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l Equipment for Use in Class I and II, Division 2, and Class III Hazardous (Classified) Locations. A dusttight enclosure has been determined to exclude dust under specified test conditions. Combustible dust is 500 microns or smaller. The AHJ determines the suitability of a dusttight enclosure or the...

l Equipment for Use in Class I and II, Division 2, and Class III Hazardous (Classified) Locations. A dusttight enclosure has been determined to exclude dust under specified test conditions. Combustible dust is 500 microns or smaller. The AHJ determines the suitability of a dusttight enclosure or the acceptance of a specific standard, test, or listing organization. See also 110.28 and Table 110.28 for enclosure requirements, as well as the enhanced content following the definition of enclosure. Duty, Continuous. (Continuous Duty) Operation at a substantially constant load for an indefinitely long time. (CMP-1) Duty, Intermittent. (Intermittent Duty) Operation for alternate intervals of (1) load and no load; or (2) load and rest; or (3) load, no load, and rest. (CMP-1) Duty, Periodic. (Periodic Duty) Intermittent operation in which the load conditions are regularly recurrent. (CMP-1) Duty, Short-Time. (Short-Time Duty) Operation at a substantially constant load for a short and definite, specified time. (CMP-1) Duty, Varying. (Varying Duty) Operation at loads, and for intervals of time, both of which may be subject to wide variation. (CMP-1) Dwelling, One-Family. (One-Family Dwelling) A building that consists solely of one dwelling unit. (CMP-1) Dwelling, Two-Family. (Two-Family Dwelling) A building that consists solely of two dwelling units. (CMP-1) Dwelling, Multifamily. (Multifamily Dwelling) A building that contains three or more dwelling units. (CMP-1) 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. (CMP-2) ENHANCED CONTENT Collapse Where dwelling units are referenced throughout the NEC, rooms in motels, hotels, and similar occupancies that have permanent provisions for living, sleeping, cooking, and sanitation are also classified as dwelling units. The exhibit below illustrates a motel or hotel room that meets this definition. Dorm rooms are not usually considered to be dwelling units because they do not meet the definition. Electric-Discharge Lighting. Systems of illumination utilizing fluorescent lamps, high-intensity discharge (HID) lamps, or neon tubing. (CMP-18) Electric Power Production and Distribution Network. Power production, distribution, and utilization equipment and facilities, such as electric utility systems that are connected to premises wiring and are external to and not controlled by a system that operates in interactive mode. (CMP-13) Electric Sign. A fixed, stationary, or portable self-contained, electrically operated and/or electrically illuminated utilization equipment with words or symbols designed to convey information or attract attention. (CMP-18) Electric Supply Stations. Locations containing the generating stations and substations, including their associated generator, storage battery, transformer, and switchgear areas. (CMP-4) Electric Vehicle (EV). An automotive-type vehicle for on-road use, such as passenger automobiles, buses, trucks, vans, neighborhood electric vehicles, and electric motorcycles, primarily powered by an electric motor that draws current from a rechargeable storage battery, fuel cell, photovoltaic array, or other source of electric current. Plug-in hybrid electric vehicles (PHEV) are electric vehicles having a second source of motive power. (CMP-12) Informational Note: Off-road, self-propelled electric mobile machines, such as industrial trucks, hoists, lifts, transports, golf carts, airline ground support equipment, tractors, and boats are not considered electric vehicles. ENHANCED CONTENT Collapse The primary difference between electric vehicles (EVs) as defined in Article 625 and EVs covered by other sections in the NEC is in their road and highway worthiness. Automotive EVs are comparable in performance and function to conventional automobiles and light trucks. Automotive EVs must be capable of complying with the Federal Motor Vehicle Safety Standards and other U.S. Department of Transportation (DOT), National Highway Traffic Safety Administration (NHTSA), and U.S. Environmental Protection Agency (EPA) requirements. A plug-in hybrid electric vehicle can be charged through either its own rechargeable energy storage system or through connection to EV supply equipment located at a home, business, or other location. The definition of the term electric vehicle includes neighborhood electric vehicles (NEVs), which are low-speed, limited-use EVs similar to golf carts but provided with automotive-grade headlights, seat belts, windshields, brakes, and other safety equipment that makes them street legal. Under NHTSA guidelines, the intended use for NEVs is in inner-city areas and planned and retirement communities where the street speed limit is 35 miles per hour or less. EVs can also be used as a power source for an optional standby system, as covered in Article 702, or as an interconnected electric power production source, as covered in Article 705. See also 625.48, which covers the transfer of power by the EV supply equipment from the premises to the EV or from the EV to the premises wiring through an interactive system. Electric Vehicle Connector. A device that, when electrically coupled (conductive or inductive) to an electric vehicle inlet, establishes an electrical connection to the electric vehicle for the purpose of power transfer and information exchange. (625) (CMP-12) Informational Note: See 625.48 for further information on interactive systems. Electric Vehicle Power Export Equipment (EVPE). The equipment, including the outlet on the vehicle, that is used to provide electrical power at voltages greater than or equal to 30 Vac or 60 Vdc to loads external to the vehicle, using the vehicle as the source of supply. (625) (CMP-12) Informational Note: Electric vehicle power export equipment and electric vehicle supply equipment or wireless power transfer equipment are sometimes contained in one piece of equipment, sometimes referred to as a bidirectional electric vehicle supply equipment (EVSE) or bidirectional wireless power transfer equipment (WPTE). Electric Vehicle Supply Equipment (EVSE). Equipment for plug-in charging, including the ungrounded, grounded, and equipment grounding conductors, and the electric vehicle connectors, attachment plugs, personnel protection system, and all other fittings, devices, power outlets, or apparatus installed specifically for the purpose of transferring energy between the premises wiring and the electric vehicle. (625) (CMP-12) Informational Note: Electric vehicle power export equipment and electric vehicle supply equipment or wireless power transfer equipment (WPTE) are sometimes contained in one piece of equipment, sometimes referred to as a bidirectional EVSE or bidirectional WPTE. ENHANCED CONTENT Collapse EV supply equipment comprises the components between the skin of the EV and the premises wiring, including any flexible cable, disconnecting means, enclosures, power outlet, and EV connector. The defined term includes all off-vehicle charging equipment and does not include charging equipment installed on the vehicle. An EV charging station at a business and a vehicle connector plugged into a vehicle is shown below. Electrical Circuit Protective System. A system consisting of components and materials intended for installation as protection for specific electrical wiring systems with respect to the disruption of electrical circuit integrity upon exterior fire exposure. (CMP-16) Electrical Datum Plane. A specified vertical distance above the normal high-water level at which electrical equipment can be installed and electrical connections can be made. (CMP-7) ENHANCED CONTENT Collapse Throughout Article 555, the physical location of electrical equipment is referenced to the electrical datum plane, which is used as a horizontal benchmark on land and on floating piers. The definition of the term electrical datum plane encompasses areas subject to tidal movement and areas in which the water level is affected only by conditions such as climate (rain or snowfall) or by human intervention (the opening or closing of dams and floodgates). In either case, the term covers the normal highest water level, such as astronomical high tides. The term does not cover extremes due to natural or manmade disasters. Electrical Ducts. Electrical conduits, or other raceways round in cross section, that are suitable for use underground or embedded in concrete. (CMP-6) Electrical Life Support Equipment. Electrically powered equipment whose continuous operation is necessary to maintain a patient’s life. [99:3.3.45] (517) (CMP-15) Electrical Resistance Trace Heating “60079-30-1”. Type of protection for the purpose of producing heat on the principle of electrical resistance and typically composed of one or more metallic conductors and/or an electrically conductive material, suitably electrically insulated and protected. (CMP-14) Informational Note: See ANSI/UL 60079-30-1, Explosive Atmospheres — Part 30-1: Electrical Resistance Trace Heating — General and Testing Requirements, for additional information. Electrically Connected. A connection capable of carrying current as distinguished from connection through electromagnetic induction. (668) (CMP-12) Electrified Truck Parking Space. A truck parking space that has been provided with an electrical system that allows truck operators to connect their vehicles while stopped and to use off-board power sources in order to operate on-board systems such as air conditioning, heating, and appliances, without any engine idling. (626) (CMP-12) Informational Note: An electrified truck parking space also includes dedicated parking areas for heavy-duty trucks at travel plazas, warehouses, shipper and consignee yards, depot facilities, and border crossings. It does not include areas such as the shoulders of highway ramps and access roads, camping and recreational vehicle sites, residential and commercial parking areas used for automotive parking or other areas where ac power is provided solely for the purpose of connecting automotive and other light electrical loads, such as engine block heaters, and at private residences. Electrified Truck Parking Space Wiring Systems. All of the electrical wiring, equipment, and appurtenances related to electrical installations within an electrified truck parking space, including the electrified parking space supply equipment. (626) (CMP-12) Electrolyte. The medium that provides the ion transport mechanism between the positive and negative electrodes of a cell. (CMP-13) Electrolytic Cell. A tank or vat in which electrochemical reactions are caused by applying electric energy for the purpose of refining or producing usable materials. (668) (CMP-12) Electrolytic Cell Line Working Zone. The space envelope wherein operation or maintenance is normally performed on or in the vicinity of exposed energized surfaces of electrolytic cell lines or their attachments. (668) (CMP-12) Electronic Power Converter. A device that uses power electronics to convert one form of electrical power into another form of electrical power. (CMP-4) Informational Note: Examples of electronic power converters include, but are not limited to, inverters, dc-to-dc converters, and electronic charge controllers. These devices have limited current capabilities based on the device ratings at continuous rated power. Electronically Protected. A motor provided with electronic control that is an integral part of the motor and protects the motor against dangerous overheating due to failure of the electronic control, overload, and failure to start. (430) (CMP-11) Emergency Luminaire, Battery-Equipped. (Battery-Equipped Emergency Luminaire) A luminaire with a rechargeable battery, a battery charging means, and an automatic load control relay. (CMP-13) Emergency Luminaire, Directly Controlled. (Directly Controlled Emergency Luminaire) A luminaire supplied by the facility emergency power system and with a control input for dimming or switching that provides an emergency illumination level upon loss of normal power. (700) (CMP-13) Informational Note: See ANSI/UL 924, Emergency Lighting and Power Equipment, for information covering directly controlled emergency luminaires. Emergency Power Supply (EPS). The source(s) of electric power of the required capacity and quality for an emergency power supply system (EPSS). (CMP-13) Emergency Power Supply System (EPSS). A complete functioning EPS system coupled to a system of conductors, disconnecting means and overcurrent protective devices, transfer switches, and all control, supervisory, and support devices up to and including the load terminals of the transfer equipment needed for the system to operate as a safe and reliable source of electric power. [110:3.3.4] (CMP-13) Emergency Systems. Those systems legally required and classed as emergency by municipal, state, federal, or other codes, or by any governmental agency having jurisdiction. These systems are intended to automatically supply illumination, power, or both, to designated areas and equipment in the event of failure of the normal supply or in the event of accident to elements of a system intended to supply, distribute, and control power and illumination essential for safety to human life. (CMP-13) Encapsulation “m”. Type of protection where electrical parts that could ignite an explosive atmosphere by either sparking or heating are enclosed in a compound in such a way that this explosive atmosphere cannot be ignited. (CMP-14) Informational Note: See ANSI/UL 60079-18, Explosive atmospheres — Part 18: Equipment protection by encapsulation “m”, for additional information. Enclosed. Surrounded by a case, housing, fence, or wall(s) that prevents persons from accidentally contacting energized parts. (CMP-1) Enclosed-Break. Having electrical make-or-break contacts such that, if an internal explosion of the flammable gas or vapor that can enter it occurs, the device will withstand the internal explosion without suffering damage and without communicating the internal explosion to the external flammable gas or vapor.(CMP-14) Informational Note: See ANSI/UL 121201, Nonincendive Electrical Equipment for Use in Class I and II, Division 2 and Class III, Divisions 1 and 2 Hazardous (Classified) Locations, for additional information. Enclosure. The case or housing of apparatus, or the fence or walls surrounding an installation to prevent personnel from accidentally contacting energized parts or to protect the equipment from physical damage. (CMP-1) Informational Note: See Table 110.28 for examples of enclosure types. ENHANCED CONTENT Collapse Enclosures are required by 110.28 to be marked with a number that identifies the environmental conditions in which that type of enclosure can be used. Enclosures that comply with the requirements for more than one type of enclosure are marked with multiple designations. See 110.28 and its enhanced content for details on enclosure markings and types, and see Table 110.28 for a list of the types of enclosures required to be used in specific locations. Energized. Electrically connected to, or is, a source of voltage. (CMP-1) ENHANCED CONTENT Collapse The term energized is not limited to equipment that is “connected to a source of voltage.” Equipment such as batteries, capacitors, and conductors with induced voltages must also be considered energized. Energized, Likely to Become. (Likely to Become Energized) Conductive material that could become energized because of the failure of electrical insulation or electrical spacing. (CMP-5) Energy Management System (EMS). A system consisting of any of the following: a monitor(s), communications equipment, a controller(s), a timer(s), or other device(s) that monitors and/or controls an electrical load or a power production or storage source. (CMP-13) Energy Storage System (ESS). One or more devices installed as a system capable of storing energy and providing electrical energy into the premises wiring system or an electric power production and distribution network. (CMP-13) Informational Note No. 1: An ESS(s) can include but is not limited to batteries, capacitors, and kinetic energy devices (e.g., flywheels and compressed air). An ESS(s) can include inverters or converters to change voltage levels or to make a change between an ac or a dc system. Informational Note No. 2: These systems differ from a stationary standby battery installation where a battery spends the majority of the time on continuous float charge or in a high state of charge, in readiness for a discharge event. Entertainment Device. A mechanical or electromechanical device that provides an entertainment experience. (522) (CMP-15) Informational Note: These devices can include animated props, show action equipment, animated figures, and special effects, coordinated with audio and lighting to provide an entertainment experience. Equipment. A general term, including fittings, devices, appliances, luminaires, apparatus, machinery, and the like used as a part of, or in connection with, an electrical installation. (CMP-1) Equipment, Mobile. (Mobile Equipment) Equipment with electrical components that is suitable to be moved only with mechanical aids or is provided with wheels for movement by a person(s) or powered devices. (513) (CMP-14) Equipment, Portable. (Portable Equipment) Equipment fed with portable cords or cables intended to be moved from one place to another. (640) (CMP-12) Equipment, Portable. (Portable Equipment) Equipment with electrical components suitable to be moved by a single person without mechanical aids. (511) (CMP-14) Equipment, Portable. (Portable Equipment) Equipment fed with portable cords or cables intended to be moved from one place to another. (520) (CMP-15) Equipment, Portable. (Portable Equipment) Equipment intended to be moved from one place to another. (530) (CMP-15) Equipment, Signal. (Signal Equipment) Includes audible and visual equipment such as chimes, gongs, lights, and displays that convey information to the user. (620) (CMP-12) Equipment Branch. A system of feeders and branch circuits arranged for delayed, automatic, or manual connection to the alternate power source and that serves primarily 3-phase power equipment. [99:3.3.50] (517) (CMP-15) Equipment Protection Level (EPL). Level of protection assigned to equipment based on its likelihood of becoming a source of ignition, and distinguishing the differences between explosive gas atmospheres and explosive dust atmospheres. (CMP-14) Informational Note: See ANSI/UL 60079-0, Explosive Atmospheres — Part 0: Equipment — General Requirements, for additional information. Equipment Rack. A framework for the support, enclosure, or both, of equipment; can be portable or stationary. (640) (CMP-12) Informational Note: See EIA/ECA 310-E-2005, Cabinets, Racks, Panels and Associated Equipment, for examples of equipment racks. ENHANCED CONTENT Collapse Energy Information Administration (EIA)/Energy Analytics Institute (ECA) 310-D, Cabinets, Racks, Panels and Associated Equipment, is the standard for commercial equipment racks. Within Article 640, both the terms equipment rack and rack are used to refer to equipment enclosures that are conceptually similar in intended use to those defined by the American National Standards Institute (ANSI)/EIA standard. Equipotential Plane. Conductive parts bonded together to reduce voltage gradients in a designated area. (682) (CMP-17) Equipotential Plane. Conductive elements that are connected together to minimize voltage differences. (CMP-7) Essential Electrical System. A system comprised of alternate power sources and all connected distribution systems and ancillary equipment, designed to ensure continuity of electrical power to designated areas and functions of a health care facility during disruption of normal power sources, and also to minimize disruption within the internal wiring system. [99:3.3.52] (517) (CMP-15) ENHANCED CONTENT Collapse Emergency systems in occupancies other than health care occupancies are installed primarily for life safety and building evacuation. The essential system in a hospital supplies power to equipment that provides life safety functions such as egress lighting and exit marking. It also supplies power to equipment directly related to patient care, including task illumination, fixed medical equipment, selected receptacles, and other special power circuits. Explosionproof Equipment. Equipment enclosed in a case that is capable of withstanding an explosion of a specified gas or vapor that might occur within it, that is capable 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. (CMP-14) Informational Note No. 1: See ANSI/UL 1203, Explosion-Proof and Dust-Ignition-Proof Electrical Equipment for Use in Hazardous (Classified) Locations, for additional information. Informational Note No. 2: See NEMA 250, Enclosures for Electrical Equipment (1000 Volts Maximum), for additional information on explosionproof enclosures that are sometimes additionally marked Type 7. Exposed (as applied to live parts). Capable of being inadvertently touched or approached nearer than a safe distance by a person. (CMP-1) Informational Note: This term applies 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. (CMP-1) ENHANCED CONTENT Collapse The exhibit below illustrates wiring methods that would be considered exposed because they are located above a suspended ceiling with lift-out panels. Exposed (Optical Fiber Cable Exposed to Accidental Contact). A conductive optical fiber cable in such a position that, in case of failure of supports or insulation, contact between the cable’s non–current-carrying conductive members and an electrical circuit might result. (CMP-16) Exposed (to Accidental Contact). A circuit in such a position that, in case of failure of supports or insulation, contact with another circuit may result. (CMP-16) Exposed Conductive Surfaces. Those surfaces that are capable of carrying electric current and that are unprotected, uninsulated, unenclosed, or unguarded, permitting personal contact. [99:3.3.54] (517) (CMP-15) Informational Note: Paint, anodizing, and similar coatings are not considered suitable insulation, unless they are listed for such use. Externally Operable. Capable of being operated without exposing the operator to contact with live parts. (CMP-1) Facility, On-Site Power Production. (On-Site Power Production Facility) The normal supply of electric power for the site that is expected to be constantly producing power. (695) (CMP-13) ENHANCED CONTENT Collapse An on-site power production facility differs in normal application from an on-site standby system such as an engine generator in that it is the normal continuous source of electrical supply for a structure and is not a utility-owned generating facility. The exhibit below illustrates a cogeneration facility that is the normal source of power for the premises wiring system and meets the definition of on-site power production facility. On-site power production is not restricted to generators. Fastened-in-Place. Mounting means of equipment in which the fastening means are specifically designed to permit removal without the use of a tool. (625) (CMP-12) Fault-Managed Power (FMP). A powering system that monitors for faults and controls current delivered to ensure fault energy is limited. (726) (CMP-3) Informational Note No. 1: The monitoring and control systems differentiate fault-managed power from electric light and powe