Code Change Summary: Two exceptions previously allowing nonmetallic boxes to be used with metal cables or conduits were combined into one and revised to reference new bonding requirements in 250.109(B).

SME commentary: In the 2026 NEC^®, the provisions governing the use of nonmetallic boxes with metallic wiring methods were reorganized and clarified to coordinate with the new bonding requirements introduced in Section 250.109(B). Section 314.5, which replaces previous Section 314.3, now consolidates two separate exceptions into a single streamlined exception that directs the Code user to 250.109(B) for bonding details when metal conduit or metal cables are connected to nonmetallic boxes. The revised exception states: “Nonmetallic boxes shall be permitted with metal conduit or metal armored cable in accordance with 250.109(B)”. This revision reflects a deliberate alignment between Articles 250 and 314 to better distinguish grounding and bonding provisions from general box installation rules.

Under prior editions, Section 314.3 included two exceptions that permitted nonmetallic boxes to be used with metal raceways or metal-armored cables when specific bonding means were provided. These exceptions created overlap with the intent of Article 250, which governs grounding and bonding methods. As technology and product use evolved, field applications increasingly included combinations of metallic wiring methods and nonmetallic enclosures, particularly in renewable energy systems and corrosion-resistant installations. The result was a growing need for a consistent, unified approach to bonding and continuity requirements across both metallic and nonmetallic enclosures.

Section 250.109(B) now addresses this need directly by establishing the bonding requirements for nonmetallic enclosures and boxes when used with metallic wiring methods. Relocating the detailed bonding rules to Article 250 ensures that all grounding and bonding performance requirements are covered under one section of the Code. The revised exception in 314.5 serves as a pointer to those requirements, clarifying that the only permissible use of metal raceways or metal cables with nonmetallic boxes is in accordance with 250.109(B).

Importantly, this revision does not provide blanket permission to modify or field drill all types of nonmetallic boxes for metallic wiring methods. Many nonmetallic box manufacturers specifically mark their products for use only with nonmetallic cable types, such as NM or ENT. The revised 314.5 language prevents misinterpretation by linking permissive use directly to the bonding methods in 250.109(B), which outline how to maintain continuity of the equipment grounding path when metallic wiring methods are interrupted by a nonmetallic box.

The coordination of these two sections enhances Code usability, ensures proper bonding practices, and eliminates redundant or conflicting provisions between Articles 250 and 314.

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 2026 NEC^® edition of NFPA 70.

2023 Code Language:

314.3 Nonmetallic Boxes. Nonmetallic boxes shall be permitted only with open wiring on insulators, concealed knob-and-tube wiring, cabled wiring methods with entirely nonmetallic sheaths, flexible cords, and nonmetallic raceways.

Exception No. 1: Where internal bonding means are provided between all entries, nonmetallic boxes shall be permitted to be used with metal raceways or metal-armored cables.

Exception No. 2: Where integral bonding means with a provision for attaching an equipment bonding jumper inside the box are provided between all threaded entries in nonmetallic boxes listed for the purpose, nonmetallic boxes shall be permitted to be used with metal raceways or metal-armored cables.

2026 Code Language:

314.5 Nonmetallic Boxes. Nonmetallic boxes shall be permitted only with open wiring on insulators, concealed knob-and-tube wiring, cabled wiring methods with entirely nonmetallic sheaths, flexible cords, and nonmetallic raceways.

Exception: Nonmetallic boxes shall be permitted with metal conduit or metal armored cable in accordance with 250.109(B).