Electrical conduit

Sunday, 21 January 2007

Electrical conduit forms the backbone of the wiring system in many buildings, both commercial and residential. In commercial and residential construction, electrical conductors which run between various locations are typically housed in an outer protective jacket. Such structures are referred to as electrical conduits. Electrical power transmission cables and lines, and telecommunications cables and lines, are frequently positioned within conduit. The conduit contains and protects the cables as they are used to transmit electrical power or communication signals. Industrial and commercial electrical distribution feeder systems are generally one of three types: cable and conduit, cable and cable tray, or electrical busway. The installation of an electrical system in a building often requires that the electrical wiring be encased in rigid conduit to protect the wiring being installed or to separate particular types of electrical service. Electrical conduit acts as passageway for electrical wires which connect one electrical service box to another. In the transmission of electrical power or signals, it is a convenient practice to house the electrical transmission wires or cables in plastic or thin metal conduits. For example, in a residential use the conduit may run from the back of an electrical meter box through a wall of a house and into a circuit breaker or fuse box in the house. The electrical wires run through the conduit from the electric meter to the circuit breaker box. In many applications, the conduit must seal out air, water, and dust, especially in pharmaceutical, chemical, food, and pulp/paper processing installations.

Electrical conduit is typically constructed from metal or plastic and comes in a variety of sizes standard to the electrical industry. The size of conduit used to run a particular electrical line depends both upon the length of the run as well as the particular power application. Conduits are employed in electrical installation in buildings, exterior walls of buildings and similar structures, and are typically identified as electrical metallic tubing (EMT), ridge metal conduit (RMC), intermediate metal conduit (IMC) and aluminum ridged conduit (ALRC) conduits. These conduits are available in two types, threaded and threadless. Electrical conduit is generally made of tubing which is threaded at both ends so that threaded fittings can be threaded onto the ends to secure the electrical service boxes. EMT conduit sections have no fittings at the ends. IMC and rigid conduit sections are manufactured with threaded ends. Metal conduit comes in standard lengths such as ten feet, can be secured in place and bent to form corners, all in customizing the electrical backbone system for a building. Sections are readily cut by ordinary hand tools and bent with special conduit benders to fit a particular application. Electrical circuits in building structures typically include junction boxes where conductors from several circuits are connected together, and switch boxes where circuit switches are installed. They also include cable of the armored type which is installed between the boxes and between conduits or portions thereof. In order to achieve the desired power distribution throughout the building, long lines of electrical metal tubes or conduits (EMT) and/or metal clad cables and/or armored cables are distributed throughout the building, with each of the conduits or cables having one end originating at the junction box. Flexible electrical conduit is frequently used in residential and commercial wiring in order to satisfy building codes, and because of the versatility imparted by the flexible nature of the conduit. Flexible spiral wound conduits or goosenecks are well known for carrying and protecting electrical conductors. Such flexible conduits have recently become miniaturized and used to carry internal wiring for communications purposes such as microphone holders. Flexible conduits are also used as protective coverings for electrical and hydraulic power harnesses in automotive vehicles. These harnesses may extend through openings in spaced panels, such, for example, as the panels of a vehicle body pillar and door, and need to be covered and protected in the space between the panels. Conduit is also frequently run underground from one part of a building to another, as well as to electrical installations outside the building. Oftentimes underground conduit running into a building is connected to aboveground electrical boxes located inside the buildings.

In a typical installation, numerous electrical junction boxes and conduits are installed in the stud spaces in the walls of the building. Standard electrical junction boxes used in commercial construction are of a uniform depth, but are available in a variety of sizes. The conduit usually extends between junction boxes where wires contained within the conduit are electrically connected to components for transmission of electricity. In order to suitably retain the conduit in the junction box, a conduit connector or fitting is employed to terminate the conduit and to mechanically and electrically support the conduit to the junction box itself. An electrical conduit connector provides a mechanical connection of the conduit to the electrical box or panel. The two most common types of electrical connectors used are a snap-in connector, and a multipart connector which may be composed of two or more components that utilizes a threaded male end in conjunction with a threaded female locknut. The most common use for electrical conduit connectors is to facilitate the connection of a conduit or cable to a junction box. The junction box can be a variety of electrical enclosures such as an outlet box, transformer enclosure, circuit panel, lighting fixture. In electrical installations, the conduit is first assembled between junction boxes before the wires are then pulled through the conduit length. The trays for the electrical conduits are made according to set lengths which frequently do not coincide with the lengths used in the field. Conduits are often used to contain electrical wires that run throughout buildings and other structures. At certain locations such electrical wires are connected to standard fixtures, such as light switches, cable outlets, electrical receptacles, and telephone outlets. Code requirements specify that the connections be contained within a housing that has sufficient interior volume to handle the frequently large number of wire connections that may be required.

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