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Chapter 2 Wiring and Protection
|
240.24(F)
|
Overcurrent protective devices shall not be located over steps of a stairway. [240.24(F)](https://2023.antflix.net#240.24(F))
|
https://2023.antflix.net#240.24(F)
|
Chapter 2 Wiring and Protection
|
240.30(A)
|
Overcurrent devices shall be protected from physical damage by one of the following: Installation in enclosures, cabinets, cutout boxes, or equipment assembliesMounting on open-type switchboards, panelboards, or control boards that are in rooms or enclosures free from dampness and easily ignitible material and are accessible only to qualified personnel [240.30(A)](https://2023.antflix.net#240.30(A))
|
https://2023.antflix.net#240.30(A)
|
Chapter 2 Wiring and Protection
|
240.30(B)
|
The operating handle of a circuit breaker shall be permitted to be accessible without opening a door or cover. [240.30(B)](https://2023.antflix.net#240.30(B))
|
https://2023.antflix.net#240.30(B)
|
Chapter 2 Wiring and Protection
|
240.32
|
Enclosures for overcurrent devices in damp or wet locations shall comply with 312.2. [240.32](https://2023.antflix.net#240.32)
|
https://2023.antflix.net#240.32
|
Chapter 2 Wiring and Protection
|
240.33
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Enclosures for overcurrent devices shall be mounted in a vertical position. Circuit breaker enclosures shall be permitted to be installed horizontally where the circuit breaker is installed in accordance with 240.81. Listed busway plug-in units shall be permitted to be mounted in orientations corresponding to the busway mounting position. [240.33](https://2023.antflix.net#240.33)
|
https://2023.antflix.net#240.33
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Chapter 2 Wiring and Protection
|
240.40
|
Cartridge fuses in circuits of any voltage, and all fuses in circuits over 150 volts to ground, shall be provided with a disconnecting means on their supply side so that each circuit containing fuses can be independently disconnected from the source of power. A cable limiter without a disconnecting means shall be permitted on the supply side of the service disconnecting means as permitted by 230.82. A single disconnecting means shall be permitted on the supply side of more than one set of fuses as permitted by 430.112, Exception, for group operation of motors, 424.22(C) for fixed electric space-heating equipment, and 425.22(C) for fixed resistance and electrode industrial process heating equipment, or where specifically permitted elsewhere in this Code. [240.40](https://2023.antflix.net#240.40)
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https://2023.antflix.net#240.40
|
Chapter 2 Wiring and Protection
|
240.41
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Arcing or suddenly moving parts shall comply with 240.41(A) and (B). [240.41](https://2023.antflix.net#240.41)
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https://2023.antflix.net#240.41
|
Chapter 2 Wiring and Protection
|
240.41(A)
|
Fuses and circuit breakers shall be located or shielded so that persons will not be burned or otherwise injured by their operation. [240.41(A)](https://2023.antflix.net#240.41(A))
|
https://2023.antflix.net#240.41(A)
|
Chapter 2 Wiring and Protection
|
240.41(B)
|
Handles or levers of circuit breakers, and similar parts that may move suddenly in such a way that persons in the vicinity are likely to be injured by being struck by them, shall be guarded or isolated. [240.41(B)](https://2023.antflix.net#240.41(B))
|
https://2023.antflix.net#240.41(B)
|
Chapter 2 Wiring and Protection
|
240.50(A)
|
Plug fuses shall be permitted to be used in the following circuits: Circuits not exceeding 125 volts between conductorsCircuits supplied by a system having a grounded neutral point where the line-to-neutral voltage does not exceed 150 volts [240.50(A)](https://2023.antflix.net#240.50(A))
|
https://2023.antflix.net#240.50(A)
|
Chapter 2 Wiring and Protection
|
240.50(B)
|
Each fuse, fuseholder, and adapter shall be marked with its ampere rating. [240.50(B)](https://2023.antflix.net#240.50(B))
|
https://2023.antflix.net#240.50(B)
|
Chapter 2 Wiring and Protection
|
240.50(C)
|
Plug fuses of 15-ampere and lower rating shall be identified by a hexagonal configuration of the window, cap, or other prominent part to distinguish them from fuses of higher ampere ratings. [240.50(C)](https://2023.antflix.net#240.50(C))
|
https://2023.antflix.net#240.50(C)
|
Chapter 2 Wiring and Protection
|
240.50(D)
|
Plug fuses, fuseholders, and adapters shall have no exposed energized parts after fuses or fuses and adapters have been installed. [240.50(D)](https://2023.antflix.net#240.50(D))
|
https://2023.antflix.net#240.50(D)
|
Chapter 2 Wiring and Protection
|
240.50(E)
|
The screw shell of a plug-type fuseholder shall be connected to the load side of the circuit. [240.50(E)](https://2023.antflix.net#240.50(E))
|
https://2023.antflix.net#240.50(E)
|
Chapter 2 Wiring and Protection
|
240.51(A)
|
Plug fuses of the Edison-base type shall be classified at not over 125 volts and 30 amperes and below. [240.51(A)](https://2023.antflix.net#240.51(A))
|
https://2023.antflix.net#240.51(A)
|
Chapter 2 Wiring and Protection
|
240.51(B)
|
Plug fuses of the Edison-base type shall be used only for replacements in existing installations where there is no evidence of overfusing or tampering. [240.51(B)](https://2023.antflix.net#240.51(B))
|
https://2023.antflix.net#240.51(B)
|
Chapter 2 Wiring and Protection
|
240.52
|
Fuseholders of the Edison-base type shall be installed only where they are made to accept Type S fuses by the use of adapters. [240.52](https://2023.antflix.net#240.52)
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https://2023.antflix.net#240.52
|
Chapter 2 Wiring and Protection
|
240.53
|
Type S fuses shall be of the plug type and shall comply with 240.53(A) and (B). [240.53](https://2023.antflix.net#240.53)
|
https://2023.antflix.net#240.53
|
Chapter 2 Wiring and Protection
|
240.53(A)
|
Type S fuses shall be classified at not over 125 volts and 0 to 15 amperes, 16 to 20 amperes, and 21 to 30 amperes. [240.53(A)](https://2023.antflix.net#240.53(A))
|
https://2023.antflix.net#240.53(A)
|
Chapter 2 Wiring and Protection
|
240.53(B)
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Type S fuses of an ampere classification as specified in 240.53(A) shall not be interchangeable with a lower ampere classification. They shall be designed so that they cannot be used in any fuseholder other than a Type S fuseholder or a fuseholder with a Type S adapter inserted. [240.53(B)](https://2023.antflix.net#240.53(B))
|
https://2023.antflix.net#240.53(B)
|
Chapter 2 Wiring and Protection
|
240.54(A)
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Type S adapters shall fit Edison-base fuseholders. [240.54(A)](https://2023.antflix.net#240.54(A))
|
https://2023.antflix.net#240.54(A)
|
Chapter 2 Wiring and Protection
|
240.54(B)
|
Type S fuseholders and adapters shall be designed so that either the fuseholder itself or the fuseholder with a Type S adapter inserted cannot be used for any fuse other than a Type S fuse. [240.54(B)](https://2023.antflix.net#240.54(B))
|
https://2023.antflix.net#240.54(B)
|
Chapter 2 Wiring and Protection
|
240.54(C)
|
Type S adapters shall be designed so that once inserted in a fuseholder, they cannot be removed. [240.54(C)](https://2023.antflix.net#240.54(C))
|
https://2023.antflix.net#240.54(C)
|
Chapter 2 Wiring and Protection
|
240.54(D)
|
Type S fuses, fuseholders, and adapters shall be designed so that tampering or shunting (bridging) would be difficult. [240.54(D)](https://2023.antflix.net#240.54(D))
|
https://2023.antflix.net#240.54(D)
|
Chapter 2 Wiring and Protection
|
240.54(E)
|
Dimensions of Type S fuses, fuseholders, and adapters shall be standardized to permit interchangeability regardless of the manufacturer. [240.54(E)](https://2023.antflix.net#240.54(E))
|
https://2023.antflix.net#240.54(E)
|
Chapter 2 Wiring and Protection
|
240.60(A)
|
Cartridge fuses and fuseholders of the 300-volt type shall be permitted to be used in the following circuits: Circuits not exceeding 300 volts between conductorsSingle-phase line-to-neutral circuits supplied from a 3-phase, 4-wire, solidly grounded neutral source where the line-to-neutral voltage does not exceed 300 volts [240.60(A)](https://2023.antflix.net#240.60(A))
|
https://2023.antflix.net#240.60(A)
|
Chapter 2 Wiring and Protection
|
240.60(B)
|
Fuseholders shall be designed so that it will be difficult to put a fuse of any given class into a fuseholder that is designed for a current lower, or voltage higher, than that of the class to which the fuse belongs. Fuseholders for current-limiting fuses shall not permit insertion of fuses that are not current-limiting. [240.60(B)](https://2023.antflix.net#240.60(B))
|
https://2023.antflix.net#240.60(B)
|
Chapter 2 Wiring and Protection
|
240.60(C)
|
Fuses shall be plainly marked, either by printing on the fuse barrel or by a label attached to the barrel showing the following: Ampere ratingVoltage ratingInterrupting rating where other than 10,000 amperesCurrent limiting where applicableThe name or trademark of the manufacturerThe interrupting rating shall not be required to be marked on fuses used for supplementary protection. [240.60(C)](https://2023.antflix.net#240.60(C))
|
https://2023.antflix.net#240.60(C)
|
Chapter 2 Wiring and Protection
|
240.60(D)
|
Class H cartridge fuses of the renewable type shall be permitted to be used only for replacement in existing installations where there is no evidence of overfusing or tampering. [240.60(D)](https://2023.antflix.net#240.60(D))
|
https://2023.antflix.net#240.60(D)
|
Chapter 2 Wiring and Protection
|
240.60(E)
|
Fuse reducers shall be listed. [240.60(E)](https://2023.antflix.net#240.60(E))
|
https://2023.antflix.net#240.60(E)
|
Chapter 2 Wiring and Protection
|
240.61
|
Cartridge fuses and fuseholders shall be classified according to voltage and amperage ranges. Fuses rated 1000 volts, nominal, or less shall be permitted to be used for voltages at or below their ratings. [240.61](https://2023.antflix.net#240.61)
|
https://2023.antflix.net#240.61
|
Chapter 2 Wiring and Protection
|
240.67
|
Where fuses rated 1200 amperes or higher are installed, 240.67(A), (B), and (C) shall apply. [240.67](https://2023.antflix.net#240.67)
|
https://2023.antflix.net#240.67
|
Chapter 2 Wiring and Protection
|
240.67(A)
|
Documentation shall be available to those authorized to design, install, operate, or inspect the installation as to the location of the fuses. Documentation shall also be provided to demonstrate that the method chosen to reduce clearing time is set to operate at a value below the available arcing current. [240.67(A)](https://2023.antflix.net#240.67(A))
|
https://2023.antflix.net#240.67(A)
|
Chapter 2 Wiring and Protection
|
240.67(B)
|
A fuse shall have a clearing time of 0.07 seconds or less at the available arcing current, or one of the following means shall be provided and shall be set to operate at less than the available arcing current: Differential relayingEnergy-reducing maintenance switching with local status indicatorEnergy-reducing active arc-flash mitigation systemCurrent-limiting, electronically actuated fusesAn approved equivalent meansInformational Note No. 1: An energy-reducing maintenance switch allows a worker to set a disconnect switch to reduce the clearing time while the worker is working within an arc-flash boundary as defined in NFPA 70E-2021, Standard for Electrical Safety in the Workplace, and then to set the disconnect switch back to a normal setting after the potentially hazardous work is complete.Informational Note No. 2: An energy-reducing active arc-flash mitigation system helps in reducing arcing duration in the electrical distribution system. No change in the disconnect switch or the settings of other devices is required during maintenance when a worker is working within an arc-flash boundary as defined in NFPA 70E-2021, Standard for Electrical Safety in the Workplace.Informational Note No. 3: IEEE 1584-2018, IEEE Guide for Performing Arc Flash Hazard Calculations, provides guidance in determining arcing current. [240.67(B)](https://2023.antflix.net#240.67(B))
|
https://2023.antflix.net#240.67(B)
|
Chapter 2 Wiring and Protection
|
240.67(C)
|
The arc energy reduction protection system shall be performance tested by primary current injection testing or another approved method when first installed on site. This testing shall be conducted by a qualified person(s) in accordance with the manufacturer's instructions. A written record of this testing shall be made and shall be available to the authority having jurisdiction. Informational Note: Some energy reduction protection systems cannot be tested using a test process of primary current injection due to either the protection method being damaged such as with the use of fuse technology or because current is not the primary method of arc detection. [240.67(C)](https://2023.antflix.net#240.67(C))
|
https://2023.antflix.net#240.67(C)
|
Chapter 2 Wiring and Protection
|
240.80
|
Circuit breakers shall be trip free and capable of being closed and opened by manual operation. Their normal method of operation by other than manual means, such as electrical or pneumatic, shall be permitted if means for manual operation are also provided. [240.80](https://2023.antflix.net#240.80)
|
https://2023.antflix.net#240.80
|
Chapter 2 Wiring and Protection
|
240.81
|
Circuit breakers shall clearly indicate whether they are in the open "off" or closed "on" position. Where circuit breaker handles are operated vertically rather than rotationally or horizontally, the "up" position of the handle shall be the "on" position. [240.81](https://2023.antflix.net#240.81)
|
https://2023.antflix.net#240.81
|
Chapter 2 Wiring and Protection
|
240.82
|
A circuit breaker shall be of such design that any alteration of its trip point (calibration) or the time required for its operation requires dismantling of the device or breaking of a seal for other than intended adjustments. [240.82](https://2023.antflix.net#240.82)
|
https://2023.antflix.net#240.82
|
Chapter 2 Wiring and Protection
|
240.83(A)
|
Circuit breakers shall be marked with their ampere rating in a manner that will be durable and visible after installation. Such marking shall be permitted to be made visible by removal of a trim or cover. [240.83(A)](https://2023.antflix.net#240.83(A))
|
https://2023.antflix.net#240.83(A)
|
Chapter 2 Wiring and Protection
|
240.83(B)
|
Circuit breakers rated at 100 amperes or less and 1000 volts or less shall have the ampere rating molded, stamped, etched, or similarly marked into their handles or escutcheon areas. [240.83(B)](https://2023.antflix.net#240.83(B))
|
https://2023.antflix.net#240.83(B)
|
Chapter 2 Wiring and Protection
|
240.83(C)
|
Every circuit breaker having an interrupting rating other than 5000 amperes shall have its interrupting rating shown on the circuit breaker. The interrupting rating shall not be required to be marked on circuit breakers used for supplementary protection. [240.83(C)](https://2023.antflix.net#240.83(C))
|
https://2023.antflix.net#240.83(C)
|
Chapter 2 Wiring and Protection
|
240.83(D)
|
Circuit breakers used as switches in 120-volt and 277-volt fluorescent lighting circuits shall be listed and shall be marked SWD or HID. Circuit breakers used as switches in high-intensity discharge lighting circuits shall be listed and shall be marked as HID. [240.83(D)](https://2023.antflix.net#240.83(D))
|
https://2023.antflix.net#240.83(D)
|
Chapter 2 Wiring and Protection
|
240.83(E)
|
Circuit breakers shall be marked with a voltage rating not less than the nominal system voltage that is indicative of their capability to interrupt fault currents between phases or phase to ground. [240.83(E)](https://2023.antflix.net#240.83(E))
|
https://2023.antflix.net#240.83(E)
|
Chapter 2 Wiring and Protection
|
240.85
|
A circuit breaker with a straight voltage rating, such as 240V or 480V, shall be permitted to be applied in a circuit in which the nominal voltage between any two conductors does not exceed the circuit breaker's voltage rating. A two-pole circuit breaker shall not be used for protecting a 3-phase, corner-grounded delta circuit unless the circuit breaker is marked 1ϕ—3ϕ to indicate such suitability. A circuit breaker with a slash rating, such as 120/240V or 480Y/277V, shall be permitted to be applied in a solidly grounded circuit where the nominal voltage of any conductor to ground does not exceed the lower of the two values of the circuit breaker's voltage rating and the nominal voltage between any two conductors does not exceed the higher value of the circuit breaker's voltage rating. Informational Note: Proper application of molded case circuit breakers on 3-phase systems, other than solidly grounded wye, particularly on corner grounded delta systems, considers the circuit breakers' individual pole-interrupting capability. [240.85](https://2023.antflix.net#240.85)
|
https://2023.antflix.net#240.85
|
Chapter 2 Wiring and Protection
|
240.86
|
Where a circuit breaker is used on a circuit having an available fault current higher than the marked interrupting rating by being connected on the load side of an approved overcurrent protective device having a higher rating, the circuit breaker shall meet the requirements specified in 240.86(A) or (B), and (C). [240.86](https://2023.antflix.net#240.86)
|
https://2023.antflix.net#240.86
|
Chapter 2 Wiring and Protection
|
240.86(A)
|
The series rated combination devices shall be selected by a licensed professional engineer engaged primarily in the design or maintenance of electrical installations. The selection shall be documented and stamped by the professional engineer. This documentation shall be available to those authorized to design, install, inspect, maintain, and operate the system. This series combination rating, including identification of the upstream device, shall be field marked on the end use equipment. For calculated applications, the engineer shall ensure that the downstream circuit breaker(s) that are part of the series combination remain passive during the interruption period of the line side fully rated, current-limiting device. Informational Note: See 110.22 for marking of series combination systems. [240.86(A)](https://2023.antflix.net#240.86(A))
|
https://2023.antflix.net#240.86(A)
|
Chapter 2 Wiring and Protection
|
240.86(B)
|
The combination of line-side overcurrent device and load-side circuit breaker(s) is tested and marked on the end use equipment, such as switchboards and panelboards. Informational Note: See 110.22 for marking of series combination systems. [240.86(B)](https://2023.antflix.net#240.86(B))
|
https://2023.antflix.net#240.86(B)
|
Chapter 2 Wiring and Protection
|
240.86(C)
|
Series ratings shall not be used in the following situations: Where motor circuits are connected between the higher-rated overcurrent device of a series-rated combination and on the lower-rated circuit breakerWhere the sum of these motor full-load currents exceeds 1 percent of the interrupting rating of the lower-rated circuit breaker [240.86(C)](https://2023.antflix.net#240.86(C))
|
https://2023.antflix.net#240.86(C)
|
Chapter 2 Wiring and Protection
|
240.87
|
Where the highest continuous current trip setting for which the actual overcurrent device installed in a circuit breaker is rated or can be adjusted is 1200 amperes or higher, 240.87(A), (B), and (C) shall apply. [240.87](https://2023.antflix.net#240.87)
|
https://2023.antflix.net#240.87
|
Chapter 2 Wiring and Protection
|
240.87(A)
|
Documentation shall be available to those authorized to design, install, operate, or inspect the installation as to the location of the circuit breaker(s). Documentation shall also be provided to demonstrate that the method chosen to reduce clearing time is set to operate at a value below the available arcing current. [240.87(A)](https://2023.antflix.net#240.87(A))
|
https://2023.antflix.net#240.87(A)
|
Chapter 2 Wiring and Protection
|
240.87(B)
|
One of the following means shall be provided and shall be set to operate at less than the available arcing current: Zone-selective interlockingDifferential relayingEnergy-reducing maintenance switching with local status indicatorEnergy-reducing active arc flash mitigation systemAn instantaneous trip setting. Temporary adjustment of the instantaneous trip setting to achieve arc energy reduction shall not be permitted.An instantaneous overrideAn approved equivalent meansInformational Note No. 1: An energy-reducing maintenance switch allows a worker to set a circuit breaker trip unit to "no intentional delay" to reduce the clearing time while the worker is working within an arc-flash boundary as defined in NFPA 70E-2021, Standard for Electrical Safety in the Workplace, and then to set the trip unit back to a normal setting after the potentially hazardous work is complete.Informational Note No. 2: An energy-reducing active arc-flash mitigation system helps in reducing arcing duration in the electrical distribution system. No change in the circuit breaker or the settings of other devices is required during maintenance when a worker is working within an arc-flash boundary as defined in NFPA 70E-2021, Standard for Electrical Safety in the Workplace.Informational Note No. 3: An instantaneous trip is a function that causes a circuit breaker to trip with no intentional delay when currents exceed the instantaneous trip setting or current level. If arcing currents are above the instantaneous trip level, the circuit breaker will trip in the minimum possible time.Informational Note No. 4: See IEEE 1584-2018, IEEE Guide for Performing Arc Flash Hazard Calculations, for guidance in determining arcing current. [240.87(B)](https://2023.antflix.net#240.87(B))
|
https://2023.antflix.net#240.87(B)
|
Chapter 2 Wiring and Protection
|
240.87(C)
|
The arc energy reduction protection system shall be performance tested by primary current injection testing or another approved method when first installed on site. This testing shall be conducted by a qualified person(s) in accordance with the manufacturer's instructions. A written record of this testing shall be made and shall be available to the authority having jurisdiction. Informational Note: Some energy reduction protection systems cannot be tested using a test process of primary current injection due to either the protection method being damaged such as with the use of fuse technology or because current is not the primary method of arc detection. [240.87(C)](https://2023.antflix.net#240.87(C))
|
https://2023.antflix.net#240.87(C)
|
Chapter 2 Wiring and Protection
|
240.89
|
Replacement trip units shall be listed for use with the circuit breaker type in which it is installed. Informational Note: The replacement trip unit can be a listed unit identical to the original or a different trip unit listed for use with the specific circuit breaker. [240.89](https://2023.antflix.net#240.89)
|
https://2023.antflix.net#240.89
|
Chapter 2 Wiring and Protection
|
240.90
|
Overcurrent protection in areas of supervised industrial installations shall comply with all of the other applicable provisions of this article, except as provided in Part VIII. Part VIII shall be permitted to apply only to those portions of the electrical system in the supervised industrial installation used exclusively for manufacturing or process control activities. [240.90](https://2023.antflix.net#240.90)
|
https://2023.antflix.net#240.90
|
Chapter 2 Wiring and Protection
|
240.91
|
Conductors shall be protected in accordance with 240.91 (A) or 240.91 (B). [240.91](https://2023.antflix.net#240.91)
|
https://2023.antflix.net#240.91
|
Chapter 2 Wiring and Protection
|
240.91(A)
|
Conductors shall be protected in accordance with 240.4. [240.91(A)](https://2023.antflix.net#240.91(A))
|
https://2023.antflix.net#240.91(A)
|
Chapter 2 Wiring and Protection
|
240.91(B)
|
Where the overcurrent device is rated over 800 amperes, the ampacity of the conductors it protects shall be equal to or greater than 95 percent of the rating of the overcurrent device in accordance with the following: The conductors are protected within recognized time vs. current limits for short-circuit currentsInformational Note: Table 240.92(B) provides time vs. short-circuit current formulas to determine limits for copper and aluminum conductors.All equipment in which the conductors terminate is listed and marked for the application. [240.91(B)](https://2023.antflix.net#240.91(B))
|
https://2023.antflix.net#240.91(B)
|
Chapter 2 Wiring and Protection
|
240.92
|
An overcurrent device shall be connected in each ungrounded circuit conductor as required in 240.92(A) through (E). [240.92](https://2023.antflix.net#240.92)
|
https://2023.antflix.net#240.92
|
Chapter 2 Wiring and Protection
|
240.92(A)
|
Feeder and branch-circuit conductors shall be protected at the point the conductors receive their supply as permitted in 240.21 or as otherwise permitted in 240.92(B), (C), (D), or (E). [240.92(A)](https://2023.antflix.net#240.92(A))
|
https://2023.antflix.net#240.92(A)
|
Chapter 2 Wiring and Protection
|
240.92(B)
|
For feeder taps specified in 240.21(B)(2), (B)(3), and (B)(4), the tap conductors shall be permitted to be sized in accordance with Table 240.92(B).Table 240.92(B) Tap Conductor Short-Circuit Current Ratings Tap conductors are considered to be protected under short-circuit conditions when their short-circuit temperature limit is not exceeded. Conductor heating under short-circuit conditions is determined by (1) or (2): (1) Short-Circuit Formula for Copper Conductors (I2/A2) t = 0.0297 log10 [(T2 + 234)/(T1 + 234)] (2) Short-Circuit Formula for Aluminum Conductors (I2/A2) t = 0.0125 log10 [(T2 + 228)/(T1 + 228)] where: I = short-circuit current in amperes A = conductor area in circular mils t = time of short circuit in seconds (for times less than or equal to 10 seconds) T1 = initial conductor temperature in degrees Celsius T2 = final conductor temperature in degrees Celsius Copper conductor with paper, rubber, varnished cloth insulation, T2 = 200 Copper conductor with thermoplastic insulation, T2 = 150 Copper conductor with cross-linked polyethylene insulation, T2 = 250 Copper conductor with ethylene propylene rubber insulation, T2 = 250 Aluminum conductor with paper, rubber, varnished cloth insulation, T2 = 200 Aluminum conductor with thermoplastic insulation, T2 = 150 Aluminum conductor with cross-linked polyethylene insulation, T2 = 250 Aluminum conductor with ethylene propylene rubber insulation, T2 = 250 [240.92(B)](https://2023.antflix.net#240.92(B))
|
https://2023.antflix.net#240.92(B)
|
Chapter 2 Wiring and Protection
|
240.92(C)
|
Conductors shall be permitted to be connected to a transformer secondary of a separately derived system, without overcurrent protection at the connection, where the conditions of 240.92(C)(1), (C)(2), and (C)(3) are met. [240.92(C)](https://2023.antflix.net#240.92(C))
|
https://2023.antflix.net#240.92(C)
|
Chapter 2 Wiring and Protection
|
240.92(C)(1)
|
The conductors shall be protected from short-circuit and ground-fault conditions by complying with one of the following conditions: The length of the secondary conductors does not exceed 30 m (100 ft), and the transformer primary overcurrent device has a rating or setting that does not exceed 150 percent of the value determined by multiplying the secondary conductor ampacity by the secondary-to-primary transformer voltage ratio.The conductors are protected by a differential relay with a trip setting equal to or less than the conductor ampacity.Informational Note: A differential relay is connected to be sensitive only to short-circuit or fault currents within the protected zone and is normally set much lower than the conductor ampacity. The differential relay is connected to trip protective devices that de-energize the protected conductors if a short-circuit condition occurs.The conductors shall be considered to be protected if calculations, made under engineering supervision, determine that the system overcurrent devices will protect the conductors within recognized time vs. current limits for all short-circuit and ground-fault conditions. [240.92(C)(1)](https://2023.antflix.net#240.92(C)(1))
|
https://2023.antflix.net#240.92(C)(1)
|
Chapter 2 Wiring and Protection
|
240.92(C)(2)
|
The conductors shall be protected against overload conditions by complying with one of the following: The conductors terminate in a single overcurrent device that will limit the load to the conductor ampacity.The sum of the overcurrent devices at the conductor termination limits the load to the conductor ampacity. The overcurrent devices shall consist of not more than six circuit breakers or sets of fuses mounted in a single enclosure, in a group of separate enclosures, or in or on a switchboard or switchgear. There shall be no more than six overcurrent devices grouped in any one location.Overcurrent relaying is connected [with a current transformer(s), if needed] to sense all of the secondary conductor current and limit the load to the conductor ampacity by opening upstream or downstream devices.Conductors shall be considered to be protected if calculations, made under engineering supervision, determine that the system overcurrent devices will protect the conductors from overload conditions. [240.92(C)(2)](https://2023.antflix.net#240.92(C)(2))
|
https://2023.antflix.net#240.92(C)(2)
|
Chapter 2 Wiring and Protection
|
240.92(C)(3)
|
The secondary conductors are protected from physical damage by being enclosed in an approved raceway or by other approved means. [240.92(C)(3)](https://2023.antflix.net#240.92(C)(3))
|
https://2023.antflix.net#240.92(C)(3)
|
Chapter 2 Wiring and Protection
|
240.92(D)
|
Outside conductors shall be permitted to be tapped to a feeder or to be connected at a transformer secondary, without overcurrent protection at the tap or connection, where all the following conditions are met: The conductors are protected from physical damage in an approved manner.The sum of the overcurrent devices at the conductor termination limits the load to the conductor ampacity. The overcurrent devices shall consist of not more than six circuit breakers or sets of fuses mounted in a single enclosure, in a group of separate enclosures, or in or on a switchboard or switchgear. There shall be no more than six overcurrent devices grouped in any one location.The tap conductors are installed outdoors of a building or structure except at the point of load termination.The overcurrent device for the conductors is an integral part of a disconnecting means or is located immediately adjacent thereto.The disconnecting means for the conductors are installed at a readily accessible location complying with one of the following:Outside of a building or structureInside, nearest the point of entrance of the conductorsWhere installed in accordance with 230.6, nearest the point of entrance of the conductors [240.92(D)](https://2023.antflix.net#240.92(D))
|
https://2023.antflix.net#240.92(D)
|
Chapter 2 Wiring and Protection
|
240.92(E)
|
Conductors supplied by the secondary side of a transformer shall be permitted to be protected by overcurrent protection provided on the primary (supply) side of the transformer, provided the primary device time—current protection characteristic, multiplied by the maximum effective primary-to-secondary transformer voltage ratio, effectively protects the secondary conductors. [240.92(E)](https://2023.antflix.net#240.92(E))
|
https://2023.antflix.net#240.92(E)
|
Chapter 2 Wiring and Protection
|
242.1
|
This article provides the general requirements, installation requirements, and connection requirements for overvoltage protection and overvoltage protective devices. Part II covers surge-protective devices (SPDs) permanently installed on premises wiring systems of not more than 1000 volts, nominal, while Part III covers surge arresters permanently installed on premises wiring systems over 1000 volts, nominal. [242.1](https://2023.antflix.net#242.1)
|
https://2023.antflix.net#242.1
|
Chapter 2 Wiring and Protection
|
242.2
|
SPDs and surge arresters shall not be reconditioned. [242.2](https://2023.antflix.net#242.2)
|
https://2023.antflix.net#242.2
|
Chapter 2 Wiring and Protection
|
242.3
|
Equipment shall be protected against overvoltage in accordance with the article in this Code that covers the type of equipment or location specified in Table 242.3. Table 242.3 Other Articles Equipment Article Class I locations 501 Class II locations 502 Community antenna television and radio distribution systems 820 Critical operations power systems 708 Elevators, dumbwaiters, escalators, moving walks, platform lifts, and stairway chairlifts 620 Emergency systems 700 Equipment over 1000 volts, nominal 495 Fire pumps 695 Industrial machinery 670 Information technology equipment 645 Modular data centers 646 Outdoor overhead conductors over 1000 volts 395 Radio and television equipment 810 Receptacles, cord connectors, and attachment plugs (caps) 406 Wind electric systems 694 [242.3](https://2023.antflix.net#242.3)
|
https://2023.antflix.net#242.3
|
Chapter 2 Wiring and Protection
|
242.6
|
An SPD shall be a listed device. [242.6](https://2023.antflix.net#242.6)
|
https://2023.antflix.net#242.6
|
Chapter 2 Wiring and Protection
|
242.8
|
The SPD shall be marked with a short-circuit current rating and shall not be installed at a point on the system where the available fault current is in excess of that rating. This marking requirement shall not apply to receptacles. [242.8](https://2023.antflix.net#242.8)
|
https://2023.antflix.net#242.8
|
Chapter 2 Wiring and Protection
|
242.9
|
An SPD shall provide indication that it is functioning properly. [242.9](https://2023.antflix.net#242.9)
|
https://2023.antflix.net#242.9
|
Chapter 2 Wiring and Protection
|
242.12
|
An SPD device shall not be installed in the following: Circuits over 1000 voltsOn ungrounded systems, impedance grounded systems, or corner grounded delta systems unless listed specifically for use on these systemsWhere the rating of the SPD is less than the maximum continuous phase-to-ground voltage at the power frequency available at the point of application [242.12](https://2023.antflix.net#242.12)
|
https://2023.antflix.net#242.12
|
Chapter 2 Wiring and Protection
|
242.13
|
Type 1 SPDs shall be installed in accordance with 242.13(A) and (B). [242.13](https://2023.antflix.net#242.13)
|
https://2023.antflix.net#242.13
|
Chapter 2 Wiring and Protection
|
242.13(A)
|
Type 1 SPDs shall be permitted to be connected in accordance with one of the following: To the supply side of the service disconnect as permitted in 230.82(4)As specified in 242.14 [242.13(A)](https://2023.antflix.net#242.13(A))
|
https://2023.antflix.net#242.13(A)
|
Chapter 2 Wiring and Protection
|
242.13(B)
|
When installed at services, Type 1 SPDs shall be connected to one of the following: Grounded service conductorGrounding electrode conductorGrounding electrode for the serviceEquipment grounding terminal in the service equipment [242.13(B)](https://2023.antflix.net#242.13(B))
|
https://2023.antflix.net#242.13(B)
|
Chapter 2 Wiring and Protection
|
242.14
|
Type 2 SPDs shall be installed in accordance with 242.14(A) through (C). [242.14](https://2023.antflix.net#242.14)
|
https://2023.antflix.net#242.14
|
Chapter 2 Wiring and Protection
|
242.14(A)
|
Type 2 SPDs shall be connected anywhere on the load side of a service disconnect overcurrent device required in 230.91 unless installed in accordance with 230.82(8). [242.14(A)](https://2023.antflix.net#242.14(A))
|
https://2023.antflix.net#242.14(A)
|
Chapter 2 Wiring and Protection
|
242.14(B)
|
Type 2 SPDs shall be connected at the building or structure anywhere on the load side of the first overcurrent device at the building or structure. [242.14(B)](https://2023.antflix.net#242.14(B))
|
https://2023.antflix.net#242.14(B)
|
Chapter 2 Wiring and Protection
|
242.14(C)
|
The SPD shall be connected on the load side of the first overcurrent device in a separately derived system. [242.14(C)](https://2023.antflix.net#242.14(C))
|
https://2023.antflix.net#242.14(C)
|
Chapter 2 Wiring and Protection
|
242.16
|
Type 3 SPDs shall be permitted to be installed on the load side of branch-circuit overcurrent protection up to the equipment served. If included in the manufacturer's instructions, the Type 3 SPD connection shall be a minimum 10 m (30 ft) of conductor distance from the service or separately derived system disconnect. [242.16](https://2023.antflix.net#242.16)
|
https://2023.antflix.net#242.16
|
Chapter 2 Wiring and Protection
|
242.18
|
Type 4 component assemblies and other component type SPDs shall only be installed by the equipment manufacturer. [242.18](https://2023.antflix.net#242.18)
|
https://2023.antflix.net#242.18
|
Chapter 2 Wiring and Protection
|
242.20
|
Where used at a point on a circuit, the SPD shall be connected to each ungrounded conductor. [242.20](https://2023.antflix.net#242.20)
|
https://2023.antflix.net#242.20
|
Chapter 2 Wiring and Protection
|
242.22
|
SPDs shall be permitted to be located indoors or outdoors and shall be made inaccessible to unqualified persons unless listed for installation in accessible locations. [242.22](https://2023.antflix.net#242.22)
|
https://2023.antflix.net#242.22
|
Chapter 2 Wiring and Protection
|
242.24
|
The conductors used to connect the SPD to the line or bus and to ground shall not be any longer than necessary and shall avoid unnecessary bends. [242.24](https://2023.antflix.net#242.24)
|
https://2023.antflix.net#242.24
|
Chapter 2 Wiring and Protection
|
242.28
|
SPD line conductors and conductors to ground shall not be smaller than 14 AWG copper or 12 AWG aluminum. [242.28](https://2023.antflix.net#242.28)
|
https://2023.antflix.net#242.28
|
Chapter 2 Wiring and Protection
|
242.30
|
An SPD shall be permitted to be connected between any two conductors - ungrounded conductor(s), grounded conductor, equipment grounding conductor, or grounding electrode conductor. The grounded conductor and the equipment grounding conductor shall be interconnected only by the normal operation of the SPD during a surge. [242.30](https://2023.antflix.net#242.30)
|
https://2023.antflix.net#242.30
|
Chapter 2 Wiring and Protection
|
242.32
|
Except as indicated in this article, SPD grounding connections shall be made as specified in Article 250, Part III. Grounding electrode conductors installed in metal enclosures shall comply with 250.64(E). [242.32](https://2023.antflix.net#242.32)
|
https://2023.antflix.net#242.32
|
Chapter 2 Wiring and Protection
|
242.40
|
A surge arrester shall not be installed where the rating of the surge arrester is less than the maximum continuous phase-to-ground voltage at the power frequency available at the point of application. [242.40](https://2023.antflix.net#242.40)
|
https://2023.antflix.net#242.40
|
Chapter 2 Wiring and Protection
|
242.42
|
The duty cycle rating of a surge arrester shall be not less than 125 percent of the maximum continuous operating voltage available at the point of application. For solidly grounded systems, the maximum continuous operating voltage shall be the phase-to-ground voltage of the system. For impedance or ungrounded systems, the maximum continuous operating voltage shall be the phase-to-phase voltage of the system. Informational Note No. 1: See IEEE C62.11-2020. Standard for Metal-Oxide Surge Arresters for Alternating-Current Power Circuits (>1 kV), and IEEE C62.22-2009, Guide for the Application of Metal-Oxide Surge Arresters for Alternating-Current Systems, for further information on surge arresters. Informational Note No. 2: The selection of a properly rated metal oxide arrester is based on considerations of maximum continuous operating voltage and the magnitude and duration of overvoltages at the arrester location as affected by phase-to-ground faults, system grounding techniques, switching surges, and other causes. See the manufacturer's application rules for selection of the specific arrester to be used at a particular location. [242.42](https://2023.antflix.net#242.42)
|
https://2023.antflix.net#242.42
|
Chapter 2 Wiring and Protection
|
242.44
|
Where used at a point on a circuit, a surge arrester shall be connected to each ungrounded conductor. A single installation of such surge arresters shall be permitted to protect a number of interconnected circuits if no circuit is exposed to surges while disconnected from the surge arresters. [242.44](https://2023.antflix.net#242.44)
|
https://2023.antflix.net#242.44
|
Chapter 2 Wiring and Protection
|
242.46
|
Surge arresters shall be permitted to be located indoors or outdoors. Surge arresters shall be made inaccessible to unqualified persons unless listed for installation in accessible locations. [242.46](https://2023.antflix.net#242.46)
|
https://2023.antflix.net#242.46
|
Chapter 2 Wiring and Protection
|
242.48
|
The conductor used to connect the surge arrester to line, bus, or equipment and to an equipment grounding conductor or grounding electrode connection point as provided in 242.50 shall not be any longer than necessary and shall avoid unnecessary bends. [242.48](https://2023.antflix.net#242.48)
|
https://2023.antflix.net#242.48
|
Chapter 2 Wiring and Protection
|
242.50
|
The arrester shall be connected to one of the following: Grounded service conductorGrounding electrode conductorGrounding electrode for the serviceEquipment grounding terminal in the service equipment [242.50](https://2023.antflix.net#242.50)
|
https://2023.antflix.net#242.50
|
Chapter 2 Wiring and Protection
|
242.52
|
The conductor between the surge arrester and the line, and the surge arrester and the grounding connection, shall not be smaller than 6 AWG copper or aluminum. [242.52](https://2023.antflix.net#242.52)
|
https://2023.antflix.net#242.52
|
Chapter 2 Wiring and Protection
|
242.54
|
The surge arrester protecting a transformer that supplies a secondary distribution system shall be interconnected as specified in 242.54(A), (B), or (C). [242.54](https://2023.antflix.net#242.54)
|
https://2023.antflix.net#242.54
|
Chapter 2 Wiring and Protection
|
242.54(A)
|
A metal interconnection shall be made to the secondary grounded circuit conductor or the secondary circuit grounding electrode conductor, if, in addition to the direct grounding connection at the surge arrester, the connection complies with 242.54(A)(1) or (A)(2). [242.54(A)](https://2023.antflix.net#242.54(A))
|
https://2023.antflix.net#242.54(A)
|
Chapter 2 Wiring and Protection
|
242.54(A)(1)
|
The grounded conductor of the secondary has a grounding connection elsewhere to a continuous metal underground water piping system. In urban water-pipe areas where there are at least four water-pipe connections on the neutral conductor and not fewer than four such connections in each mile of neutral conductor, the metal interconnection shall be permitted to be made to the secondary neutral conductor with omission of the direct grounding connection at the surge arrester. [242.54(A)(1)](https://2023.antflix.net#242.54(A)(1))
|
https://2023.antflix.net#242.54(A)(1)
|
Chapter 2 Wiring and Protection
|
242.54(A)(2)
|
The grounded conductor of the secondary system is part of a multigrounded neutral system or static wire of which the primary neutral conductor or static wire has at least four grounding connections in each 1.6 km (1 mile) of line in addition to a grounding connection at each service. [242.54(A)(2)](https://2023.antflix.net#242.54(A)(2))
|
https://2023.antflix.net#242.54(A)(2)
|
Chapter 2 Wiring and Protection
|
242.54(B)
|
Where the surge arrester grounding electrode conductor is not connected as in 242.54(A), or where the secondary is not grounded as in 242.54(A) but is otherwise grounded as in 250.52, an interconnection shall be made through a spark gap or listed device as required by 242.54(B)(1) or (B)(2). [242.54(B)](https://2023.antflix.net#242.54(B))
|
https://2023.antflix.net#242.54(B)
|
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