/ Sparky Edition Reference
NEC Article 100 Glossary
Plain-English explanations of the NEC's core definitions, written and reviewed by Masterbuild's licensed PE. Original wording, not a copy of the code text. English shown below; enable JavaScript for the searchable bilingual English/Spanish version with field notes on every term.
- Accessible. Equipment that can be reached to inspect, repair, or replace without damaging the building — not buried behind finished surfaces.
- Accessible, Readily. Capable of being reached quickly, without climbing over obstacles, using ladders, or moving furniture — a stricter standard than plain “accessible.â€
- Agricultural Building. A structure designed and constructed to house livestock or agricultural equipment/supplies, with combustible dust, corrosive atmosphere, and washdown conditions common.
- Ambulatory Health Care Occupancy. A building or portion used to provide services to four or more patients at the same time, who are rendered incapable of self-preservation due to anesthesia, sedation, or physical/cognitive limitation.
- Ampacity. The maximum current a conductor can carry continuously, under the conditions of use, without exceeding its temperature rating.
- Appliance. Utilization equipment, generally factory-built in standardized sizes, that performs a specific function such as heating, cooking, or refrigerating.
- Approved. Acceptable to the authority having jurisdiction (the code official) — a determination made locally, not a factory listing.
- Attachment Plug (Plug Cap) (Plug). A device on the end of a flexible cord that, when inserted into a receptacle, connects the cord's conductors to the supply conductors.
- Automatic. Self-acting, operating by its own mechanism when actuated by some impersonal influence, such as a change in current, pressure, or temperature.
- Battery System. An interconnected assembly of battery cells, control/protection equipment, and interconnections designed to supply DC power.
- Bonded (Bonding). Connected to establish electrical continuity and conductivity between metal parts that must be electrically joined.
- Bonding Jumper. A reliable conductor used to ensure electrical conductivity between metal parts required to be electrically connected.
- Branch Circuit. The conductors between the final overcurrent device protecting the circuit and the outlet(s).
- Branch Circuit, Appliance. A branch circuit supplying outlets for one or more appliances, with no permanently connected luminaires 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 piece of utilization equipment.
- Branch-Circuit Selection Current. For a hermetic refrigerant motor-compressor, the value used instead of rated-load current to size branch-circuit conductors, disconnects, and controllers, marked on the equipment when it differs from rated-load current.
- Building. A structure that stands alone or is separated from adjoining structures by fire walls.
- Cabinet. An enclosure designed for either surface or flush mounting and equipped with a frame, mat, or trim in which a swinging door or doors are hung.
- Cable Tray System. A unit or assembly of units or sections forming a rigid structural system for supporting cables and raceways, including ladder, ventilated trough/channel, solid-bottom, and similar structures.
- 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.
- Class 1, Class 2, Class 3 Circuits. Remote-control, signaling, and power-limited circuits classified by voltage and power limits, with Class 2/3 circuits limited enough that they don't need the same overcurrent protection, wiring methods, or separation rules as regular power wiring.
- Clothes Closet. A nonhabitable room or space intended primarily for storage of garments and apparel.
- Communications Circuit / Raceway. The circuit or raceway extending from a communications utility or premises equipment, used for voice, data, or similar low-voltage signal transmission, governed by NEC Article 800.
- Concealed. Rendered inaccessible by the structure or finish of the building; wires in concealed raceways are considered concealed even if accessible by withdrawing them.
- Concrete-Encased Electrode ("Ufer Ground"). A grounding electrode consisting of at least 20 ft of rebar or bare copper conductor encased in at least 2 in. of concrete, located near the bottom of a foundation or footing in direct contact with earth.
- Conductor (Bare, Covered, Insulated). Bare: no covering or insulation. Covered: encased in material not recognized as electrical insulation. Insulated: encased in material recognized as electrical insulation.
- Conduit Body. A separate portion of a conduit or tubing system that provides access through a removable cover to the interior of the system at a junction or terminal point.
- Connected Load. The sum of the rated capacities of all utilization equipment connected to a circuit, feeder, or service, before any demand factor is applied.
- Connector, Intercell / Interrack. Flexible or rigid conductor assemblies used to connect adjacent battery cells (intercell) or adjacent battery racks/trays (interrack) in a storage battery system.
- 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 governs, in a predetermined manner, the electric power delivered to the equipment to which it is connected.
- Controller Disconnecting Means. A disconnecting means located within sight of, or lockable at, a motor controller, used to disconnect the controller from its supply.
- Coordination (Selective). Localization of an overcurrent condition to restrict outages to the circuit or equipment affected, accomplished by choosing and setting protective devices so only the nearest upstream device opens.
- Correction Factor. A multiplier applied to conductor ampacity to account for ambient temperature conditions different from the base temperature used in the ampacity tables.
- Demand Factor. The ratio of the maximum demand of a system to the total connected load of that system.
- Device. A unit of an electrical system that carries or controls electric energy as its principal function, but does not utilize it.
- 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.
- Duty, Continuous / Intermittent / Periodic / Short-Time / Varying. A rating describing the load-time pattern equipment is designed for — Continuous (steady, indefinite), Intermittent (alternating load/no-load or load/rest), Periodic (intermittent with recurring identical cycles), Short-Time (constant load for a short, specified interval), Varying (load and time both vary widely).
- Dwelling Unit / One-Family / Two-Family / Multifamily Dwelling. Dwelling Unit: a single unit providing complete independent living facilities (cooking, sanitation, sleeping). One-family: one dwelling unit. Two-family: two units. Multifamily: three or more units.
- Electric Vehicle (EV). An automotive-type vehicle for highway use, primarily powered by an electric motor drawing current from a rechargeable storage battery or other portable energy storage device.
- Electric Vehicle Supply Equipment (EVSE). Conductors, EV connectors, attachment plugs, and all other fittings, devices, power outlets, or apparatus installed for delivering energy to an EV.
- Electrical Metallic Tubing (EMT) / Electrical Nonmetallic Tubing (ENT). EMT: an unthreaded thin-wall metal raceway that may serve as an equipment grounding conductor path when properly installed. ENT: a pliable, corrugated, nonmetallic raceway that cannot serve as an EGC and needs its own conductor for that purpose.
- Electroplating (Electrolytic Cells, Systems). An electrochemical process using low-voltage, high-current DC power supplies (rectifiers) to deposit or remove metal from a workpiece, governed by NEC Article 669.
- Enclosed / Enclosure. Enclosed: surrounded by a case, housing, fence, or wall that prevents persons from accidentally contacting energized parts. Enclosure: the case or housing that provides that protection.
- Enclosure Type Rating (NEMA 3R, 4, 4X, 12). Standardized enclosure classifications describing the degree of protection against ingress of water, dust, and corrosion — 3R for rain/sleet, 4/4X for washdown and corrosion resistance, 12 for dust/dripping-liquid in indoor industrial settings.
- Energized. Electrically connected to, or is, a source of voltage.
- Energy Storage System (ESS). One or more components assembled to store energy and supply electrical energy at a future time, such as battery, flywheel, or capacitor-based systems.
- Equipment. A general term including material, fittings, devices, appliances, luminaires, apparatus, machinery, and similar items used as part of, or in connection with, an electrical installation.
- Equipment Grounding Conductor (EGC). The conductive path that connects normally non-current-carrying metal parts of equipment to the system grounded conductor, grounding electrode conductor, or both.
- Exposed (Wiring Methods). On or attached to the surface, or behind panels designed to allow access.
- Fault Current, Available. The largest amount of current capable of being delivered at a point on the system during a short-circuit condition.
- 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.
- Feeder Tap. A set of conductors, smaller than the feeder they're connected to, permitted without full-size overcurrent protection at the tap point under specific length, ampacity, and enclosure conditions in NEC 240.21.
- Field Evaluation Body. An organization or part of an organization that performs field evaluations of electrical or other equipment, providing an on-site listing/labeling determination when factory listing isn't available.
- Fire Alarm Circuit (Power-Limited / Non-Power-Limited). Circuits that supply power to, or carry signals for, a fire alarm system, classified as power-limited (low-energy, Class-2-like) or non-power-limited (higher energy, requiring stricter wiring methods).
- Fire Pump (Electrical Supply). A pump, and its electrical supply and controller, dedicated to providing water flow and pressure for a fire protection system, with its own dedicated feeder requirements under NEC Article 695.
- Fitting. An accessory such as a locknut, bushing, or other part of a wiring system intended primarily to perform a mechanical rather than an electrical function.
- Fountain. Fully or partially constructed decorative water features, including splash pads, ornamental pools, and reflection pools, that are not intended for swimming or wading.
- Full-Load Current (Motor). The current a motor draws when operating at its rated load, voltage, and frequency — used for conductor ampacity and overload-protection sizing, taken from NEC tables rather than the motor nameplate in most cases.
- Fuse. An overcurrent protective device with a circuit-opening fusible link that melts and opens the circuit when subjected to overcurrent.
- Garage (Commercial). A building or portion of a building in which one or more self-propelled vehicles are kept for storage, repair, exhibition, or sale.
- Ground. The earth.
- Ground Fault. An unintentional, electrically conductive connection between an ungrounded conductor and normally non-current-carrying conductive parts, equipment, or ground.
- Ground Ring. A grounding electrode encircling a building or structure, buried at least 30 in. deep, consisting of at least 20 ft of bare copper conductor sized per the NEC's largest-service-conductor table.
- Ground-Fault Circuit-Interrupter (GFCI). A device intended for the protection of personnel that de-energizes a circuit or portion thereof within an established period of time when a ground-fault current exceeds the values established for a Class A device.
- Ground-Fault Protection of Equipment (GFPE). A system intended to provide protection of equipment from damaging line-to-ground fault currents by causing a disconnecting means to open all ungrounded conductors of the faulted circuit.
- Grounded (Grounded Conductor). Grounded: connected to ground or to a conductive body that extends the ground connection. Grounded Conductor: a system or circuit conductor that is intentionally grounded (the neutral, on most systems).
- Grounding Conductor. A conductor used to connect equipment or the grounded circuit of a wiring system to a grounding electrode.
- Grounding Electrode. A conducting object through which a direct connection to earth is established.
- Grounding Electrode Conductor (GEC). A conductor used to connect the system grounded conductor or the equipment to a grounding electrode or to a point on the grounding electrode system.
- Grounding Electrode, Rod / Pipe / Plate. Made electrodes driven into the earth (rod or pipe, minimum length/diameter set by the NEC) or buried in direct contact with soil (plate, minimum surface area), used when no qualifying electrode already exists on site.
- Guarded. Covered, shielded, fenced, enclosed, or otherwise protected by 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 / Guest Suite. An accommodation combining living, sleeping, sanitary, and (for a suite) storage/cooking facilities within a hotel, motel, or similar building.
- Handhole Enclosure. An enclosure with an open or closed bottom, sized to allow entry for installing/maintaining underground conductors/cables/equipment, but not intended for personnel entry.
- Hazardous (Classified) Location. An area where fire or explosion hazards may exist due to flammable gases, vapors, liquids, combustible dust, or ignitable fibers, classified by Class/Division or Zone system.
- Health Care Facilities. Buildings or portions of buildings in which medical, dental, psychiatric, nursing, obstetrical, or surgical care is provided.
- Heating System, Induction / Skin-Effect / Impedance. Induction Heating: heats a material via electromagnetically induced current. Skin-Effect Heating: heats a pipe/vessel via high-frequency current concentrated near its surface. Impedance Heating: passes current directly through the material or pipe to be heated using its own electrical resistance.
- Identified (as applied to equipment). Recognized as suitable for the specific purpose, function, use, environment, application, and so forth, where described in a particular NEC requirement.
- Identified Conductor (Marking). A conductor marked or colored to distinguish its function — white/gray for grounded conductors, green for equipment grounding conductors — recognized system-wide for quick field identification.
- Impedance Protected (Motor). A motor with windings that have a sufficiently high impedance to limit locked-rotor current to a level that avoids overheating damage during a stalled condition.
- In Sight From (Within Sight From, Within Sight). Visible and not more than 50 ft (15 m) distant from the other object.
- Information Technology Equipment (ITE). Equipment such as computers, servers, and peripherals used to store, process, or transfer information, historically governed by dedicated rules (NEC Article 645) for reduced-clearance disconnects and under-floor wiring in a controlled environment.
- Interconnected Electric Power Production Sources. Generating sources (PV, wind, fuel cells, generators) operating in parallel with a primary source of electricity, such as a utility.
- Interrupter Switch. A switch capable of making, carrying, and interrupting specified currents under normal circuit conditions, and also making and carrying for a specified time and interrupting fault currents.
- Interrupting Rating. The highest current at rated voltage that a device is intended to interrupt under standard test conditions.
- Intrinsically Safe System / Simple Apparatus. An assembly of interconnected intrinsically safe apparatus, associated apparatus, and interconnecting cable in which the circuits are incapable of causing ignition in a hazardous location. Simple Apparatus: a passive component that cannot generate more than 1.2V, 0.1A, 25mW, or 20µJ.
- Inverter, Interactive / Multimode / Stand-Alone. Interactive: operates in parallel with and can deliver power to an electric primary source supply. Multimode: can operate either interactive or stand-alone. Stand-Alone: supplies power independently of an electric power production and distribution network.
- Irrigation Machine. An electrically driven or controlled machine, such as a center-pivot irrigation system, with one or more motors, along with the controls, switches, and other electrical equipment for its use.
- Isolated (as applied to location). Not readily accessible to persons unless special means for access are used.
- Isolated Ground. An equipment grounding conductor arrangement that isolates a receptacle's grounding terminal from the metal raceway/box system, run back to a single point to reduce electrical noise on sensitive equipment.
- Labeled. Equipment or materials to which has been attached a label, symbol, or other identifying mark of an organization acceptable to the authority having jurisdiction and concerned with product evaluation.
- Legally Required Standby Systems. Systems required by municipal, state, federal, or other codes to automatically supply power to selected loads (other than emergency systems) when normal power is lost.
- Life Safety Branch / Essential Electrical System. A system of feeders and branch circuits, part of a health care facility's essential electrical system, that supplies illumination, receptacles, and equipment essential for life safety after normal power loss.
- Lighting Outlet. An outlet intended for the direct connection of a lampholder, a luminaire, or a pendant cord terminating in a lampholder.
- Line Isolation Monitor. A test instrument that continually checks the balanced and unbalanced impedance from each line of an isolated power system to ground, alarming when total hazard current exceeds a threshold.
- Line-to-Line / Line-to-Neutral. Line-to-Line: an electrical reference between two ungrounded (current-carrying) conductors. Line-to-Neutral: an electrical reference between an ungrounded conductor and the neutral conductor.
- Listed. Equipment, materials, or services included in a list published by an organization acceptable to the authority having jurisdiction and concerned with evaluation of products, that maintains periodic inspection of production and states compliance with appropriate standards.
- Load Management System. Equipment, including hardware and software, that monitors and controls electric loads, sometimes limiting current or power to keep a system within its rated capacity.
- Load Side. The conductors that extend from equipment toward the load, as opposed to the line side, which extends toward the power source.
- Location, Anesthetizing. Any space designated for the administration of any flammable or nonflammable inhalation anesthetic in the course of examination or treatment, including relevant induction rooms.
- Location, Damp / Dry / Wet. Damp: partially protected locations subject to moderate moisture (e.g., under a canopy). Dry: not normally subject to dampness or wetness. Wet: unprotected and exposed to weather, or subject to saturation with water or other liquids.
- Locked-Rotor Current. The steady-state current a motor draws when its rotor is stalled, at rated voltage and frequency — significantly higher than full-load running current.
- Low-Voltage Suspended Ceiling Power Distribution System. A system using the metal grid of a suspended ceiling, specifically listed for the purpose, as current-carrying conductors for low-voltage lighting or equipment.
- Luminaire. A complete lighting unit consisting of a light source plus the parts that position it, protect it, and connect it to the power supply.
- Luminaire, Dry-Niche / No-Niche / Wet-Niche. Pool/fountain luminaire types defined by whether they sit in a sealed dry recess (Dry-Niche), mount without a recess (No-Niche), or sit directly in water inside a forming shell (Wet-Niche).
- Machine Room. An enclosed space outside a hoistway or elevator car containing machinery, controllers, or other elevator/lift equipment.
- Main Bonding Jumper / System Bonding Jumper / Supply-Side Bonding Jumper. Main Bonding Jumper: connects the grounded conductor to the equipment grounding conductor at the service. System Bonding Jumper: the same connection at a separately derived system. Supply-Side Bonding Jumper: a bonding conductor installed on the supply side of a service or separately derived system's disconnect/OCPD.
- Manufactured Home. A factory-built structure built to the federal HUD manufactured home standard, transportable in sections, designed for use as a dwelling with permanent chassis.
- Manufactured Wiring System. A system of pre-assembled circuit and outlet components, factory-wired and listed as a system, installed in structures.
- Marina. A facility, generally on the waterfront, that stores, services, fuels, or sells boats, or provides dockage or storage for five or more boats.
- Membrane Enclosure. A temporary enclosure using a nonrigid material (fabric, plastic sheeting) to define a construction area, often used in health care or industrial infection/dust-control settings.
- Metal Shield Connections. Means of connection for the flat conductive shielding tape or braid on certain cable types, providing a controlled path for grounding the cable's electrostatic or electromagnetic shield.
- Microgrid System. An electric power system containing multiple electric power sources (utility, PV, storage, generator) and loads capable of operating in parallel with, or independently from, the primary power source.
- Mobile Home Park / Lot. Park: a contiguous parcel of land used for mobile home sites. Lot: a designated portion of that parcel intended for the exclusive placement of one mobile home and its accessory structures.
- Motor Control Center. An assembly of one or more enclosed sections with a common power bus and primarily containing motor control units.
- Motor Fuel Dispensing Facility. That portion of a property where motor fuel is stored and dispensed from fixed equipment into the fuel tanks of self-propelled vehicles or approved containers.
- Multioutlet Assembly. A surface, flush, or freestanding raceway assembly designed to hold conductors and receptacles, field- or factory-assembled.
- Nameplate Rating. The electrical characteristics (voltage, current, power, frequency) a manufacturer marks directly on a piece of equipment as its rated operating values.
- Neon Tubing. Electric-discharge luminous tubing bent into shapes to form letters, parts of letters, skeleton tubing, outline lighting, or art forms.
- Neutral Conductor. The conductor connected to the neutral point of a system that is intended to carry current under normal conditions.
- Neutral Point. The common point on a wye-connected system, or the midpoint on a single-phase, 3-wire system, that is intended to carry current under normal conditions.
- Nonincendive Equipment / Circuit / Component. Equipment, circuits, or components that, in normal operation, are incapable of igniting a specified flammable gas-air, vapor-air, or dust-air mixture.
- Nonlinear Load. A load where the current waveform after a half-cycle of energization does not follow the voltage waveform's shape.
- Normal / Emergency Power Source. A power source, on the load side of a transfer switch, that can be arranged to supply both normal and emergency loads.
- Nurses Station. A space intended to provide a center of nursing activity for a group of patients, where patient monitoring, medications, and staff communication typically occur.
- Nursing Home. A building or portion of a building used for the lodging, boarding, and nursing care of four or more persons, on a 24-hour basis, who because of mental or physical incapacity may be unable to provide for their own needs and safety.
- Optical Radiation (Equipment). Electromagnetic radiation at wavelengths between about 100 nm and 1 mm (encompassing UV, visible, and IR light), relevant to equipment such as lasers and certain lighting/medical devices covered by specific NEC provisions.
- Organ, Electronic / Pipe. Electronic Organ: a musical instrument producing sound electronically. Pipe Organ: a musical instrument producing sound acoustically through pipes, with an associated electric/electronic wind-supply and control system.
- Outlet. A point on the wiring system at which current is taken to supply utilization equipment.
- Overcurrent. Any current in excess of the rated current of equipment or the ampacity of a conductor; may result from overload, short circuit, or ground fault.
- Overcurrent Protective Device, Supplementary. A device intended to provide limited overcurrent protection for specific applications and utilization equipment, such as internal circuits of an appliance, not intended as a substitute for branch-circuit overcurrent protection.
- Overload. Operation of equipment in excess of normal, full-load rating, or of a conductor in excess of rated ampacity, that when it persists for a sufficient length of time could cause damage or dangerous overheating; a fault, such as a short circuit or ground fault, is not an overload.
- Overload Relay / Thermal Protector. Overload Relay: a device operative on excessive current, but designed to trip before damage occurs, that opens a motor's control circuit rather than the power circuit directly. Thermal Protector: a protective device assembled as an integral part of a motor, responding to motor temperature.
- Panelboard. A single panel or group of panel units designed for assembly in the form of a single panel, including buses, automatic overcurrent devices, with or without switches for the control of light, heat, or power circuits, designed to be placed in a cabinet or cutout box.
- Park Trailer. A recreational-vehicle-type unit built on a single chassis, mounted on wheels, primarily designed to provide seasonal or temporary living quarters, connected to utilities for site-dependent support systems.
- Patient Care Space Category. A classification (Category 1-4) of spaces within a health care facility based on the impact of an electrical system failure on patients and staff.
- Patient Equipment Grounding Point. A jack or terminal that serves as the collection point for redundant grounding of electrical appliances serving a patient care vicinity, or for grounding other items in the patient vicinity.
- Performance Area / Stage. The stage and audience seating area of a theater, television/film studio, or similar space used for performances, including any area used by performers.
- Photovoltaic (PV) Array. A mechanically integrated assembly of PV modules, together with support structure and foundation, that acts as a single electricity-producing unit.
- Photovoltaic (PV) Module. A complete, environmentally protected unit consisting of solar cells, optics, and other components designed to generate DC power when exposed to sunlight.
- Photovoltaic (PV) System. The total components and subsystems that, in combination, convert solar energy into electric energy suitable for connection to a utilization load.
- Plenum. A compartment or chamber to which one or more air ducts are connected and that forms part of the air distribution system.
- Pool, Immersion. A pool used for ceremonial or religious purposes, or for physical therapy, that is not intended for swimming or recreational bathing.
- Pool, Permanently Installed. A pool constructed in the ground, partially in the ground, or above ground, and designed to hold water at a depth greater than 42 in. and to remain in place year-round.
- Pool, Storable. A pool with a maximum water depth of 42 in., or a maximum wall height of 42 in. above grade regardless of depth, that can be disassembled for storage.
- Portable (equipment). A device intended for indoor or outdoor use that is moved from one location to another and is not fastened in place, typically connected by cord and plug.
- Portable Power Distribution Unit. Equipment that includes overcurrent protection and multiple receptacles or connectors, designed to distribute power temporarily, commonly used on film/TV production, events, and construction sites.
- Portable Structures. Units designed to be moved, including trailers, and used for offices, sales, or similar purposes at a temporary or semi-permanent site.
- Power Export Equipment (EV). Equipment on an EV, or connected to it, that provides power from the vehicle's onboard energy storage to premises wiring or an external load.
- Power Supply, Class 2. A power source, either inherently limited or using a listed transformer/electronic device, that supplies a Class 2 circuit and limits output to safe, low-energy levels.
- Premises Wiring (System). Interior and exterior wiring, including power, lighting, control, and signal circuit wiring, together with all their associated hardware, fittings, and wiring devices, on the premises from the service point or power source to the outlets, that is not classified as “internal wiring.â€
- Process Seal. A seal between electrical apparatus/wiring and a flammable or combustible fluid process, intended to minimize the possibility of the process fluid entering the electrical system.
- Psychiatric Hospital. A building used exclusively for the psychiatric care of four or more inpatients on a 24-hour basis.
- Qualified Person. One who has skills and knowledge related to the construction and operation of the electrical equipment and installations, and has received safety training on the hazards involved.
- Raceway. An enclosed channel of metal or nonmetallic materials designed expressly for holding wires, cables, or busbars, with additional functions as permitted in the NEC.
- Rapid Shutdown (PV Systems). A required function that reduces shock hazard for emergency responders by de-energizing PV system conductors to specified voltage limits within specified time limits when initiated.
- Rated-Load Current. For a hermetic refrigerant motor-compressor, the current marked on the equipment nameplate when it's tested and rated under standard operating conditions.
- Receptacle. A contact device installed at an outlet for the connection of a single attachment plug, or for the direct connection of electrical utilization equipment designed to mate with the corresponding contact device.
- Receptacle Outlet. An outlet where one or more receptacles are installed.
- Recreational Vehicle / RV Park / RV Site. A vehicular unit primarily designed for recreational camping or travel use, and the parcels of land (park) or specific areas (site) developed for RV parking with utility connections.
- Reference Grounding Point. The ground bus of the panelboard or isolated power system panel serving a patient care space, established as the reference point for equipment grounding conductors in that area.
- Separately Derived System. A premises wiring system whose power is derived from a source (transformer, generator, converter) with no direct electrical connection to the supply conductors of another system.
- Series Rating / Short-Circuit Current Rating (SCCR). Series Rating: a listed combination of specific overcurrent devices that can be applied at available fault currents higher than the interrupting rating of the downstream device alone, verified by testing. SCCR: the maximum fault current an assembly can safely withstand.
- Service. The conductors and equipment connecting the serving utility to the wiring system of the premises served.
- Service Conductors. The conductors from the service point to the service disconnecting means.
- Service Drop. The overhead conductors between the utility electric supply system and the service point.
- Service Equipment. The necessary equipment, generally consisting of a circuit breaker(s) or switch(es) and fuse(s) and their accessories, connected to the load end of service conductors and intended to constitute the main control and cutoff of the supply.
- Service Head (Weatherhead). A fitting installed at the top of a service raceway or service cable to keep water from entering the service-entrance conductors while allowing conductors to exit for connection to the service drop.
- Service Lateral. The underground conductors between the utility electric supply system and the service point.
- Service Point. The point of connection between the facilities of the serving utility and the premises wiring.
- Service-Entrance Conductors. The service conductors between the terminals of the service equipment and a point usually outside the building, clear of building walls, where joined by tap or splice to the service drop or service lateral.
- Shore Power. The electrical equipment required to power a boat, including the shore power cable and wiring device, but not the boat's onboard electrical system.
- Sign / Outline Lighting. Sign: a fixed, stationary, or portable self-contained electrically illuminated utilization equipment with a static or changing message. Outline Lighting: an arrangement of incandescent lamps, LEDs, or tubing to outline or call attention to a building feature or sign.
- Spa, Permanently Installed / Portable (Hot Tub). A hydromassage pool or tub, permanently installed or listed as self-contained/portable, not designed to have its water discharged after each use.
- Stage Switchboard, Fixed / Portable. Fixed: a permanently installed switchboard used for controlling stage lighting circuits. Portable: a switchboard mounted on a moveable frame, connected by cord/cable/plug, used similarly but relocatable.
- Stand-Alone System. A system that supplies power independently of an electric power production and distribution network — i.e., an off-grid PV or generator system.
- Standby / Emergency Generator (Power Source, Alternate). An alternate source of electric power, other than the normal utility supply, intended to serve some or all of a premises' loads when normal power is lost.
- Structure. That which is built or constructed, other than equipment.
- Structure, Relocatable. A factory-assembled structure, transportable in one or more sections, designed to be used with or without a permanent foundation, not including recreational vehicles or manufactured/mobile homes.
- Substation. An assemblage of equipment — switches, interrupting devices, transformers — through which electric energy is passed for distribution, transmission, or transformation.
- Supervised Industrial Installation. Portions of an industrial facility where conditions of maintenance and supervision ensure only qualified persons monitor and service the installation, and where the industrial process is served by 2500 kVA or more of transformer capacity.
- Switch, General-Use / Isolating / Motor-Circuit. General-Use: a switch for general distribution and branch-circuit use, rated in amperes and capable of interrupting rated current. Isolating: intended for isolating a circuit from its source, not to be operated under load. Motor-Circuit: rated in horsepower, capable of interrupting the rated current of a motor at rated voltage.
- Switchboard. A large single panel, frame, or assembly of panels having a frame-mounted assembly of switches, overcurrent, and other protective devices, with or without instruments, intended for service entrance, feeder, or branch-circuit distribution.
- Switchgear. An assembly completely enclosed on all sides and top, containing primarily electric supply distribution equipment such as switches, interrupting devices, and buses.
- Temporary Equipment / Wiring. Wiring and equipment installed for a limited time — construction power, special events, testing — not intended for permanent use, with a fixed permitted duration and removal requirement.
- Third-Party Testing Laboratory Mark (UL, ETL, CSA, etc.). The physical label or symbol applied by a Nationally Recognized Testing Laboratory (NRTL) confirming a product has been evaluated against the applicable safety standard — the practical evidence behind the “listed†definition.
- Transfer Switch, Automatic / Bypass Isolation. Automatic: self-acting equipment that transfers a load between two power sources. Bypass Isolation: a transfer switch arrangement that allows manual bypass of the automatic switch for maintenance without interrupting power to the load.
- Transformer. Equipment, single-phase or polyphase, that transforms electrical energy from one voltage/current combination to another using electromagnetic induction.
- Transformer Secondary Conductor. A conductor, other than a service conductor, connected to the secondary winding of a transformer and running to the first overcurrent device that protects it.
- Truck / Vehicle (EV context). A motor vehicle designed for the transportation of persons or property, referenced in the NEC for equipment such as flanged surface inlets and EV supply equipment connections.
- Trunk Cable. A portable extension cable containing six or more current-carrying conductors, used to distribute power to multiple branch circuits or loads at a temporary event or production.
- Twofer. An assembly containing one male plug and two female cord connectors intended for portable stage/entertainment equipment, allowing two loads to be supplied from a single outlet.
- Ungrounded. Not connected to ground or to a conductive body that extends the ground connection.
- Unit Equipment (Emergency). A battery-equipped emergency luminaire assembly consisting of a rechargeable battery, charger, provisions for one or more lamp heads, and a relaying device to energize the lamps on loss of normal power.
- Utilization Equipment. Equipment that utilizes electric energy for electronic, electromechanical, chemical, heating, lighting, or similar purposes.
- Vending Machine. Self-service equipment that dispenses products or services, wholly or partly automatically, upon insertion of a coin, paper currency, token, card, or key, or by direct payment of any kind.
- Ventilated. Provided with a means to permit circulation of air sufficient to remove an excess of heat, fumes, or vapors.
- Voltage Drop. The reduction in voltage between the source and the load caused by conductor impedance, generally recommended to be limited to 3% on branch circuits and 5% total (feeder plus branch circuit) for reasonable equipment operation, per NEC informational notes.
- Voltage, High / Low / To Ground. High Voltage: over 600V (1000V for AC per newer text). Low Voltage: at or below that threshold, per equipment listing. Voltage to Ground: for grounded systems, the voltage between a given conductor and ground; for ungrounded systems, the greatest voltage between the conductor and any other conductor.
- Voltage, Nominal. A nominal value assigned to a circuit or system for the purpose of conveniently designating its voltage class (e.g., 120, 208, 240, 480).
- Watertight / Raintight / Rainproof. Watertight: constructed so water will not enter under specified test conditions. Raintight: constructed or protected so exposure to a beating rain will not result in water entering. Rainproof: constructed, protected, or treated so exposure to a beating rain will not interfere with successful operation.
- Weatherproof. Constructed or protected so that exposure to the weather will not interfere with successful operation.
- Wireways, Metal / Nonmetallic. Sheet-metal or flame-retardant nonmetallic troughs with hinged or removable covers, for housing and protecting wires and cable, in which conductors are laid in place after the wireway is installed.
- Wiring Device. An electrical device with a yoke, or used with wiring systems, such as switches, receptacles, attachment plugs, and wall plates.
- Withstand Rating. The maximum current, at a given voltage and power factor/duration, that equipment can carry without sustaining damage, distinct from its interrupting rating.
- Work Surface. A fixed, stationary, or portable surface used to support work activities, typically in an office furniture or systems-furniture layout.
- Working Space (Working Clearance). The clear depth, width, and height maintained in front of electrical equipment to allow safe operation and maintenance access, sized by voltage and condition per the NEC's clearance tables.
- Zone. A physically identifiable area, such as separate rooms, defined by the extent of hazardous (classified) location classification or fire/life-safety subdivision, depending on context.
Need this checked against your project?
This glossary is general reference. For a determination tied to your drawings, equipment schedule, or AHJ, send the project background and get a written scope.
IMC glossary: Section 202 Terms · Free archive: Daily Code Talk · Field Guides: Resources · Main site: masterbuildconsulting.com
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