Article 378

Nonmetallic Wireways

Part I. General

1. Scope. This article covers the use, installation, and construction specifications for nonmetallic wireways and associ‐ ated fittings.
2. Definition.

Nonmetallic Wireways. Flame-retardant, nonmetallic troughs with removable covers for housing and protecting electrical wires and cables in which conductors are laid in place after the raceway has been installed as a complete system.

378.6 Listing Requirements. Nonmetallic wireways and associ‐ ated fittings shall be listed.

Part II. Installation

378.10 Uses Permitted. The use of nonmetallic wireways shall be permitted in the following:

1. Only for exposed work, except as permitted in 378.10(4).
2. Where subject to corrosive environments where identified for the use.
3. In wet locations where listed for the purpose.Informational Note: Extreme cold may cause nonmetallic wire‐ ways to become brittle and therefore more susceptible to damage from physical contact.
4. As extensions to pass transversely through walls if the length passing through the wall is unbroken. Access to the conductors shall be maintained on both sides of the wall.

378.12 Uses Not Permitted. Nonmetallic wireways shall not be used in the following:

1. Where subject to physical damage
2. In any hazardous (classified) location, except as permit‐ ted by other articles in this Code
3. Where exposed to sunlight unless listed and marked as suitable for the purpose
4. Where subject to ambient temperatures other than those for which nonmetallic wireway is listed378.20 ARTICLE 380 — MULTIOUTLET ASSEMBLY
5. For conductors whose insulation temperature limitations would exceed those for which the nonmetallic wireway is listed

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1. Conductors Connected in Parallel. Where single conductor cables comprising each phase, neutral, or grounded conductor of an alternating-current circuit are connected in parallel as permitted in 310.10(H), the conductors shall be installed in groups consisting of not more than one conductor per phase, neutral, or grounded conductor to prevent current imbalance in the paralleled conductors due to inductive reac‐ tance.
2. Size of Conductors. No conductor larger than that for which the nonmetallic wireway is designed shall be installed in any nonmetallic wireway.
3. Number of Conductors. The sum of cross-sectional areas of all contained conductors or cables at any cross section of the nonmetallic wireway shall not exceed 20 percent of the interior cross-sectional area of the nonmetallic wireway. Conductors for signaling circuits or controller conductors between a motor and its starter and used only for starting duty shall not be considered as current-carrying conductors.The adjustment factors specified in 310.15(B)(3)(a) shall be applicable to the current-carrying conductors up to and includ‐ ing the 20 percent fill specified in the first paragraph of this section.
4. Insulated Conductors. Insulated conductors installed in a nonmetallic wireway shall comply with 378.23(A) and (B).

1. Deflected Insulated Conductors. Where insulated conductors are deflected within a nonmetallic wireway, either at the ends or where conduits, fittings, or other raceways or cables enter or leave the nonmetallic wireway, or where the direction of the nonmetallic wireway is deflected greater than 30 degrees, dimensions corresponding to one wire per termi‐ nal in Table 312.6(A) shall apply.
2. Nonmetallic Wireways Used as Pull Boxes. Where insula‐ ted conductors 4 AWG or larger are pulled through a wireway, the distance between raceway and cable entries enclosing the same conductor shall not be less than that required in 314.28(A)(1) for straight pulls and in 314.28(A)(2) for angle pulls. When transposing cable size into raceway size, the mini‐ mum metric designator (trade size) raceway required for the number and size of conductors in the cable shall be used.

378.30 Securing and Supporting. Nonmetallic wireway shall be supported in accordance with 378.30(A) and (B).

1. Horizontal Support. Nonmetallic wireways shall be supported where run horizontally at intervals not to exceed 900 mm (3 ft), and at each end or joint, unless listed for other support intervals. In no case shall the distance between supports exceed 3 m (10 ft).
2. Vertical Support. Vertical runs of nonmetallic wireway shall be securely supported at intervals not exceeding 1.2 m (4 ft), unless listed for other support intervals, and shall not have more than one joint between supports. Adjoining nonme‐ tallic wireway sections shall be securely fastened together to provide a rigid joint.

378.44 Expansion Fittings. Expansion fittings for nonmetallic wireway shall be provided to compensate for thermal expan‐

sion and contraction where the length change is expected to be 6 mm (0.25 in.) or greater in a straight run.

Informational Note: See Table 352.44 for expansion characteris‐ tics of PVC conduit. The expansion characteristics of PVC nonmetallic wireway are identical.

378.56 Splices and Taps. Splices and taps shall be permitted within a nonmetallic wireway, provided they are accessible. The conductors, including splices and taps, shall not fill the nonme‐ tallic wireway to more than 75 percent of its area at that point.

378.58 Dead Ends. Dead ends of nonmetallic wireway shall be closed using listed fittings.

378.60 Grounding. Where equipment grounding is required, a separate equipment grounding conductor shall be installed in the nonmetallic wireway. A separate equipment grounding conductor shall not be required where the grounded conduc‐ tor is used to ground equipment as permitted in 250.142.

378.70 Extensions from Nonmetallic Wireways. Extensions from nonmetallic wireway shall be made with cord pendants or any wiring method of Chapter 3. A separate equipment grounding conductor shall be installed in, or an equipment grounding connection shall be made to, any of the wiring methods used for the extension.

Part III. Construction Specifications

378.120 Marking. Nonmetallic wireways shall be marked so that the manufacturer’s name or trademark and interior cross- sectional area in square inches shall be visible after installation. Marking for limited smoke shall be permitted on the nonmetal‐ lic wireways that have limited smoke-producing characteristics.