MESSENGER SUPPORTED WIRING

70-209 and at least as high as the insulating supports, placed on each side of and close to the wiring; (2) by a substantial running board at least ½ inch (12.7 mm) thick back of the conductors with side protections. Running boards shall extend at least 1 inch (25.4 mm) outside the conductors, but not more than 2 inches (50.8 mm), and the protecting sides shall be at least 2 inches (50.8 mm) high and at least 1 inch (25.4 mm) nominal in thickness; (3) by boxing made as above and furnished with a cover kept at least 1 inch (25.4 mm) away from the conductors within. Where protecting vertical conductors on side walls, the boxing shall be closed at the top and the holes through which the conductors pass shall be bushed; (4) by rigid metal conduit, intermediate metal conduit, rigid nonmetallic conduit, or electrical metallic tubing, in which case the rules of Article 345, 346, 347, or 348 shall apply; or by metal piping, in which case the conductors shall be encased in continuous lengths of approved flexible tubing. The conductors passing through metal enclosures shall be so grouped that current in both directions is approximately equal. 320-15. Unfinished Attics and Roof Spaces. Conductors in unfinished attics and roof spaces shall comply with (a) or (b) below. (a) Accessible by Stairway or Permanent Ladder. Conductors shall be installed along the side of or through bored holes in floor joists, studs, or rafters. Where run through bored holes, conductors in the joists and in studs or rafters to a height of not less than 7 feet (2.13 m) above the floor or floor joists shall be protected by substantial running boards extending not less than 1 inch (25.4 mm) on each side of the conductors. Running boards shall be securely fastened in place. Running boards and guard strips shall not be required for conductors installed along the sides of joists, studs, or rafters. (b) Not Accessible by Stairway or Permanent Ladder. Conductors shall be installed along the sides of or through bored holes in floor joists, studs, or rafters. Exception: In buildings completed before wiring is installed and having head room at all points of less than 3 feet (914 mm). 320-16. Switches. Surface-type snap switches shall be mounted in accordance with Section 380-10(a), and boxes shall not be required. Other type switches shall be installed in accordance with Section 380-4.