The ampacity shall be in accordance with the
60°C (140°F) conductor temperature rating. The 90°C
(194°F) rating shall be permitted to be used for
ampacity derating purposes, provided the final derated
ampacity does not exceed that for a 60°C (140°F) rated
conductor. The ampacity of Types NM, NMC, and NMS
cable installed in cable tray shall be determined in
accordance with 392.11.
Where more than two NM cables 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 fire- or draft-stopped using thermal insulation, caulk, or sealing foam, the allowable ampacity of each conductor shall be adjusted in accordance with Table 310.15(B)(2)(a) and the provisions of 310.15(A)(2), Exception, shall not apply.

Where more than two NM cables containing two or more current-carrying conductors are installed in contact with thermal insulation without maintaining spacing be- tween cables, the allowable ampacity of each

conductor shall be adjusted in accordance with Table

310.15(B)(2)(a).

III. Construction Specifications

334.100 Construction. The outer cable sheath of non- metallic-sheathed cable shall be a nonmetallic material.

334.104 Conductors. The 600-volt insulated conductors shall be sizes 14 AWG through 2 AWG copper conductors or sizes 12 AWG through 2 AWG aluminum or copper-clad aluminum conductors. The communications conductors shall comply with Part V of Article 800.

334.108 Equipment Grounding Conductor. In addition to the insulated conductors, the cable shall have an insulated, covered, or bare equipment grounding conductor.

334.112 Insulation. The insulated power conductors shall be one of the types listed in Table 310.13(A) that are suitable for branch-circuit wiring or one that is identified for use in these cables. Conductor insulation shall be rated at 90°C (194°F).

FPN: Types NM, NMC, and NMS cable identified by the markings NM-B, NMC-B, and NMS-B meet this requirement.

334.116 Sheath. The outer sheath of nonmetallic- sheathed cable shall comply with 334.116(A), (B), and (C).

(A) Type NM. The overall covering shall be flame retar- dant and moisture resistant.

Type NMC. The overall covering shall be flame re- tardant, moisture resistant, fungus resistant, and corro- sion resistant.

(C) Type NMS. The overall covering shall be flame retar- dant and moisture resistant. The sheath shall be applied so as to separate the power conductors from the communications conductors.