Article 320 Armored Cable: Type AC

This article covers the use, installation, and construction specifications for armored cable, Type AC.

The definition in this section shall apply within this article and throughout the Code.

Type AC cable and associated fittings shall be listed.

Type AC cable shall be permitted as follows:

1. For feeders and branch circuits in both exposed and concealed installations
2. In cable trays
3. In dry locations
4. Embedded in plaster finish on brick or other masonry, except in damp or wet locations
5. To be run or fished in the air voids of masonry block or tile walls where such walls are not exposed or subject to excessive moisture or dampness

Type AC cable shall not be used as follows:

1. Where subject to physical damage
2. In damp or wet locations
3. In air voids of masonry block or tile walls where such walls are exposed or subject to excessive moisture or dampness
4. Where exposed to corrosive conditions
5. Embedded in plaster finish on brick or other masonry in damp or wet locations

Exposed runs of cable, except as provided in 300.11(B), shall closely follow the surface of the building 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.

Type AC cable shall be protected in accordance with 300.4(A), (C), and (D) where installed through or parallel to framing members.

Type AC cables in accessible attics or roof spaces shall be installed as specified in 320.23(A) and (B).

Where run across the top of floor joists, or within 2.1 m (7 ft) of the floor or floor joists across the face of rafters or studding, the cable shall be protected by guard strips that are at least as high as the cable. Where this space is not accessible by permanently installed stairs or ladders, protection shall only be required within 1.8 m (6 ft) of the nearest edge of the scuttle hole or attic entrance.

Where the cable is installed parallel to the sides of rafters, studs, or ceiling or floor joists, neither guard strips nor running boards shall be required, and the installation shall also comply with 300.4(D).

Bends in Type AC cable shall be made such that the cable is not damaged. The radius of the curve of the inner edge of any bend shall not be less than five times the diameter of the Type AC cable.

Type AC 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.

Unless otherwise permitted, Type AC cable shall be secured within 300 mm (12 in.) of every outlet box, junction box, cabinet, or fitting and at intervals not exceeding 1.4 m (4¹/₂ ft).

Unless otherwise permitted, Type AC cable shall be supported at intervals not exceeding 1.4 m (4¹/₂ ft).

Type AC 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 impracticable
2. Is not more than 600 mm (2 ft) in length at terminals where flexibility is necessary
3. Is not more than 1.8 m (6 ft) in length from the last point of cable support to the point of connection to a luminaire(s) or other electrical equipment and the cable and point of connection are within an accessible ceiling

At all points where the armor of AC cable terminates, a fitting shall be provided to protect wires from abrasion, unless the design of the outlet boxes or fittings is such as to afford equivalent protection, and, in addition, an insulating bushing or its equivalent protection shall be provided between the conductors and the armor. The connector or clamp by which the Type AC cable is fastened to boxes or cabinets shall be of such design that the insulating bushing or its equivalent will be visible for inspection. Where change is made from Type AC cable to other cable or raceway wiring methods, a box, fitting, or conduit body shall be installed at junction points as required in 300.15.

The ampacity shall be determined in accordance with 310.14.

Armored cable installed in thermal insulation shall have conductors rated at 90°C (194°F). The ampacity of cable installed in these applications shall not exceed that of a 60°C (140°F) rated conductor. The 90°C (194°F) rating shall be permitted to be used for ampacity adjustment and correction calculations; however, the ampacity shall not exceed that of a 60°C (140°F) rated conductor.

The ampacity of Type AC cable installed in cable tray shall be determined in accordance with 392.80(A).

Type AC cable shall have an armor of flexible metal tape and shall have an internal bonding strip of copper or aluminum in intimate contact with the armor for its entire length.

Insulated conductors shall be of a type listed in Table 310.4(A) or those identified for use in this cable. In addition, the conductors shall have an overall moisture-resistant and fire-retardant fibrous covering. For Type ACT, a moisture-resistant fibrous covering shall be required only on the individual conductors.

Type AC cable shall provide an adequate path for fault current as required by 250.4(A)(5) or (B)(4) to act as an equipment grounding conductor.

The cable shall be marked in accordance with 310.8, except that Type AC shall have ready identification of the manufacturer by distinctive external markings on the cable armor throughout its entire length.