NONMETALLIC-SHEATHED CABLE

70-229 (a) 600 Volts. Insulated conductors in sizes No. 18 and 16 shall be of a type listed in Table 402-3, with a maximum operating temperature not less than 90°C (194°F), and as permitted by Section 725-16. Conductors larger than No. 16 shall be of a type listed in Table 310-13 or of a type identified for use in MC cable. (b) Over 600 Volts. Insulated conductors shall be of a type listed in Tables 310-61 through 310-67. 334-22. Metallic Sheath. The metallic covering shall be one of the following types: smooth metallic sheath, welded and corrugated metallic sheath, interlocking metal tape armor. The metallic sheath shall be continuous and close fitting. Supplemental protection of an outer covering of corrosion-resistant material shall be permitted and shall be required where such protection is needed. The sheath shall not be used as a current-carrying conductor. (FPN): See Section 300-6 for protection against corrosion. 334-23. Grounding. Type MC cable shall provide an adequate path for equipment grounding as required by Article 250. 334-24. Marking. The provisions of Section 310-11 shall apply. Cables that are flame-retardant and have limited-smoke characteristics shall be permitted to be identified with the suffix LS. ARTICLE 336 - NONMETALLIC-SHEATHED CABLE Types NM and NMC A. General 336-1. Definition. Nonmetallic-sheathed cable is a factory assembly of two or more insulated conductors having an outer sheath of moistureresistant, flame-retardant, nonmetallic material. 336-2. Other Articles. In addition to the provisions of this article, installations of nonmetallic-sheathed cable shall comply with the other applicable provisions of this Code, especially Articles 300 and 310. 336-3. Uses Permitted. Type NM and Type NMC cables shall be permitted to be used in one- and two-family dwellings, multifamily dwellings, and other structures, except as prohibited in Section 336-4. Where installed in cable trays, cables shall be identified for this use. (FPN): See Section 310-10 for temperature limitation of conductors. (a) Type NM. Type NM cable shall be permitted for both exposed and concealed work in normally dry locations. It shall be permissible to install or fish Type NM cable in air voids in masonry block or tile walls where such walls are not exposed or subject to excessive moisture or dampness. 70-230 NATIONAL ELECTRICAL CODE (b) Type NMC. Type NMC cable shall be permitted (1) for both exposed and concealed work in dry, moist, damp, or corrosive locations; (2) in outside and inside walls of masonry block or tile; (3) in a shallow chase in masonry, concrete, or adobe protected against nails or screws by a steel plate at least 1/16 inch (1.59 mm) thick and covered with plaster, adobe, or similar finish. 336-4. Uses Not Permitted. (a) Type NM or NMC. Types NM and NMC cables shall not be used (1) in any dwelling or structure exceeding three floors above grade; (2) as service-entrance cable; (3) in commercial garages having hazardous (classified) locations as provided in Section 511-3; (4) in theaters and similar locations, except as provided in Article 518, Places of Assembly; (5) in motion picture studios; (6) in storage battery rooms; (7) in hoistways; (8) embedded in poured cement, concrete, or aggregate; or (9) in any hazardous (classified) location except as permitted by Sections 501-4(b), Exception and 504-20. For the purpose of this article, the first floor of a building shall be that floor that has 50 percent or more of the exterior wall surface area level with or above finished grade. One additional level that is the first level and not designed for human habitation and used only for vehicle parking, storage, or similar use shall be permitted. (b) Type NM. Type NM cable shall not be installed (1) where exposed to corrosive fumes or vapors; (2) where embedded in masonry, concrete, adobe, fill, or plaster; (3) in a shallow chase in masonry, concrete, or adobe and covered with plaster, adobe, or similar finish. B. Installation 336-10. Exposed Work - General. In exposed work, except as provided in Sections 300-11(a), 336-12, and 336-13, the cable shall be installed as specified in (a) and (b) below. (a) To Follow Surface. The cable shall closely follow the surface of the building finish or of running boards. (b) Protection from Physical Damage. The cable shall be protected from physical damage where necessary by conduit, electrical metallic tubing, Schedule 80 PVC rigid nonmetallic conduit, pipe, guard strips, or other means. Where passing through a floor, the cable shall be enclosed in rigid metal conduit, intermediate metal conduit, electrical metallic tubing, Schedule 80 PVC rigid nonmetallic conduit, or other metal pipe extending at least 6 inches (152 mm) above the floor. 336-11. Through or Parallel to Joists, Studs, and Rafters. Type NM or NMC cable shall comply with Section 300-4 where installed through or parallel to joists, studs, rafters, or similar wood or metal members. 336-12. In Unfinished Basements. Where the cable is run at angles with joists in unfinished basements, it shall be permissible to secure cables not smaller than two No. 6 or three No. 8 conductors directly to the lower edges of the joists. Smaller cables shall either be run through bored holes ARTICLE 336 - NONMETALLIC-SHEATHED CABLE 70-231 in joists or on running boards. Where run parallel to the joists, cable of any size shall be secured to the sides of joists in accordance with Section 300-4(d). 336-13. In Accessible Attics. The installation of cable in accessible attics or roof spaces shall also comply with Section 333-12. 336-14. Bends. Bends in cable shall be so made, and other handling shall be such, that the protective coverings of the cable will not be damaged, and no bend shall have a radius less than five times the diameter of the cable. 336-15. Supports. Nonmetallic-sheathed cable shall be secured by staples, cable ties, straps, or similar fittings so designed and installed as not to damage the cable. Cable shall be secured in place at intervals not exceeding 4½ feet (1.37 m) and within 12 inches (305 mm) from every cabinet, box, or fitting. Two conductor cables shall not be stapled on edge. Cables run through holes in wooden joists, rafters, or studs shall be considered to be supported. (FPN): See Section 370-17(c) for support where nonmetallic boxes are used. Exception No. 1: For concealed work in finished buildings or finished panels for prefabricated buildings where such supporting is impracticable, it shall be permissible to fish the cable between access points. Exception No. 2: A wiring device identified for the use, without a separate outlet box, incorporating an integral cable clamp shall be permitted where the cable is secured in place at intervals not exceeding 4½ feet (1.37 m) and within 12 inches (305 mm) from the wiring device wall opening, and there shall be at least a 12-inch (305-mm) loop of unbroken cable or 6 inches (152 mm) of a cable end available on the interior side of the finished wall to permit replacement. 336-16. Devices of Insulating Material. Switch, outlet, and tap devices of insulating material shall be permitted to be used without boxes in exposed cable wiring and for rewiring in existing buildings where the cable is concealed and fished. Openings in such devices shall form a close fit around the outer covering of the cable, and the device shall fully enclose that part of the cable from which any part of the covering has been removed. Where connections to conductors are by binding-screw terminals, there shall be available as many terminals as conductors. Exception: Where cables are clamped within the structure and terminals are of a type identified for use with multiconductors. 336-17. Boxes of Insulating Material. Nonmetallic outlet boxes shall be permitted as provided in Section 370-3. 336-18. Devices with Integral Enclosures. Wiring devices with integral enclosures identified for such use shall be permitted as provided in Section 300-15(b), Exception No. 4. 70-232 NATIONAL ELECTRICAL CODE C. Construction Specifications 336-25. Construction. The insulated conductors of Types NM and NMC cable shall be in conformity with Section 336-26. The conductors shall be sizes No. 14 through 2 with copper conductors or sizes No. 12 through 2 with aluminum or copper-clad aluminum conductors. In addition to the insulated conductors, the cable shall be permitted to have an insulated or bare conductor for equipment grounding purposes only. Where provided, the grounding conductor shall be sized in accordance with Article 250. (a) Type NM. The overall covering shall be flame-retardant and moisture-resistant. (b) Type NMC. The overall covering shall be flame-retardant, moistureresistant, fungus-resistant, and corrosion-resistant. 336-26. Conductors. The insulated conductors shall be one of the types listed in Table 310-13 that is suitable for branch-circuit wiring or one that is identified for use in these cables. Conductors shall be rated at 90°C (194°F). The ampacity of Types NM and NMC cable shall be that of 60°C- (140°F-) conductors and shall comply with Section 310-15. 336-27. Marking. In addition to the provisions of Section 310-11, the cable shall have a distinctive marking on the exterior for its entire length specifying the cable type. Cables that are flame-retardant and have limitedsmoke characteristics shall be permitted to be identified with the suffix LS.