CELLULAR METAL FLOOR RACEWAYS

356-1. Definitions. For the purposes of this article, a "cellular metal floor raceway" shall be defined as the hollow spaces of cellular metal floors, together with suitable fittings, that may be approved as enclosures for electric conductors. A "cell" shall be defined as a single, enclosed tubular space in a cellular metal floor member, the axis of the cell being parallel to the axis of the metal floor member. A "header" shall be defined as a transverse raceway for electric conductors, providing access to predetermined cells of a cellular metal floor, thereby permitting the installation of electric conductors from a distribution center to the cells. 356-2. Uses Not Permitted. Conductors shall not be installed in cellular metal floor raceways (1) where subject to corrosive vapor; (2) in any hazardous (classified) location except as permitted by Section 504-20, and in Class I, Division 2 locations as permitted in the exception to Section 501- 4(b); nor (3) in commercial garages, other than for supplying ceiling outlets or extensions to the area below the floor but not above. (FPN): See Section 300-8 for installation of conductors with other systems. 356-3. Other Articles. Cellular metal floor raceways shall comply with the applicable provisions of Article 300. A. Installation 356-4. Size of Conductors. No conductor larger than No. 1/0 shall be installed, except by special permission. 356-5. Maximum Number of Conductors in: Raceway. The combined cross-sectional area of all conductors or cables shall not exceed 40 percent of the interiori cross-sectional area of the cell or header. (FPN): For conductor cross-sectional area, see Tables 5, 5A, 6, and 8 and the I applicable Notes to Tables at the beginning of Chapter 9. 356-6. Splices and Taps. Splices and taps shall be made only in header access units or junction boxes. For the purposes of this section, so-called loop wiring (continuous unbroken conductor connecting the individual outlets) shall not be considered to be a splice or tap. 356-7. Discontinued Outlets. When an outlet is abandoned, discontinued, or removed, the sections of circuit conductors supplying the outlet 70-266 NATIONAL ELECTRICAL CODE shall be removed from the raceway. No splices or reinsulated conductors, such as would be the case with abandoned outlets on loop wiring, shall be allowed in raceways. 356-8. Markers. A suitable number of markers shall be installed for the future locating of cells. 356-9. Junction Boxes. Junction boxes shall be leveled to the floor grade and sealed against the free entrance of water or concrete. Junction boxes used with these raceways shall be of metal and shall be electrically continuous with the raceway. 356-10. Inserts. Inserts shall be leveled to the floor grade and sealed against the entrance of concrete. Inserts shall be of metal and shall be electrically continuous with the raceway. In cutting through the cell wall and setting inserts, chips and other dirt shall not be allowed to remain in the raceway, and tools shall be used that are designed to prevent the tool from entering the cell and damaging the conductors. 356-11. Connection to Cabinets and Extensions from Cells. Connections between raceways and distribution centers and wall outlets shall be made by means of flexible metal conduit where not installed in concrete, rigid metal conduit, intermediate metal conduit, electrical metallic tubing, or approved fittings. Where there are provisions for the termination of an equipment grounding conductor, nonmetallic conduit, electrical nonmetallic tubing, or liquidtight flexible nonmetallic conduit where not installed in concrete, shall be permitted. B. Construction Specifications 356-12. General. Cellular metal floor raceways shall be so constructed that adequate electrical and mechanical continuity of the complete system will be secured. They shall provide a complete enclosure for the conductors. The interior surfaces shall be free from burrs and sharp edges, and surfaces over which conductors are drawn shall be smooth. Suitable bushings or fittings having smooth rounded edges shall be provided where conductors pass.