Article 372

Cellular Concrete Floor Raceways

Part I. General

1. Scope. This article covers cellular concrete floor race‐ ways, the hollow spaces in floors constructed of precast cellular concrete slabs, together with suitable metal fittings designed to provide access to the floor cells.
2. Definitions.

Cell. A single, enclosed tubular space in a floor made of precast cellular concrete slabs, the direction of the cell being parallel to the direction of the floor member.

Header. Transverse metal raceways for electrical conductors, providing access to predetermined cells of a precast cellular concrete floor, thereby permitting the installation of electrical conductors from a distribution center to the floor cells.

ARTICLE 374 — CELLULAR METAL FLOOR RACEWAYS 374.18

Part II. Installations

372.12 Uses Not Permitted. Conductors shall not be installed in precast cellular concrete floor raceways as follows:

1. Where subject to corrosive vapor
2. In any hazardous (classified) location, except as permit‐ ted by other articles in this Code
3. In commercial garages, other than for supplying ceiling outlets or extensions to the area below the floor but not above

Informational Note: See 300.8 for installation of conductors with other systems.

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372.18 Cellular Concrete Floor Raceways Installation. Instal‐ lation of cellular concrete floor raceways shall comply with 372.18(A) through 372.18(E).

1. Header. The header shall be installed in a straight line at right angles to the cells. The header shall be mechanically secured to the top of the precast cellular concrete floor. The end joints shall be closed by a metal closure fitting and sealed against the entrance of concrete. The header shall be electri‐ cally continuous throughout its entire length and shall be elec‐ trically bonded to the enclosure of the distribution center.
2. Connection to Cabinets and Other Enclosures. Connec‐ tions from headers to cabinets and other enclosures shall be made by means of listed metal raceways and listed fittings.
3. Junction Boxes. Junction boxes shall be leveled to the floor grade and sealed against the free entrance of water or concrete. Junction boxes shall be of metal and shall be mechanically and electrically continuous with the header.
4. Inserts. Inserts shall be leveled and sealed against the entrance of concrete. Inserts shall be of metal and shall be fitted with grounded-type receptacles. A grounding conductor shall connect the insert receptacles to a positive ground connection provided on the header. Where cutting through the cell wall for setting inserts or other purposes (such as providing access openings between header and cells), chips and other dirt shall not be allowed to remain in the raceway, and the tool used shall be designed so as to prevent the tool from entering the cell and damaging the conductors.
5. Markers. A suitable number of markers shall be installed for the future location of cells.

372.20 Size of Conductors. No conductor larger than 1/0 AWG shall be installed, except by special permission.

1. Maximum Number of Conductors. The combined cross-sectional area of all conductors or cables shall not exceed 40 percent of the cross-sectional area of the cell or header.
2. Ampacity of Conductors. The ampacity adjustment factors as provided in 310.15(B)(3) shall apply to conductors installed in cellular concrete floor raceways.

372.56 Splices and Taps. Splices and taps shall be made only in header access units or junction boxes. A continuous unbro‐ ken conductor connecting the individual outlets is not a splice or tap.

372.58 Discontinued Outlets. When an outlet is abandoned, discontinued, or removed, the sections of circuit conductors supplying the outlet shall be removed from the raceway. No splices or reinsulated conductors, such as would be the case of abandoned outlets on loop wiring, shall be allowed in raceways.