RIGID NONMETALLIC CONDUIT

70-249 (c) Physical Damage. Where subject to physical damage unless identified for such use. (d) Ambient Temperatures. Where subject to ambient temperatures exceeding those for which the conduit is approved. (e) Insulation Temperature Limitations. For conductors whose insulation temperature limitations would exceed those for which the conduit is approved. (f) Theaters and Similar Locations. In theaters and similar locations, except as provided in Articles 518 and 520. 347-4. Other Articles. Installation of rigid nonmetallic conduit shall comply with the applicable provisions of Article 300. Where equipment grounding is required by Article 250, a separate equipment grounding conductor shall be installed in the conduit. Exception: As permitted in Section 250-91(b), Exception No. 3 for direct-current circuits. A. Installations 347-5. Trimming. All cut ends shall be trimmed inside and outside to remove rough edges. 347-6. Joints. All joints between lengths of conduit, and between conduit and couplings, fittings, and boxes, shall be made by an approved method. 347-8. Supports. Rigid nonmetallic conduit shall be installed as a complete system as provided in Section 300-18 and shall be supported as required in Table 347-8. In addition, conduit shall be securely fastened within 3 feet (914 mm) of each outlet box, junction box, device box, conduit body, or other conduit termination. Rigid nonmetallic conduit shall be fastened so that movement from thermal expansion or contraction will be permitted. Table 347-8. Support of Rigid Nonmetallic Conduit Conduit Size Maximum Spacing Between (Inches) Supports (Feet) ½-1 3 1½-2 5 2½₂-3 6 3½₂-5 7 6 8 For SI units: (Supports) one foot = 0.3048 meter. 347-9. Expansion Joints. Expansion joints for rigid nonmetallic conduit shall be provided to compensate for thermal expansion and contraction. Exception: Where the computed length change due to thermal expansion or contraction, according to Table 10, Chapter 9, is less than .25 inches 70-250 NATIONAL ELECTRICAL CODE (6.36 mm) in a straight run between securely mounted items such as boxes, cabinets, elbows, or other conduit terminations, an expansion joint shall not be required. (FPN): See Table 10 in Chapter 9 for expansion characteristics of PVC rigid nonmetallic conduit. 347-10. Minimum Size. No conduit smaller than 1/2-inch electrical trade size shall be used. 347-11. Number of Conductors. The number of conductors permitted in a single conduit shall not exceed the percentage fill specified in Table 1, Chapter 9. (FPN): For conductor cross-sectional area, see Tables 5, 5A, 6, and 8 and the applicable Notes to Tables at the beginning of Chapter 9. 347-12. Bushings. Where a conduit enters a box or other fitting, a bushing or adapter shall be provided to protect the wire from abrasion unless the design of the box or fitting is such as to provide equivalent protection. (FPN): See Section 373-6(c) for the protection of conductors No. 4 and larger at bushings. 347-13. Bends - How Made. Bends of rigid nonmetallic conduit shall be so made that the conduit will not be damaged and that the internal diameter of the conduit will not be effectively reduced. Field bends shall be made only with bending equipment identified for the purpose, and the radius of the curve of the inner edge of such bends shall not be less than shown in Table 346-10. 347-14. Bends - Number in One Run. There shall not be more than the equivalent of four quarter bends (360 degrees total) between pull points, e.g., conduit bodies and boxes. 347-15. Boxes and Fittings. Boxes and fittings shall comply with the applicable provisions of Article 370. 347-16. Splices and Taps. Splices and taps shall be made only in junction boxes, outlet boxes, device boxes, or conduit bodies. See Article 370. B. Construction Specifications 347-17. General. Rigid nonmetallic conduit shall comply with the following: Marking. Each length of nonmetallic conduit shall be clearly and durably marked at least every 10 feet (3.05 m) as required in the first sentence of Section 110-21. The type of material shall also be included in the marking unless it is visually identifiable. For conduit recognized for use aboveground, these markings shall be permanent. For conduit limited to underground use only, these markings shall be sufficiently durable to remain legible until the material is installed. Conduit shall be permitted to be surface marked to indicate special characteristics of the material. (FPN): Examples of these optional markings include but are not limited to "LS" for limited-smoke and markings such as "sunlight-resistant."