314.17(B) Boxes and Conduit Bodies.
Code Change Summary: Revised code section on the installation requirements for conductors in boxes and conduit bodies.
In the 2020 NEC®, the requirements previously found in 314.17(B) and (C) were combined into a revised Section 314.17(B). This new section provides requirements for conductors and cables with an overall nonmetallic sheath or jacket entering boxes and enclosures.
One of the biggest takeaways from the revised 2020 code language in this section is the relief provided for cables installed in raceways where it is impossible to physically secure the cable to the box or conduit body. For nonmetallic boxes, the 2017 code language required “in all instances, all permitted wiring methods shall be secured to the boxes”. The revised 2020 code language will not require a nonmetallic cable to be secured to a box or conduit body under the following conditions:
- Where installed in a raceway to provide physical protection in accordance with 300.15(C) which states: 15(C) Protection. A box or conduit body shall not be required where cables enter or exit from conduit or tubing that is used to provide cable support or protection against physical damage. A fitting shall be provided on the end(s) of the conduit or tubing to protect the cable from abrasion.
- Where the raceway is complete between boxes, conduit bodies, or both and encloses individual conductors or nonmetallic cable assemblies or both. For these installations, the conductors or cable assemblies shall not be required to be additionally secured.
Below is a preview of the NEC®. See the actual NEC® text at NFPA.ORG for the complete code section. Once there, click on their link to free access to the 2020 NEC® edition of NFPA 70.
2017 Code Language:
314.17(B) Metal Boxes and Conduit Bodies. Where metal boxes or conduit bodies are installed with messenger-supported wiring, open wiring on insulators, or concealed knob-and-tube wiring, conductors shall enter through insulating bushings or, in dry locations, through flexible tubing extending from the last insulating support to not less than 6 mm (1∕4 in.) inside the box and beyond any cable clamps. Where nonmetallic-sheathed cable or multiconductor Type UF cable is used, the sheath shall extend not less than 6 mm (1∕4 in.) inside the box and beyond any cable clamp. Except as provided in 300.15(C), the wiring shall be firmly secured to the box or conduit body. Where raceway or cable is installed with metal boxes or conduit bodies, the raceway or cable shall be secured to such boxes and conduit bodies.
314.17(C) Nonmetallic Boxes and Conduit Bodies. Nonmetallic boxes and conduit bodies shall be suitable for the lowest temperature-rated conductor entering the box. Where nonmetallic boxes and conduit bodies are used with messenger supported wiring, open wiring on insulators, or concealed knob-and-tube wiring, the conductors shall enter the box through individual holes. Where flexible tubing is used to enclose the conductors, the tubing shall extend from the last insulating support to not less than 6 mm (1∕4 in.) inside the box and beyond any cable clamp. Where nonmetallic-sheathed cable or multiconductor Type UF cable is used, the sheath shall extend not less than 6 mm (1∕4 in.) inside the box and beyond any cable clamp. In all instances, all permitted wiring methods shall be secured to the boxes.
Exception: Where nonmetallic-sheathed cable or multiconductor Type UF cable is used with single gang boxes not larger than a nominal size 57 mm × 100 mm (2 ¼ in. × 4 in.) mounted in walls or ceilings, and where the cable is fastened within 200 mm (8 in.) of the box measured along the sheath and where the sheath extends through a cable knockout not less than 6 mm (1∕4 in.), securing the cable to the box shall not be required. Multiple cable entries shall be permitted in a single cable knockout opening.
2020 Code Language:
314.17(B) Boxes and Conduit Bodies. The installation of the conductors in boxes and conduit bodies shall comply with 314.17(B)(1) through (B)(4).
(1) Conductors Entering Through Individual Holes or Through Flexible Tubing. For messenger-supported wiring, open wiring on insulators, or concealed knob-and-tube wiring, the conductors shall enter the box through individual holes. In installations where metal boxes or conduit bodies are used with conductors unprotected by flexible tubing, the individual openings shall be provided with insulating bushings. Where flexible tubing is used to enclose the conductors, the tubing shall extend from the last insulating support to not less than 6 mm (1∕ 4 in.) inside the box or conduit body and beyond any cable clamp. The wiring method shall be secured to the box or conduit body.
N (2) Conductors Entering Through Cable Clamps. Where cable assemblies with nonmetallic sheathes are used, the sheath shall extend not less than 6 mm (1∕ 4 in.) inside the box and beyond any cable clamp. Except as provided in 300.15(C), the wiring method shall be secured to the box or conduit body.
Exception: Where nonmetallic-sheathed cable is used with single gang nonmetallic boxes not larger than a nominal size 57 mm × 100 mm (2 ¼ in. × 4 in.) mounted in walls or ceilings, and where the cable is fastened within 200 mm (8 in.) of the box measured along the sheath and where the sheath extends through a cable knockout not less than 6 mm (1/4 in.), securing the cable to the box shall not be required. Multiple cable entries shall be permitted in a single cable knockout opening.
N (3) Conductors Entering Through Raceways. Where the raceway is complete between boxes, conduit bodies, or both and encloses individual conductors or nonmetallic cable assemblies or both, the conductors or cable assemblies shall not be required to be additionally secured. Where raceways enclose cable assemblies as provided in 300.15(C), the cable assembly shall not be required to be additionally secured within the box or conduit body.
N (4) Temperature Limitation. Nonmetallic boxes and conduit bodies shall be suitable for the lowest temperature-rated conductor entering the box or conduit body.