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ing means, and the service/transformer overcurrent protective device (OCPD) are underground service conductors. The conductors between the transformer secondary and the line side of the building disconnecting means are feeders and are subject to the requirements in 240.21(C)(4) for outside conductor...

ing means, and the service/transformer overcurrent protective device (OCPD) are underground service conductors. The conductors between the transformer secondary and the line side of the building disconnecting means are feeders and are subject to the requirements in 240.21(C)(4) for outside conductors connected to a transformer secondary. Conductors (not shown) on the load side of the building disconnecting means are also feeders. Each building or structure is required to have a disconnecting means, in accordance with 225.31. 235.402 Service-Entrance Conductors. Service-entrance conductors to buildings or enclosures shall be installed to conform to 235.402(A) and (B). (A) Conductor Size. Service-entrance conductors shall not be smaller than 6 AWG unless in multiconductor cable. Multiconductor cable shall not be smaller than 8 AWG. (B) Wiring Methods. Service-entrance conductors shall be installed by one of the wiring methods covered in 305.3 and 305.15. 235.404 Isolating Switches. (A) Where Required. Where oil switches or air, oil, vacuum, or sulfur hexafluoride circuit breakers constitute the service disconnecting means, an isolating switch with visible break contacts shall be installed on the supply side of the disconnecting means and all associated service equipment. Exception: An isolating switch shall not be required where the circuit breaker or switch is mounted on removable truck panels or switchgear units where both of the following conditions apply: * (1) Cannot be opened unless the circuit is disconnected * (2) Where all energized parts are automatically disconnected when the circuit breaker or switch is removed from the normal operating position (B) Fuses as Isolating Switch. Where fuses are of the type that can be operated as a disconnecting switch, a set of such fuses shall be permitted as the isolating switch. (C) Accessible to Qualified Persons Only. The isolating switch shall be accessible to qualified persons only. (D) Connection to Ground. Isolating switches shall be provided with a means for readily connecting the load side conductors to a grounding electrode system, equipment ground busbar, or grounded steel structure when disconnected from the source of supply. A means for grounding the load side conductors to a grounding electrode system, equipment grounding busbar, or grounded structural steel shall not be required for any duplicate isolating switch installed and maintained by the electric supply company. 235.405 Disconnecting Means. (A) Location. The service disconnecting means shall be located in accordance with 230.70. For either overhead or underground primary distribution systems on private property, the service disconnect shall be permitted to be located in a location that is not readily accessible, if the disconnecting means can be operated by mechanical linkage from a readily accessible point, or electronically in accordance with 235.405(C), where applicable. ENHANCED CONTENT Collapse The general requirement for service disconnecting means in systems rated over 1000 volts is that it be readily accessible. Because ready access might not be possible, or desirable (if it could put employees at risk), the use of a readily accessible operating mechanism or an electronic switching device is an acceptable alternative. (B) Type. Each service disconnect shall simultaneously disconnect all ungrounded service conductors that it controls and shall have a fault-closing rating that is not less than the available fault current at its supply terminals. Where fused switches or separately mounted fuses are instal?led, the fuse characteristics shall be permitted to contribute to the fault-closing rating of the disconnecting means. (C) Remote Control. For multibuilding, industrial installations under single management, the service disconnecting means shall be permitted to be located at a separate building or structure. In such cases, the service disconnecting means shall be permitted to be electrically operated by a readily accessible, remote-control device. 235.406 Overcurrent Devices as Disconnecting Means. Where the circuit breaker or alternative for it, as specified in 235.408 for service overcurrent devices, meets the requirements specified in 235.405, it shall constitute the service disconnecting means. 235.408 Protection Requirements. A short-circuit protective device shall be provided on the load side of, or as an integral part of, the service disconnect, and shall protect all ungrounded conductors that it supplies. The protective device shall be capable of detecting and interrupting all values of current, in excess of its trip setting or melting point, that can occur at its location. A fuse rated in continuous amperes not to exceed three times the ampacity of the conductor, or a circuit breaker with a trip setting of not more than six times the ampacity of the conductors, shall be considered as providing the required short-circuit protection. Informational Note: See Table 315.60(C)(1) through Table 315.60(C)(20) for ampacities of conductors rated 2001 volts to 35,000 volts. Overcurrent devices shall conform to 235.408(A) and (B). (A) Equipment Type. Equipment used to protect service-entrance conductors shall meet the requirements of Article 495, Part II. (B) Enclosed Overcurrent Devices. The restriction to 80 percent of the rating for an enclosed overcurrent device for continuous loads shall not apply to overcurrent devices instal?led in systems operating at over 1000 volts. 235.409 Surge Arresters. Surge arresters installed in accordance with the requirements of Parts II and III of Article 242 shall be permitted on each ungrounded overhead service conductor. Informational Note: Surge arresters may be referred to as lightning arresters in older documents. 235.410 Service Equipment - General. Service equipment, including instrument transformers, shall conform to Part I of Article 495. 235.411 Switchgear. Switchgear shall consist of a substantial metal structure and a sheet metal enclosure. Where installed over a combustible floor, suitable protection thereto shall be provided. ENHANCED CONTENT Collapse A vault in accordance with 235.412 can be used in lieu of switchgear for voltages below 35,000 volts. 235.412 Over 35,000 Volts. Where the voltage exceeds 35,000 volts between conductors that enter a building, they shall terminate in a switchgear compartment or a vault conforming to the requirements of 450.41 through 450.48. Article 240 Overcurrent Protection Part I. General 240.1 Scope. Parts I through VII of this article provide the general requirements for overcurrent protection and overcurrent protective devices not more than 1000 volts, nominal. Part VIII covers overcurrent protection for those portions of supervised industrial installations operating at voltages of not more than 1000 volts, nominal. Informational Note No. 1: Overcurrent protection for conductors and equipment is provided to open the circuit if the current reaches a value that will cause an excessive or dangerous temperature in conductors or conductor insulation. Informational Note No. 2: See 110.9 for requirements for interrupting ratings and 110.10 for requirements for protection against fault currents. ENHANCED CONTENT Collapse Definitions. Each of the following terms has a definition in Article 100 that is unique to its use in Article 240: Current-limiting overcurrent protective device Supervised industrial installation Tap conductor 240.2 Reconditioned Equipment. (A) Reconditioning Not Permitted. The following equipment shall not be reconditioned: * (1) Equipment providing ground-fault protection of equipment * (2) Ground-fault circuit interrupters * (3) Low-voltage fuseholders and low-voltage nonrenewable fuses * (4) Molded-case circuit breakers * (5) Low-voltage power circuit breaker electronic trip units. (B) Reconditioning Permitted. The following equipment shall be permitted to be reconditioned: * (1) Low-voltage power circuit breakers * (2) Electromechanical protective relays and current transformers Reconditioned equipment shall be listed as reconditioned and comply with 110.21(A)(2). 240.3 Other Articles. Equipment shall be protected against overcurrent in accordance with the article in this Code that covers the type of equipment specified in Table 240.3. Table 240.3 Other Articles Equipment Article Air-conditioning and refrigerating equipment 440 Appliances 422 Assembly occupancies 518 Audio signal processing, amplification, and reproduction equipment 640 Branch circuits 210 Busways 368 Capacitors 460 Class 1 power-limited circuits and Class 1 power-limited remote- control and signaling circuits 724 Class 2 and Class 3 remote-control, signaling, and power-limited circuits 725 Cranes and hoists 610 Electric signs and outline lighting 600 Electric welders 630 Electrolytic cells 668 Elevators, dumbwaiters, escalators, moving walks, wheelchair lifts, and stairway chairlifts 620 Emergency systems 700 Fire alarm systems 760 Fire pumps 695 Fixed electric heating equipment for pipelines and vessels 427 Fixed electric space-heating equipment 424 Fixed outdoor electric deicing and snow-melting equipment 426 Generators 445 Health care facilities 517 Induction and dielectric heating equipment 665 Industrial machinery 670 Luminaires, lampholders, and lamps 410 Motion picture and television studios and similar locations 530 Motors, motor circuits, and controllers 430 Phase converters 455 Pipe organs 650 Receptacles 406 Services 230 Solar photovoltaic systems 690 Switchboards, switchgear, and panelboards 408 Theaters, audience areas of motion picture and television studios, and similar locations 520 Transformers and transformer vaults 450 X-ray equipment 660 240.4 Protection of Conductors. Conductors, other than flexible cords, flexible cables, and fixture wires, shall be protected against overcurrent in accordance with their ampacities specified in 310.14, unless otherwise permitted or required in 240.4(A) through (H). Informational Note: See ICEA P-32-382-2018, Short Circuit Characteristics of Insulated Cables, for information on allowable short-circuit currents for insulated copper and aluminum conductors. (A) Power Loss Hazard. Conductor overload protection shall not be required where the interruption of the circuit would create a hazard, such as in a material-handling magnet circuit or fire pump circuit. Short-circuit protection shall be provided. Informational Note: See NFPA 20-2019, Standard for the Installation of Stationary Pumps for Fire Protection. (B) Overcurrent Devices Rated 800 Amperes or Less. The next higher standard overcurrent device rating (above the ampacity of the conductors being protected) shall be permitted to be used, provided all of the following conditions are met: * (1) The conductors being protected are not part of a branch circuit supplying more than one receptacle for cord-and-plug-connected portable loads. * (2) The ampacity of the conductors does not correspond with the standard ampere rating of a fuse or a circuit breaker without overload trip adjustments above its rating (but that shall be permitted to have other trip or rating adjustments). * (3) The next higher standard rating selected does not exceed 800 amperes. If the overcurrent protective device is an adjustable trip deviceinstalled in accordance with 240.4(B)(1), (B)(2), and (B)(3), it shall be permitted to be set to a value that does not exceed the next higher standard value above the ampacity of the conductors being protected as shown in Table 240.6(A) where restricted access in accordance with 240.6(C) is provided. ENHANCED CONTENT Collapse Table 240.6(A) lists the standard ratings of overcurrent devices. Where the ampacity of the conductor specified in Article 310 does not match the rating of the standard overcurrent device, 240.4(B) permits the use of the next larger standard overcurrent device. All three conditions must be met for this permission to apply. For example, in Table 310.16, the ampacity for 3 AWG, 75øC copper, Type THWN, is listed as 100 amperes. That conductor would have to be protected by an overcurrent protective device (OCPD) rated not more than 100 amperes unless otherwise permitted in 240.4(E), (F), or (G). Section 240.4(B) does not modify or change the allowable ampacity of the conductor - it serves only to provide a reasonable increase in the permitted OCPD rating where the allowable ampacity and the standard OCPD ratings do not correspond. For example, a 500-kcmil THWN copper conductor has an allowable ampacity of 380 amperes, specified in Table 310.16. This conductor can supply a load not exceeding 380 amperes and, in accordance with 240.4(B), can be protected by a 400-ampere OCPD. Application of 310.12 is permitted only for single-phase, 120/240-volt, residential services and feeder conductors that supply the entire load of the dwelling unit. The service and main power feeder loads permitted to be supplied by the conductor types and sizes exceed the conductor ampacities for the same conductor types and sizes specified in Table 310.16. The overcurrent protection for these residential supply conductors is also permitted to be based on the increased rating allowed by 310.12. The increased ratings are based on the significant diversity inherent to most dwelling unit loads and the fact that only the two ungrounded service or feeder conductors are considered to be current carrying. See also Example D7 in Annex D for a table of conductor sizes for feeders and services based on the application of the equation in 310.12. (C) Overcurrent Devices Rated over 800 Amperes. Where the overcurrent device is rated over 800 amperes, the ampacity of the conductors it protects shall be equal to or greater than the rating of the overcurrent device defined in 240.6. (D) Small Conductors. Unless specifically permitted in 240.4(E) or (G), the overcurrent protection shall not exceed that required by 240.4(D)(1) through (D)(8) after any correction factors for ambient temperature and number of conductors have been applied. (1) 18 AWG Copper. 7 amperes, provided all the following conditions are met: * (1) Continuous loads do not exceed 5.6 amperes. * (2) Overcurrent protection is provided by one of the following: o a. Branch-circuit-rated circuit breakers listed and marked for use with 18 AWG copper conductor o b. Branch-circuit-rated fuses listed and marked for use with 18 AWG copper conductor o c. Class CC, Class CF, Class J, or Class T fuses (2) 16 AWG Copper. 10 amperes, provided all the following conditions are met: * (1) Continuous loads do not exceed 8 amperes. * (2) Overcurrent protection is provided by one of the following: o a. Branch-circuit-rated circuit breakers listed and marked for use with 16 AWG copper conductor o b. Branch-circuit-rated fuses listed and marked for use with 16 AWG copper conductor o c. Class CC, Class CF, Class J, or Class T fuses (3) 14 AWG Copper-Clad Aluminum. 10 amperes, provided all the following conditions are met: * (1) Continuous loads do not exceed 8 amperes * (2) Overcurrent protection is provided by one of the following: o a. Branch-circuit-rated circuit breakers are listed and marked for use with 14 AWG copper-clad aluminum conductor. o b. Branch-circuit-rated fuses are listed and marked for use with 14 AWG copper-clad aluminum conductor. (4) 14 AWG Copper. 15 amperes (5) 12 AWG Aluminum and Copper-Clad Aluminum. 15 amperes (6) 12 AWG Copper. 20 amperes (7) 10 AWG Aluminum and Copper-Clad Aluminum. 25 amperes (8) 10 AWG Copper. 30 amperes (E) Tap Conductors. Tap conductors shall be permitted to be protected against overcurrent in accordance with the following: * (1) 210.19(C) and (D), Household Ranges and Cooking Appliances and Other Loads * (2) 240.5(B)(2), Fixture Wire * (3) 240.21, Location in Circuit * (4) 368.17(B), Reduction in Ampacity Size of Busway * (5) 368.17(C), Feeder or Branch Circuits (busway taps) * (6) 430.53(D), Single Motor Taps (F) Transformer Secondary Conductors. Single-phase (other than 2-wire) and multiphase (other than delta-delta, 3-wire) transformer secondary conductors shall not be considered to be protected by the primary overcurrent protective device. Conductors supplied by the secondary side of a single-phase transformer having a 2-wire (single-voltage) secondary, or a three-phase, delta-delta connected transformer having a 3-wire (single-voltage) secondary, shall be permitted to be protected by overcurrent protection provided on the primary (supply) side of the transformer, provided this protection is in accordance with 450.3 and does not exceed the value determined by multiplying the secondary conductor ampacity by the secondary-to-primary transformer voltage ratio. (G) Overcurrent Protection for Specific Conductor Applications. Overcurrent protection for the specific conductors shall be permitted to be provided as referenced in Table 240.4(G). Table 240.4(G) Specific Conductor Applications Conductor Article Section Air-conditioning and refrigeration equipment circuit conductors 440, Parts III, IV, VI Capacitor circuit conductors 460 460.8(B) and 460.25 Control and instrumentation circuit conductors (Type ITC) 335 335.9 Electric welder circuit conductors 630 630.12 and 630.32 Fire alarm system circuit conductors 760 760.43, 760.45, 760.121, and Chapter 9, Tables 12(A) and 12(B) Motor-operated appliance circuit conductors 422, Part II Motor and motor-control circuit conductors 430, Parts II, III, IV, V, VI, VII Phase converter supply conductors 455 455.7 Remote-control, signaling, and power- limited circuit conductors 725 724.43, 724.45, 725.60, and Chapter 9, Tables 11(A) and 11(B) Secondary tie conductors 450 450.6 (H) Dwelling Unit Service and Feeder Conductors. Dwelling unit service and feeder conductors shall be permitted to be protected against overcurrent at the ampacity values in 310.12. 240.5 Protection of Flexible Cords, Flexible Cables, and Fixture Wires. Flexible cord and flexible cable, including tinsel cord and extension cords, and fixture wires shall be protected against overcurrent by either 240.5(A) or (B). (A) Ampacities. Flexible cord and flexible cable shall be protected by an overcurrent device in accordance with their ampacity as specified in Table 400.5(A)(1) and Table 400.5(A)(2). Fixture wire shall be protected against overcurrent in accordance with its ampacity as specified in Table 402.5. Supplementary overcurrent protection, as covered in 240.10, shall be permitted to be an acceptable means for providing this protection. (B) Branch-Circuit Overcurrent Device. Flexible cord shall be protected, where supplied by a branch circuit, in accordance with one of the methods described in 240.5(B)(1), (B)(3), or (B)(4). Fixture wire shall be protected, where supplied by a branch circuit, in accordance with 240.5(B)(2). (1) Supply Cord of Listed Appliance or Luminaire. Where flexible cord or tinsel cord is approved for and used with a specific listed appliance or luminaire, it shall be considered to be protected when applied within the appliance or luminaire listing requirements. For the purposes of this section, a luminaire may be either portable or permanent. (2) Fixture Wire. Fixture wire shall be permitted to be tapped to the branch-circuit conductor of a branch circuit in accordance with the following: * (1) 15- or 20-ampere circuits - 18 AWG, up to 15 m (50 ft) of run length * (2) 15- or 20-ampere circuits - 16 AWG, up to 30 m (100 ft) of run length * (3) 20-ampere circuits - 14 AWG and larger * (4) 30-ampere circuits - 14 AWG and larger * (5) 40-ampere circuits - 12 AWG and larger * (6) 50-ampere circuits - 12 AWG and larger (3) Extension Cord Sets. Flexible cord used in listed extension cord sets shall be considered to be protected when applied within the extension cord listing requirements. (4) Field Assembled Extension Cord Sets. Flexible cord used in extension cords made with separately listed and installed components shall be permitted to be supplied by a branch circuit in accordance with the following: 20-ampere circuits - 16 AWG and larger 240.6 Standard Ampere Ratings. (A) Fuses and Fixed-Trip Circuit Breakers. The standard ampere ratings for fuses and inverse time circuit breakers shall be considered as shown in Table 240.6(A). Additional standard ampere ratings for fuses shall be 1, 3, 6, and 601. The use of fuses and inverse time circuit breakers with nonstandard ampere ratings shall be permitted. Table 240.6(A) Standard Ampere Ratings for Fuses and Inverse Time Circuit Breakers Standard Ampere Ratings 10 15 20 25 30 35 40 45 50 60 70 80 90 100 110 125 150 175 200 225 250 300 350 400 450 500 600 700 800 1000 1200 1600 2000 2500 3000 4000 5000 6000 - - (B) Adjustable-Trip Circuit Breakers. The rating of adjustable-trip circuit breakers having external means for adjusting the current setting (long-time pickup setting), not meeting the requirements of 240.6(C), shall be the maximum setting possible. ENHANCED CONTENT Collapse The set long-time pickup rating of an adjustable-trip circuit breaker is permitted to be considered the circuit-breaker rating where access to the adjustment means is limited. Access limitation can be provided by locating the adjustment means behind sealable covers, as shown below. The purpose of limiting access to the adjustment prevents tampering or readjustment by unqualified personnel. (Courtesy of Square D by Schneider Electric) (C) Local Restricted Access Adjustable-Trip Circuit Breakers. A circuit breaker(s) that has restricted access to the adjusting means shall be permitted to have an ampere rating(s) that is equal to the adjusted current setting (long-time pickup setting). Restricted access shall be achieved by one of the following methods: * (1) Located behind removable and sealable covers over the adjusting means * (2) Located behind bolted equipment enclosure doors * (3) Located behind locked doors accessible only to qualified personnel * (4) Password protected, with password accessible only to qualified personnel Informational Note: See NFPA 730, Guide for Premises Security, and ANSI/TIA-5017, Telecommunications Physical Network Security Standard, for information regarding physical security. (D) Remotely Accessible Adjustable-Trip Circuit Breakers. A circuit breaker(s) that can be adjusted remotely to modify the adjusting means shall be permitted to have an ampere rating(s) that is equal to the adjusted current setting (long-time pickup setting). Remote access shall be achieved by one of the following methods: * (1) Connected directly through a local nonnetworked interface. * (2) Connected through a networked interface complying with one of the following methods: o a. The circuit breaker and associated software for adjusting the settings are identified as being evaluated for cybersecurity. o b. A cybersecurity assessment of the network is completed. Documentation of the assessment and certification shall be made available to those authorized to inspect, operate, and maintain the system. Informational Note No. 1: See ANSI/ISA 62443, Cybersecurity Standards series, UL 2900 Cybersecurity Standard series, or the NIST Framework for Improving Critical Infrastructure Cybersecurity, Version 1.1 for assessment requirements. Informational Note No. 2: Examples of the commissioning certification used to demonstrate the system has been investigated for cybersecurity vulnerabilities could be one of the following: * (1) The ISA Security Compliance Institute (ISCI) conformity assessment program * (2) Certification of compliance by a nationally recognized test laboratory * (3) Manufacturer certification for the specific type and brand of system provided Informational Note No. 3: Cybersecurity is a specialized field requiring constant, vigilant attention to security vulnerabilities that could arise due to software defects, system configuration changes, or user interactions. Installation of devices that can be secured is an important first step but not sufficient to guarantee a secure system. 240.7 Listing Requirements. The following shall be listed: * (1) Branch-circuit overcurrent protective devices *