WI Electrician key terms

The maximum continuous current, in amperes, that a conductor can carry without exceeding its temperature rating under the conditions of use. It depends on conductor size, insulation type, and ambient temperature.

The required reduction of a conductor's ampacity when more than three current-carrying conductors are installed together in a raceway or cable, because bundled conductors cannot shed heat as effectively.

A multiplier applied to a conductor's base ampacity to account for installation in surroundings hotter or colder than the standard reference temperature assumed by the conductor's insulation rating.

A breaker or fuse designed to open a circuit automatically when current exceeds a set value, protecting conductors and equipment from overheating and short circuits.

A device that de-energizes a circuit within a fraction of a second when it senses current leaking from the hot conductor to ground, protecting people from electric shock.

A device that detects the characteristic current signature of a dangerous arcing fault in branch-circuit wiring and opens the circuit to prevent fire ignition.

The conductive path that connects the non-current-carrying metal parts of equipment to the grounding system, providing a low-impedance route for fault current to trip the overcurrent device.

The conductor that connects the grounded circuit conductor or equipment grounding system to the grounding electrode, such as a ground rod or metal water pipe.

A conductive object, such as a rod, pipe, plate, or concrete-encased electrode, that establishes a direct electrical connection to the earth.

A reliable conductor that ensures electrical continuity between metal parts that must be electrically connected, such as around a water meter or between service equipment enclosures.

The conductors that carry power from the utility service point, such as the drop or lateral, to the service equipment disconnect inside or on the building.

The set of equipment, usually a panel with a main disconnect and overcurrent devices, that receives power from the service conductors and provides the means to disconnect the building supply.

All circuit conductors between the service equipment, or another power supply source, and the final branch-circuit overcurrent devices that protect the loads.

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

An enclosed channel of metal or nonmetallic material, such as conduit or tubing, designed expressly to hold wires and cables and to provide physical protection.

The calculated volume of an outlet, device, or junction box required to safely contain all conductors, devices, and fittings, based on counting each item against a per-conductor volume allowance.

An enclosure where conductors are spliced or connected to devices, providing a protected location for terminations and access for maintenance.

An opening in the wiring system at which current is taken to supply utilization equipment, typically through a plug-in receptacle device mounted in a box.

A 20-ampere branch circuit in a dwelling that supplies receptacle outlets for kitchen countertop and similar appliances, required to serve no other outlets.

The ratio of the maximum demand on a system to the total connected load, used to size service and feeder conductors because not all loads operate at once.

A structured method of adding general lighting, small-appliance, appliance, and heating or cooling loads to determine the minimum capacity required for a service or feeder.

The reduction in voltage along a conductor caused by its resistance and reactance as current flows, which can cause poor equipment performance if excessive.

The fuse or breaker that protects a motor branch circuit against short circuits and grounds, sized independently of the motor overload protection and permitted to exceed conductor ampacity under code rules.

A device, such as a thermal overload relay, that protects the motor winding from sustained excess current due to mechanical overload, sized to the motor's full-load current.

The current a motor draws at rated load and rated voltage, taken from code tables rather than the nameplate for conductor and protection sizing.

A device or assembly that starts and stops a motor and, in the case of a starter, may include overload protection and the means to connect and disconnect the motor circuit.

A device or group of devices that can open all ungrounded conductors of a circuit from the source of supply, allowing equipment to be safely de-energized for service.

A safety procedure in which an energy-isolating device is locked and tagged to prevent unexpected energization of equipment while workers service or maintain it.

Clothing and gear, such as insulated gloves, arc-rated clothing, and face shields, worn to protect a worker from electrical, thermal, and arc-flash hazards.

A dangerous release of energy caused by an electrical arc through air, producing intense heat, light, and pressure that can injure workers and damage equipment.

An arrangement where a downstream breaker or fuse is protected by a listed upstream device, permitting the combination to interrupt a fault current greater than the downstream device's individual rating.

The maximum available fault current a component or assembly can safely withstand without damage when a short circuit occurs at its terminals.

An area where flammable gases, vapors, dusts, or fibers may be present in quantities sufficient to ignite, requiring special wiring methods and equipment approved for the classification.

A circuit designed so that any spark or thermal effect produced under normal or fault conditions cannot ignite a flammable atmosphere, typically by limiting energy.

Enclosures and devices designed to contain an internal explosion and prevent ignition of surrounding flammable atmospheres, used in certain classified locations.

A formal authorization issued by the local authority before regulated electrical work begins, allowing inspection of the installation at required stages.

The review of permitted electrical work by a certified inspector to verify compliance with the adopted electrical code and administrative rules before the work is approved.

The organization, office, or individual responsible for approving equipment, materials, installations, and procedures, and for enforcing the electrical code in a given area.

An individual who holds a valid credential from the state or local licensing body at the appropriate level, such as journeyman or master, authorizing them to perform regulated electrical work.

A licensed electrician qualified to perform electrical installation work under general supervision, typically after completing an apprenticeship and passing a competency examination.

A licensed electrician with advanced experience and examination credentials who may design, supervise, and contract for electrical work, and often may pull permits and supervise journeymen.