dust, and dirt ingress. The three main types of gaskets or seals include:
NEMA enclosures can include additional components to facilitate the internal mounting of electronics and electrical equipment. Key components for mounting devices inside a NEMA enclosure include:
NEMA enclosures may benefit from thermal management to ensure that temperatures within the enclosure remain within a range where electronics and electrical components can function properly.
A NEMA enclosure can be designed to allow enclosed devices to operate efficiently even in frigid, outdoor settings. In some cases, the enclosure may be encased in ice. For low-temperature applications, insulation or an internal heater might be beneficial.
In environments such as investment metal casting foundries, forges, heat treating operations, glass melting furnaces, primary metal furnaces, and oil refineries, elevated temperatures may be present. In these scenarios, drives, transformers, and process controllers housed in NEMA enclosures might require fans, air conditioning, or other cooling solutions to maintain instrumentation within allowable operating ranges.
Some thermal management accessories or options can include:
Additional enclosure parts include:
When ordering a NEMA enclosure, the NEMA rating number is the primary specification to consider. This rating indicates the level of protection the enclosure provides against environmental factors.
The dimensions and shape of the enclosure are also crucial specifications. The size and shape should accommodate the electrical or electronic devices to be protected. The enclosure must be large enough to allow for in-place repairs or removal for servicing.
It is important to ensure sufficient clearance between the electrical devices and the walls of the metal NEMA enclosure. This clearance allows for proper wiring installation and helps prevent electrical shorts or ground faults to the enclosure housing.
Additionally, consider the available space in the facility, on a machine tool, or within a piece of process equipment when determining the enclosure size.
Another important factor is that any modifications made to the enclosure, such as adding holes or altering the door's position, can nullify its NEMA rating. These changes should be carefully considered to maintain the enclosure's protective qualities.
NEMA enclosures typically have rectangular box shapes, but they can be custom-made in many different shapes and with many additional features.
| Application Conditions & NEMA Type Selection | ||
|---|---|---|
| Application | Environment or Conditions | NEMA Enclosures Types |
| Industrial - Manufacturing Floor of Factory Warehouse | Indoor with dirt, dust, and dripping on corrosive liquid/water | NEMA 2 - Drip Tight NEMA 12 |
| Industrial - Manufacturing Floor of Factory Warehouse | Indoor with dirt, dust, and machinery requiring washdown or hose down with non-corrosive liquid or water | NEMA 4 - Water Tight/Hose Down |
| Industrial - Manufacturing Floor or process plant | Using oils, lubricants, metal working fluids, & coolants | NEMA 13 - Oil Tight |
| Industrial - Manufacturing Floor or Process Plant, Steel & Metal Mills, Cement Plants, Ceramic | Using non-combustible dust and particulates | NEMA 5 - Dust Tight |
| Commercial & Contractor | Indoor & Outdoor - falling rain, snow, and ice main concerns | NEMA 1 - General Purpose NEMA 3, 3R, 3S - Weather Resistant |
| Utility Power or Gas Distribution, Cable/Telephone/Network Equipment | Indoor & outdoor, non-corrosive water, rain | NEMA 4 - Water Tight/Hose Down NEMA 12 - General Purpose |
| Food & Beverages Facilities, Farm / Agricultural, Chemical Process Plants, Marine | Wet indoor or outdoor, rain, ice, and corrosive liquids | NEMA 4X - Water Tight (Weatherproof) wit Corrosion Protection (X) |
| Ships, Chemical Plants, and Oil & Gas Refineries | Indoor & outdoor NEPA flammable chemicals hazardous class locations | NEMA 7 - Explosion Proof NEMA 8 - Oil Immersed |
| Metal Mills, Metal Powder, Coke & Coal, Flour & Grain Processing Facilities | Indoor NFPA combustible powder class locations | NEMA 9 - Dust ignition Proof |
| Mining - Underground Hazardous / Flammable Class Locations | Potential for Combustible Dust or Gas | NEMA 10 - MSHA Complaint |
Manufacturers typically offer a catalog of standard shapes and sizes for NEMA enclosures. However, for specialized applications with sufficient order volumes, custom shapes and sizes can be produced to meet specific requirements.
Like many engineers, I tend to prefer using standard or catalog parts, assuming they are less expensive than custom options.
In theory, catalog, standard, and COTS (Commercial Off-The-Shelf) parts are readily available and require no additional engineering.
However, it’s important to conduct a thorough cost-benefit analysis when deciding between standard and custom parts.
In many cases, even catalog NEMA enclosures will need some level of customization or configuration for industrial control panels and various applications. Many NEMA enclosure suppliers offer configuration tools that let you tailor or select the necessary features and options for your specific needs.
If accommodating a standard enclosure requires significant modifications to your design, opting for a custom NEMA enclosure might be a more suitable choice.
Another consideration is whether additional modifications or retrofitting will be needed for the NEMA enclosure to suit your application. You should ask yourself:
Leveraging the skills of the enclosure manufacturer is usually the best option for modification and customization of an enclosure.
NEMA enclosures are manufactured in a wide range of NEMA types to provide the appropriate level of protection for your application from dust to dripping or wet locations to water immersion.
NEMA enclosures are available in a wide range of shapes, configurations, mounting styles, and NEMA ratings.
Many NEMA enclosure manufacturers are familiar with the nuances and unique requirements of specific industry applications. They can provide products specialized for different industries.
NEMA enclosures can be designed and built to meet additional ratings such as:
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