Chapter
stringclasses 6
values | Reference
stringlengths 1
17
| Body
stringlengths 62
23.1k
| URL
stringlengths 26
42
|
|---|---|---|---|
Chapter 2 Wiring and Protection
|
242.54(B)(1)
|
For ungrounded or unigrounded primary systems, the spark gap or a listed device shall have a 60-Hz breakdown voltage of at least twice the primary circuit voltage but not necessarily more than 10 kV, and there shall be at least one other ground on the grounded conductor of the secondary that is not less than 6.0 m (20 ft) distant from the surge-arrester grounding electrode. [242.54(B)(1)](https://2023.antflix.net#242.54(B)(1))
|
https://2023.antflix.net#242.54(B)(1)
|
Chapter 2 Wiring and Protection
|
242.54(B)(2)
|
For multigrounded neutral primary systems, the spark gap or listed device shall have a 60-Hz breakdown of not more than 3 kV, and there shall be at least one other ground on the grounded conductor of the secondary that is not less than 6.0 m (20 ft) distant from the surge-arrester grounding electrode. [242.54(B)(2)](https://2023.antflix.net#242.54(B)(2))
|
https://2023.antflix.net#242.54(B)(2)
|
Chapter 2 Wiring and Protection
|
242.54(C)
|
An interconnection of the surge-arrester ground and the secondary neutral conductor, other than as provided in 242.54(A) or (B), shall be permitted to be made only by special permission. [242.54(C)](https://2023.antflix.net#242.54(C))
|
https://2023.antflix.net#242.54(C)
|
Chapter 2 Wiring and Protection
|
242.56
|
Except as indicated in this article, surge-arrester grounding electrode conductor connections shall be made as specified in Article 250, Parts III and X. Grounding electrode conductors installed in metal enclosures shall comply with 250.64(E). [242.56](https://2023.antflix.net#242.56)
|
https://2023.antflix.net#242.56
|
Chapter 2 Wiring and Protection
|
245.1
|
This article covers overcurrent protection requirements for systems over 1000 volts ac, 1500 volts dc, nominal. [245.1](https://2023.antflix.net#245.1)
|
https://2023.antflix.net#245.1
|
Chapter 2 Wiring and Protection
|
245.2(A)
|
The following reconditioned equipment shall be permitted: Medium- and high-voltage circuit breakersElectromechanical protective relays and current transformers [245.2(A)](https://2023.antflix.net#245.2(A))
|
https://2023.antflix.net#245.2(A)
|
Chapter 2 Wiring and Protection
|
245.2(B)
|
Medium-voltage fuseholders and medium-voltage nonrenewable fuses shall not be permitted. [245.2(B)](https://2023.antflix.net#245.2(B))
|
https://2023.antflix.net#245.2(B)
|
Chapter 2 Wiring and Protection
|
245.21(A)(1)
|
Circuit breakers installed indoors shall be mounted either in metal-enclosed units or fire-resistant cell-mounted units, or they shall be permitted to be open-mounted in locations accessible to qualified persons only.Circuit breakers used to control oil-filled transformers in a vault shall either be located outside the transformer vault or be capable of operation from outside the vault.Oil circuit breakers shall be arranged or located so that adjacent readily combustible structures or materials are safeguarded in an approved manner. [245.21(A)(1)](https://2023.antflix.net#245.21(A)(1))
|
https://2023.antflix.net#245.21(A)(1)
|
Chapter 2 Wiring and Protection
|
245.21(A)(2)
|
Circuit breakers shall have the following equipment or operating characteristics: An accessible mechanical or other identified means for manual tripping, independent of control powerBe release free (trip free)If capable of being opened or closed manually while energized, main contacts that operate independently of the speed of the manual operationA mechanical position indicator at the circuit breaker to show the open or closed position of the main contactsA means of indicating the open and closed position of the breaker at the point(s) from which they may be operated [245.21(A)(2)](https://2023.antflix.net#245.21(A)(2))
|
https://2023.antflix.net#245.21(A)(2)
|
Chapter 2 Wiring and Protection
|
245.21(A)(3)
|
A circuit breaker shall have a permanent and legible nameplate showing the manufacturer's name or trademark, manufacturer's type or identification number, continuous current rating, interrupting rating in megavolt-amperes (MVA) or amperes, and maximum voltage rating. Modification of a circuit breaker affecting its rating(s) shall be accompanied by an appropriate change of nameplate information. [245.21(A)(3)](https://2023.antflix.net#245.21(A)(3))
|
https://2023.antflix.net#245.21(A)(3)
|
Chapter 2 Wiring and Protection
|
245.21(A)(4)
|
Circuit breakers shall have the following ratings: The continuous current rating of a circuit breaker shall not be less than the maximum continuous current through the circuit breaker.The interrupting rating of a circuit breaker shall not be less than the available fault current the circuit breaker will be required to interrupt, including contributions from all connected sources of energy.The closing rating of a circuit breaker shall not be less than the maximum asymmetrical fault current into which the circuit breaker can be closed.The momentary rating of a circuit breaker shall not be less than the maximum asymmetrical fault current at the point of installation.The rated maximum voltage of a circuit breaker shall not be less than the maximum circuit voltage. [245.21(A)(4)](https://2023.antflix.net#245.21(A)(4))
|
https://2023.antflix.net#245.21(A)(4)
|
Chapter 2 Wiring and Protection
|
245.21(A)(5)
|
Retrofit trip units shall be listed for use with the specific circuit breaker with which it is installed. [245.21(A)(5)](https://2023.antflix.net#245.21(A)(5))
|
https://2023.antflix.net#245.21(A)(5)
|
Chapter 2 Wiring and Protection
|
245.21(B)(1)
|
Where fuses are used to protect conductors and equipment, a fuse shall be placed in each ungrounded conductor. Two power fuses shall be permitted to be used in parallel to protect the same load if both fuses have identical ratings and both fuses are installed in an identified common mounting with electrical connections that divide the current equally. Power fuses of the vented type shall not be used indoors, underground, or in metal enclosures unless identified for the use. [245.21(B)(1)](https://2023.antflix.net#245.21(B)(1))
|
https://2023.antflix.net#245.21(B)(1)
|
Chapter 2 Wiring and Protection
|
245.21(B)(2)
|
The interrupting rating of power fuses shall not be less than the available fault current the fuse is required to interrupt, including contributions from all connected sources of energy. [245.21(B)(2)](https://2023.antflix.net#245.21(B)(2))
|
https://2023.antflix.net#245.21(B)(2)
|
Chapter 2 Wiring and Protection
|
245.21(B)(3)
|
The maximum voltage rating of power fuses shall not be less than the maximum circuit voltage. Fuses having a minimum recommended operating voltage shall not be applied below this voltage. [245.21(B)(3)](https://2023.antflix.net#245.21(B)(3))
|
https://2023.antflix.net#245.21(B)(3)
|
Chapter 2 Wiring and Protection
|
245.21(B)(4)
|
Fuse mountings and fuse units shall have permanent and legible nameplates showing the manufacturer's type or designation, continuous current rating, interrupting current rating, and maximum voltage rating. [245.21(B)(4)](https://2023.antflix.net#245.21(B)(4))
|
https://2023.antflix.net#245.21(B)(4)
|
Chapter 2 Wiring and Protection
|
245.21(B)(5)
|
Fuses that expel flame in opening the circuit shall be designed or arranged so that they function properly without hazard to persons or property. [245.21(B)(5)](https://2023.antflix.net#245.21(B)(5))
|
https://2023.antflix.net#245.21(B)(5)
|
Chapter 2 Wiring and Protection
|
245.21(B)(6)
|
Fuseholders shall be designed or installed so that they are de-energized while a fuse is being replaced. A field-applied permanent and legible sign, in accordance with 110.21(B), shall be installed immediately adjacent to the fuseholders and shall be worded as follows: DANGER - DISCONNECT CIRCUIT BEFORE REPLACING FUSES. Exception: Fuses and fuseholders designed to permit fuse replacement by qualified persons using identified equipment without de-energizing the fuseholder shall be permitted. [245.21(B)(6)](https://2023.antflix.net#245.21(B)(6))
|
https://2023.antflix.net#245.21(B)(6)
|
Chapter 2 Wiring and Protection
|
245.21(B)(7)
|
Switchgear and substations that use high-voltage fuses shall be provided with a gang-operated disconnecting switch. Isolation of the fuses from the circuit shall be provided by either connecting a switch between the source and the fuses or providing roll-out switch and fuse-type construction. The switch shall be of the load-interrupter type, unless mechanically or electrically interlocked with a load-interrupting device arranged to reduce the load to the interrupting capability of the switch. Exception: More than one switch shall be permitted as the disconnecting means for one set of fuses where the switches are installed to provide connection to more than one set of supply conductors. The switches shall be mechanically or electrically interlocked to permit access to the fuses only when all switches are open. A conspicuous sign shall be placed at the fuses identifying the presence of more than one source. [245.21(B)(7)](https://2023.antflix.net#245.21(B)(7))
|
https://2023.antflix.net#245.21(B)(7)
|
Chapter 2 Wiring and Protection
|
245.21(C)(1)
|
Cutouts shall be located so that they may be readily and safely operated and re-fused, and so that the exhaust of the fuses does not endanger persons. Distribution cutouts shall not be used indoors, underground, or in metal enclosures. [245.21(C)(1)](https://2023.antflix.net#245.21(C)(1))
|
https://2023.antflix.net#245.21(C)(1)
|
Chapter 2 Wiring and Protection
|
245.21(C)(2)
|
Where fused cutouts are not suitable to interrupt the circuit manually while carrying full load, an approved means shall be installed to interrupt the entire load. Unless the fused cutouts are interlocked with the switch to prevent opening of the cutouts under load, a conspicuous sign shall be placed at such cutouts identifying that they shall not be operated under load. [245.21(C)(2)](https://2023.antflix.net#245.21(C)(2))
|
https://2023.antflix.net#245.21(C)(2)
|
Chapter 2 Wiring and Protection
|
245.21(C)(3)
|
The interrupting rating of distribution cutouts shall not be less than the available fault current the cutout is required to interrupt, including contributions from all connected sources of energy. [245.21(C)(3)](https://2023.antflix.net#245.21(C)(3))
|
https://2023.antflix.net#245.21(C)(3)
|
Chapter 2 Wiring and Protection
|
245.21(C)(4)
|
The maximum voltage rating of cutouts shall not be less than the maximum circuit voltage. [245.21(C)(4)](https://2023.antflix.net#245.21(C)(4))
|
https://2023.antflix.net#245.21(C)(4)
|
Chapter 2 Wiring and Protection
|
245.21(C)(5)
|
Distribution cutouts shall have on their body, door, or fuse tube a permanent and legible nameplate or identification showing the manufacturer's type or designation, continuous current rating, maximum voltage rating, and interrupting rating. [245.21(C)(5)](https://2023.antflix.net#245.21(C)(5))
|
https://2023.antflix.net#245.21(C)(5)
|
Chapter 2 Wiring and Protection
|
245.21(C)(6)
|
Fuse links shall have a permanent and legible identification showing continuous current rating and type. [245.21(C)(6)](https://2023.antflix.net#245.21(C)(6))
|
https://2023.antflix.net#245.21(C)(6)
|
Chapter 2 Wiring and Protection
|
245.21(C)(7)
|
The height of cutouts mounted outdoors on structures shall provide safe clearance between lowest energized parts (open or closed position) and standing surfaces, in accordance with 110.34(E). [245.21(C)(7)](https://2023.antflix.net#245.21(C)(7))
|
https://2023.antflix.net#245.21(C)(7)
|
Chapter 2 Wiring and Protection
|
245.21(D)(1)
|
The continuous current rating of oil-filled cutouts shall not be less than the maximum continuous current through the cutout. [245.21(D)(1)](https://2023.antflix.net#245.21(D)(1))
|
https://2023.antflix.net#245.21(D)(1)
|
Chapter 2 Wiring and Protection
|
245.21(D)(2)
|
The interrupting rating of oil-filled cutouts shall not be less than the available fault current the oil-filled cutout is required to interrupt, including contributions from all connected sources of energy. [245.21(D)(2)](https://2023.antflix.net#245.21(D)(2))
|
https://2023.antflix.net#245.21(D)(2)
|
Chapter 2 Wiring and Protection
|
245.21(D)(3)
|
The maximum voltage rating of oil-filled cutouts shall not be less than the maximum circuit voltage. [245.21(D)(3)](https://2023.antflix.net#245.21(D)(3))
|
https://2023.antflix.net#245.21(D)(3)
|
Chapter 2 Wiring and Protection
|
245.21(D)(4)
|
Oil-filled cutouts shall have a fault closing rating not less than the maximum asymmetrical fault current that can occur at the cutout location, unless suitable interlocks or operating procedures preclude the possibility of closing into a fault. [245.21(D)(4)](https://2023.antflix.net#245.21(D)(4))
|
https://2023.antflix.net#245.21(D)(4)
|
Chapter 2 Wiring and Protection
|
245.21(D)(5)
|
Oil-filled cutouts shall have a permanent and legible nameplate showing the rated continuous current, rated maximum voltage, and rated interrupting current. [245.21(D)(5)](https://2023.antflix.net#245.21(D)(5))
|
https://2023.antflix.net#245.21(D)(5)
|
Chapter 2 Wiring and Protection
|
245.21(D)(6)
|
Fuse links shall have a permanent and legible identification showing the rated continuous current. [245.21(D)(6)](https://2023.antflix.net#245.21(D)(6))
|
https://2023.antflix.net#245.21(D)(6)
|
Chapter 2 Wiring and Protection
|
245.21(D)(7)
|
Cutouts shall be located so that they are readily and safely accessible for re-fusing, with the top of the cutout not over 1.5 m (5 ft) above the floor or platform. [245.21(D)(7)](https://2023.antflix.net#245.21(D)(7))
|
https://2023.antflix.net#245.21(D)(7)
|
Chapter 2 Wiring and Protection
|
245.21(D)(8)
|
Suitable barriers or enclosures shall be provided to prevent contact with nonshielded cables or energized parts of oil-filled cutouts. [245.21(D)(8)](https://2023.antflix.net#245.21(D)(8))
|
https://2023.antflix.net#245.21(D)(8)
|
Chapter 2 Wiring and Protection
|
245.21(E)
|
Load-interrupter switches shall be permitted if suitable fuses or circuit breakers are used in conjunction with these devices to interrupt available fault currents. Where these devices are used in combination, they shall be coordinated electrically so that they will safely withstand the effects of closing, carrying, or interrupting all possible currents up to the assigned maximum short-circuit rating. Where more than one switch is installed with interconnected load terminals to provide for alternate connection to different supply conductors, each switch shall be provided with a warning sign identifying the presence of more than one source. Each warning sign or label shall comply with 110.21. [245.21(E)](https://2023.antflix.net#245.21(E))
|
https://2023.antflix.net#245.21(E)
|
Chapter 2 Wiring and Protection
|
245.21(E)(1)
|
The continuous current rating of interrupter switches shall equal or exceed the maximum continuous current at the point of installation. [245.21(E)(1)](https://2023.antflix.net#245.21(E)(1))
|
https://2023.antflix.net#245.21(E)(1)
|
Chapter 2 Wiring and Protection
|
245.21(E)(2)
|
The maximum voltage rating of interrupter switches shall equal or exceed the maximum circuit voltage. [245.21(E)(2)](https://2023.antflix.net#245.21(E)(2))
|
https://2023.antflix.net#245.21(E)(2)
|
Chapter 2 Wiring and Protection
|
245.21(E)(3)
|
Interrupter switches shall have a permanent and legible nameplate, including the following information: manufacturer's type or designation, continuous current rating, interrupting current rating, fault closing rating, maximum voltage rating. [245.21(E)(3)](https://2023.antflix.net#245.21(E)(3))
|
https://2023.antflix.net#245.21(E)(3)
|
Chapter 2 Wiring and Protection
|
245.21(E)(4)
|
The switching mechanism shall be arranged to be operated from a location where the operator is not exposed to energized parts and shall be arranged to open all ungrounded conductors of the circuit simultaneously with one operation. Switches shall be arranged to be locked in the open position. Metal-enclosed switches shall be operable from outside the enclosure. [245.21(E)(4)](https://2023.antflix.net#245.21(E)(4))
|
https://2023.antflix.net#245.21(E)(4)
|
Chapter 2 Wiring and Protection
|
245.21(E)(5)
|
The stored-energy operator shall be permitted to be left in the uncharged position after the switch has been closed if a single movement of the operating handle charges the operator and opens the switch. [245.21(E)(5)](https://2023.antflix.net#245.21(E)(5))
|
https://2023.antflix.net#245.21(E)(5)
|
Chapter 2 Wiring and Protection
|
245.21(E)(6)
|
The supply terminals of fused interrupter switches shall be installed at the top of the switch enclosure, or, if the terminals are located elsewhere, the equipment shall have barriers installed to prevent persons from accidentally contacting energized parts or dropping tools or fuses into energized parts. [245.21(E)(6)](https://2023.antflix.net#245.21(E)(6))
|
https://2023.antflix.net#245.21(E)(6)
|
Chapter 2 Wiring and Protection
|
245.26(A)
|
Feeder and branch-circuit conductors shall have overcurrent protection in each ungrounded conductor located at the point where the conductor receives its supply or at an alternative location in the circuit when designed under engineering supervision that includes but is not limited to considering the appropriate fault studies and time-current coordination analysis of the protective devices and the conductor damage curves. The overcurrent protection shall be permitted to be provided by either 250.184(B) or (A)(2). [245.26(A)](https://2023.antflix.net#245.26(A))
|
https://2023.antflix.net#245.26(A)
|
Chapter 2 Wiring and Protection
|
245.26(A)(1)
|
Circuit breakers used for overcurrent protection of 3-phase circuits shall have a minimum of three overcurrent relay elements operated from three current transformers. The separate overcurrent relay elements (or protective functions) shall be permitted to be part of a single electronic protective relay unit. On 3-phase, 3-wire circuits, an overcurrent relay element in the residual circuit of the current transformers shall be permitted to replace one of the phase relay elements. An overcurrent relay element, operated from a current transformer that links all phases of a 3-phase, 3-wire circuit, shall be permitted to replace the residual relay element and one of the phase-conductor current transformers. Where the neutral conductor is not regrounded on the load side of the circuit as permitted in 250.184(B), the current transformer shall be permitted to link all 3-phase conductors and the grounded circuit conductor (neutral). [245.26(A)(1)](https://2023.antflix.net#245.26(A)(1))
|
https://2023.antflix.net#245.26(A)(1)
|
Chapter 2 Wiring and Protection
|
245.26(A)(2)
|
A fuse shall be connected in series with each ungrounded conductor. [245.26(A)(2)](https://2023.antflix.net#245.26(A)(2))
|
https://2023.antflix.net#245.26(A)(2)
|
Chapter 2 Wiring and Protection
|
245.26(B)
|
The protective device(s) shall be capable of detecting and interrupting all values of current that can occur at their location in excess of their trip-setting or melting point. [245.26(B)](https://2023.antflix.net#245.26(B))
|
https://2023.antflix.net#245.26(B)
|
Chapter 2 Wiring and Protection
|
245.26(C)
|
The operating time of the protective device, the available short-circuit current, and the conductor used shall be coordinated to prevent damaging or dangerous temperatures in conductors or conductor insulation under short-circuit conditions. [245.26(C)](https://2023.antflix.net#245.26(C))
|
https://2023.antflix.net#245.26(C)
|
Chapter 2 Wiring and Protection
|
245.27(A)
|
The continuous ampere rating of a fuse shall not exceed three times the ampacity of the conductors. The long-time trip element setting of a breaker or the minimum trip setting of an electronically actuated fuse shall not exceed six times the ampacity of the conductor. For fire pumps, conductors shall be permitted to be protected for overcurrent in accordance with 695.4(B)(2). [245.27(A)](https://2023.antflix.net#245.27(A))
|
https://2023.antflix.net#245.27(A)
|
Chapter 2 Wiring and Protection
|
245.27(B)
|
Conductors tapped to a feeder shall be permitted to be protected by the feeder overcurrent device where that overcurrent device also protects the tap conductor. [245.27(B)](https://2023.antflix.net#245.27(B))
|
https://2023.antflix.net#245.27(B)
|
Chapter 2 Wiring and Protection
|
250.1
|
This article covers general requirements for grounding and bonding of electrical installations and the following specific requirements: Systems, circuits, and equipment required, permitted, or not permitted to be groundedCircuit conductor to be grounded on grounded systemsLocation of grounding connectionsTypes and sizes of grounding and bonding conductors and electrodesMethods of grounding and bondingConditions under which isolation, insulation, or guards are permitted to be substituted for groundingInformational Note: See Informational Note Figure 250.1 for information on the organization of this article covering grounding and bonding requirements.Informational Note Figure 250.1 Grounding and Bonding. [250.1](https://2023.antflix.net#250.1)
|
https://2023.antflix.net#250.1
|
Chapter 2 Wiring and Protection
|
250.4
|
The following general requirements identify what grounding and bonding of electrical systems are required to accomplish. The prescriptive methods contained in this article shall be followed to comply with the performance requirements of this section. [250.4](https://2023.antflix.net#250.4)
|
https://2023.antflix.net#250.4
|
Chapter 2 Wiring and Protection
|
250.4(A)(1)
|
Electrical systems that are grounded shall be connected to earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during normal operation. Informational Note No. 1: An important consideration for limiting the imposed voltage is the routing of bonding and grounding electrode conductors so that they are not any longer than necessary to complete the connection without disturbing the permanent parts of the installation and so that unnecessary bends and loops are avoided. Informational Note No. 2: See NFPA 780-2020, Standard for the Installation of Lightning Protection Systems, for information on installation of grounding and bonding for lightning protection systems. [250.4(A)(1)](https://2023.antflix.net#250.4(A)(1))
|
https://2023.antflix.net#250.4(A)(1)
|
Chapter 2 Wiring and Protection
|
250.4(A)(2)
|
Normally noncurrent-carrying conductive materials enclosing electrical conductors or equipment, or forming part of such equipment, shall be connected to earth so as to limit the voltage to ground on these materials. [250.4(A)(2)](https://2023.antflix.net#250.4(A)(2))
|
https://2023.antflix.net#250.4(A)(2)
|
Chapter 2 Wiring and Protection
|
250.4(A)(3)
|
Normally non-current-carrying conductive materials enclosing electrical conductors or equipment, or forming part of such equipment, shall be connected together and to the electrical supply source in a manner that establishes an effective ground-fault current path. [250.4(A)(3)](https://2023.antflix.net#250.4(A)(3))
|
https://2023.antflix.net#250.4(A)(3)
|
Chapter 2 Wiring and Protection
|
250.4(A)(4)
|
Normally non-current-carrying electrically conductive materials that are likely to become energized shall be connected together and to the electrical supply source in a manner that establishes an effective ground-fault current path. [250.4(A)(4)](https://2023.antflix.net#250.4(A)(4))
|
https://2023.antflix.net#250.4(A)(4)
|
Chapter 2 Wiring and Protection
|
250.4(A)(5)
|
Electrical equipment and wiring and other electrically conductive material likely to become energized shall be installed in a manner that creates a low-impedance circuit facilitating the operation of the overcurrent device or ground detector for impedance grounded systems. It shall be capable of safely carrying the maximum ground-fault current likely to be imposed on it from any point on the wiring system where a ground fault occurs to the electrical supply source. The earth shall not be considered as an effective ground-fault current path. [250.4(A)(5)](https://2023.antflix.net#250.4(A)(5))
|
https://2023.antflix.net#250.4(A)(5)
|
Chapter 2 Wiring and Protection
|
250.4(B)(1)
|
Non-current-carrying conductive materials enclosing electrical conductors or equipment, or forming part of such equipment, shall be connected to earth in a manner that will limit the voltage imposed by lightning or unintentional contact with higher-voltage lines and limit the voltage to ground on these materials. Informational Note: See NFPA 780-2020, Standard for the Installation of Lightning Protection Systems, for information on installation of grounding and bonding for lightning protection systems. [250.4(B)(1)](https://2023.antflix.net#250.4(B)(1))
|
https://2023.antflix.net#250.4(B)(1)
|
Chapter 2 Wiring and Protection
|
250.4(B)(2)
|
Non-current-carrying conductive materials enclosing electrical conductors or equipment, or forming part of such equipment, shall be connected together and to the supply system grounded equipment in a manner that creates a low-impedance path for ground-fault current that is capable of carrying the maximum fault current likely to be imposed on it. [250.4(B)(2)](https://2023.antflix.net#250.4(B)(2))
|
https://2023.antflix.net#250.4(B)(2)
|
Chapter 2 Wiring and Protection
|
250.4(B)(3)
|
Electrically conductive materials that are likely to become energized shall be connected together and to the supply system grounded equipment in a manner that creates a low-impedance path for ground-fault current that is capable of carrying the maximum fault current likely to be imposed on it. [250.4(B)(3)](https://2023.antflix.net#250.4(B)(3))
|
https://2023.antflix.net#250.4(B)(3)
|
Chapter 2 Wiring and Protection
|
250.4(B)(4)
|
Electrical equipment, wiring, and other electrically conductive material likely to become energized shall be installed in a manner that creates a low-impedance circuit from any point on the wiring system to the electrical supply source to facilitate the operation of overcurrent devices should a second ground fault from a different phase occur on the wiring system. The earth shall not be considered as an effective fault-current path. [250.4(B)(4)](https://2023.antflix.net#250.4(B)(4))
|
https://2023.antflix.net#250.4(B)(4)
|
Chapter 2 Wiring and Protection
|
250.6(A)
|
The grounding and bonding of electrical systems, circuit conductors, surge arresters, surge-protective devices, and conductive normally non-current-carrying metal parts of equipment shall be installed and arranged in a manner that will prevent objectionable current. [250.6(A)](https://2023.antflix.net#250.6(A))
|
https://2023.antflix.net#250.6(A)
|
Chapter 2 Wiring and Protection
|
250.6(B)
|
If the use of multiple grounding or bonding connections results in objectionable current and the requirements of 250.4(A)(5) or (B)(4) are met, one or more of the following alterations shall be permitted: Discontinue one or more but not all of such grounding or bonding connections.Change the locations of the grounding or bonding connections.Interrupt the continuity of the conductor or conductive path causing the objectionable current.Take other remedial and approved action. [250.6(B)](https://2023.antflix.net#250.6(B))
|
https://2023.antflix.net#250.6(B)
|
Chapter 2 Wiring and Protection
|
250.6(C)
|
Currents resulting from abnormal conditions such as ground faults, and from currents resulting from required grounding and bonding connections shall not be classified as objectionable current for the purposes specified in 250.6(A) and (B). [250.6(C)](https://2023.antflix.net#250.6(C))
|
https://2023.antflix.net#250.6(C)
|
Chapter 2 Wiring and Protection
|
250.6(D)
|
This section shall not be considered as permitting electronic equipment to be operated on ac systems or branch circuits that are not connected to an equipment grounding conductor as required by this article. Currents that introduce electromagnetic interference or data errors in electronic equipment shall not be considered the objectionable currents addressed in this section. [250.6(D)](https://2023.antflix.net#250.6(D))
|
https://2023.antflix.net#250.6(D)
|
Chapter 2 Wiring and Protection
|
250.6(E)
|
If isolation of objectionable direct currents from a cathodic protection system is required, a listed isolator device shall be permitted in the equipment grounding conductor path to provide an effective return path for ac ground-fault current while blocking the flow of direct currents. [250.6(E)](https://2023.antflix.net#250.6(E))
|
https://2023.antflix.net#250.6(E)
|
Chapter 2 Wiring and Protection
|
250.8(A)
|
Equipment grounding conductors, grounding electrode conductors, and bonding jumpers shall be connected by one or more of the following means: Listed pressure connectorsTerminal barsPressure connectors listed as grounding and bonding equipmentExothermic welding processMachine screw-type fasteners that engage not less than two threads or are secured with a nutThread-forming machine screws that engage not less than two threads in the enclosureConnections that are part of a listed assemblyOther listed means [250.8(A)](https://2023.antflix.net#250.8(A))
|
https://2023.antflix.net#250.8(A)
|
Chapter 2 Wiring and Protection
|
250.8(B)
|
Connection devices or fittings that depend solely on solder shall not be used. [250.8(B)](https://2023.antflix.net#250.8(B))
|
https://2023.antflix.net#250.8(B)
|
Chapter 2 Wiring and Protection
|
250.10
|
Ground clamps or other fittings exposed to physical damage shall be enclosed in metal, wood, or equivalent protective covering. [250.10](https://2023.antflix.net#250.10)
|
https://2023.antflix.net#250.10
|
Chapter 2 Wiring and Protection
|
250.12
|
Nonconductive coatings (such as paint, lacquer, and enamel) on equipment to be grounded or bonded shall be removed from threads and other contact surfaces to ensure electrical continuity or shall be connected by means of fittings designed to make such removal unnecessary. [250.12](https://2023.antflix.net#250.12)
|
https://2023.antflix.net#250.12
|
Chapter 2 Wiring and Protection
|
250.20
|
Alternating-current systems shall be grounded in accordance with 250.20(A), (B), (C), or (D), unless prohibited elsewhere in this Code. Other systems shall be permitted to be grounded. If such systems are grounded, they shall comply with the applicable provisions of this article. Informational Note No. 1: An example of a system permitted to be grounded is a corner-grounded delta transformer connection. Informational Note No. 2: See 503.155, 517.61, 517.160, 668.10, and 680.23(A)(2) for examples of circuits prohibited to be grounded. [250.20](https://2023.antflix.net#250.20)
|
https://2023.antflix.net#250.20
|
Chapter 2 Wiring and Protection
|
250.20(A)
|
Alternating-current systems of less than 50 volts shall be grounded under any of the following conditions: If supplied by transformers, if the transformer supply system exceeds 150 volts to groundIf supplied by transformers, if the transformer supply system is ungroundedIf installed outside as overhead conductors [250.20(A)](https://2023.antflix.net#250.20(A))
|
https://2023.antflix.net#250.20(A)
|
Chapter 2 Wiring and Protection
|
250.20(B)
|
Alternating-current systems of 50 volts to 1000 volts that supply premises wiring and premises wiring systems shall be grounded under any of the following conditions: If the system can be grounded so that the maximum voltage to ground on the ungrounded conductors does not exceed 150 voltsIf the system is 3-phase, 4-wire, wye connected in which the neutral conductor is used as a circuit conductorIf the system is 3-phase, 4-wire, delta connected in which the midpoint of one phase winding is used as a circuit conductorInformational Note: See NFPA 70E-2021. Standard for Electrical Safety in the Workplace, Annex O, for information on impedance grounding to reduce arc-flash hazards. [250.20(B)](https://2023.antflix.net#250.20(B))
|
https://2023.antflix.net#250.20(B)
|
Chapter 2 Wiring and Protection
|
250.20(C)
|
Alternating-current systems supplying mobile or portable equipment shall be grounded in accordance with 250.188. If supplying other than mobile or portable equipment, such systems shall be permitted to be grounded. [250.20(C)](https://2023.antflix.net#250.20(C))
|
https://2023.antflix.net#250.20(C)
|
Chapter 2 Wiring and Protection
|
250.20(D)
|
Impedance grounded systems shall be grounded in accordance with 250.36 or 250.187, as applicable. [250.20(D)](https://2023.antflix.net#250.20(D))
|
https://2023.antflix.net#250.20(D)
|
Chapter 2 Wiring and Protection
|
250.21(A)
|
The following ac systems of 50 volts to 1000 volts shall be permitted to be grounded but shall not be required to be grounded: Electrical systems used exclusively to supply industrial electric furnaces used for applications such as melting, refining, or temperingSeparately derived systems used exclusively for rectifiers that supply only adjustable-speed industrial drivesSeparately derived systems supplied by transformers that have a primary voltage rating of 1000 volts or less if all the following conditions are met:The system is used exclusively for control circuits.The conditions of maintenance and supervision ensure that only qualified persons service the installation.Continuity of control power is required.Other systems that are not required to be grounded in accordance with 250.20(B) [250.21(A)](https://2023.antflix.net#250.21(A))
|
https://2023.antflix.net#250.21(A)
|
Chapter 2 Wiring and Protection
|
250.21(B)
|
Ground detectors shall be installed in accordance with the following: Ungrounded ac systems as permitted in 250.21(A)(1) through (A)(4) operating at not less than 120 volts and at 1000 volts or less shall have ground detectors installed on the system.The ground detection sensing equipment shall be connected as close as practicable to where the system receives its supply. [250.21(B)](https://2023.antflix.net#250.21(B))
|
https://2023.antflix.net#250.21(B)
|
Chapter 2 Wiring and Protection
|
250.21(C)
|
Ungrounded systems shall be legibly marked "Caution: Ungrounded System Operating - ____ Volts Between Conductors" at the source or first disconnecting means of the system. The marking shall be of sufficient durability to withstand the environment involved. [250.21(C)](https://2023.antflix.net#250.21(C))
|
https://2023.antflix.net#250.21(C)
|
Chapter 2 Wiring and Protection
|
250.24(A)
|
A premises wiring system supplied by a grounded ac service shall have a grounding electrode conductor connected to the grounded service conductor, at each service, in accordance with 250.24(A)(1) through (A)(4). [250.24(A)](https://2023.antflix.net#250.24(A))
|
https://2023.antflix.net#250.24(A)
|
Chapter 2 Wiring and Protection
|
250.24(A)(1)
|
The grounding electrode conductor connection shall be made at any accessible point from the load end of the overhead service conductors, service drop, underground service conductors, or service lateral to the terminal or bus to which the grounded service conductor is connected at the service disconnecting means. Informational Note: See Article 100 for definitions of Service Conductors, Overhead; Service Conductors, Underground; Service Drop; and Service Lateral. [250.24(A)(1)](https://2023.antflix.net#250.24(A)(1))
|
https://2023.antflix.net#250.24(A)(1)
|
Chapter 2 Wiring and Protection
|
250.24(A)(2)
|
If the transformer supplying the service is located outside the building, at least one additional grounding connection shall be made from the grounded service conductor to a grounding electrode, either at the transformer or elsewhere outside the building. Exception: The additional grounding electrode conductor connection shall not be made on impedance grounded systems. Impedance grounded systems shall meet the requirements of 250.36 or 250.187, as applicable. [250.24(A)(2)](https://2023.antflix.net#250.24(A)(2))
|
https://2023.antflix.net#250.24(A)(2)
|
Chapter 2 Wiring and Protection
|
250.24(A)(3)
|
For services that are dual fed (double ended) in a common enclosure or grouped together in separate enclosures and employing a secondary tie, a single grounding electrode conductor connection to the tie point of the grounded conductor(s) from each power source shall be permitted. [250.24(A)(3)](https://2023.antflix.net#250.24(A)(3))
|
https://2023.antflix.net#250.24(A)(3)
|
Chapter 2 Wiring and Protection
|
250.24(A)(4)
|
If the main bonding jumper specified in 250.28 is a wire or busbar and is installed from the grounded conductor terminal bar or bus to the equipment grounding terminal bar or bus in the service equipment, the grounding electrode conductor shall be permitted to be connected to the equipment grounding terminal, bar, or bus to which the main bonding jumper is connected. [250.24(A)(4)](https://2023.antflix.net#250.24(A)(4))
|
https://2023.antflix.net#250.24(A)(4)
|
Chapter 2 Wiring and Protection
|
250.24(B)
|
A grounded conductor shall not be connected to normally non-current-carrying metal parts of equipment, to equipment grounding conductor(s), or be reconnected to ground on the load side of the service disconnecting means except as otherwise permitted in this article. Informational Note: See 250.30 for separately derived systems, 250.32 for connections at separate buildings or structures, and 250.142 for use of the grounded circuit conductor for grounding equipment. [250.24(B)](https://2023.antflix.net#250.24(B))
|
https://2023.antflix.net#250.24(B)
|
Chapter 2 Wiring and Protection
|
250.24(C)
|
For a grounded system, an unspliced main bonding jumper shall be used to connect the equipment grounding conductor(s) and the service-disconnect enclosure to the grounded conductor within the enclosure for each service disconnect in accordance with 250.28. Exception No. 1: If more than one service disconnecting means is located in an assembly listed for use as service equipment, an unspliced main bonding jumper shall bond the grounded conductor(s) to the assembly enclosure. Exception No. 2: Impedance grounded systems shall be permitted to be connected in accordance with 250.36 and 250.187. [250.24(C)](https://2023.antflix.net#250.24(C))
|
https://2023.antflix.net#250.24(C)
|
Chapter 2 Wiring and Protection
|
250.24(D)
|
If an ac system operating at 1000 volts or less is grounded at any point, the grounded conductor(s) shall be routed with the ungrounded conductors to each service disconnecting means and shall be connected to each disconnecting means grounded conductor(s) terminal or bus. A main bonding jumper shall connect the grounded conductor(s) to each service disconnecting means enclosure. The grounded conductor(s) shall be installed in accordance with 250.24(D)(1) through (D)(4).
Exception: If two or more service disconnecting means are located in a single assembly listed for use as service equipment, it shall be permitted to connect the grounded conductor(s) to the assembly common grounded conductor(s) terminal or bus. The assembly shall include a main bonding jumper for connecting the grounded conductor(s) to the assembly enclosure. [250.24(D)](https://2023.antflix.net#250.24(D))
|
https://2023.antflix.net#250.24(D)
|
Chapter 2 Wiring and Protection
|
250.24(D)(1)
|
The grounded conductor shall not be smaller than specified in Table 250.102(C)(1). [250.24(D)(1)](https://2023.antflix.net#250.24(D)(1))
|
https://2023.antflix.net#250.24(D)(1)
|
Chapter 2 Wiring and Protection
|
250.24(D)(2)
|
If the ungrounded service-entrance conductors are connected in parallel in two or more raceways or cables, the grounded conductors shall also be installed in each raceway or cable and shall be connected in parallel. The size of each grounded conductor(s) in each raceway or cable shall not be smaller than 1/0 AWG and shall be sized in accordance with 250.24(D)(2)(a) or (D)(2)(b) in accordance with 250.24(D)(1). Shall be based on the largest ungrounded conductor in each raceway or cable.Shall be based on the sum of the circular mil areas of the largest ungrounded conductors from each set connected in parallel in each raceway or cable.Informational Note: See 310.10(G) for grounded conductors connected in parallel. [250.24(D)(2)](https://2023.antflix.net#250.24(D)(2))
|
https://2023.antflix.net#250.24(D)(2)
|
Chapter 2 Wiring and Protection
|
250.24(D)(3)
|
The grounded conductor of a 3-phase, 3-wire delta service shall have an ampacity not less than that of the ungrounded conductors. [250.24(D)(3)](https://2023.antflix.net#250.24(D)(3))
|
https://2023.antflix.net#250.24(D)(3)
|
Chapter 2 Wiring and Protection
|
250.24(D)(4)
|
The impedance grounding conductor on an impedance grounded system shall be connected in accordance with 250.36 or 250.187, as applicable. [250.24(D)(4)](https://2023.antflix.net#250.24(D)(4))
|
https://2023.antflix.net#250.24(D)(4)
|
Chapter 2 Wiring and Protection
|
250.24(E)
|
A grounding electrode conductor shall be used to connect the equipment grounding conductors, the service-equipment enclosures, and, if the system is grounded, the grounded service conductor to the grounding electrode(s) required by Part III of this article. This conductor shall be sized in accordance with 250.66. Impedance grounded system connections shall be made in accordance with 250.36 or 250.187, as applicable. [250.24(E)](https://2023.antflix.net#250.24(E))
|
https://2023.antflix.net#250.24(E)
|
Chapter 2 Wiring and Protection
|
250.24(F)
|
A premises wiring system that is supplied by an ac service that is ungrounded shall have, at each service, a grounding electrode conductor connected to the grounding electrode(s) required by Part III of this article. The grounding electrode conductor shall be connected to a metal enclosure of the service conductors at any accessible point from the load end of the overhead service conductors, service drop, underground service conductors, or service lateral to the service disconnecting means. [250.24(F)](https://2023.antflix.net#250.24(F))
|
https://2023.antflix.net#250.24(F)
|
Chapter 2 Wiring and Protection
|
250.25
|
The grounding of systems connected on the supply side of the service disconnect, in accordance with 230.82, that are in enclosures separate from the service equipment enclosure shall comply with 250.25(A) or (B). [250.25](https://2023.antflix.net#250.25)
|
https://2023.antflix.net#250.25
|
Chapter 2 Wiring and Protection
|
250.25(A)
|
If the utility supply system is grounded, the grounding of systems permitted to be connected on the supply side of the service disconnect and are installed in one or more separate enclosures from the service equipment enclosure shall comply with the requirements of 250.24(A) through (D). [250.25(A)](https://2023.antflix.net#250.25(A))
|
https://2023.antflix.net#250.25(A)
|
Chapter 2 Wiring and Protection
|
250.25(B)
|
If the utility supply system is ungrounded, the grounding of systems permitted to be connected on the supply side of the service disconnect and are installed in one or more separate enclosures from the service equipment enclosure shall comply with the requirements of 250.24(F). [250.25(B)](https://2023.antflix.net#250.25(B))
|
https://2023.antflix.net#250.25(B)
|
Chapter 2 Wiring and Protection
|
250.26
|
If an ac premises wiring system is grounded, the conductor to be grounded shall be one of the following: Single-phase, 2-wire - one conductorSingle-phase, 3-wire - the neutral conductorMultiphase systems having one wire common to all phases - the neutral conductorMultiphase systems if one phase is grounded - that phase conductorMultiphase systems in which one phase is used as in (2) - the neutral conductor [250.26](https://2023.antflix.net#250.26)
|
https://2023.antflix.net#250.26
|
Chapter 2 Wiring and Protection
|
250.28
|
For a grounded system, main bonding jumpers and system bonding jumpers shall be installed as follows: [250.28](https://2023.antflix.net#250.28)
|
https://2023.antflix.net#250.28
|
Chapter 2 Wiring and Protection
|
250.28(A)
|
Main bonding jumpers and system bonding jumpers shall be of copper, aluminum, copper-clad aluminum, or other corrosion-resistant material. A main bonding jumper and a system bonding jumper shall be a wire, bus, screw, or similar suitable conductor. [250.28(A)](https://2023.antflix.net#250.28(A))
|
https://2023.antflix.net#250.28(A)
|
Chapter 2 Wiring and Protection
|
250.28(B)
|
If a main bonding jumper or a system bonding jumper is a screw only, the screw shall be identified with a green finish that shall be visible with the screw installed. [250.28(B)](https://2023.antflix.net#250.28(B))
|
https://2023.antflix.net#250.28(B)
|
Chapter 2 Wiring and Protection
|
250.28(C)
|
Main bonding jumpers and system bonding jumpers shall be connected by one or more of the methods in 250.8 that is suitable for the material of the bonding jumper and enclosure. [250.28(C)](https://2023.antflix.net#250.28(C))
|
https://2023.antflix.net#250.28(C)
|
Chapter 2 Wiring and Protection
|
250.28(D)
|
Main bonding jumpers and system bonding jumpers shall be sized in accordance with 250.28(D)(1) through (D)(3). [250.28(D)](https://2023.antflix.net#250.28(D))
|
https://2023.antflix.net#250.28(D)
|
Chapter 2 Wiring and Protection
|
250.28(D)(1)
|
Main bonding jumpers and system bonding jumpers shall not be smaller than specified in Table 250.102(C)(1). [250.28(D)(1)](https://2023.antflix.net#250.28(D)(1))
|
https://2023.antflix.net#250.28(D)(1)
|
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.