xat

hment plugs and cords with three or more wires (including the equipment grounding conductor), shall have means to identify the terminal for the grounded circuit conductor (if any). 200.11 Polarity of Connections. No grounded conductor shall be attached to any terminal or lead so as to reverse the de...

hment plugs and cords with three or more wires (including the equipment grounding conductor), shall have means to identify the terminal for the grounded circuit conductor (if any). 200.11 Polarity of Connections. No grounded conductor shall be attached to any terminal or lead so as to reverse the designated polarity. Article 210 Branch Circuits Not Over 1000 Volts ac, 1500 Volts dc, Nominal Part I. General 210.1 Scope. This article provides the general requirements for branch circuits not over 1000 volts ac, 1500 volts dc, nominal. Informational Note: See Part II of Article 235 for requirements for branch circuits over 1000 volts ac, 1500 volts dc, nominal. 210.2 Reconditioned Equipment. The following shall not be reconditioned: * (1) Equipment that provides ground-fault circuit-interrupter protection for personnel * (2) Equipment that provides arc-fault circuit-interrupter protection 210.3 Other Articles for Specific-Purpose Branch Circuits. Table 210.3 lists references for specific equipment and applications not located in Chapters 5, 6, and 7 that amend or supplement the requirements of this article. Table 210.3 Specific-Purpose Branch Circuits Equipment Article Section Air-conditioning and refrigerating equipment 440.6, 440.31, and 440.32 Busways 368.17 Central heating equipment other than fixed electric space-heating equipment 422.12 Fixed electric heating equipment for pipelines and vessels 427.4 Fixed electric space-heating equipment 424.4 Fixed outdoor electrical deicing and snow- melting equipment 426.4 Infrared lamp industrial heating equipment 422.48 and 424.3 Motors, motor circuits, and controllers 430 Switchboards and panelboards 408.52 210.4 Multiwire Branch Circuits. (A) General. Branch circuits recognized by this article shall be permitted as multiwire circuits. A multiwire circuit shall be permitted to be considered as multiple circuits. Except as permitted in 300.3(B)(4), all conductors of a multiwire branch circuit shall originate from the equipment containing the branch-circuit overcurrent protective device or protective devices. Informational Note No. 1: A 3-phase, 4-wire, wye-connected power system used to supply power to nonlinear loads might necessitate that the power system design allow for the possibility of high harmonic currents on the neutral conductor. Informational Note No. 2: See 300.13(B) for continuity of grounded conductors on multiwire circuits. ENHANCED CONTENT Collapse Using a multiwire branch circuit as multiple circuits satisfies the requirement for providing two small appliance branch circuits for countertop receptacle outlets in a dwelling unit kitchen. Power supplies for equipment such as computers, printers, electric-discharge lighting systems, and adjustable-speed motor drives can introduce harmonic currents in the system neutral conductor. The resulting total harmonic distortion current could exceed the load current of the device itself. See also 310.15(E) and its enhanced content for information on neutral conductor ampacity. (B) Disconnecting Means. Each multiwire branch circuit shall be provided with a means that will simultaneously disconnect all ungrounded conductors at the point where the branch circuit originates. Informational Note: See 240.15(B) for information on the use of single-pole circuit breakers as the disconnecting means. ENHANCED CONTENT Collapse A simultaneous disconnecting means reduces the risk of shock to personnel working on equipment supplied by the multiwire branch circuit. In former editions of the NEC, this requirement applied only where the multiwire branch circuit supplied equipment mounted to a common yoke or strap. For a single-phase installation, the disconnecting means could be two single- pole circuit breakers with an identified handle tie or a 2-pole circuit breaker, as shown in the exhibit below. For a 3-phase installation, a 3-pole circuit breaker, three single-pole circuit breakers with an identified handle tie, or a 3-pole switch with branch circuit overcurrent protection provides the required simultaneous opening of the ungrounded conductors. (C) Line-to-Neutral Loads. Multiwire branch circuits shall supply only line-to-neutral loads. Exception No. 1: A multiwire branch circuit that supplies only one utilization equipment shall be permitted to supply line-to-line loads. Exception No. 2: A multiwire branch circuit shall be permitted to supply line-to-line loads if all ungrounded conductors of the multiwire branch circuit are opened simultaneously by the branch-circuit overcurrent device. ENHANCED CONTENT Collapse A multiwire branch circuit is a branch circuit that consists of two or more ungrounded conductors that have a voltage between them, and a grounded conductor that has equal voltage between it and each ungrounded conductor of the circuit and that is connected to the neutral or grounded conductor of the system. The most commonly used multiwire branch circuit consists of two ungrounded conductors and one grounded conductor supplied from a 120/240-volt, single-phase, 3-wire system. Such multiwire circuits supply appliances that have both line-to-line and line-to-neutral connected loads, such as electric ranges and clothes dryers, or supply loads that are line-to- neutral connected only, such as the split-wired combination device shown in the exhibit below. A single-phase, 120/240-volt multiwire branch circuit is also permitted to supply a device with a 250-volt rated receptacle (line-to-line) and a 125-volt rated receptacle (line-to-neutral), as shown in the exhibit below, provided the branch-circuit overcurrent device simultaneously opens both of the ungrounded conductors. Multiwire branch circuits have many advantages, including using three wires to do the work of four (in place of two 2-wire circuits), less raceway fill, easier balancing and phasing of a system, and less voltage drop. Multiwire branch circuits can be derived from a 120/240-volt, single-phase system; a 208Y/120- volt and 480Y/277-volt, 3-phase, 4-wire system; or a 240/120-volt, 3-phase, 4- wire delta system. If two ungrounded conductors and a common neutral of a multiwire branch circuit are supplied from a 208Y/120-volt, 3-phase, 4-wire system, the neutral carries the same current as the phase conductor with the highest current and, therefore, should be the same size. If loads are connected line-to-line (i.e., utilization equipment connected between 2 or 3 phases), 2-pole or 3-pole circuit breakers are required to disconnect all ungrounded conductors simultaneously. Use of single-pole circuit breakers with handle ties for 240-volt equipment might not open all ungrounded conductors. See also… * 210.19 and its enhanced content for more on voltage drop for branch circuits * 210.4(A) and its enhanced content for more on 3-phase, 4-wire system neutral conductors * 240.15(B)(1) for more on circuit breaker overcurrent protection of ungrounded conductors on multiwire branch circuits * 300.13(B) and its enhanced content for hazards associated with device removal on multiwire branch circuits (D) Grouping. The ungrounded and grounded circuit conductors of each multiwire branch circuit shall be grouped in accordance with 200.4(B). 210.5 Identification for Branch Circuits. (A) Grounded Conductor. The grounded conductor of a branch circuit shall be identified in accordance with 200.6. (B) Equipment Grounding Conductor. The equipment grounding conductor shall be identified in accordance with 250.119. (C) Identification of Ungrounded Conductors. Ungrounded conductors shall be identified in accordance with 210.5(C)(1) or (2), as applicable. (1) Branch Circuits Supplied from More Than One Nominal Voltage System. Where the premises wiring system has branch circuits supplied from more than one nominal voltage system, each ungrounded conductor of a branch circuit shall be identified by phase or line and by nominal voltage system at all termination, connection, and splice points in accordance with 210.5(C)(1)(a) and (C)(1)(b). Different systems within the same premises that have the same nominal voltage shall be permitted to use the same identification. * (a) Means of Identification. The means of identification shall be permitted to be by separate color coding, marking tape, tagging, or other approved means. * (b) Posting of Identification Means. The method used for conductors originating within each branch-circuit panelboard or similar branch- circuit distribution equipment shall be documented in a manner that is readily available or shall be permanently posted at each branch-circuit panelboard or similar branch-circuit distribution equipment. The label shall be of sufficient durability to withstand the environment involved and shall not be handwritten. Exception: In existing installations where a voltage system(s) already exists and a different voltage system is being added, it shall be permissible to mark only the new system voltage. Existing unidentified systems shall not be required to be identified at each termination, connection, and splice point in accordance with 210.5(C)(1)(a) and (C)(1)(b). Labeling shall be required at each voltage system distribution equipment to identify that only one voltage system has been marked for a new system(s). The new system label(s) shall include the words “other unidentified systems exist on the premises.” ENHANCED CONTENT Collapse The requirement for the identification of ungrounded branch-circuit conductors covers all branch-circuit configurations. The identification requirement applies only where more than one nominal voltage system supplies branch circuits (e.g., a 208Y/120-volt system and a 480Y/277-volt system) and requires that the conductors be identified by system and phase. Different systems within the same premises having the same system voltage class do not have to be identified differently. For example, in a building with five transformers on different floors supplying multiple 208Y/120-volt, three- phase, 4-wire separately derived systems to supply lighting and receptacle loads, the branch circuits conductors supplied from the five different systems having the same voltage characteristics can be identified using a common conductor identification system or scheme throughout the building. Unlike the requirement of 200.6(D) for identifying the grounded conductors supplied from different voltage systems, application of this requirement is not predicated on the different system conductors sharing a common raceway, cabinet, or enclosure. Means of Identification. Although color coding is a popular method, other types of marking or tagging are acceptable alternatives. Whatever identification method is used, it must be consistent throughout the premises. This affords a higher level of safety for personnel working on premises electrical systems having ungrounded conductors supplied from multiple nominal voltage systems. If the identification legend is posted at electrical distribution equipment, the marking has to describe only the identification scheme for the ungrounded conductors supplied from that particular equipment. The exhibit below shows an example of two different nominal voltage systems in a building. Each ungrounded system conductor is identified by color-coded marking tape. A label indicating the means of the identification is permanently located at each panelboard. Although there are commonly employed color schemes used in the electrical industry, the NEC only specifies color designations of ungrounded conductors for a few applications including heating cables, intrinsically safe circuits, isolated systems in health care facilities, or 4-wire delta (high-leg) systems. For identification of dc systems, see 210.5(C)(2). Exception. Systems installed prior to the adoption of the 2005 NEC were not required to be identified. The NEC is not retroactive, so only new installations would require identification. However, if existing installations are not marked, this section requires the new installation labeling to include a warning indicating there are existing unidentified systems. (2) Branch Circuits Supplied from Direct-Current Systems. Where a branch circuit is supplied from a dc system operating at more than 60 volts, each ungrounded conductor of 4 AWG or larger shall be identified by polarity at all termination, connection, and splice points by marking tape, tagging, or other approved means; each ungrounded conductor of 6 AWG or smaller shall be identified by polarity at all termination, connection, and splice points in compliance with 210.5(C)(2)(a) and (b). The identification methods utilized for conductors originating within each branch-circuit panelboard or similar branch-circuit distribution equipment shall be documented in a manner that is readily available or shall be permanently posted at each branch-circuit panelboard or similar branch-circuit distribution equipment. * (a) Positive Polarity, Sizes 6 AWG or Smaller. Where the positive polarity of a dc system does not serve as the connection point for the grounded conductor, each positive ungrounded conductor shall be identified by one of the following means: o (1) A continuous red outer finish o (2) A continuous red stripe durably marked along the conductor’s entire length on insulation of a color other than green, white, gray, or black o (3) Imprinted plus signs (+) or the word POSITIVE or POS durably marked on insulation of a color other than green, white, gray, or black and repeated at intervals not exceeding 610 mm (24 in.) in accordance with 310.8(B) o (4) An approved permanent marking means such as sleeving or shrink-tubing that is suitable for the conductor size, at all termination, connection, and splice points, with imprinted plus signs (+) or the word POSITIVE or POS durably marked on insulation of a color other than green, white, gray, or black * (b) Negative Polarity, Sizes 6 AWG or Smaller. Where the negative polarity of a dc system does not serve as the connection point for the grounded conductor, each negative ungrounded conductor shall be identified by one of the following means: * (1) A continuous black outer finish * (2) A continuous black stripe durably marked along the conductor’s entire length on insulation of a color other than green, white, gray, or red * (3) Imprinted minus signs (-) or the word NEGATIVE or NEG durably marked on insulation of a color other than green, white, gray, or red and repeated at intervals not exceeding 610 mm (24 in.) in accordance with 310.8(B) * (4) An approved permanent marking means such as sleeving or shrink- tubing that is suitable for the conductor size, at all termination, connection, and splice points, with imprinted minus signs (-) or the word NEGATIVE or NEG durably marked on insulation of a color other than green, white, gray, or red ENHANCED CONTENT Collapse The requirements for the identification of ungrounded conductors are based on whether the system is negatively or positively grounded. Negatively grounded and positively grounded 2-wire dc systems must employ a grounded conductor identified in accordance with 200.6. Grounded conductors of negatively grounded and positively grounded 2-wire dc systems are also required to be identifiable and distinguishable from ungrounded conductors of 3-wire dc systems and of 2-wire dc systems employing high-impedance references to ground. The identification method must be documented and readily available, or it must be posted at each branch-circuit panelboard or branch-circuit distribution equipment. 210.6 Branch-Circuit Voltage Limitations. The nominal voltage of branch circuits shall not exceed the values permitted by 210.6(A) through (D). (A) Occupancy Limitation. In dwelling units and guest rooms or guest suites of hotels, motels, and similar occupancies, the voltage shall not exceed 120 volts, nominal, between conductors that supply the terminals of the following: * (1) Luminaires * (2) Cord-and-plug-connected loads 1440 volt-amperes, nominal, or less or less than 1/4 hp ENHANCED CONTENT Collapse The term similar occupancies in 210.6(A) refers to sleeping rooms in dormitories, fraternities, sororities, nursing homes, and other such facilities. This requirement is intended to reduce the exposure of residents in these types of occupancies to electric shock hazards when using or servicing permanently installed luminaires and cord-and-plug-connected portable lamps and appliances. Small loads, such as those of 1440 volt-amperes or less and motors of less than 1/4 horsepower, are limited to 120-volt circuits. High-wattage cord-and- plug-connected loads, such as electric ranges, clothes dryers, and some window air conditioners, could be connected to a 208-volt or 240-volt circuit. (B) 120 Volts Between Conductors. Circuits not exceeding 120 volts, nominal, between conductors shall be permitted to supply the following: * (1) The terminals of lampholders applied within their voltage ratings * (2) Auxiliary equipment of electric-discharge lamps Informational Note: See 410.137 for auxiliary equipment limitations. * (3) Cord-and-plug-connected or permanently connected utilization equipment ENHANCED CONTENT Collapse Auxiliary equipment includes ballasts and starting devices for fluorescent and high-intensity-discharge (e.g., mercury vapor, metal halide, and sodium) lamps. (C) 277 Volts to Ground. Circuits exceeding 120 volts, nominal, between conductors and not exceeding 277 volts, nominal, to ground shall be permitted to supply cord-and-plug- connected or permanently connected utilization equipment, or the following types of listed luminaires: * (1) Electric-discharge luminaires with integral ballasts * (2) LED luminaires with LED drivers between the branch circuit and the lampholders * (3) Incandescent or LED luminaires, equipped with medium-base or smaller screw shell lampholders, where the lampholders are supplied at 120 volts or less from the output of a stepdown autotransformer, LED driver, or other type of power supply that is an integral component of the luminaire Informational Note No. 1: See 410.90 for requirements regarding the connection of screw shell lampholders to grounded conductors. * (4) Luminaires equipped with mogul-base screw shell lampholders * (5) Luminaires equipped with lampholders, other than the screw shell type, when used within the voltage ratings of their lampholders * (6) Luminaires without lampholders Informational Note No. 2: Luminaires with nonserviceable LEDs are examples of luminaires without lampholders. * (7) Auxiliary equipment of electric-discharge or LED-type lamps Informational Note No. 3: See 410.137 for auxiliary equipment limitations. * (8) Luminaires converted with listed retrofit kits incorporating integral LED light sources or accepting LED lamps that also conform with 210.6(C)(1), (C)(2), (C)(3), (C)(4), or (C)(5) ENHANCED CONTENT Collapse An incandescent luminaire is permitted on a 277-volt circuit only if it is a listed luminaire with an integral autotransformer and an output to the lampholder that does not exceed 120 volts. In this application, the autotransformer supplies 120 volts to the lampholder, and the grounded conductor is connected to the screw shell of the lampholder. Listed light-emitting diode (LED) luminaires supplied by an integral LED driver with 120-volt output can be supplied by 277-volt circuits. This application is similar to a branch circuit derived from an autotransformer, except that the 120-volt circuit is the internal wiring of the luminaire. The exhibits below show some examples of luminaires permitted to be connected to branch circuits. Medium-base screw shell lampholders must not be directly connected to 277-volt branch circuits. Other types of lampholders may be connected to 277-volt circuits but only if the lampholders have a 277- volt rating. A 277- volt branch circuit may be connected to a listed electric- discharge luminaire or to a listed autotransformer-type incandescent luminaire with a medium-base screw shell lampholder. Typical examples of cord-and-plug-connected equipment include through-the- wall heating and air-conditioning units and restaurant deep fat fryers that operate at 480 volts, 3 phase, from a grounded wye system. Luminaires listed for and connected to a 480-volt source may be used in applications permitted by 210.6(C), provided the 480-volt system is in fact a grounded wye system that contains a grounded conductor (thus limiting the system “voltage to ground” to the 277-volt level). (D) 1000 Volts ac or 1500 Volts dc Between Conductors. Circuits exceeding 277 volts, nominal, to ground and not exceeding 1000 volts ac or 1500 volts dc, nominal, between conductors shall be permitted to supply the following: * (1) The auxiliary equipment of electric-discharge lamps mounted in permanently installed luminaires where the luminaires are mounted in accordance with one of the following: o a. Not less than a height of 6.7 m (22 ft) on poles or similar structures for the illumination of outdoor areas such as highways, roads, bridges, athletic fields, or parking lots o b. Not less than a height of 5.5 m (18 ft) on other structures such as tunnels Informational Note: See 410.137 for auxiliary equipment limitations. * (2) Cord-and-plug-connected or permanently connected utilization equipment other than luminaires * (3) Luminaires powered from direct-current systems where either of the following apply: o a. The luminaire contains a listed, dc-rated ballast that provides isolation between the dc power source and the lamp circuit and protection from electric shock when changing lamps. o b. The luminaire contains a listed, dc-rated ballast and has no provision for changing lamps. Exception No. 1 to (B), (C), and (D): For lampholders of infrared industrial heating appliances as provided in 425.14. Exception No. 2 to (B), (C), and (D): For railway properties as descri?bed in 110.19. 210.7 Multiple Branch Circuits. If two or more branch circuits supply devices or equipment on the same yoke or mounting strap, a means to simultaneously disconnect the ungrounded supply conductors shall be provided at the point at which the branch circuits originate. 210.8 Ground-Fault Circuit-Interrupter Protection for Personnel. A listed Class A GFCI shall provide protection in accordance with 210.8(A) through (F). The GFCI shall be installed in a readily accessible location. Informational Note: See 215.9 for GFCI protection on feeders. For the purposes of this section, the distance from receptacles shall be measured as the shortest path the power supply cord connected to the receptacle would follow without piercing a floor, wall, ceiling, or fixed barrier. ENHANCED CONTENT Collapse The Consumer Product Safety Commission (CPSC) has reported a decrease in the number of electrocutions in the United States since the introduction of ground-fault circuit-interrupter (GFCI) devices in the 1971 NEC. Most safety experts agree that GFCIs are directly responsible for saving numerous lives and preventing countless injuries. The exhibit below shows a typical circuit arrangement of a GFCI. The line conductors are passed through a sensor and are connected to a shunt-trip device. As long as the current in the conductors is equal, the device remains in a closed position. If one of the conductors comes in contact with a grounded object, either directly or through a person’s body, some of the current returns by the alternative path, resulting in an unbalanced current. The toroidal coil senses the unbalanced current, and the shunt-trip mechanism reacts to open the circuit. The circuit design does not require the presence of an equipment grounding conductor, which is the reason 406.4(D)(2)(c) permits the use of GFCIs as replacements for receptacles where a grounding means does not exist. A variety of GFCIs are available, including portable and plug-in types and circuit-breaker types, types built into attachment plug caps, and receptacle types. Each type has a test switch so that units can be checked periodically to ensure proper operation. The manufacturer’s installation and use instructions specify monthly testing. To facilitate this important ongoing