Electrical Definitions

The definitions below relate to terms commonly used in the electrical engineering/design field. They are based on the 2008 National Electrical Code, Article 100.

Accessible (as applied to Equipment) = Admitting close approach; not guarded by locked doors, elevation or other effective means.

Accessible (as applied to wiring methods) = Capable of being removed or exposed without damaging the building structure or finish or not permanently closed in by the structure or finish of the building.

Accessible, Readily (Ready Accessible) = Capable of being reached quickly for operation, renewal, or inspections without requiring those to whom ready access is requisite to climb over or remove obstacles or to resort to portable ladders, and so forth.

Ampacity = The current, in amperes, that a conductor can carry continuously under the conditions of use without exceeding its temperature rating.

Appliance = Utilization equipment, generally other than industrial, that is normally built in standardized sizes or types and is installed or connected as a unit to perform one or more functions such as clothes washing, air conditioning, food mixing, deep frying and so forth.

Approved = Acceptable to the authority having jurisdiction.

Askarel = A generic term for a group of nonflammable synthetic chlorinated hydrocarbons used as electrical insulating media. Askarels of various compositional types are used. Under arcing conditions, the gases produced, while consisting predominantly of noncombustible hydrogen chloride, can include varying amounts of combustible gases, depending on the askarel type.

Attachment Plug (Plug Cap) (Plug) = A device that, by insertion into a receptacle, establishes a connection between the conductors of the attached flexible cord and the conductors attached permanently to the receptacle.

Authority Having Jurisdiction (AHJ) = The organization, office, or individual responsible for approving equipment, materials, an installation, or a procedure. This term is typically used when describing the local building department which issues a permit for a new construction.

Automatic = Self-acting, operating by its own mechanism when actuated by some impersonal influence, as, for example, a change in current, pressure, temperature, or mechanical configuration.

Bathroom = An area including a basin with one or more of the following: a toilet, a tub or a shower.

Bonding (Bonded) = The permanent joining of metallic parts to form an electrically conductive path that ensures electrical continuity and the capacity to conduct safely any current likely to be imposed.

Bonding Jumper = A reliable conductor to ensure the required electrical conductivity between metal parts required to be electrically connected.

Bonding Jumper (Equipment) = The connection between two or more portions of the equipment grounding conductor.

Bonding Jumper (Main) = The connection between the grounded circuit conductor and the equipment grounding conductor at the service.

Bonding Jumper, System = The connection between the grounded circuit conductor and the equipment grounding conductor at a separately derived system.

Branch Circuit = The circuit conductors between the final overcurrent device protecting the circuit and the outlet(s).

Branch Circuit, Appliance = A branch circuit that supplies energy to one or more outlets to which appliances are to be connected and that has no permanently connected luminaries (lighting fixtures) that are not part of an appliance.

Branch Circuit, General-Purpose = A branch circuit that supplies two or more receptacles or outlets for lighting and appliances.

Branch Circuit, Individual = A branch circuit that supplies only one utilization equipment.

Branch Circuit, Multiwire = A branch circuit that consists of two or more ungrounded conductors that have a voltage between them, and a grounded conductor that has equal voltage between it and each ungrounded conductor of the circuit and that is connected to the neutral or grounded conductor of the system.

Building = A structure that stands alone or that is cut off from adjoining structures by fire walls with all openings therein protected by approved fire doors.

Cabinet = An enclosure that is designed for either surface mounting or flush mounting and is provided with a frame, mat or trim in which a swinging door or doors are or can be hung.

Circuit Breaker= A device designed to open and close a circuit by nonautomatic means and to open the circuit automatically on a predetermined overcurrent without damage to itself when properly applied within its rating.

Concealed = Rendered inaccessible by the structure or finish of the building. Wires in concealed raceways are considered concealed , even though they may become accessible by withdrawing them.

Conductor, Bare = A conductor having no covering or electrical insulation whatsoever.

Conductor, Covered = A conductor encased within material of composition or thickness that is not recognized by the NEC as electrical insulation.

Conductor, Insulated = A conductor encased within material of composition and thickness that is recognized by the NEC as electrical insulation.

Conduit Body = A separate portion of a conduit or tubing system that provides access through a removable cover(s) to the interior of the system at a junction of two or more sections of the system or at a terminal point of the system. Boxes such as FS or FD or larger cast or sheet metal boxes are not classified as conduit bodies.

Connector, Pressure (Solderless) = A device that establishes a connection between two or more conductors or between one or more conductors and a terminal by means of mechanical pressure and without the use of solder.

Continuous Load = A load where the maximum current is expected to continue for 3 hours or more.

Controller = A device or group of devices that serves to govern, in some predetermined manner, the electric power delivered to the apparatus to which it is connected.

Cooking Unit, Counter-Mounted = A cooking appliance designed for mounting in or on a counter and consisting of one or more heating elements, internal wiring and built-in or mountable controls.

Coordination (Selective) = Localization of an overcurrent condition to restrict outages to the circuit or equipment affected, accomplished by the choice of overcurrent protective devices and their rating or settings.

Copper-Clad Aluminum Conductors = Conductors drawn from a copper-clad aluminum rod with copper metallurgically bonded to an aluminum core. The copper forms a minimum of 10 percent of the cross- sectional area of a solid conductor or each strand of a stranded conductor.

Cutout Box = An enclosure designed for surface mounting that has swinging doors or covers secured directly to and telescoping with the walls of the box proper.

Dead Front = Without live parts exposed to a person on the operating side of the equipment.

Demand Factor = The ratio of the maximum demand of a system, or part of a system, to the total connected load of a system of the part of the system under consideration.

Device = A unit of an electrical system that is intended to carry or control but not utilize electric energy.

Disconnecting Means = A device, or group of devices, or other means by which the conductors of a circuit can be disconnected from their source of supply.

Dusttight = Constructed so that dust will not enter the enclosing case under specified test conditions.

Duty, Continuous = Operation at a substantially constant load for an indefinitely long time.

Duty, Intermittent = Operation for alternate intervals of (1) load and no load; or (2) load and rest; or (3) load, no load, and rest.

Duty, Periodic = Intermittent operation in which the load conditions are regularly recurrent.

Duty, Short-time = Operation at a substantially constant load for a short and definite, specified time.

Duty, Varying = Operation at loads, and for intervals of time, both of which may be subject to wide variation.

Dwelling Unit = A single unit, providing complete and independent living facilities for one or more persons, including permanent provisions for living, sleeping, cooking and sanitation.

Dwelling, One-Family = A building that consists solely of one dwelling unit.

Dwelling, Two-Family = A building that consists solely of two dwelling units.

Dwelling, Multifamily = A building that contains three or more dwelling units.

Electric Sign = A fixed, stationary, or portable self-contained, electrically illuminated utilization equipment with words or symbols designed to convey information or attract attention.

Enclosed = Surrounded by a case, housing, fence or wall(s) that prevents persons from accidentally contacting energized parts.

Enclosure = The case or housing of apparatus, or the fence or walls surrounding the installation to prevent personnel from accidentally contacting energized parts or to protect the equipment from physical damage.

Energized = Electrically connected to, or is, a source of voltage.

Equipment = A general term including material, fittings, devices, appliances, luminaries (fixtures), apparatus and the like used as part of, or in connection with, an electrical installation.

Explosionproof Apparatus = Apparatus enclosed in a case that is capable of withstanding an explosion of a specified gas or vapor that may occur within it and of preventing the ignition of a specified gas or vapor surrounding the enclosure by sparks, flashes, or explosion of the gas or vapor within, and that operates at such an external temperature that a surrounding flammable atmosphere will not be ignited thereby.

Exposed (as applied to live parts) = Capable of being inadvertently touched or approached nearer than a safe distance by a person. It is applied to parts that are not suitably guarded, isolated, or insulated.

Exposed (as applied to wiring methods) = On or attached to the surface or behind panels designed to allow access.

Externally Operable = Capable of being operated without exposing the operator to contact with live parts.

Feeder = All circuit conductors between the service equipment, the source of a separately derived system, or other power supply source and the final branch-circuit overcurrent device.

Festoon Lighting = A string of outdoor lights that is suspended between two points.

Fitting = An accessory such as a locknut, bushing, or other part of a wiring system that is intended primarily to perform a mechanical rather than an electrical function.

Garage = A building or portion of a building in which one or more self-propelled vehicles can be kept for use, sale, storage, rental, repair, exhibition, or demonstration purposes.

Ground = A conducting connection, whether intentional or accidental, between an electrical circuit or equipment and the earth or to some conducting body that serves in place of the earth.

Grounded = Connected to the earth or to some conducting body that serves in place of the earth.

Grounded, Effectively = Intentionally connected to the earth through a ground connection or connections of sufficiently low impedance and having sufficient current-carrying capacity to prevent the buildup of voltages that may result in undue hazards to connected equipment or to persons.

Grounded, Solidly = Connected to ground without inserting any resistor or impedance device.

Grounded Conductor = A system or circuit conductor that is intentionally grounded.

Ground Fault Circuit Interrupter (GFCI) = A device intended for the protection of personnel that functions to de-energize a circuit or portion thereof within an established period of time when a current to ground exceeds the values established for a Class A device.

Ground-Fault Protection of Equipment = A system intended to provide protection of equipment from damaging line-to-ground fault currents by operating to cause a disconnecting means to open all ungrounded conductors of the faulted circuit. This protection is provided at current levels less than those required to protect conductors from damage through the operation of a supply circuit overcurrent device.

Grounding Conductor = A conductor used to connect equipment or the grounded circuit of a wiring system to a grounding electrode or electrodes.

Grounding Conductor, Equipment = The conductor used to connect the non-current-carrying metal parts of equipment, raceways, and other enclosures to the system grounded conductor, the grounding electrode conductor, or both, at the service equipment or at the source of a separately derived system.

Grounding Electrode = A device that establishes an electrical connection to the earth.

Grounding Electrode Conductor = The conductor used to connect the grounding electrode(s) to the equipment grounding conductor, to the grounded conductor, or to both, at the service, at each building or structure where supplied by a feeder(s) or branch circuit(s), or at the source of a separately derived system.

Guarded = Covered, shielded, fenced, enclosed, or otherwise protected by means of suitable covers, casings, barriers, rails, screens, mats, or platforms to remove the likelihood of approach or contact by persons or objects to a point of danger.

Guest Room = An accommodation combining living, sleeping, sanitary, and storage facilities within a compartment.

Guest Suite = An accommodation with two or more contiguous rooms comprising a compartment, with or without doors between such rooms, that provides living, sleeping, sanitary, and storage facilities.

Handhole Enclosure = An enclosure identified for use in underground systems, provided with an open or closed bottom, and sized to allow personnel to reach into, but not enter, for the purpose of installing, operating, or maintaining equipment or wiring or both.

Hoistway = Any shaftway, hatchway, well hole, or other vertical opening or space in which an elevator or dumbwaiter is designed to operate.

Identified (as applied to equipment) = Recognizable as suitable for the specific purpose, function, use, environment, application, and so forth, where described in a particular NEC requirement.

In Sight From (Within Sight From, Within Sight) = Where the NEC specifies that one equipment shall be “in sight from”, “within sight from”, or “within sight”, and so forth, of another equipment, the specified equipment is to be visible and not more than 15m (50ft) distant from the other.

Interrupting Rating = The highest current at rated voltage that a device is intended to interrupt under standard test conditions.

Isolated (as applied to location) = Not readily accessible to persons unless special means for access are used.

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