PDFWAC 296-46B-334
Nonmetallic-sheathed cable.
010 Nonmetallic-sheathed cable.
(1) The building classification, for subsections (2), (3), and (4) of this section, will be as determined by the building official. For the purposes of this section, Type III, IV-HT and V may be as defined in the International Building Code adopted in the state of Washington. The installer must provide the inspector documentation substantiating the type of building construction and finish material rating(s) prior to any electrical inspection.
(2) This section replaces NEC 334.10(2). In multifamily dwellings, Type NM, Type NMC, and Type NMS cable(s) may be used in structures of Types III, IV-HT, and V construction except as prohibited in NEC 334.12.
(3) This section replaces NEC 334.10(3). In all other structures, Type NM, Type NMC, and Type NMS cable(s) may be used in structures of Types III, IV-HT, and V construction except as prohibited in NEC 334.12. All cable(s) must be concealed within walls, floors, or ceilings that provide a thermal barrier of material that has at least a 15-minute finish rating as identified in listings of fire-rated assemblies.
(4) This section replaces NEC 334.10(4). Cable trays in structures of Types III, IV-HT, and V construction, where the cable(s) is identified for the use, except as prohibited in NEC 334.12.
015 Exposed work.
(5) Where Type NMC cable is installed in shallow chases in plaster, masonry, concrete, adobe or similar material, the cable must be protected against nails or screws by:
(a) A steel plate at least 1/16 inch thick and covered with plaster, adobe, or similar finish; or
(b) Being recessed in a chase at least 2 3/4 inches deep, as measured from the finished surface, and covered with plaster, adobe, or similar finish. The cable(s) must be at least 2 1/2 inches from the finished surface.
(6) The requirements for nonmetallic sheathed cable protection in NEC 334.15(C) do not apply in crawl spaces.
(7) Wet or damp locations prohibited in NEC 334.12(B)(4) do not include the interior of conduits installed outdoors used for physical protection of NM cables under the following conditions:
(a) Cables emerging from a building interior, attic, or crawlspace remain unbroken until terminated; and
(b) Flexible metal conduits are not used; and
(c) No conduit systems are longer than 10 feet or below grade; and
(d) Conduits are sealed to prevent air movement and are arranged to naturally drain.
080 Ampacity of Types NM and NMC cable carrying suffix letter "-B".
(8)(a) The ampacity of Types NM and NMC cable carrying suffix letter "-B" shall be determined in accordance with NEC 310.14.
(b) The ampacity of #10 AWG and smaller ungrounded conductors shall not exceed that of a 60°C (140°F) rated conductor.
(c) The ampacity of ungrounded conductors larger than #10 AWG shall not exceed that of a 75°C (167°F) rated conductor.
(d) The 90°C (194°F) rating shall be permitted to be used for ampacity adjustment and correction calculations, provided the final calculated ampacity for #10 AWG and smaller ungrounded conductors does not exceed that of a 60°C (140°F) rated conductor or exceed that of a 75°C (167°F) rated conductor for ungrounded conductors larger than #10 AWG.
(e) The ampacity of Types NM and NMC cable carrying suffix letter "-B" installed in cable trays shall be determined in accordance with NEC 392.80(A).
(f) Where more than two NM cables carrying suffix letter "-B" containing two or more current-carrying conductors are installed, without maintaining spacing between the cables, through the same opening in wood framing that is to be sealed with thermal insulation, caulk, or sealing foam, the ampacity of each conductor shall be adjusted in accordance with NEC Table 310.15(C)(1) and NEC 310.14(A)(2), Exception, shall not apply.
(g) Where more than two NM cables carrying suffix letter "-B" containing two or more current-carrying conductors are installed in contact with thermal insulation without maintaining spacing between cables, the ampacity of each conductor shall be adjusted in accordance with NEC Table 310.15(C)(1) and NEC 310.14(A)(2), Exception, shall not apply.
[Statutory Authority: Chapter 19.28 RCW, RCW 19.28.031, and 19.28.251. WSR 25-23-069, s 296-46B-334, filed 11/18/25, effective 12/19/25; WSR 24-05-085, § 296-46B-334, filed 2/21/24, effective 4/1/24; WSR 20-11-053 and 20-14-083, § 296-46B-334, filed 5/19/20 and 6/30/20, effective 10/29/20. Statutory Authority: Chapter 19.28 RCW, RCW 19.28.010 and 19.28.031. WSR 17-12-021, § 296-46B-334, filed 5/30/17, effective 7/1/17. Statutory Authority: RCW 19.28.006, 19.28.010, 19.28.031, 19.28.041, 19.28.061, 19.28.101, 19.28.131, 19.28.161, 19.28.171, 19.28.191, 19.28.201, 19.28.211, 19.28.241, 19.28.251, 19.28.281, 19.28.311, 19.28.321, 19.28.400, 19.28.420, 19.28.490, 19.28.551. WSR 08-24-048, § 296-46B-334, filed 11/25/08, effective 12/31/08; WSR 05-10-024, § 296-46B-334, filed 4/26/05, effective 6/30/05. Statutory Authority: RCW 19.28.006, 19.28.010, 19.28.031, 19.28.041, 19.28.061, 19.28.101, 19.28.131, 19.28.161, 19.28.171, 19.28.191, 19.28.201, 19.28.211, 19.28.241, 19.28.251, 19.28.271, 19.28.311, 19.28.321, 19.28.400, 19.28.420, 19.28.490, 19.28.551, 2003 c 399, 2003 c 211, 2003 c 78, and 2003 c 242. WSR 04-12-049, § 296-46B-334, filed 5/28/04, effective 6/30/04. Statutory Authority: RCW 19.28.006, 19.28.010, 19.28.031, 19.28.041, 19.28.061, 19.28.101, 19.28.131, 19.28.161, 19.28.171, 19.28.191, 19.28.201, 19.28.211, 19.28.241, 19.28.251, 19.28.271, 19.28.311, 19.28.321, 19.28.400, 19.28.420, 19.28.490, 19.28.551, 2002 c 249, chapters 34.05 and 19.28 RCW. WSR 03-09-111, § 296-46B-334, filed 4/22/03, effective 5/23/03.]