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P-9) Transition Assembly. An assembly to facilitate connection of the flat conductor cable (Type FCC) system to other wiring systems, incorporating (1) a means of electrical interconnection and (2) a suitable box or covering for providing electrical safety and protection against physical damage. (32...

P-9) Transition Assembly. An assembly to facilitate connection of the flat conductor cable (Type FCC) system to other wiring systems, incorporating (1) a means of electrical interconnection and (2) a suitable box or covering for providing electrical safety and protection against physical damage. (324) (CMP-6) Transport Refrigerated Unit (TRU). A trailer or container, with integrated cooling or heating, or both, used for the purpose of maintaining the desired environment of temperature-sensitive goods or products. (626) (CMP-12) Transportable. X-ray equipment that is to be installed in a vehicle or that may be readily disassembled for transport in a vehicle. (660) (CMP-12) Truck. A motor vehicle designed for the transportation of goods, services, and equipment. (626) (CMP-12) Truck Coupler. A truck flanged surface inlet and mating cord connector. (626) (CMP-12) Truck Flanged Surface Inlet. The device(s) on the truck into which the connector(s) is inserted to provide electric energy and other services. This device is part of the truck coupler. For the purposes of this article, the truck flanged surface inlet is considered to be part of the truck and not part of the electrified truck parking space supply equipment. (626) (CMP-12) Trunk Cable. A portable extension cable containing six or more branch circuits, a male multipole plug, and a female multipole receptacle. (520) (CMP-15) Tubing, Electrical Metallic (EMT). (Electrical Metallic Tubing) An unthreaded thinwall raceway of circular cross section designed for the physical protection and routing of conductors and cables and for use as an equipment grounding conductor when installed utilizing appropriate fittings. (CMP-8) Tubing, Electrical Nonmetallic (ENT). (Electrical Nonmetallic Tubing) A nonmetallic, pliable, corrugated raceway of circular cross section with integral or associated couplings, connectors, and fittings for the installation of electrical conductors. It is composed of a material that is resistant to moisture and chemical atmospheres and is flame retardant. A pliable raceway is a raceway that can be bent by hand with a reasonable force but without other assistance. (CMP-8) Tubing, Flexible Metallic (FMT). (Flexible Metallic Tubing) A metal raceway that is circular in cross section, flexible, and liquidtight without a nonmetallic jacket. (CMP-8) Two-Fer. An assembly containing one male plug and two female cord connectors used to connect two loads to one branch circuit. (520) (CMP-15) ENHANCED CONTENT Collapse A two-fer consists of two cord connectors on separate cords connected to a single supply cord. Type of Protection “n”. Type of protection where electrical equipment, in normal operation, is not capable of igniting a surrounding explosive gas atmosphere and a fault capable of causing ignition is not likely to occur. (CMP-14) Informational Note: See ANSI/UL 60079-15, Explosive Atmospheres — Part 15: Equipment Protection by Type of Protection “n”, for additional information. Ungrounded. Not connected to ground or to a conductive body that extends the ground connection. (CMP-5) Uninterruptible Power Supply (UPS). A device or system that provides quality and continuity of ac power through the use of a stored-energy device as the backup power source for a period of time when the normal power supply is incapable of performing acceptably. (CMP-13) Unit Equipment. A battery-equipped emergency luminaire that illuminates only as part of the emergency illumination system and is not illuminated when the normal supply is available. (CMP-13) Utilization Equipment. Equipment that utilizes electric energy for electronic, electromechanical, chemical, heating, lighting, or similar purposes. (CMP-1) Valve Actuator Motor (VAM) Assemblies. A manufactured assembly, used to operate a valve, consisting of an actuator motor and other components such as motor controllers, torque switches, limit switches, and overload protection. (430) (CMP-11) Informational Note: VAMs typically have short-time duty and high-torque characteristics. Ventilated. Provided with a means to permit circulation of air sufficient to remove an excess of heat, fumes, or vapors. (CMP-14) ENHANCED CONTENT Collapse See also 110.13(B) and its enhanced content for information on cooling of equipment. Vessel. A container such as a barrel, drum, or tank for holding fluids or other material. (CMP-17) Volatile Flammable Liquid. A flammable liquid having a flash point below 38°C (100°F), or a flammable liquid whose temperature is above its flash point, or a Class II combustible liquid that has a vapor pressure not exceeding 276 kPa (40 psia) at 38°C (100°F) and whose temperature is above its flash point. (CMP-14) ENHANCED CONTENT Collapse The flash point is defined as the minimum temperature of a liquid at which sufficient vapor is given off to form an ignitible mixture with the air, near the surface of the liquid or within the vessel used to contain the liquid. An ignitible mixture is defined as a mixture within the explosive or flammable range (between upper and lower limits) that is capable of the propagation of flame away from the source of ignition when ignited. Some emission of vapors takes place below the flash point but not enough to form an ignitible mixture. Voltage (of a circuit). The greatest root-mean-square (rms) (effective) difference of potential between any two conductors of the circuit concerned. (CMP-1) Informational Note: Some systems, such as 3-phase 4-wire, single-phase 3-wire, and 3-wire direct current, may have various circuits of various voltages. ENHANCED CONTENT Collapse Common 3-phase, 4-wire wye systems are 480/277 volts and 208/120 volts. The voltage of the circuit is the higher voltage between any two-phase conductors (i.e., 480 volts or 208 volts). The voltage of a single-phase, 2-wire feeder or branch-circuit (with a grounded conductor) derived from these systems would be the voltage between the two conductors (i.e., 277 volts or 120 volts). The same applies to dc or single-phase, 3-wire systems where there are two voltages. Voltage, High. (High Voltage) A potential difference of more than 1000 volts, nominal. (CMP-9) Informational Note: Circuits and equipment rated at potential differences of more than 1000 volts and up to 52 kV are also commonly referred to as medium voltage. Voltage, Low. (Low Voltage). An electromotive force rated 24 volts, nominal, or less. (551) (CMP-7) Voltage, Nominal. (Nominal Voltage) A nominal value assigned to a circuit or system for the purpose of conveniently designating its voltage class (e.g., 120/240 volts, 480Y/277 volts, 600 volts). (CMP-1) Informational Note No. 1: The actual voltage at which a circuit operates can vary from the nominal within a range that permits satisfactory operation of equipment. Informational Note No. 2: See ANSI C84.1-2011, Voltage Ratings for Electric Power Systems and Equipment (60 Hz). ENHANCED CONTENT Collapse See also 220.5(A), which provides nominal voltages for use in computing branch-circuit and feeder loads. Voltage, Nominal (as applied to battery or cell).(Nominal Voltage) The value assigned to a cell or battery of a given voltage class for the purpose of convenient designation. The operating voltage of the cell or battery may vary above or below this value. (CMP-13) Informational Note: The most common nominal cell voltages are 2 volts per cell for the lead-acid batteries, 1.2 volts per cell for alkali batteries, and 3.2 to 3.8 volts per cell for Li-ion batteries. Nominal voltages might vary with different chemistries. Voltage to Ground. For grounded circuits, the voltage between the given conductor and that point or conductor of the circuit that is grounded; for ungrounded circuits, the greatest voltage between the given conductor and any other conductor of the circuit. (CMP-1) ENHANCED CONTENT Collapse This definition can be best illustrated using examples. For a 3-phase, 4-wire delta system with the center of one leg grounded, there are three voltages to ground — that is, on a 240-volt system, two legs would each have 120 volts to ground, and the third, commonly referred to as the “high leg,” would have 208 volts to ground. See also 110.15, 230.56, and 408.3(E) for requirements pertaining to special markings and arrangements on such circuit conductors. Watertight. Constructed so that moisture will not enter the enclosure under specified test conditions. (CMP-1) Weatherproof. Constructed or protected so that exposure to the weather will not interfere with successful operation. (CMP-1) Informational Note: Rainproof, raintight, or watertight equipment can fulfill the requirements for weatherproof where varying weather conditions other than wetness, such as snow, ice, dust, or temperature extremes, are not a factor. Wharf. A structure at the shoreline that has a platform built along and parallel to a body of water with either an open deck or a superstructure. [307:3.3.28] (555) (CMP-7) Wind Turbine. A mechanical device that converts wind energy to electrical energy. (CMP-4) Wind Turbine Output Circuit. (Turbine Output Circuit) The circuit conductors between the internal components of a wind turbine (which might include an alternator, integrated rectifier, controller, and/or inverter) and other equipment. (694) (CMP-4) Wire. A factory assembly of one or more insulated conductors without an overall covering. (805) (CMP-16) Wireless Power Transfer (WPT). The transfer of electrical energy from a power source to an electrical load via magnetic fields by a contactless means between a primary device and a secondary device. (625) (CMP-12) Wireless Power Transfer Equipment (WPTE). Equipment installed specifically for the purpose of transferring energy between the premises wiring and the electric vehicle without physical electrical contact. (625) (CMP-12) Informational Note No. 1: The general form of WPTE consists of two physical packages: a control box and a primary pad. Informational Note No. 2: Electric vehicle power export equipment and wireless power transfer equipment are sometimes contained in one set of equipment, sometimes referred to as a bidirectional WPTE. Wireways, Metal. (Metal Wireways) Sheet metal troughs with hinged or removable covers for housing and protecting electrical wires and cable and in which conductors are laid in place after the raceway has been installed as a complete system. (CMP-8) Wireways, Nonmetallic. (Nonmetallic Wireways) Flame-retardant, nonmetallic troughs with removable covers for housing and protecting electrical wires and cables in which conductors are laid in place after the raceway has been installed as a complete system. (CMP-8) Work Surface. A fixed, stationary, or portable surface typically intended for dry use and for tasks other than food preparation, personal lavation, or laundering that presents an incidental risk of spillage of smaller quantities of beverages and other liquids upon outlets mounted directly on or recessed in the surface. (CMP-2) Informational Note No. 1: See UL 111, Outline of Investigation for Multioutlet Assemblies, and UL 962A, Furniture Power Distribution Units, which establish the performance evaluation criteria and construction criteria. Informational Note No. 2: See 406.5(F), 406.5(G)(1), and 406.5(H) for information on receptacles for work surfaces distinguished from receptacles for counters and countertops. Zone. A physically identifiable area (such as barriers or separation by distance) within an information technology equipment room, with dedicated power and cooling systems for the information technology equipment or systems. (645) (CMP-12) Article 110 General Requirements for Electrical Installations Part I. General 110.1 Scope. This article covers general requirements for the examination and approval, installation and use, access to and spaces about electrical conductors and equipment; enclosures intended for personnel entry; and tunnel installations. Informational Note: See Informative Annex J for information regarding ADA accessibility design. 110.2 Approval. The conductors and equipment required or permitted by this Code shall be acceptable only if approved. Informational Note: See 90.7, Examination of Equipment for Safety, and 110.3, Examination, Identification, Installation, and Use of Equipment. See definitions of Approved, Identified, Labeled, and Listed. ENHANCED CONTENT Collapse Approval of electrical equipment is the responsibility of the authority having jurisdiction (AHJ). Many approvals are based on tests and listings of testing laboratories. Unique equipment is often approved following a field evaluation by a qualified third-party laboratory or qualified individual. 110.3 Examination, Identification, Installation, Use, and Listing (Product Certification) of Equipment. ENHANCED CONTENT Collapse Listing or labeling is the most common method of establishing suitability. This section does not require listing or labeling of equipment, but it does require considerable evaluation for approval. Before approving the installation, the AHJ may require evidence of compliance with 110.3. (A) Examination. In judging equipment, considerations such as the following shall be evaluated: * (1) Suitability for installation and use in conformity with this Code Informational Note No. 1: Equipment may be new, reconditioned, refurbished, or remanufactured. Informational Note No. 2: Suitability of equipment use may be identified by a description marked on or provided with a product to identify the suitability of the product for a specific purpose, environment, or application. Special conditions of use or other limitations and other pertinent information may be marked on the equipment, included in the product instructions, or included in the appropriate listing and labeling information. Suitability of equipment may be evidenced by listing or labeling. * (2) Mechanical strength and durability, including, for parts designed to enclose and protect other equipment, the adequacy of the protection thus provided * (3) Wire-bending and connection space * (4) Electrical insulation * (5) Heating effects under normal conditions of use and also under abnormal conditions likely to arise in service * (6) Arcing effects * (7) Classification by type, size, voltage, current capacity, and specific use * (8) Cybersecurity for network-connected life safety equipment to address its ability to withstand unauthorized updates and malicious attacks while continuing to perform its intended safety functionality Informational Note No. 3: See the ANSI/ISA 62443 series of standards for industrial automation and control systems, the UL 2900 series of standards for software cybersecurity for network-connectable products, and UL 5500, Standard for Remote Software Updates, which are standards that provide frameworks to mitigate current and future security cybersecurity vulnerabilities and address software integrity in systems of electrical equipment. * (9) Other factors that contribute to the practical safeguarding of persons using or likely to come in contact with the equipment ENHANCED CONTENT Collapse Examples of “special conditions of use” include elevated or reduced ambient temperatures, special environmental limitations, stringent power quality requirements, and specific types of overcurrent protective devices (OCPDs). The additional information needed for such special cases might be marked on the equipment, included as part of the listing information in a listing directory, or included in the information furnished with the equipment. (B) Installation and Use. Equipment that is listed, labeled, or both, or identified for a use shall be installed and used in accordance with any instructions included in the listing, labeling, or identification. Informational Note: The installation and use instructions may be provided in the form of printed material, quick response (QR) code, or the address on the internet where users can download the required instructions. ENHANCED CONTENT Collapse Manufacturers’ listing and labeling installation instructions must be followed, even if the equipment itself is not required to be listed. For example, 210.52 permits permanently installed electric baseboard heaters to be equipped with receptacle outlets that meet the requirements for the wall space utilized by such heaters. The installation instructions for permanent baseboard heaters indicate that the heaters should not be mounted beneath a receptacle. In dwelling units, the use of low-density heating units more than 12 feet in length is common. Therefore, to meet the requirements of 210.52(A) and the installation instructions, a receptacle must either be part of the heating unit or be installed in the floor close to the wall but not above the heating unit. The Informational Note to 210.52 provides specific details. Listing and labeling are the most common methods of establishing suitability. This section does not require listing or labeling of equipment. Before approving the installation, the AHJ may require evidence of compliance with 110.3. Some sections do require listed or labeled equipment. For example, 250.8 specifies “listed pressure connectors . . . pressure connectors listed as grounding and bonding equipment [or] . . . other listed means” as connection methods for grounding and bonding conductors. Listing organizations typically require the use of their listing mark on the equipment as the means of determining if the product is listed. Where it is impractical to have the listing mark on the equipment, the listing organization usually requires that the listing mark be on the smallest unit container in which the product is packaged. Since 110.3(B) requires compliance with the listing requirements, the appropriate certification mark is required if that is a requirement of the listing entity. (C) Listing. Product testing, evaluation, and listing (product certification) shall be performed by recognized qualified electrical testing laboratories and shall be in accordance with applicable product standards recognized as achieving equivalent and effective safety for equipment installed to comply with this Code. Informational Note: The Occupational Safety and Health Administration (OSHA) recognizes qualified electrical testing laboratories that perform evaluations, testing, and certification of certain products to ensure that they meet the requirements of both the construction and general industry OSHA electrical standards. If the listing (product certification) is done under a qualified electrical testing laboratory program, this listing mark signifies that the tested and certified product complies with the requirements of one or more appropriate product safety test standards. 110.4 Voltages. The voltage considered shall be that at which the circuit operates. The voltage rating of electrical equipment shall not be less than the nominal voltage of a circuit to which it is connected. 110.5 Conductors. Conductors used to carry current shall be of copper, aluminum, or copper-clad aluminum unless otherwise provided in this Code. If the conductor material is not specified, the sizes given in this Code shall apply to copper conductors. If other materials are used, the size shall be changed accordingly. ENHANCED CONTENT Collapse See also 310.3(B), which specifies the alloy for aluminum conductors and for copper- clad aluminum conductors. 110.6 Conductor Sizes. Conductor sizes are expressed in American Wire Gauge (AWG) or in circular mils. ENHANCED CONTENT Collapse For copper, aluminum, or copper-clad aluminum conductors up to size 4/0 AWG, the NEC uses the American Wire Gage (AWG) for size identification, which is the same as the Brown and Sharpe (BS) Wire Gage. Wire sizes up to size 4/0 AWG are expressed as XX AWG, with XX being the wire size. Conductors larger than 4/0 AWG are sized in circular mils, beginning with 250,000 circular mils. Prior to the 1990 edition, a 250,000-circular mil conductor was labeled 250 MCM. The designation MCM was defined as 1000 circular mils (the first M being the roman numeral 1000). Beginning in the 1990 edition, the notation was changed to kcmil to recognize the accepted convention that k indicates 1000. UL standards and IEEE standards also use the notation kcmil rather than MCM. Table 8 in Chapter 9 and its associated commentary provide the circular mil area for AWG-sized conductors. Where stranded conductors are used, the circular mil area of each strand must be multiplied by the number of strands to determine the circular mil area of the conductor. 110.7 Wiring Integrity. Completed wiring installations shall be free from short circuits, ground faults, or any connections to ground other than as required or permitted elsewhere in this Code. ENHANCED CONTENT Collapse Failure of the insulation system is one of the most common causes of problems in electrical installations. The principal causes of insulation failures are heat, moisture, dirt, and physical damage (abrasion or nicks) occurring during and after installation. Some hazards are exposure to chemical attack, excessive voltage stresses, saltwater environments or flood waters, or even sunlight (UV degradation). Overcurrent protective devices must be selected and coordinated using tables of insulation thermal-withstand ability to ensure that the damage point of an insulated conductor is never reached. Those tables, entitled “Allowable Short-Circuit Currents for Insulated Copper (or Aluminum) Conductors,” are contained in the Insulated Cable Engineers Association publication ICEA P-32-382, Short-Circuit Characteristics of Insulated Cable. See also 110.10 for selection criteria for other circuit components. Insulation tests are performed on new or existing installations to determine the quality or condition of the insulation of conductors and equipment. In an insulation resistance test, a voltage ranging from 100 to 5000 (usually 500 to 1000 volts for systems of 1000 volts or less), supplied from a source of constant potential, is applied across the insulation. A megohmmeter is usually the potential source, and it indicates the insulation resistance directly on a scale calibrated in megohms (Mê). The quality of the insulation is evaluated based on the level of the insulation resistance. The field data obtained should be corrected to the standard temperature for the class of equipment being tested because insulation resistance of many types of insulation varies with temperature. The megohm value of insulation resistance obtained is inversely proportional to the volume of insulation tested. For example, a cable 1000 feet long would be expected to have one-tenth the insulation resistance of a cable 100 feet long if all other conditions are identical. Pictured below is a typical megohmmeter insulation tester. Information on specific test methods is available from instrument manufacturers. (Reproduced with permission, Fluke Corporation) For more information on test methods and on establishing a preventive maintenance program, see NFPA 70B, Recommended Practice for Electrical Equipment Maintenance. 110.8 Wiring Methods. Only wiring methods recognized as suitable are included in this Code. The recognized methods of wiring shall be permitted to be installed in any type of building, occupancy, or premises wiring system, except as otherwise provided in this Code. 110.9 Interrupting Rating. Equipment intended to interrupt current at fault levels shall have an interrupting rating at nominal circuit voltage at least equal to the available fault current at the line terminals of the equipment. Equipment intended to interrupt current at other than fault levels shall have an interrupting rating at nominal circuit voltage at least equal to the current that must be interrupted. ENHANCED CONTENT Collapse Fuses or circuit breakers that do not have adequate interrupting ratings could rupture while attempting to clear a short circuit. The interrupting rating of an overcurrent protective device is determined under standard test conditions. The rating should meet or exceed the actual installation needs. Interrupting ra