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Article 330

Metal-Clad Cable: Type MC

328.120 Marking. Medium voltage cable shall be marked as required by 310.120.

Part I. General

  1. Scope. This article covers the use, installation, and construction specifications of metal-clad cable, Type MC.
  2. Definition.

Metal Clad Cable, Type MC. A factory assembly of one or more insulated circuit conductors with or without optical fiber members enclosed in an armor of interlocking metal tape, or a smooth or corrugated metallic sheath.

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330.6 Listing Requirements. Type MC cable shall be listed. Fittings used for connecting Type MC cable to boxes, cabinets, or other equipment shall be listed and identified for such use.

Part II. Installation

330.10 Uses Permitted.

  1. General Uses. Type MC cable shall be permitted as follows:
    1. For services, feeders, and branch circuits.
    2. For power, lighting, control, and signal circuits.
    3. Indoors or outdoors.
    4. Exposed or concealed.
    5. To be direct buried where identified for such use.
    6. In cable tray where identified for such use.
    7. In any raceway.
    8. As aerial cable on a messenger.
    9. In hazardous (classified) locations where specifically permitted by other articles in this Code.
      • (10) In dry locations and embedded in plaster finish on brick
      or other masonry except in damp or wet locations.
      1. In wet locations where a corrosion-resistant jacket is provided over the metallic covering and any of the following conditions are met:
        1. The metallic covering is impervious to moisture.
        2. A jacket resistant to moisture is provided under the metal covering.
        3. The insulated conductors under the metallic cover‐ ing are listed for use in wet locations.
      2. Where single-conductor cables are used, all phase conductors and, where used, the grounded conductor shall be grouped together to minimize induced voltage on the sheath.
  2. Specific Uses. Type MC cable shall be permitted to be installed in compliance with Parts II and III of Article 725 and

770.133 as applicable and in accordance with 330.10(B)(1) through (B)(4).

Informational Note: The “Uses Permitted” is not an all-inclusive list.

  1. Cable Tray. Type MC cable installed in cable tray shall comply with 392.10, 392.12, 392.18, 392.20, 392.22, 392.30, 392.46, 392.56, 392.60(C), and 392.80.
  2. Direct Buried. Direct-buried cable shall comply with 300.5 or 300.50, as appropriate.
  3. Installed as Service-Entrance Cable. Type MC cable instal‐ led as service-entrance cable shall be permitted in accordance with 230.43.
  4. Installed Outside of Buildings or Structures or as Aerial Cable. Type MC cable installed outside of buildings or struc‐ tures or as aerial cable shall comply with 225.10, 396.10, and 396.12.

330.12 Uses Not Permitted. Type MC cable shall not be used under either of the following conditions:

  1. Where subject to physical damage
  2. Where exposed to any of the destructive corrosive condi‐ tions in (a) or (b), unless the metallic sheath or armor is resistant to the conditions or is protected by material resistant to the conditions:
    1. Direct buried in the earth or embedded in concrete unless identified for direct burial
    2. Exposed to cinder fills, strong chlorides, caustic alka‐ lis, or vapors of chlorine or of hydrochloric acidsimageN330.15 Exposed Work. Exposed runs of cable, except as provi‐ ded in 300.11(A), shall closely follow the surface of the build‐ ing finish or of running boards. Exposed runs shall also be permitted to be installed on the underside of joists where supported at each joist and located so as not to be subject to physical damage.330.17 Through or Parallel to Framing Members. Type MC cable shall be protected in accordance with 300.4(A), (C), and(D) where installed through or parallel to framing members.
      1. In Accessible Attics. The installation of Type MC cable in accessible attics or roof spaces shall also comply with 320.23.
      2. Bending Radius. Bends in Type MC cable shall be so made that the cable will not be damaged. The radius of the curve of the inner edge of any bend shall not be less than required in 330.24(A) through (C).
      1. Smooth Sheath.
        1. Ten times the external diameter of the metallic sheath for cable not more than 19 mm (3∕4 in.) in external diameter
        2. Twelve times the external diameter of the metallic sheath for cable more than 19 mm (3∕4 in.) but not more than 38 mm (11∕2 in.) in external diameter
        3. Fifteen times the external diameter of the metallic sheath for cable more than 38 mm (11∕2 in.) in external diameter
        ARTICLE 332 — MINERAL-INSULATED, METAL-SHEATHED CABLE: TYPE MI 332.2
      2. Interlocked-Type Armor or Corrugated Sheath. Seven times the external diameter of the metallic sheath.
      3. Shielded Conductors. Twelve times the overall diameter of one of the individual conductors or seven times the overall diameter of the multiconductor cable, whichever is greater.
      1. Securing and Supporting.
        1. General. Type MC cable shall be supported and secured by staples; cable ties listed and identified for securement and support; straps, hangers, or similar fittings; or other approved means designed and installed so as not to damage the cable.
        2. Securing. Unless otherwise provided, cables shall be secured at intervals not exceeding 1.8 m (6 ft). Cables contain‐ ing four or fewer conductors sized no larger than 10 AWG shall be secured within 300 mm (12 in.) of every box, cabinet, fitting, or other cable termination. In vertical installations, listed cables with ungrounded conductors 250 kcmil and larger shall be permitted to be secured at intervals not exceeding 3 m (10 ft).
        3. Supporting. Unless otherwise provided, cables shall be supported at intervals not exceeding 1.8 m (6 ft).Horizontal runs of Type MC cable installed in wooden or metal framing members or similar supporting means shall be considered supported and secured where such support does not exceed 1.8-m (6-ft) intervals.
        4. Unsupported Cables. Type MC cable shall be permitted to be unsupported and unsecured where the cable complies with any of the following:
        1. Is fished between access points through concealed spaces in finished buildings or structures and supporting is impractical.
        2. Is not more than 1.8 m (6 ft) in length from the last point of cable support to the point of connection to luminaires or other electrical equipment and the cable and point of connection are within an accessible ceiling.
        3. Is Type MC of the interlocked armor type in lengths not exceeding 900 mm (3 ft) from the last point where it is securely fastened and is used to connect equipment where flexibility is necessary to minimize the transmission of vibration from equipment or to provide flexibility for equipment that requires movement after installation.
        For the purpose of this section, Type MC cable fittings shall be permitted as a means of cable support.
      2. Single Conductors. Where single-conductor cables with a nonferrous armor or sheath are used, the installation shall comply with 300.20.
      •330.80 Ampacity. The ampacity of Type MC cable shall bedetermined in accordance with 310.15 or 310.60 for 14 AWG and larger conductors and in accordance with Table 402.5 for 18 AWG and 16 AWG conductors. The installation shall not exceed the temperature ratings of terminations and equip‐ ment.
      1. Type MC Cable Installed in Cable Tray. The ampacities for Type MC cable installed in cable tray shall be determined in accordance with 392.80.
      2. Single Type MC Conductors Grouped Together. Where single Type MC conductors are grouped together in a triangu‐ lar or square configuration and installed on a messenger or

      exposed with a maintained free airspace of not less than2.15 times one conductor diameter (2.15 × O.D.) of the largest conductor contained within the configuration and adjacent conductor configurations or cables, the ampacity of the conductors shall not exceed the allowable ampacities in the following tables:(1) Table 310.15(B)(20) for conductors rated 0 through 2000 volts(2) Table 310.60(C)(67) and Table 310.60(C)(68) for conductors rated over 2000 volts
      Part III. Construction Specifications330.104 Conductors. Conductors shall be of copper, alumi‐ num, copper-clad aluminum, nickel or nickel-coated copper, solid or stranded. The minimum conductor size shall be 18 AWG copper, nickel or nickel-coated copper, or 12 AWG aluminum or copper-clad aluminum.330.108 Equipment Grounding Conductor. Where Type MC cable is used to provide an equipment grounding conductor, it shall comply with 250.118(10) and 250.122.330.112 Insulation. Insulated conductors shall comply with 330.112(A) or (B).
      1. 1000 Volts or Less. Insulated conductors in sizes 18 AWG and 16 AWG 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 725.49. Conductors larger than 16 AWG shall be of a type listed in Table 310.104(A) or of a type identi‐ fied for use in Type MC cable.
      2. Over 1000 Volts. Insulated conductors shall be of a type listed in Table 310.104(B) and Table 310.104(C).
      330.116 Sheath. Metallic covering shall be one of the follow‐ ing types: smooth metallic sheath, corrugated metallic sheath, or interlocking metal tape armor. The metallic sheath shall be continuous and close fitting. A nonmagnetic sheath or armor shall be used on single conductor Type MC. 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.Informational Note: See 300.6 for protection against corrosion.

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