Enclosure (electrical)

"Knock-outs" redirects here. For other uses, see Knockout (disambiguation).

A municipal electrical enclosure

Allen Bradley PLC installed in an electrical enclosure

An electrical enclosure is a cabinet for electrical or electronic equipment to mount switches, knobs and displays and to prevent electrical shock to equipment users and protect the contents from the environment. The enclosure is the only part of the equipment which is seen by users; in many cases it is designed not only for its utilitarian requirements, but also to be pleasing to the eye. Regulations may dictate the features and performance of enclosures for electrical equipment in hazardous areas, such as petrochemical plants or coal mines. Electronic packaging may place many demands on an enclosure for heat dissipation, radio frequency interference and electrostatic discharge protection, as well as functional, esthetic and commercial constraints.

Standards

In the United States, the National Electrical Manufacturers Association (NEMA) publishes NEMA enclosure typesstandards for the performance of various classes of electrical enclosures. The NEMA standards cover corrosion resistance, ability to protect from rain and submersion, etc.

For IEC member countries, standard IEC 60529 is classifying the ingress protection rating (IP Codes) of enclosures.

Materials

Electrical enclosures are usually made from rigid plastics, metals, particularly stainless steel, carbon steel, and aluminum. Steel cabinets may be painted or galvanized. Mass-produced equipment will generally have a customized enclosure, but standardized enclosures are made for custom-built or small production runs of equipment.

Terminology

Enclosures for some purposes have partially punched openings (knockouts) which can be removed to accommodate cables, connectors, or conduits. Where they are small and primarily intended to conceal electrical junctions from sight, or protect them from tampering, they are also known as junction boxes, street cabinets or technically as serving area interface.

Telecommunications

Telcordia Technologies has proposed generic requirements for telecommunication equipment cabinets. These requirements were developed with the input of United States service providers,^[1] and are intended to provide a suitable environment for telecommunication companies’ electronic and passive equipment that is housed in above-ground cabinets or enclosures (typically pad- or pole-mounted) in an outside plant environment. The proposed standard includes functional design criteria, generic mechanical and environmental requirements, desired features, and performance tests.

Telecommunication huts are fully assembled or modular field-assembled transportable structures capable of housing an electronic communications system. These huts provide a controlled internal environment for the communications equipment and occasional craftspersons. The huts are designed with locks, security, and alarms to discourage access by unauthorized persons. Huts can be provided with a decorative facade to comply with local building requirements. Telecommunications huts are designed to withstand climate conditions existing throughout the USA including rain, snow, sleet, high winds, ice, sand storms, earthquakes and lightning.

Electronic equipment cabinets can be placed in both indoor and outdoor locations. As described in industry standards GR-3031^[2] and GR-3033,^[3] the cabinets consist of the outer-finished closure box along with its integral hardware components, such as bonding and grounding connections; internal walls and braces for splicing chambers and battery compartments; frame and shelving tracks; and doors, seals, and hinges.

Battery backup cabinets

Battery backup cabinets are used specifically and exclusively for backup battery facilities in both indoor and outdoor locations. As detailed in GR-3033, these cabinets may or may not have separate chambers for the electronics used to monitor, alarm, and control them.

Indoor battery backup cabinets include cabinets placed inside the outer physical envelope of a building or structure where the space has active environmental controls to control temperature, humidity, and air quality of the ambient space. This includes cabinets located in domed, covered stadiums and enclosed garages. It also includes cabinets placed inside the outer physical envelope of a building or structure where the space has no active environmental controls (e.g., cabinets found in unheated/uncooled mechanical or furnace rooms).

Outdoor battery backup cabinets include cabinets placed outside the outer physical envelope of a building or structure (e.g., cabinets mounted on roofs, or on the outside of buildings), and cabinets located in open parking garages and open stadiums where the cabinets can be exposed to outside weather conditions and pollution levels.

References

External links

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