MI Journeyman Electrician key terms

The organization or individual - often a local electrical inspector or building department - with legal authority to enforce the code, interpret its requirements, and approve materials and installations within a given area.

Acceptable to the authority having jurisdiction. An installation or material becomes approved when the inspector or governing body with legal authority has accepted it for the specific use intended.

Equipment or material that appears in a published list from a recognized testing laboratory, showing it has been tested and found suitable for a specific purpose under stated conditions.

Someone who has the skills and knowledge related to the construction and operation of electrical equipment and installations and has received safety training to recognize and avoid the hazards involved.

The National Electrical Code as adopted into Michigan law through the state's electrical code rules, including Michigan amendments, and enforced statewide by the electrical division and by local inspectors.

Written consent from the authority having jurisdiction allowing an installation the code does not cover by a specific rule. It is required wherever the code says work may be done only by special permission.

The point where service conductors from the utility connect to the premises wiring - typically at the service drop, at the service lateral, or at the terminals of the service equipment.

The overhead service conductors run by the utility from the last pole or transformer to the service point at the building, including splices and the attachment to the structure.

The underground service conductors run from the utility's distribution line or transformer to the service point, usually at the meter or service equipment on the premises.

All circuit conductors between the service equipment, the source of a separately derived system, or another supply source and the final branch-circuit overcurrent device that supplies the load.

The circuit conductors between the final overcurrent device protecting the circuit and the outlets or utilization equipment that the circuit supplies.

A branch circuit made up of two or more ungrounded conductors with different voltages to the neutral and a shared grounded conductor, with the ungrounded conductors connected to different phases.

A load expected to run at maximum current for three hours or more. Continuous loads are figured at 125 percent of their current when sizing conductors and overcurrent protection.

The ratio of the maximum demand of a system, or part of it, to the total connected load. It lets you size conductors and services for realistic loads rather than every load running at once.

The maximum current, in amperes, that a conductor can carry continuously under the conditions of use without exceeding its temperature rating, after adjustment for ambient temperature and conductor count.

An enclosed channel of metal or nonmetallic material designed for holding wires, cables, or busbars, such as conduit, electrical tubing, or wireway.

The percentage of a raceway's internal cross-sectional area taken up by conductors. Code limits the fill so conductors do not overheat and can be pulled in without damage.

The calculation of how many conductors, devices, and fittings an outlet or junction box may hold, based on each item's volume allowance compared with the box's cubic-inch capacity.

A thin-wall, unthreaded steel or aluminum raceway joined with couplings and fittings. It is common indoors and in concrete and must be secured and supported at code-specified intervals.

An assembly of insulated conductors wrapped in a flexible outer jacket, such as nonmetallic-sheathed cable, used mainly for residential branch circuits and secured and supported as the code requires.

The smallest curve a raceway or cable may be bent without damaging the conductors or the raceway itself, set by code as a multiple of the raceway diameter or cable size.

A point on the wiring system where current is taken to supply utilization equipment. It includes receptacles, luminaires, and the junction points that serve them.

A contact device installed at an outlet for the connection of an attachment plug. It supplies cord-and-plug-connected equipment and may be single, duplex, or of another configuration.

Equipment that uses electrical energy for electronic, electromechanical, chemical, heating, lighting, or similar purposes. Appliances, motors, and luminaires are everyday examples.

A device or group of devices that can disconnect the conductors of a circuit from their source of supply, used to de-energize equipment safely for servicing or in an emergency.

The clear, unobstructed area in front of electrical equipment that must be kept free so people can safely work on it. Depth and width depend on voltage and site conditions.

A complete lighting unit, including the lamp or lamps and the parts that hold them, position them, and connect them to the power supply.

The circuit conductor that is intentionally connected to earth at the source - usually the neutral - and that carries current during normal operation.

The conductive path run with circuit conductors that connects metal enclosures and equipment to the grounding system, giving fault current a low-impedance path back to the source.

A conductive object in direct contact with the earth, such as a ground rod, metal water pipe, or concrete-encased electrode, that ties the grounding system to the earth.

The connection between the grounded circuit conductor and the equipment grounding conductor, or the supply-side bonding jumper, at the service or at a separately derived system.

A device such as a fuse or circuit breaker that opens a circuit when current exceeds a set value, protecting conductors and equipment from overheating, short circuits, and ground faults.

A device that senses a small current difference between the ungrounded and grounded conductors and quickly opens the circuit to prevent shock, required in bathrooms, kitchens, outdoors, and other wet or damp areas.

A device that detects the current and voltage patterns of arcing faults and opens the circuit, protecting branch circuits from fires started by damaged or loose wiring.

The highest current a fuse or circuit breaker is designed to safely interrupt at its rated voltage. It must equal or exceed the available fault current where the device is installed.

An area where fire or explosion hazards may exist because of flammable gases, vapors, dusts, or fibers. Equipment installed there must be specially listed and marked for the hazard.