Now that we’ve finished going over the changes to Chapter 2 in the 2023 National Electrical Code, let’s move on to Chapter 3.
Article 300 General Requirements for Wiring Methods and Materials, and new Article 305 Requirements for Wiring Methods and Materials for Systems Rated Over 1,000 Volts AC, 1,500 Volts, Nominal. Article 300 was reorganized to limit it to systems rated 1,000V AC nominal or less and 1,500V DC nominal or less. It had previously consisted of two parts but no longer has any. The second part applied to medium- and high-voltage systems and has been incorporated into the new Article 305.
300.2 Limitations. This section provides the new voltage limitations for Article 300. However, it also notes that the Chapter 3 wiring methods are permitted for over 1,000V AC, 1,500V DC, where specifically permitted elsewhere in the Code .
300.4(E) Cables, Raceways, or Boxes Under Metal-Corrugated Decking. The requirement for providing space separation beneath roof decks and cables, raceways or boxes first appeared in the 2008 Code . This section now only applies to installations of wiring methods beneath metal-corrugated roof decking. The substantiation noted that metal roof decking fasteners use longer metal self-tapping fasteners to comply with the roof hold-down requirements.
300.7(B) Informational Note No. 2—Expansion, Expansion-Deflection, Deflection Fittings. A new informational note was added referencing NEMA FB 2.40, which provides installation guidelines on expansion and deflection fittings for raceways.
300.15 Boxes, Conduit Bodies, or Fittings—Where Required. Section 300.15 indicates where boxes or conduit bodies are required. This section’s wording was clarified to indicate that a box or conduit body is needed to provide access to conductor splices, conductor junction points and termination points. The revised wording clarifies that the rule applies to junctions and terminations for conductors, not for conduits.
300.25 Exit Enclosures (Stair Towers). Stair towers are often free-standing structures independently supported from the building. Some are not. They are typically sturdy, fire-resistive structures built of concrete block that provides enhanced passive fire protection for occupants to exit the building. Only electrical equipment necessary for occupants to exit the building (e.g., egress lighting) is permitted within the stair tower. Exterior lighting is permitted to be supplied by the circuit that supplies lighting in the stair tower.
300.26, Remote-Control and Signaling Circuit Classification. This new section will help to clarify how remote-control and signaling circuits are classified and where the requirements are. Class 2 and 3 power-limited remote-control and signaling circuits continue to be covered by Article 725. Class 1 remote-control and signaling circuits were removed from Article 725. Class 1 power-limited remote-control and signaling circuits have been relocated to new article 724. Non-power-limited remote-control and signaling circuits are no longer considered to be Class 1 circuits and are now governed by 300.2–300.25.
312.8 Splices, Taps, and Feed Through Conductors. This is a new section added to recognize the additional bending space needed for conductors 4 AWG and larger. Where splices, angle or U pulls are made of insulated conductors, Section 314.28(A)(2) requires the distance between the raceway and the opposite wall to be at least six times the largest trade size in a row.
312.10 Screws or Other Fasteners. New requirements have been added for screws and other fasteners used on cabinets, cutout boxes and meter socket enclosures. Screws and other fasteners installed in the field that enter the wiring space are required to be those provided or specified by the manufacturer. If not supplied or specified by the manufacturer, this section provides three criteria that can be used, where applicable. To prevent damage to conductors, screws and other fasteners must have blunt ends. Screws that extend into the enclosure more than ¼ inch must be protected by an approved means. Screws or other fasteners that then extend not more than 7/16 inch are permitted if they are located within 3/8 inch of an enclosure wall.
314.5 Screws or Other Fasteners. Requirements were also added for screws for outlet, device, pull and junction boxes; conduit bodies; fittings; and handhole enclosures. The requirements for screws that enter the wiring space are similar to those in 312.10. This section provides detailed requirements for screws that attach or penetrate a cover.
314.16(B). Box Fill Calculations Three changes were made to the box fill requirements in 314.16(B). The second paragraph in (B)(2) was deleted because the product it applied to is no longer manufactured.
The equipment grounding conductor (EGC) fill requirements in (B)(5) were revised so that they no longer apply to equipment bonding jumpers. If the conductor is run in a raceway, it would be an EGC. Equipment bonding jumpers begin and end in the enclosure. Conductors that do not leave an enclosure are not included in calculations.
The language has also been clarified on the application of the ¼-volume allowance for EGCs, which is based on the largest EGC in the box.
A new volume allowance was added to (B)(6) for terminal blocks. The volume allowance is based on the largest conductor terminated to the terminal block assembly within the box.
314.24 Dimensions of Boxes. The title of this section was changed from Depth of Boxes to Dimensions of Boxes. Entry of conductors at the center portion of the rear of a box, or conductors that enter from the side of a box that is not deep enough, can expose conductors to damage if the device projects too deeply into the box. A new (C) Clearances for Side Wiring Entrances was added. It requires protection from abrasion by requiring the device or equipment not project beyond the centerline of the knockout, or by maintaining clearance between the device or equipment and the box’s side wall.
314.25 Covers and Canopies. This section was revised to clarify that conduit body enclosures must be enclosed by a cover, lampholder or device. Since conduit bodies can contain splices, terminations and devices, they should also be covered. The language in (A) and the informational note were revised to clarify that they apply to EGCs.
314.27 Outlet Boxes, Ceiling Suspended (Paddle) Fans. This section was revised to require outlet boxes for the sole support of ceiling suspended (paddle) fans to be marked inside so that the marking can be seen during a rough-in inspection. (C)(2) was simplified to recognize boxes that provide direct access through the box to structural framing capable of supporting a paddle fan, without the need to remove the box. The locking support and receptacle and the compatible attachment fitting are now referred to as weight-supporting ceiling receptacle and weight-supporting attachment fitting.