Code Change Summary: New requirements added regarding conductors 4 AWG and larger installed in enclosures for switches or overcurrent devices.

NEC Article 312 is all about cabinets, cutout boxes and meter socket enclosures. NEC^® Section 312.8(A) is all about proper use of wiring space within enclosures for switches and overcurrent devices where splices, taps, and feed-through conductor installations may occur such as a panelboard cabinet.

Electricians pride themselves on a neat and workmanlike panelboard installation when making final terminations to the overcurrent devices, lugs, and grounding terminals. A clean installation typically will not include making splices to other conductors within the panelboard cabinet but sometimes vandalism or other factors may warrant the need to splice or extend conductors.

Last code cycle, the NEC^® had three requirements applying to splices, taps, and feed-through conductor installations in an overcurrent device enclosure. In the 2023 NEC^® there are four.

In Section 312.8(A), the 2023 NEC^® permits splices, taps and feed-through conductor installations within an overcurrent device enclosure if the following conditions are met:

(1) The total of all conductors installed at any cross section of the wiring space cannot exceed 40 % of the cross-sectional area of that space.

(2) The total area of all conductors, splices, and taps installed at any cross section of the wiring space cannot exceed 75 % of the cross-sectional area of that space.

(3) The bending space for conductors 4 AWG and larger must comply with Section 314.28(A)(2).

(4) A warning label complying with Section 110.21(B) must be applied to the enclosure to identify the closest disconnecting means for any feed-through conductors.

New list item 3 above was added in the 2023 NEC^® to address angle pulls, u-pulls, or splices that can occur when making splices, taps, or feed-through conductor installations within an overcurrent device enclosure. Angle pulls, u-pulls, or splices of insulated conductors 4 AWG and larger inside an overcurrent device enclosure require special attention to ensure they are not bent to the point where the conductor insulation is compromised.

Since the rules for angle pulls, u-pulls, and splices are located in Article 314 (applicable to outlet, device, pull, and junction boxes; conduit bodies; fittings; and handhole enclosures), technically, without this new code language above in Section 312.8(A)(3), it would be difficult to provide a code reference to justify adherence to the rules in 314.28(A)(2) for an enclosure type within the scope of Article 312.

Whether an angle pull, u-pull, or splice of insulated conductors 4 AWG or larger is made in a box covered in Article 314, or a panelboard cabinet covered in Article 312, the goal is still the same which is to avoid compromising the integrity of the conductor insulation.

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 2023 NEC^® edition of NFPA 70.