Electrical wiring in general refers to insulated conductors used to carry electricity, and associated devices. This article describes general aspects of electrical wiring as used to provide power in buildings and structures, commonly referred to as building wiring. This article is intended to describe common features of electrical wiring that may apply worldwide. For information regarding specific national electrical codes, refer to the articles mentioned in the next section. Separate articles cover long-distance electric power transmission and electric power distribution.
Electrical engineering is a field of engineering that generally deals with the study and application of electricity, electronics, and electromagnetism. This field first became an identifiable occupation in the latter half of the 19th century after commercialization of the electric telegraph, the telephone, and electric power distribution and use. It now covers a wide range of subfields including electronics, digital computers, power engineering, telecommunications, control systems, RF engineering, and signal processing.
Electrical engineering may include electronic engineering. Where a distinction is made, usually outside of the United States, electrical engineering is considered to deal with the problems associated with systems such as electric power transmission and electrical machines, whereas electronic engineering deals with the study of electronic systems including computers, communication systems, integrated circuits, and radar.
Electrical wiring in North America follows regulations and standards for installation of building wiring. Electrical wiring in the United States is generally in compliance with the National Electrical Code, a standard sponsored by the National Fire Protection Association which has been periodically revised since 1897. Local amendments or supplements to this model code are common in American cities or states. For electrical wiring in Canada, the Canadian Electrical Code is a very similar standard published in Canada by the Canadian Standards Association since 1927.
Although much of the electrician's field terminology matches that of the electrical codes, usages can vary.
A distribution board (or panelboard) is a component of an electricity supply system which divides an electrical power feed into subsidiary circuits, while providing a protective fuse or circuit breaker for each circuit, in a common enclosure. Normally, a main switch, and in recent boards, one or more Residual-current devices (RCD) or Residual Current Breakers with Overcurrent protection (RCBO), will also be incorporated.
Distribution boards are also referred to as a:
Knob and tube wiring (sometimes abbreviated K&T) was an early standardized method of electrical wiring in buildings, in common use in North America from about 1880 to the 1930s. It consisted of single-insulated copper conductors run within wall or ceiling cavities, passing through joist and stud drill-holes via protective porcelain insulating tubes, and supported along their length on nailed-down porcelain knob insulators. Where conductors entered a wiring device such as a lamp or switch, or were pulled into a wall, they were protected by flexible cloth insulating sleeving called loom. The first insulation was asphalt-saturated cotton cloth, then rubber became common. Wire splices in such installations were twisted together for good mechanical strength, then soldered and wrapped with rubber insulating tape and friction tape (asphalt saturated cloth), or made inside metal junction boxes.
Knob and tube wiring was eventually displaced from interior wiring systems because of the high cost of installation compared with use of power cables, which combined both power conductors of a circuit in one run (and which later included grounding conductors).
In mining, "bootleg ground" may refer to overburden that contains undetonated explosives.
In building wiring, a bootleg ground is an electrical ground that is wired from the neutral side of a receptacle or light fixture in an older 2-wire home. This essentially connects the neutral side of the receptacle to the casing of an appliance or lamp. It can be a hazard because the neutral wire is a current-carrying conductor. In addition, a fault condition to a bootleg ground will not trip a GFCI breaker or a receptacle that is wired from the load side of a GFCI receptacle. Bootleg grounding is illegal and against code in many places. A safer and legal alternative to bootleg grounding (where a local electrical code allows it) is to install a GFCI and leave the ground screw unconnected, then place a label that says "No Equipment Ground" on the GFCI and all downstream receptacles.