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Chapter 3 Wiring Methods and Materials
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300.6(A)
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Ferrous metal raceways, cable trays, cablebus, auxiliary gutters, cable armor, boxes, cable sheathing, cabinets, enclosures (other than surrounding fences and walls), elbows, couplings, nipples, fittings, supports, and support hardware shall be suitably protected against corrosion inside and outside (except threads at joints) by a coating of approved corrosion-resistant material. Where corrosion protection is necessary and the conduit is threaded anywhere other than at the factory where the product is listed, the threads shall be coated with an approved electrically conductive, corrosion-resistant compound. Exception: Stainless steel shall not be required to have protective coatings. [300.6(A)](https://2023.antflix.net#300.6(A))
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https://2023.antflix.net#300.6(A)
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Chapter 3 Wiring Methods and Materials
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300.6(A)(1)
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Where protected from corrosion solely by enamel, ferrous metal raceways, cable trays, cablebus, auxiliary gutters, cable armor, boxes, cable sheathing, cabinets, enclosures (other than surrounding fences and walls), elbows, couplings, nipples, fittings, supports, and support hardware shall not be used outdoors or in wet locations as described in 300.6(D). [300.6(A)(1)](https://2023.antflix.net#300.6(A)(1))
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https://2023.antflix.net#300.6(A)(1)
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Chapter 3 Wiring Methods and Materials
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300.6(A)(2)
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Where boxes, cabinets, or enclosures (other than surrounding fences and walls) have an approved system of organic coatings and are marked "Raintight," "Rainproof," or "Outdoor Type," they shall be permitted outdoors. [300.6(A)(2)](https://2023.antflix.net#300.6(A)(2))
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https://2023.antflix.net#300.6(A)(2)
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Chapter 3 Wiring Methods and Materials
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300.6(A)(3)
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Ferrous metal raceways, cable armor, boxes, cable sheathing, cabinets, enclosures (other than surrounding fences and walls), elbows, couplings, nipples, fittings, supports, and support hardware shall be permitted to be installed in concrete, in direct contact with the earth, or in areas subject to severe corrosive influences where made of material approved for the condition or where provided with corrosion protection approved for the condition. [300.6(A)(3)](https://2023.antflix.net#300.6(A)(3))
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https://2023.antflix.net#300.6(A)(3)
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Chapter 3 Wiring Methods and Materials
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300.6(B)
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Aluminum raceways, cable trays, cablebus, auxiliary gutters, cable armor, boxes, cable sheathing, cabinets, enclosures (other than surrounding fences and walls), elbows, couplings, nipples, fittings, supports, and support hardware embedded or encased in concrete or in direct contact with the earth shall be provided with supplementary corrosion protection. [300.6(B)](https://2023.antflix.net#300.6(B))
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https://2023.antflix.net#300.6(B)
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Chapter 3 Wiring Methods and Materials
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300.6(C)
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Nonmetallic raceways, cable trays, cablebus, auxiliary gutters, boxes, cables with a nonmetallic outer jacket and internal metal armor or jacket, cable sheathing, cabinets, enclosures (other than surrounding fences and walls), elbows, couplings, nipples, fittings, supports, and support hardware shall be made of material approved for the condition and shall comply with 300.6(C)(1) and (C)(2) as applicable to the specific installation. [300.6(C)](https://2023.antflix.net#300.6(C))
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https://2023.antflix.net#300.6(C)
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Chapter 3 Wiring Methods and Materials
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300.6(C)(1)
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Where exposed to sunlight, the materials shall be listed as sunlight resistant or shall be identified as sunlight resistant. [300.6(C)(1)](https://2023.antflix.net#300.6(C)(1))
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https://2023.antflix.net#300.6(C)(1)
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Chapter 3 Wiring Methods and Materials
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300.6(C)(2)
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Where subject to exposure to chemical solvents, vapors, splashing, or immersion, materials or coatings shall either be inherently resistant to chemicals based on their listing or be identified for the specific chemical reagent. [300.6(C)(2)](https://2023.antflix.net#300.6(C)(2))
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https://2023.antflix.net#300.6(C)(2)
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Chapter 3 Wiring Methods and Materials
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300.6(D)
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In portions of dairy processing facilities, laundries, canneries, and other indoor wet locations, and in locations where walls are frequently washed or where there are surfaces of absorbent materials, such as damp paper or wood, the entire wiring system, where installed exposed, including all boxes, cabinets, enclosures (other than surrounding fences and walls), fittings, raceways, and cable used therewith, shall be mounted so that there is at least a 6 mm (1/4 in.) airspace between it and the wall or supporting surface. Exception: Nonmetallic raceways, boxes, and fittings shall be permitted to be installed without the airspace on a concrete, masonry, tile, or similar surface. Informational Note: In general, areas where acids and alkali chemicals are handled and stored might present such corrosive conditions, particularly when wet or damp. Severe corrosive conditions might also be present in portions of meatpacking plants, tanneries, glue houses, and some stables; in installations immediately adjacent to a seashore and swimming pool areas; in areas where chemical deicers are used; and in storage cellars or rooms for hides, casings, fertilizer, salt, and bulk chemicals. [300.6(D)](https://2023.antflix.net#300.6(D))
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https://2023.antflix.net#300.6(D)
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Chapter 3 Wiring Methods and Materials
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300.7(A)
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Where portions of a raceway or sleeve are known to be subjected to different temperatures, and where condensation is known to be a problem, as in cold storage areas of buildings or where passing from the interior to the exterior of a building, the raceway or sleeve shall be sealed to prevent the circulation of warm air to a colder section of the raceway or sleeve. Sealants shall be identified for use with cable insulation, conductor insulation, a bare conductor, a shield, or other components. An explosionproof seal shall not be required for this purpose. [300.7(A)](https://2023.antflix.net#300.7(A))
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https://2023.antflix.net#300.7(A)
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Chapter 3 Wiring Methods and Materials
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300.7(B)
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Raceways shall be provided with expansion, expansion-deflection, or deflection fittings where necessary to compensate for thermal expansion, deflection, and contraction. Informational Note No. 1: Table 352.44(A) and Table 355.44 provide the expansion information for polyvinyl chloride (PVC) and for reinforced thermosetting resin conduit (RTRC), respectively. A nominal number for steel conduit can be determined by multiplying the expansion length in Table 352.44(A) by 0.20. The coefficient of expansion for steel electrical metallic tubing, intermediate metal conduit, and rigid metal conduit is 1.170 × 10-5 (0.0000117) mm per mm of conduit for each °C in temperature change) [0.650 × 10-5 (0.0000065 in. per in. of conduit for each °F in temperature change)]. A nominal number for aluminum conduit and aluminum electrical metallic tubing can be determined by multiplying the expansion length in Table 352.44(A) by 0.40. The coefficient of expansion for aluminum electrical metallic tubing and aluminum rigid metal conduit is 2.34 × 10-5 (0.0000234 mm per mm of conduit for each °C in temperature change) [1.30 × 10-5 (0.000013 in. per in. of conduit for each °F in temperature change)]. Informational Note No. 2: See NEMA FB 2.40-2019, Installation Guidelines for Expansion and Expansion/Deflection Fittings, for further information on expansion and expansion deflection fittings. [300.7(B)](https://2023.antflix.net#300.7(B))
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https://2023.antflix.net#300.7(B)
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Chapter 3 Wiring Methods and Materials
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300.8
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Raceways or cable trays containing electrical conductors shall not contain any pipe, tube, or equal for steam, water, air, gas, drainage, or any service other than electrical. [300.8](https://2023.antflix.net#300.8)
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https://2023.antflix.net#300.8
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Chapter 3 Wiring Methods and Materials
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300.9
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Where raceways are installed in wet locations above grade, the interior of these raceways shall be considered to be a wet location. Insulated conductors and cables installed in raceways in wet locations above grade shall comply with 310.10(C). [300.9](https://2023.antflix.net#300.9)
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https://2023.antflix.net#300.9
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Chapter 3 Wiring Methods and Materials
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300.10
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Metal raceways, cable armor, and other metal enclosures for conductors shall be metallically joined together into a continuous electrical conductor and shall be connected to all boxes, fittings, and cabinets to provide effective electrical continuity. Unless specifically permitted elsewhere in this Code, raceways and cable assemblies shall be mechanically secured to boxes, fittings, cabinets, and other enclosures. Exception No. 1: Short sections of raceways used to provide support or protection of cable assemblies from physical damage shall not be required to be made electrically continuous. Exception No. 2: Equipment enclosures to be isolated, as permitted by 250.96(B), shall not be required to be metallically joined to the metal raceway. [300.10](https://2023.antflix.net#300.10)
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https://2023.antflix.net#300.10
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Chapter 3 Wiring Methods and Materials
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300.11(A)
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Raceways, cable assemblies, boxes, cabinets, and fittings shall be securely fastened in place. [300.11(A)](https://2023.antflix.net#300.11(A))
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https://2023.antflix.net#300.11(A)
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Chapter 3 Wiring Methods and Materials
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300.11(B)
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Support wires that do not provide secure support shall not be the sole support. Support wires and associated fittings that provide secure support and that are installed in addition to the ceiling grid support wires shall be permitted as the sole support. Where independent support wires are used, they shall be secured at both ends. Cables and raceways shall not be supported by ceiling grids. [300.11(B)](https://2023.antflix.net#300.11(B))
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https://2023.antflix.net#300.11(B)
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Chapter 3 Wiring Methods and Materials
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300.11(B)(1)
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Wiring located within the cavity of a fire-rated floor-ceiling or roof-ceiling assembly shall not be secured to, or supported by, the ceiling assembly, including the ceiling support wires. An independent means of secure support shall be provided and shall be permitted to be attached to the assembly. Where independent support wires are used, they shall be distinguishable by color, tagging, or other effective means from those that are part of the fire-rated design. Exception: The ceiling support system shall be permitted to support wiring and equipment that have been tested as part of the fire-rated assembly. Informational Note: See ASTM E119, Standard Test Methods for Fire Tests of Building Construction and Materials, for one method of testing to determine fire rating. [300.11(B)(1)](https://2023.antflix.net#300.11(B)(1))
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https://2023.antflix.net#300.11(B)(1)
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Chapter 3 Wiring Methods and Materials
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300.11(B)(2)
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Wiring located within the cavity of a non-fire-rated floor-ceiling or roof-ceiling assembly shall not be secured to, or supported by, the ceiling assembly, including the ceiling support wires. An independent means of secure support shall be provided and shall be permitted to be attached to the assembly. Where independent support wires are used, they shall be distinguishable by color, tagging, or other effective means. Exception: The ceiling support system shall be permitted to support branch-circuit wiring and associated equipment where installed in accordance with the ceiling system manufacturer's instructions. [300.11(B)(2)](https://2023.antflix.net#300.11(B)(2))
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https://2023.antflix.net#300.11(B)(2)
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Chapter 3 Wiring Methods and Materials
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300.11(C)
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Raceways shall be used only as a means of support for other raceways, cables, or nonelectrical equipment under any of the following conditions: Where the raceway or means of support is identified as a means of supportWhere the raceway contains power supply conductors for electrically controlled equipment and is used to support Class 2 or Class 3 circuit conductors or cables that are solely for the purpose of connection to the equipment control circuitsWhere the raceway is used to support boxes or conduit bodies in accordance with 314.23 or to support luminaires in accordance with 410.36(E) [300.11(C)](https://2023.antflix.net#300.11(C))
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https://2023.antflix.net#300.11(C)
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Chapter 3 Wiring Methods and Materials
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300.11(D)
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Cable wiring methods shall not be used as a means of support for other cables, raceways, or nonelectrical equipment. [300.11(D)](https://2023.antflix.net#300.11(D))
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https://2023.antflix.net#300.11(D)
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Chapter 3 Wiring Methods and Materials
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300.12
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Raceways, cable armors, and cable sheaths shall be continuous between cabinets, boxes, conduit bodies, fittings, or other enclosures or outlets. Exception No. 1: Short sections of raceways used to provide support or protection of cable assemblies from physical damage shall not be required to be mechanically continuous. Exception No. 2: Raceways and cables installed into the bottom of open bottom equipment, such as switchboards, motor control centers, and floor or pad-mounted transformers, shall not be required to be mechanically secured to the equipment. [300.12](https://2023.antflix.net#300.12)
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https://2023.antflix.net#300.12
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Chapter 3 Wiring Methods and Materials
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300.13(A)
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Conductors in raceways shall be continuous between outlets, boxes, devices, and so forth. There shall be no splice or tap within a raceway unless permitted by 300.15, 368.56(A), 376.56, 378.56, 384.56, 386.56, 388.56, or 390.56. [300.13(A)](https://2023.antflix.net#300.13(A))
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https://2023.antflix.net#300.13(A)
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Chapter 3 Wiring Methods and Materials
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300.13(B)
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In multiwire branch circuits, the continuity of a grounded conductor shall not depend on device connections such as lampholders, receptacles, and so forth where the removal of such devices would interrupt the continuity. [300.13(B)](https://2023.antflix.net#300.13(B))
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https://2023.antflix.net#300.13(B)
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Chapter 3 Wiring Methods and Materials
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300.14
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At least 150 mm (6 in.) of free conductor, measured from the point in the box where it emerges from its raceway or cable sheath, shall be left at each outlet, junction, and switch point for splices or the connection of luminaires or devices. The 150 mm (6 in.) free conductor shall be permitted to be spliced or unspliced. Where the opening to an outlet, junction, or switch point is less than 200 mm (8 in.) in any dimension, each conductor shall be long enough to extend at least 75 mm (3 in.) outside the opening. Exception: Conductors that are not spliced or terminated at the outlet, junction, or switch point shall not be required to comply with 300.14. [300.14](https://2023.antflix.net#300.14)
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https://2023.antflix.net#300.14
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Chapter 3 Wiring Methods and Materials
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300.15
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A box shall be installed at each outlet and switch point for concealed knob-and-tube wiring. Fittings and connectors shall be used only with the specific wiring methods for which they are designed and listed. Where the wiring method is conduit, tubing, Type AC cable, Type MC cable, Type MI cable, nonmetallic-sheathed cable, or other cables, a box or conduit body shall be installed at each outlet point, switch point, conductor splice point, conductor junction point, conductor termination point, wiring method transition point, or conductor pull point, unless otherwise permitted in 300.15(A) through (L). [300.15](https://2023.antflix.net#300.15)
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https://2023.antflix.net#300.15
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Chapter 3 Wiring Methods and Materials
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300.15(A)
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A box or conduit body shall not be required for each splice, junction, switch, pull, termination, or outlet points in wiring methods with removable covers, such as wireways, multioutlet assemblies, auxiliary gutters, and surface raceways. The covers shall be accessible after installation. [300.15(A)](https://2023.antflix.net#300.15(A))
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https://2023.antflix.net#300.15(A)
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Chapter 3 Wiring Methods and Materials
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300.15(B)
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An integral junction box or wiring compartment as part of approved equipment shall be permitted in lieu of a box. [300.15(B)](https://2023.antflix.net#300.15(B))
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https://2023.antflix.net#300.15(B)
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Chapter 3 Wiring Methods and Materials
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300.15(C)
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A box or conduit body shall not be required where cables enter or exit from conduit or tubing that is used to provide cable support or protection against physical damage. A fitting shall be provided on the end(s) of the conduit or tubing to protect the cable from abrasion. [300.15(C)](https://2023.antflix.net#300.15(C))
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https://2023.antflix.net#300.15(C)
|
Chapter 3 Wiring Methods and Materials
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300.15(D)
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A box or conduit body shall not be required where accessible fittings are used for straight-through splices in mineral-insulated metal-sheathed cable. [300.15(D)](https://2023.antflix.net#300.15(D))
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https://2023.antflix.net#300.15(D)
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Chapter 3 Wiring Methods and Materials
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300.15(E)
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A wiring device with integral enclosure identified for the use, having brackets that securely fasten the device to walls or ceilings of conventional on-site frame construction, for use with nonmetallic-sheathed cable, shall be permitted in lieu of a box or conduit body. Informational Note: See 334.30(C); 545.10; 550.15(I); 551.47(E), Exception No. 1; and 552.48(E), Exception No. 1. [300.15(E)](https://2023.antflix.net#300.15(E))
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https://2023.antflix.net#300.15(E)
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Chapter 3 Wiring Methods and Materials
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300.15(F)
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A fitting identified for the use shall be permitted in lieu of a box or conduit body where conductors are not spliced or terminated within the fitting. The fitting shall be accessible after installation, unless listed for concealed installation. [300.15(F)](https://2023.antflix.net#300.15(F))
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https://2023.antflix.net#300.15(F)
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Chapter 3 Wiring Methods and Materials
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300.15(G)
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As permitted in 300.5(E), a box or conduit body shall not be required for splices and taps in direct-buried conductors and cables. [300.15(G)](https://2023.antflix.net#300.15(G))
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https://2023.antflix.net#300.15(G)
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Chapter 3 Wiring Methods and Materials
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300.15(H)
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As permitted in 334.40(B), a box or conduit body shall not be required for insulated devices supplied by nonmetallic-sheathed cable. [300.15(H)](https://2023.antflix.net#300.15(H))
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https://2023.antflix.net#300.15(H)
|
Chapter 3 Wiring Methods and Materials
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300.15(I)
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A box or conduit body shall not be required where a splice, switch, terminal, or pull point is in a cabinet or cutout box, in an enclosure for a switch or overcurrent device as permitted in 312.8, in a motor controller as permitted in 430.10(A), or in a motor control center. [300.15(I)](https://2023.antflix.net#300.15(I))
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https://2023.antflix.net#300.15(I)
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Chapter 3 Wiring Methods and Materials
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300.15(J)
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A box or conduit body shall not be required where a luminaire is used as a raceway as permitted in 410.64. [300.15(J)](https://2023.antflix.net#300.15(J))
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https://2023.antflix.net#300.15(J)
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Chapter 3 Wiring Methods and Materials
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300.15(K)
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A box or conduit body shall not be required for splices where conductors are embedded as permitted in 424.40, 424.41 (D), 426.22(C), 426.24(A), and 427.19(A). [300.15(K)](https://2023.antflix.net#300.15(K))
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https://2023.antflix.net#300.15(K)
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Chapter 3 Wiring Methods and Materials
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300.15(L)
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A box or conduit body shall not be required for conductors in manholes or handhole enclosures, except where connecting to electrical equipment. The installation shall comply with Part V of Article 110 for manholes, and 314.30 for handhole enclosures. [300.15(L)](https://2023.antflix.net#300.15(L))
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https://2023.antflix.net#300.15(L)
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Chapter 3 Wiring Methods and Materials
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300.16(A)
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A box, conduit body, or terminal fitting having a separately bushed hole for each conductor shall be used wherever a change is made from conduit, electrical metallic tubing, electrical nonmetallic tubing, nonmetallic-sheathed cable, Type AC cable, Type MC cable, or mineral-insulated, metal-sheathed cable and surface raceway wiring to open wiring or to concealed knob-and-tube wiring. A fitting used for this purpose shall contain no taps or splices and shall not be used at luminaire outlets. A conduit body used for this purpose shall contain no taps or splices unless it complies with 314.16(C)(2). [300.16(A)](https://2023.antflix.net#300.16(A))
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https://2023.antflix.net#300.16(A)
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Chapter 3 Wiring Methods and Materials
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300.16(B)
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A bushing shall be permitted in lieu of a box or terminal where the conductors emerge from a raceway and enter or terminate at equipment, such as open switchboards, unenclosed control equipment, or similar equipment. The bushing shall be of the insulating type for other than lead-sheathed conductors. [300.16(B)](https://2023.antflix.net#300.16(B))
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https://2023.antflix.net#300.16(B)
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Chapter 3 Wiring Methods and Materials
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300.17
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The number and size of conductors and cables in any raceway shall not be more than will permit dissipation of the heat and ready installation or withdrawal of the conductors or cables without damage to the conductors or cables, or to their insulation. Informational Note: See the following sections of this Code. intermediate metal conduit, 342.22; rigid metal conduit, 344.22: flexible metal conduit, 348.22; liquidtight flexible metal conduit, 350.22; PVC conduit, 352.22; HDPE conduit, 353.22; RTRC, 355.22; liquidtight nonmetallic flexible conduit, 356.22; electrical metallic tubing, 358.22; flexible metallic tubing, 360.22; electrical nonmetallic tubing, 362.22; cellular concrete floor raceways, 372.22; cellular metal floor raceways, 374.22: metal wireways, 376.22; nonmetallic wireways, 378.22; surface metal raceways, 386.22; surface nonmetallic raceways, 388.22; underfloor raceways, 390.22; fixture wire, 402.7; theaters, 520.6; signs, 600.31(C); elevators, 620.33; audio signal processing, amplification, and reproduction equipment, 640.23(A) and 640.24; Class 1 circuits, 724.3(A); Class 2, Class 3, Class 4, and power-limited fire alarm (PLFA) circuits, 722.3(A); non-power-limited fire alarm (NPLFA) circuits, 760.3(H); and optical fiber cables and raceways, 770.110(B). [300.17](https://2023.antflix.net#300.17)
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https://2023.antflix.net#300.17
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Chapter 3 Wiring Methods and Materials
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300.18(A)
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Raceways other than busways, listed manufactured assemblies in accordance with 604.100, or exposed raceways having hinged or removable covers shall be installed complete between outlet, junction, or splicing points prior to the installation of conductors or cables. Where required to facilitate the installation of utilization equipment, the raceway shall be permitted to be initially installed without a terminating connection at the equipment. Prewired raceway assemblies shall be permitted only where specifically permitted in this Code for the applicable wiring method. Exception: Short sections of raceways used to contain conductors or cable assemblies for protection from physical damage shall not be required to be installed complete between outlet, junction, or splicing points. [300.18(A)](https://2023.antflix.net#300.18(A))
|
https://2023.antflix.net#300.18(A)
|
Chapter 3 Wiring Methods and Materials
|
300.18(B)
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Metal raceways shall not be supported, terminated, or connected by welding to the raceway unless specifically designed to be or otherwise specifically permitted to be in this Code. [300.18(B)](https://2023.antflix.net#300.18(B))
|
https://2023.antflix.net#300.18(B)
|
Chapter 3 Wiring Methods and Materials
|
300.19(A)
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Conductors in vertical raceways shall be supported if the vertical rise exceeds the values in Table 300.19(A). At least one support method shall be provided for each conductor at the top of the vertical raceway or as close to the top as practical. Intermediate supports shall be provided as necessary to limit supported conductor lengths to not greater than those values specified in Table 300.19(A). Exception: Steel wire armor cable shall be supported at the top of the riser with a cable support that clamps the steel wire armor. A safety device shall be permitted at the lower end of the riser to hold the cable in the event there is slippage of the cable in the wire-armored cable support. Additional wedge-type supports shall be permitted to relieve the strain on the equipment terminals caused by expansion of the cable under load.
Table 300.19(A) Spacings for Conductor Supports Conductor Size Support of Conductors in Vertical Raceways Conductors Aluminum or Copper-Clad Aluminum Copper m ft m ft 18 AWG through 8 AWG Not greater than 30 100 30 100 6AWG through 1/0 AWG Not greater than 60 200 30 100 2/0 AWG through 4/0 AWG Not greater than 55 180 25 80 Over 4/0 AWG through 350 kcmil Not greater than 41 135 18 60 Over 350 kcmil through 500 kcmil Not greater than 36 120 15 50 Over 500 kcmil through 750 kcmil Not greater than 28 95 12 40 Over 750 kcmil Not greater than 26 85 11 35 [300.19(A)](https://2023.antflix.net#300.19(A))
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https://2023.antflix.net#300.19(A)
|
Chapter 3 Wiring Methods and Materials
|
300.19(B)
|
Support methods and spacing intervals for fire-resistive cables and conductors shall comply with any restrictions provided in the listing of the electrical circuit protective system or fire-resistive cable system used and in no case shall exceed the values in Table 300.19(A). [300.19(B)](https://2023.antflix.net#300.19(B))
|
https://2023.antflix.net#300.19(B)
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Chapter 3 Wiring Methods and Materials
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300.19(C)
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One of the following methods of support shall be used: Clamping devices constructed of or employing insulating wedges inserted in the ends of the raceways. Where clamping of insulation does not adequately support the cable, the conductor also shall be clamped.Inserting boxes at the required intervals in which insulating supports are installed and secured in an approved manner to withstand the weight of the conductors attached thereto, the boxes being provided with covers.In junction boxes, deflecting the cables not less than 90 degrees and carrying them horizontally to a distance not less than twice the diameter of the cable, with the cables being carried on two or more insulating supports and additionally secured thereto by tie wires, if desired. Where this method is used, cables shall be supported at intervals not greater than 20 percent of the support spacing in Table 300.19(A).Other approved means. [300.19(C)](https://2023.antflix.net#300.19(C))
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https://2023.antflix.net#300.19(C)
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Chapter 3 Wiring Methods and Materials
|
300.20(A)
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Where conductors carrying alternating current are installed in ferrous metal enclosures or ferrous metal raceways, they shall be arranged so as to avoid heating the surrounding ferrous metal by induction. To accomplish this, all phase conductors and, where used, the grounded conductor and all equipment grounding conductors shall be grouped together. Exception No. 1: Equipment grounding conductors for certain existing installations shall be permitted to be installed separate from their associated circuit conductors where run in accordance with 250.130(C). Exception No. 2: A single conductor shall be permitted to be installed in a ferromagnetic enclosure and used for skin-effect heating in accordance with 426.42 and 427.47. [300.20(A)](https://2023.antflix.net#300.20(A))
|
https://2023.antflix.net#300.20(A)
|
Chapter 3 Wiring Methods and Materials
|
300.20(B)
|
Where a single conductor carrying alternating current passes through metal with magnetic properties, the inductive effect shall be minimized by either cutting slots in the metal between the individual holes through which the individual conductors pass or passing all the conductors in the circuit through an insulating wall sufficiently large for all of the conductors of the circuit. Exception: In the case of circuits supplying vacuum or electric-discharge lighting systems or signs or X-ray apparatus, the currents carried by the conductors are so small that the inductive heating effect can be ignored where these conductors are placed in metal enclosures or pass through metal. Informational Note: Because aluminum is not a magnetic metal, there will be no heating due to hysteresis; however, induced currents will be present. They will not be of sufficient magnitude to require grouping of conductors or special treatment in passing conductors through aluminum wall sections. [300.20(B)](https://2023.antflix.net#300.20(B))
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https://2023.antflix.net#300.20(B)
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Chapter 3 Wiring Methods and Materials
|
300.21
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Electrical installations in hollow spaces, vertical shafts, and ventilation or air-handling ducts shall be made so that the possible spread of fire or products of combustion will not be substantially increased. Openings around electrical penetrations into or through fire-resistant-rated walls, partitions, floors, or ceilings shall be firestopped using approved methods to maintain the fire resistance rating. Informational Note: Directories of electrical construction materials published by qualified testing laboratories contain many listing installation restrictions necessary to maintain the fire-resistive rating of assemblies where penetrations or openings are made. Building codes also contain restrictions on membrane penetrations on opposite sides of a fire-resistance-rated wall assembly. An example is the 600-mm (24-in.) minimum horizontal separation that usually applies between boxes installed on opposite sides of the wall. Assistance in complying with the requirements of 300.21 can be found in building codes, fire resistance directories, and product listings. [300.21](https://2023.antflix.net#300.21)
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https://2023.antflix.net#300.21
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Chapter 3 Wiring Methods and Materials
|
300.22
|
The requirements of this section shall apply to the installation and uses of electrical wiring and equipment in ducts used for dust, loose stock, or vapor removal; ducts specifically fabricated for environmental air; and other spaces used for environmental air (plenums). Informational Note: See Part VI of Article 424 for requirements on duct heaters. [300.22](https://2023.antflix.net#300.22)
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https://2023.antflix.net#300.22
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Chapter 3 Wiring Methods and Materials
|
300.22(A)
|
No wiring systems of any type shall be installed in ducts used to transport dust, loose stock, or flammable vapors. No wiring system of any type shall be installed in any duct, or shaft containing only such ducts, used for vapor removal or for ventilation of commercial-type cooking equipment. [300.22(A)](https://2023.antflix.net#300.22(A))
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https://2023.antflix.net#300.22(A)
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Chapter 3 Wiring Methods and Materials
|
300.22(B)
|
Equipment, devices, and the wiring methods specified in this section shall be permitted within such ducts only if necessary for the direct action upon, or sensing of, the contained air. Where equipment or devices are installed and illumination is necessary to facilitate maintenance and repair, enclosed gasketed-type luminaires shall be permitted. Only wiring methods consisting of Type MI cable without an overall nonmetallic covering, Type MC cable employing a smooth or corrugated impervious metal sheath without an overall nonmetallic covering, electrical metallic tubing, flexible metallic tubing, intermediate metal conduit, or rigid metal conduit without an overall nonmetallic covering shall be installed in ducts specifically fabricated to transport environmental air. Flexible metal conduit shall be permitted, in lengths not to exceed 1.2 m (4 ft), to connect physically adjustable equipment and devices permitted to be in these fabricated ducts. The connectors used with flexible metal conduit shall effectively close any openings in the connection. Exception: Wiring methods and cabling systems, listed for use in other spaces used for environmental air (plenums), shall be permitted to be installed in ducts specifically fabricated for environmental air-handling purposes under both of the following conditions: (1) The wiring methods or cabling systems shall be permitted only if necessary to connect to equipment or devices associated with the direct action upon or sensing of the contained air. (2) The total length of such wiring methods or cabling systems shall not exceed 1.2 m (4 ft). [300.22(B)](https://2023.antflix.net#300.22(B))
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https://2023.antflix.net#300.22(B)
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Chapter 3 Wiring Methods and Materials
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300.22(C)
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This section shall apply to spaces not specifically fabricated for environmental air-handling purposes but used for air-handling purposes as a plenum. This section shall not apply to habitable rooms or areas of buildings, the prime purpose of which is not air handling. Informational Note No. 1: The space over a hung ceiling used for environmental air-handling purposes is an example of the type of other space to which this section applies. Informational Note No. 2: See NFPA 90A, Standard for the Installation of Air-Conditioning and Ventilating Systems, and other mechanical codes for information on how the term other spaces used for environmental air (plenum), as used in this section, correlates with the use of the term plenum where the plenum is used for return air purposes, as well as some other air-handling spaces. Exception: This section shall not apply to the joist or stud spaces of dwelling units where the wiring passes through such spaces perpendicular to the long dimension of such spaces. [300.22(C)](https://2023.antflix.net#300.22(C))
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https://2023.antflix.net#300.22(C)
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Chapter 3 Wiring Methods and Materials
|
300.22(C)(1)
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The wiring methods for other spaces used for environmental air shall be limited to totally enclosed, nonventilated, insulated busway having no provisions for plugin connections, Type MI cable without an overall nonmetallic covering, Type MC cable without an overall nonmetallic covering, Type AC cable, or other factory-assembled multiconductor control or power cable that is specifically listed for use within an air-handling space, or listed prefabricated cable assemblies of metallic manufactured wiring systems without nonmetallic sheath. Other types of cables, conductors, and raceways shall be permitted to be installed in electrical metallic tubing, flexible metallic tubing, intermediate metal conduit, rigid metal conduit without an overall nonmetallic covering, flexible metal conduit, or, where accessible, surface metal raceway or metal wireway with metal covers. Nonmetallic cable ties and other nonmetallic cable accessories used to secure and support cables shall be listed as having low smoke and heat release properties. Informational Note: See UL 2043, Fire Test for Heat and Visible Smoke Release for Discrete Products and Their Accessories Installed in Air-Handling Spaces, for one method of testing low smoke and heat release properties for nonmetallic cable ties and other nonmetallic cable accessories to determine a maximum peak optical density of 0.50 or less, an average optical density of 0.15 or less, and a peak heat release rate of 100 kW or less. [300.22(C)(1)](https://2023.antflix.net#300.22(C)(1))
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https://2023.antflix.net#300.22(C)(1)
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Chapter 3 Wiring Methods and Materials
|
300.22(C)(2)
|
The requirements in 300.22(C)(2)(a) or (C)(2)(b) shall apply to the use of metallic cable tray systems in other spaces used for environmental air (plenums), where accessible. Metal Cable Tray Systems. Metal cable tray systems shall be permitted to support the wiring methods specified in 300.22(C)(1).Solid Side and Bottom Metal Cable. Tray Systems. Solid side and bottom metal cable tray systems with solid metal covers shall be permitted to enclose wiring methods and cables not already covered in 300.22(C)(1) in accordance with 392.10(A) and (B). [300.22(C)(2)](https://2023.antflix.net#300.22(C)(2))
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https://2023.antflix.net#300.22(C)(2)
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Chapter 3 Wiring Methods and Materials
|
300.22(C)(3)
|
Electrical equipment with a metal enclosure, or electrical equipment with a nonmetallic enclosure listed for use within an air-handling space and having low smoke and heat release properties, and associated wiring material suitable for the ambient temperature shall be permitted to be installed in such other spaces unless prohibited elsewhere in this Code. Informational Note: See UL 2043, Fire Test for Heat and Visible Smoke Release for Discrete Products and Their Accessories Installed in Air-Handling Spaces, for one method of testing low smoke and heat release properties to determine that the equipment exhibits a maximum peak optical density of 0.50 or less, an average optical density of 0.15 or less, and a peak heat release rate of 100 kW or less. Exception: Integral fan systems shall be permitted where specifically identified for use within an air-handling space. [300.22(C)(3)](https://2023.antflix.net#300.22(C)(3))
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https://2023.antflix.net#300.22(C)(3)
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Chapter 3 Wiring Methods and Materials
|
300.22(D)
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Where the installation complies with the special requirements specified in 645.4, electrical wiring in air-handling areas beneath raised floors for information technology equipment shall be permitted in accordance with 645.5(E). [300.22(D)](https://2023.antflix.net#300.22(D))
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https://2023.antflix.net#300.22(D)
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Chapter 3 Wiring Methods and Materials
|
300.23
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Cables, raceways, and equipment installed behind panels designed to allow access, including suspended ceiling panels, shall be arranged and secured to allow the removal of panels and access to the equipment. [300.23](https://2023.antflix.net#300.23)
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https://2023.antflix.net#300.23
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Chapter 3 Wiring Methods and Materials
|
300.25
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Where an exit enclosure is required to have a fire resistance rating, only electrical wiring methods serving equipment permitted by the authority having jurisdiction in the exit enclosure shall be installed within the exit enclosure. Exception: Where egress lighting is required on outside exterior doorways from the exit enclosure, luminaires shall be permitted to be supplied from the inside of the exit enclosure. Informational Note: See NFPA 101-2021, Life Safety Code, 7.1.3.2.1 (10)(b), for more information. [300.25](https://2023.antflix.net#300.25)
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https://2023.antflix.net#300.25
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Chapter 3 Wiring Methods and Materials
|
300.26
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Remote-control and signaling circuits shall be classified as either power-limited or non-power-limited and comply with the following:Class 1 power-limited remote-control and signaling circuits shall comply with 724.3.Class 2 and Class 3 power-limited remote-control and signaling circuits shall comply with 725.3.Non-power-limited remote-control and signaling circuits shall be installed in accordance with 300.2 through 300.25. [300.26](https://2023.antflix.net#300.26)
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https://2023.antflix.net#300.26
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Chapter 3 Wiring Methods and Materials
|
305.1
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This article covers wiring methods and materials for systems rated over 1000 volts ac, 1500 volts dc, nominal. [305.1](https://2023.antflix.net#305.1)
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https://2023.antflix.net#305.1
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Chapter 3 Wiring Methods and Materials
|
305.3
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Conductors shall be permitted to be installed in accordance with any of the wiring methods identified in Table 305.3. Exposed runs of Type MV cables, bare conductors, and bare busbars shall be permitted in locations accessible only to qualified persons. Busbars shall be permitted to be either copper or aluminum. Exception: Airfield lighting cable used in series circuits that are powered by regulators and installed in restricted airport lighting vaults shall be permitted as exposed cable installations. Informational Note: An example of a common application is FAA L-824 cables installed as exposed runs within a restricted vault area. Table 305.3 Wiring Methods Permitted for Use in Systems Rated Over 1000 Volts ac, 1500 Volts dc, Nominal Wiring Methods Permitted for Use Above 1000 Volts ac, 1500 Volts dc Voltage Levels Reference Pull and junction boxes, conduit bodies, and handhole enclosures Over 1000 Article 314, Part IV Metal-clad cable (Type MC) 1000—35,000 Article 330 Type P cable 1000—2000 Article 337 Intermediate metal conduit (IMC) Over 1000 Article 342 Rigid metal conduit (RMC) Over 1000 Article 344 Rigid polyvinyl chloride conduit (PVC) Over 1000 Article 352 Reinforced thermosetting resin conduit (RTRC) Over 1000 Article 355 Electrical metallic tubing (EMT) Over 1000 Article 358 Auxiliary gutters Over 1000 Article 366 Busway Over 1000 Article 368, Part IV Cablebus 1000—35,000 Article 370 Cable trays 1000—35,000 Article 392 Messenger-supported wiring 1000—35,000 Article 396 Outdoor overhead conductors Over 1000 Article 395 Insulated bus pipe (IBP) 1000—35,000 ac Article 369 [305.3](https://2023.antflix.net#305.3)
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https://2023.antflix.net#305.3
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Chapter 3 Wiring Methods and Materials
|
305.4
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Conductors of circuits rated over 1000 volts ac, 1500 volts dc, nominal, shall not occupy the same equipment wiring enclosure, cable, or raceway with conductors of circuits rated 1000 volts ac, 1500 volts dc, nominal, or less unless otherwise permitted as follows: Where contained within the individual wiring enclosure, primary leads of electric-discharge lamp ballasts insulated for the primary voltage of the ballast shall be permitted to occupy the same luminaire, sign, or outline lighting enclosure as the branch-circuit conductors.Excitation, control, relay, and ammeter conductors used in connection with any individual motor or starter shall be permitted to occupy the same enclosure as the motor-circuit conductors.Conductors of different voltage ratings shall be permitted in motors, transformers, switchgear, switchboards, control assemblies, and similar equipment.If the conductors of each system in a manhole are permanently and effectively separated from the conductors of the other systems and securely fastened to racks, insulators, or other approved supports, conductors of different voltage ratings shall be permitted.Conductors having nonshielded insulation and operating at different voltage levels shall not occupy the same enclosure, cable, or raceway. [305.4](https://2023.antflix.net#305.4)
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https://2023.antflix.net#305.4
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Chapter 3 Wiring Methods and Materials
|
305.5
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The conductor shall not be bent to a radius less than 8 times the overall diameter for nonshielded conductors or 12 times the overall diameter for shielded or lead-covered conductors during or after installation. For multiconductor or multiplexed single-conductor cables having individually shielded conductors, the minimum bending radius shall be 12 times the diameter of the individually shielded conductors or 7 times the overall diameter, whichever is greater. [305.5](https://2023.antflix.net#305.5)
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https://2023.antflix.net#305.5
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Chapter 3 Wiring Methods and Materials
|
305.6
|
Metallic raceways and associated conductors shall be arranged to avoid heating of the raceway in accordance with 300.20. [305.6](https://2023.antflix.net#305.6)
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https://2023.antflix.net#305.6
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Chapter 3 Wiring Methods and Materials
|
305.7
|
Suitable covers shall be installed on all boxes, fittings, and similar enclosures to prevent accidental contact with energized parts or physical damage to parts or insulation. [305.7](https://2023.antflix.net#305.7)
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https://2023.antflix.net#305.7
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Chapter 3 Wiring Methods and Materials
|
305.8
|
Where raceways are installed in wet locations above grade, the interior of these raceways shall be considered to be a wet location. Insulated conductors and cables installed in raceways in wet locations above grade shall be either moisture-impervious metal-sheathed or of a type listed for use in wet locations. [305.8](https://2023.antflix.net#305.8)
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https://2023.antflix.net#305.8
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Chapter 3 Wiring Methods and Materials
|
305.9
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Exposed runs of braid-covered insulated conductors shall have a flame-retardant braid. If the conductors used do not have this protection, a flame-retardant saturant shall be applied to the braid covering after installation. This treated braid covering shall be stripped back a safe distance at conductor terminals, according to the operating voltage. Where practicable, this distance shall not be less than 25 mm (1 in.) for each kilovolt of the conductor-to-ground voltage of the circuit. [305.9](https://2023.antflix.net#305.9)
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https://2023.antflix.net#305.9
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Chapter 3 Wiring Methods and Materials
|
305.10
|
Metallic and semiconducting insulation shielding components of shielded cables shall be removed for a distance dependent on the circuit voltage and insulation. Stress reduction means shall be provided at all terminations of factory-applied shielding. Metallic shielding components such as tapes, wires, or braids, or combinations of them, shall be connected to an equipment grounding conductor, an equipment grounding busbar, or a grounding electrode. [305.10](https://2023.antflix.net#305.10)
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https://2023.antflix.net#305.10
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Chapter 3 Wiring Methods and Materials
|
305.11
|
Where cable conductors emerge from a metal sheath and where protection against moisture or physical damage is necessary, the insulation of the conductors shall be protected by a cable sheath terminating device. [305.11](https://2023.antflix.net#305.11)
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https://2023.antflix.net#305.11
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Chapter 3 Wiring Methods and Materials
|
305.12
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Danger signs shall be conspicuously posted at points of access to conductors in all raceway systems and cable systems. The sign(s) shall meet the requirements in 110.21(B), shall be readily visible, and shall state the following: DANGER-HIGH VOLTAGE-KEEP OUT [305.12](https://2023.antflix.net#305.12)
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https://2023.antflix.net#305.12
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Chapter 3 Wiring Methods and Materials
|
305.15(A)
|
Underground conductors shall be identified for the voltage and conditions under which they are installed. Conductors used for direct-burial applications shall be of a type identified for such use. Underground cables shall be installed in accordance with 305.15(A)(1), (A)(2), or (A)(3), and the installation shall meet the depth requirements of Table 305.15(A).
Table 305.15(A) Minimum Cover Requirements Circuit Voltage General Conditions (not otherwise specified) Special Conditions (use if applicable) Column 1 Column 2 Column 3 Column 4 Column 5 Column 6 Direct-Buried Cables1 Electrical Metallic Tubing, RTRC, PVC, and HDPE Conduit2 Rigid Metal Conduit and Intermediate Metal Conduit Raceways Under Buildings or Exterior Concrete Slabs, 100 mm (4 in.) Minimum Thickness3 Cables in Airport Runways or Adjacent Areas Where Trespass Is Prohibited Areas Subject to Vehicular Traffic, Such as Thoroughfares and Commercial Parking Areas mm in. mm in. mm in. mm in. mm in. mm in. Over 1000 V ac, 1500 V dc, through 22 kV 750 30 450 18 150 6 100 4 450 18 600 24 Over 22 kV through 40 kV 900 36 600 24 150 6 100 4 450 18 600 24 Over 40 kV 1000 42 750 30 150 6 100 4 450 18 600 24 Notes:Cover shall be defined as the shortest distance in millimeters (inches) measured between a point on the top surface of any direct-buried conductor, cable, conduit, or other raceway and the top surface of finished grade, concrete, or similar cover.Lesser depths shall be permitted where cables and conductors rise for terminations or splices or where access is otherwise required.Where solid rock prevents compliance with the cover depths specified in this table, the wiring shall be installed in a metal or nonmetallic raceway permitted for direct burial. The raceways shall be covered by a minimum of 50 mm (2 in.) of concrete extending down to rock.In industrial establishments, where conditions of maintenance and supervision ensure that qualified persons will service the installation, the minimum cover requirements for other than rigid metal conduit and intermediate metal conduit shall be permitted to be reduced 150 mm (6 in.) for each 50 mm (2 in.) of concrete or equivalent placed entirely within the trench over the underground installation.1Underground direct-buried cables that are not encased or protected by concrete and are buried 750 mm (30 in.) or more below grade shall have their location identified by a warning ribbon that is placed in the trench at least 300 mm (12 in.) above the cables.2Listed by a qualified testing agency as suitable for direct burial without encasement. All other nonmetallic systems shall require 50 mm (2 in.) of concrete or equivalent above conduit in addition to the table depth.3The slab shall extend a minimum of 150 mm (6 in.) beyond the underground installation, and a warning ribbon or other effective means suitable for the conditions shall be placed above the underground installation. [305.15(A)](https://2023.antflix.net#305.15(A))
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https://2023.antflix.net#305.15(A)
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Chapter 3 Wiring Methods and Materials
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305.15(A)(1)
|
Underground cables, including nonshielded, Type MC and moisture-impervious metal sheath cables, shall have those sheaths grounded through an effective grounding path meeting the requirements of 250.4(A)(5) or 250.4(B)(4). They shall be direct buried or installed in raceways identified for the use. [305.15(A)(1)](https://2023.antflix.net#305.15(A)(1))
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https://2023.antflix.net#305.15(A)(1)
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Chapter 3 Wiring Methods and Materials
|
305.15(A)(2)
|
In industrial establishments, where conditions of maintenance and supervision ensure that only qualified persons service the installed cable, nonshielded single-conductor cables with insulation types up to 2000 volts that are listed for direct burial shall be permitted to be directly buried. [305.15(A)(2)](https://2023.antflix.net#305.15(A)(2))
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https://2023.antflix.net#305.15(A)(2)
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Chapter 3 Wiring Methods and Materials
|
305.15(A)(3)
|
Other nonshielded cables not covered in 305.15(A)(1) or (A)(2) shall be installed in rigid metal conduit, intermediate metal conduit, or rigid nonmetallic conduit encased in not less than 75 mm (3 in.) of concrete. [305.15(A)(3)](https://2023.antflix.net#305.15(A)(3))
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https://2023.antflix.net#305.15(A)(3)
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Chapter 3 Wiring Methods and Materials
|
305.15(B)
|
The interior of enclosures or raceways installed underground shall be considered to be a wet location. Insulated conductors and cables installed in these enclosures or raceways in underground installations shall be listed for use in wet locations and shall be either moisture-impervious metal-sheathed or of a type listed for use in wet locations. Any connections or splices in an underground installation shall be approved for wet locations. [305.15(B)](https://2023.antflix.net#305.15(B))
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https://2023.antflix.net#305.15(B)
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Chapter 3 Wiring Methods and Materials
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305.15(C)
|
Conductors emerging from the ground shall be enclosed in listed raceways. Raceways installed on poles shall be of rigid metal conduit, intermediate metal conduit, RTRC-XW, Schedule 80 PVC conduit, or equivalent, extending from the minimum cover depth specified in Table 305.15(A) to a point 2.5 m (8 ft) above finished grade. Conductors entering a building shall be protected by an approved enclosure or raceway from the minimum cover depth to the point of entrance. Where direct-buried conductors, raceways, or cables are subject to movement by settlement or frost, they shall be installed to prevent damage to the enclosed conductors or to the equipment connected to the raceways. Metallic enclosures shall be grounded. [305.15(C)](https://2023.antflix.net#305.15(C))
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https://2023.antflix.net#305.15(C)
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Chapter 3 Wiring Methods and Materials
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305.15(D)
|
Direct burial cables shall be permitted to be spliced or tapped without the use of splice boxes if they are installed using materials suitable for the application. The taps and splices shall be watertight and protected from mechanical damage. Where cables are shielded, the shielding shall be continuous across the splice or tap. Exception: At splices of an engineered cabling system, metallic shields of direct-buried single-conductor cables with maintained spacing between phases shall be permitted to be interrupted and overlapped. Where shields are interrupted and overlapped, each shield section shall be grounded at one point. [305.15(D)](https://2023.antflix.net#305.15(D))
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https://2023.antflix.net#305.15(D)
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Chapter 3 Wiring Methods and Materials
|
305.15(E)
|
Backfill containing large rocks, paving materials, cinders, large or sharply angular substances, or corrosive materials shall not be placed in an excavation where materials can damage or contribute to the corrosion of raceways, cables, or other substructures or where it might prevent adequate compaction of fill. Protection in the form of granular or selected material or suitable sleeves shall be provided to prevent physical damage to the raceway or cable. [305.15(E)](https://2023.antflix.net#305.15(E))
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https://2023.antflix.net#305.15(E)
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Chapter 3 Wiring Methods and Materials
|
305.15(F)
|
Where a raceway enters from an underground system, the end within the building shall be sealed with an identified compound to prevent the entrance of moisture. Informational Note: Presence of hazardous gases or vapors might also necessitate sealing of underground conduits or raceways entering buildings. [305.15(F)](https://2023.antflix.net#305.15(F))
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https://2023.antflix.net#305.15(F)
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Chapter 3 Wiring Methods and Materials
|
310.1
|
This article covers general requirements for conductors rated up to and including 2000 volts and their type designations, insulations, markings, mechanical strengths, ampacity ratings, and uses. These requirements do not apply to conductors that form an integral part of equipment, such as motors, motor controllers, and similar equipment, or to conductors specifically provided for elsewhere in this Code. [310.1](https://2023.antflix.net#310.1)
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https://2023.antflix.net#310.1
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Chapter 3 Wiring Methods and Materials
|
310.3(A)
|
The minimum size of conductors for voltage ratings up to and including 2000 volts shall be 14 AWG copper or 12 AWG aluminum or copper-clad aluminum, except as permitted elsewhere in this Code. [310.3(A)](https://2023.antflix.net#310.3(A))
|
https://2023.antflix.net#310.3(A)
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Chapter 3 Wiring Methods and Materials
|
310.3(B)
|
Conductors in this article shall be of copper, aluminum, or copper-clad aluminum, unless otherwise specified. Aluminum and copper-clad aluminum shall comply with the following: Solid aluminum conductors 8, 10, and 12 AWG shall be made of an AA-8000 series electrical grade aluminum alloy conductor material.Stranded aluminum conductors 8 AWG through 1000 kcmil marked as Type RHH. RHW, XHHW, XHHN, XHWN, THW, THHW, THWN, THHN, service-entrance Type SE Style U, and SE Style R shall be made of an AA-8000 series electrical grade aluminum alloy conductor material.For copper-clad aluminum conductors, the copper shall form a minimum 10 percent of the cross-sectional area of a solid conductor or each strand of a stranded conductor. The aluminum core of a copper-clad aluminum conductor shall be made of an AA-8000 series electrical grade aluminum alloy conductor material.Copper-clad aluminum conductor material shall be listed. [310.3(B)](https://2023.antflix.net#310.3(B))
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https://2023.antflix.net#310.3(B)
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Chapter 3 Wiring Methods and Materials
|
310.3(C)
|
Where installed in raceways, conductors 8 AWG and larger shall be stranded, unless specifically permitted or required elsewhere in this Code to be solid. [310.3(C)](https://2023.antflix.net#310.3(C))
|
https://2023.antflix.net#310.3(C)
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Chapter 3 Wiring Methods and Materials
|
310.3(D)
|
Conductors not specifically permitted elsewhere in this Code to be covered or bare shall be insulated. Informational Note: See 250.184 for insulation of neutral conductors of a solidly grounded high-voltage system. [310.3(D)](https://2023.antflix.net#310.3(D))
|
https://2023.antflix.net#310.3(D)
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Chapter 3 Wiring Methods and Materials
|
310.4
|
Insulated conductors shall comply with Table 310.4(1) and Table 310.4(2). Informational Note: Thermoplastic insulation may stiffen at temperatures lower than —10°C (+14°F). Thermoplastic insulation may also be deformed at normal temperatures where subjected to pressure, such as at points of support. Table 310.4(1) Conductor Applications and Insulations Rated 600 Volts Trade Name Type Letter Maximum Operating Temperature Application Provisions Insulation Thickness of Insulation Outer Covering1 AWG or kcmil mm mils Fluorinated ethylene propylene FEP or FEPB 90°C(194°F) Dry and damp locations Fluorinated ethylene propylene 14—10 0.51 20 None 8—2 0.76 30 200°C(392°F) Dry locations - special applications2 Fluorinated ethylene propylene 14—8 0.36 14 Glass braid 6—2 0.36 14 Glass or other suitable braid material Mineral insulation (metal sheathed) MI 90°C(194°F) Dry and wet locations Magnesium oxide 18—163 0.58 23 Copper or alloy steel 16—10 0.91 36 250°C(482°F) For special applications2 9—4 1.27 50 3—500 1.40 55 Moisture-, heat-, and oil-resistant thermoplastic MTW 60°C(140°F) Machine tool wiring in wet locations Flame-retardant, moisture-, heat-, and oil-resistant thermoplastic (A) (B) (A) (B) (A) None (B) Nylon jacket or equivalent 90°C(194°F) Machine tool wiring in dry locations. 22—12 0.76 0.38 30 15 10 0.76 0.51 30 20 8 1.14 0.76 45 30 Informational Note: See NFPA 79-2021.Electrical Standard for Industrial Machinery. 6 1.52 0.76 60 30 4—2 1.52 1.02 60 40 1—4/0 2.03 1.27 80 50 213—500 2.41 1.52 95 60 501—1000 2.79 1.78 110 70 Paper 85°C(185°F) For underground service conductors, or by special permission Paper Lead sheath Perfluoro-alkoxy PFA 90°C(194°F) Dry and damp locations Perfluoro-alkoxy 14—10 0.51 20 None 8—2 0.76 30 200°C(392°F) Dry locations - special applications2 1—4/0 1.14 45 Perfluoro-alkoxy PFAH 250°C(482°F) Dry locations only. Only for leads within apparatus or within raceways connected to apparatus (nickel or nickel-coated copper only) Perfluoro-alkoxy 14—10 0.51 20 None 8—2 0.76 30 1—4/0 1.14 45 Thermoset RHH 90°C(194°F) Dry and damp locations 14—10 1.14 45 Moisture-resistant, flame-retardant, nonmetallic covering1 8—2 1.52 60 1—4/0 2.03 80 213—500 2.41 95 501—1000 2.79 110 1001—2000 3.18 125 Moisture-resistant thermoset RHW 75°C(167°F) Dry and wet locations Flame-retardant, moisture-resistant thermoset 14—10 1.14 45 Moisture-resistant, flame-retardant, nonmetallic covering 8—2 1.52 60 1—4/0 2.03 80 RHW-2 90°C(194°F) 213—500 2.41 95 501—1000 2.79 110 1001—2000 3.18 125 Silicone SA 90°C(194°F) Dry and damp locations Silicone rubber 14—10 1.14 45 Glass or other suitable braid material 8—2 1.52 60 1—4/0 2.03 80 200°C(392°F) For special application2 213—500 2.41 95 501—1000 2.79 110 1001—2000 3.18 125 Thermoset SIS 90°C (194°F) Switchboard and switchgear wiring only Flame-retardant thermoset 14—10 0.76 30 None 8—2 1.14 45 1—4/0 1.40 55 Thermoplastic and fibrous outer braid TBS 90°C (194°F) Switchboard and switchgear wiring only Thermoplastic 14—10 0.76 30 Flame-retardant, nonmetallic covering 8 1.14 45 6—2 1.52 60 1—4/0 2.03 80 Extended polytetra-fluoro-ethylene TFE 250°C (482°F) Dry locations only. Only for leads within apparatus or within raceways connected to apparatus, or as open wiring (nickel or nickel-coated copper only) Extruded polytetra-fluoroethylene 14—10 0.51 20 None 8—2 0.76 30 1—4/0 1.14 45 Heat-resistant thermoplastic THHN 90°C (194°F) Dry and damp locations Flame-retardant, heat-resistant thermoplastic 14—12 0.38 15 Nylon jacket or equivalent 10 0.51 20 8—6 0.76 30 4—2 1.02 40 1—4/0 1.27 50 250—500 1.52 60 501—1000 1.78 70 Moisture- and heat-resistant thermoplastic THHW 75°C (167°F) Wet location Flame-retardant, moisture- and heat-resistant thermoplastic 14—10 0.76 30 None 8 1.14 45 6—2 1.52 60 90°C (194°F) Dry location 1—4/0 2.03 80 213—500 2.41 95 501—1000 2.79 110 1001—2000 3.18 125 Moisture- and heat-resistant thermoplastic THW 75°C (167°F) Dry and wet locations Flame-retardant, moisture- and heat-resistant thermoplastic 14—10 0.76 30 None 8 1.14 45 90°C (194°F) Special applications within electric discharge lighting equipment. Limited to 1000 open-circuit volts or less. (Size 14—8 only as permitted in 410.68.) 6—2 1.52 60 1—4/0 2.03 80 213—500 2.41 95 501—1000 2.79 110 1001—2000 3.18 125 THW-2 90°C (194°F) Dry and wet locations Moisture- and heat-resistant thermoplastic THWN 75°C (167°F) Dry and wet locations Flame-retardant, moisture- and heat-resistant thermoplastic 14—12 0.38 15 Nylon jacket or equivalent 10 0.51 20 8—6 0.76 30 4—2 1.02 40 THWN-2 90°C (194°F) 1—4/0 1.27 50 250—500 1.52 60 501—1000 1.78 70 Moisture-resistant thermoplastic TW 60°C (140°F) Dry and wet locations Flame-retardant, moisture-resistant thermoplastic 14—10 0.76 30 None 8 1.14 45 6—2 1.52 60 1—4/0 2.03 80 213—500 2.41 95 501—1000 2.79 110 1001—2000 3.18 125 Underground feeder and branch-circuit cable - single conductor (for Type UF cable employing more than one conductor, see Part II of Article 340). UF 60°C 140°C See Part II of Article 340. Moisture-resistant 14—10 1.52 605 Integral with insulation 8—2 2.03 805 75°C (167°F)4 Moisture- and heat-resistant 1—4/0 2.41 955 Underground service-entrance cable - single conductor (for Type USE cable employing more than one conductor, see Part II of Article 338). USE 75°C(167°F)4 See Part II of Article 338. Heat- and moisture-resistant 14—10 1.14 45 Moisture-resistant nonmetallic covering (See 338.2.) 8—2 1.52 60 USE-2 90°C(194°F) Dry and wet locations 1—4/0 2.03 80 213—500 2.41 956 501—1000 2.79 110 1001—2000 3.18 125 Thermoset XHH 90°C(194°F) Dry and damp locations Flame-retardant thermoset 14—10 0.76 30 None 8—2 1.14 45 1—4/0 1.40 55 213—500 1.65 65 501—1000 2.03 80 1001—2000 2.41 95 Thermoset XHHN 90°C(194°F) Dry and damp locations Flame-retardant thermoset 14—12 0.38 15 Nylon jacket or equivalent 10 0.51 20 8—6 0.76 30 4—2 1.02 40 1—4/0 1.27 50 250—500 1.52 60 501—1000 1.78 70 Moisture-resistant thermoset XHHW 90°C(194°F) Dry and damp locations Flame-retardant, moisture-resistant thermoset 14—10 0.76 30 None 8—2 1.14 45 75°C(167°F) Wet locations 1—4/0 1.40 55 213—500 1.65 65 501—1000 2.03 80 1001—2000 2.41 95 Moisture-resistant thermoset XHHW-2 90°C(194°F) Dry and wet locations Flame-retardant, moisture-resistant thermoset 14—10 0.76 30 None 8—2 1.14 45 1—4/0 1.40 55 213—500 1.65 65 501—1000 2.03 80 1001—2000 2.41 95 Moisture-resistant thermoset XHWN 75°C(167°F) Dry and wet locations Flame-retardant, moisture-resistant thermoset 14—12 0.38 15 Nylon jacket or equivalent 10 0.51 20 8—6 0.76 30 XHWN-2 90°C(194°F) 4—2 1.02 40 1—4/0 1.27 50 250—500 1.52 60 501—1000 1.78 70 Modified ethylene tetrafluoro-ethylene Z 90°C(194°F) Dry and damp locations Modified ethylene tetrafluoro-ethylene 14—12 0.38 15 None 10 0.51 20 150°C(302°F) Dry locations - special applications2 8—4 0.64 25 3—1 0.89 35 1/0—4/0 1.14 45 Modified ethylene tetrafluoro-ethylene ZW 75°C(167°F) Wet locations Modified ethylene tetrafluoro-ethylene 14—10 0.76 30 None 8—2 1.14 45 90°C(194°F) Dry and damp locations 150°C(302°F) Dry locations - special applications2 ZW-2 90°C(194°F) Dry and wet locations Note: Conductors in Table 310.4(1) shall be permitted to be rated up to 1000 volts if listed and marked. 1Outer coverings shall not be required where listed without a covering. 2Higher temperature rated constructions shall be permitted where design conditions require maximum conductor operating temperatures above 90°C (194°F). 3Conductor sizes shall be permitted for signaling circuits permitting 300-volt insulation. 4The ampacity of Type UF cable shall be limited in accordance with 340.80. 5Type UF insulation thickness shall include the integral jacket. 6Insulation thickness shall be permitted to be 2.03 mm (80 mils) for listed Type USE conductors that have been subjected to special investigations. The nonmetallic covering over individual rubber-covered conductors of aluminum-sheathed cable and of lead-sheathed or multiconductor cable shall not be required to be flame retardant. Table 310.4(2) Thickness of Insulation for Nonshielded Types RHH and RHW Solid Dielectric Insulated Conductors Rated 2000 Volts Conductor Size(AWG or kcmil) Column A1 Column B2 mm mils mm mils 14—10 2.03 80 1.52 60 8 2.03 80 1.78 70 6—2 2.41 95 1.78 70 1—2/0 2.79 110 2.29 90 3/0—4/0 2.79 110 2.29 90 213—500 3.18 125 2.67 105 501—1000 3.56 140 3.05 120 1001—2000 3.56 140 3.56 140 1Column A insulations shall be limited to natural, SBR, and butyl rubbers. 2Column B insulations shall be materials such as cross-linked polyethylene, ethylene propylene rubber, and composites thereof. [310.4](https://2023.antflix.net#310.4)
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https://2023.antflix.net#310.4
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Chapter 3 Wiring Methods and Materials
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310.6(A)
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Insulated or covered grounded conductors shall be identified in accordance with 200.6. [310.6(A)](https://2023.antflix.net#310.6(A))
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https://2023.antflix.net#310.6(A)
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Chapter 3 Wiring Methods and Materials
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310.6(B)
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Equipment grounding conductors shall be identified in accordance with 250.119. [310.6(B)](https://2023.antflix.net#310.6(B))
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https://2023.antflix.net#310.6(B)
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Chapter 3 Wiring Methods and Materials
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310.6(C)
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Conductors that are intended for use as ungrounded conductors, whether used as a single conductor or in multiconductor cables, shall be finished to be clearly distinguishable from grounded conductors and equipment grounding conductors. Distinguishing markings shall not conflict in any manner with the surface markings required by 310.8(B)(1). Branch-circuit ungrounded conductors shall be identified in accordance with 210.5(C). Feeders shall be identified in accordance with 215.12(C) Exception: Conductor identification shall be permitted in accordance with 200.7. [310.6(C)](https://2023.antflix.net#310.6(C))
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https://2023.antflix.net#310.6(C)
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Chapter 3 Wiring Methods and Materials
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310.8(A)
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All conductors and cables shall be marked to indicate the following information, using the applicable method described in 310.8(B): The maximum rated voltage.The proper type letter or letters for the type of wire or cable as specified elsewhere in this Code.The manufacturer's name, trademark, or other distinctive marking by which the organization responsible for the product can be readily identified.The AWG size or circular mil area.Informational Note: See Chapter 9, Table 8, Conductor Properties, for conductor area expressed in SI units for conductor sizes specified in AWG or circular mil area.Cable assemblies where the neutral conductor is smaller than the ungrounded conductors shall be so marked. [310.8(A)](https://2023.antflix.net#310.8(A))
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https://2023.antflix.net#310.8(A)
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Chapter 3 Wiring Methods and Materials
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310.8(B)(1)
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The following conductors and cables shall be durably marked on the surface: Single-conductor and multiconductor thermoset and thermoplastic-insulated wire and cableNonmetallic-sheathed cableService-entrance cableUnderground feeder and branch-circuit cableTray cableIrrigation cablePower-limited tray cableInstrumentation tray cableThe AWG size or circular mil area shall be repeated at intervals not exceeding 610 mm (24 in.). All other markings shall be repeated at intervals not exceeding 1.0 m (40 in.). [310.8(B)(1)](https://2023.antflix.net#310.8(B)(1))
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https://2023.antflix.net#310.8(B)(1)
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Chapter 3 Wiring Methods and Materials
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310.8(B)(2)
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Metal-covered multiconductor cables shall employ a marker tape located within the cable and running for its complete length. Exception No. 1: Type MI cable shall not require a marker tape. Exception No. 2: Type AC cable shall not require a marker tape. Exception No. 3: The information required in 310.8(A) shall be permitted to be durably marked on the outer nonmetallic covering of Type MC, Type ITC, or Type PLTC cables at intervals not exceeding 1.0 m (40 in.). Exception No. 4: The information required in 310.8(A) shall be permitted to be durably marked on a nonmetallic covering under the metallic sheath of Type EEC or Type PLTC cable at intervals not exceeding 1.0 m (40 in.). Informational Note: Included in the group of metal-covered cables are Type AC cable, Type MC cable, and lead-sheathed cable. [310.8(B)(2)](https://2023.antflix.net#310.8(B)(2))
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https://2023.antflix.net#310.8(B)(2)
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Chapter 3 Wiring Methods and Materials
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310.8(B)(3)
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The following conductors and cables shall be marked by means of a printed tag attached to the coil, reel, or carton: Type MI cableSwitchboard wiresMetal-covered, single-conductor cablesType AC cable [310.8(B)(3)](https://2023.antflix.net#310.8(B)(3))
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https://2023.antflix.net#310.8(B)(3)
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Chapter 3 Wiring Methods and Materials
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310.8(B)(4)
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The information required in 310.8(A)(4) shall be permitted to be marked on the surface of the individual insulated conductors for the following multiconductor cables: Type MC cableTray cableIrrigation cablePower-limited tray cablePower-limited fire alarm cableInstrumentation tray cable [310.8(B)(4)](https://2023.antflix.net#310.8(B)(4))
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https://2023.antflix.net#310.8(B)(4)
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Chapter 3 Wiring Methods and Materials
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310.8(C)
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A type letter or letters used alone shall indicate a single insulated conductor. The letter suffixes shall be indicated as follows: D - For two insulated conductors laid parallel within an outer nonmetallic coveringM - For an assembly of two or more insulated conductors twisted spirally within an outer nonmetallic covering [310.8(C)](https://2023.antflix.net#310.8(C))
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https://2023.antflix.net#310.8(C)
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Chapter 3 Wiring Methods and Materials
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310.8(D)
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All conductors and cables contained in Chapter 3 shall be permitted to be surface marked to indicate special characteristics of the cable materials. These markings include, but are not limited to, markings for limited smoke, sunlight resistant, and so forth. [310.8(D)](https://2023.antflix.net#310.8(D))
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https://2023.antflix.net#310.8(D)
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Chapter 3 Wiring Methods and Materials
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310.10
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The conductors described in 310.4 shall be permitted for use in any of the wiring methods covered in Chapter 3 and as specified in their respective tables or as permitted elsewhere in this Code. [310.10](https://2023.antflix.net#310.10)
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https://2023.antflix.net#310.10
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Chapter 3 Wiring Methods and Materials
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310.10(A)
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Insulated conductors and cables used in dry locations shall be any of the types identified in this Code. [310.10(A)](https://2023.antflix.net#310.10(A))
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https://2023.antflix.net#310.10(A)
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Chapter 3 Wiring Methods and Materials
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310.10(B)
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Insulated conductors and cables used in dry and damp locations shall be Types FEP, FEPB, MTW, PFA, RHH, RHW, RHW-2, SA, THHN, THW, THW-2, THHW, THWN, THWN-2, TW, XHH, XHHW, XHHW-2, XHHN, XHWN, XHWN-2, Z, or ZW. [310.10(B)](https://2023.antflix.net#310.10(B))
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https://2023.antflix.net#310.10(B)
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Chapter 3 Wiring Methods and Materials
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310.10(C)
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Insulated conductors and cables used in wet locations shall comply with one of the following: Be moisture-impervious metal-sheathedBe types MTW, RHW, RHW-2, TW, THW, THW-2, THHW, THWN, THWN-2, XHHW, XHHW-2, XHWN, XHWN-2 or ZWBe of a type listed for use in wet locations [310.10(C)](https://2023.antflix.net#310.10(C))
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https://2023.antflix.net#310.10(C)
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Chapter 3 Wiring Methods and Materials
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310.10(D)
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Insulated conductors or cables used where exposed to direct rays of the sun shall comply with one of the following: Conductors and cables shall be listed being sunlight resistant.Conductors and cables shall be covered with insulating material, such as tape or sleeving, that is listed as being sunlight resistant. [310.10(D)](https://2023.antflix.net#310.10(D))
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https://2023.antflix.net#310.10(D)
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