The 2026 edition of the National Electrical Code was issued by the NFPA Standards Council on Aug. 25, 2025, with an effective date of Sept. 9, 2025. This edition supersedes all previous editions and is available for adoption by authorities having jurisdiction. This edition experienced the continuing evolution in extensive changes in NEC structure and arrangement.

Some noticeable changes include several new articles, some deleted annexes and changes in the titles of chapters 5–8. Some changes to grounding and bonding requirements in this edition of the NEC are worthy of a much deeper dive. This article reviews a few significant revisions and new rules related to electrical grounding and bonding for installations and systems, more specifically sizing of wire-type equipment grounding conductors (EGCs) for medium- and high-voltage circuits and systems.

NEC changes 

Let’s begin by reviewing changes to the structure of the NEC relative to grounding and bonding rules. First, previous Part X of Article 250 has been relocated to new Article 270. This new article now contains the electric minimum grounding and bonding requirements for systems over 1,000V AC and 1,500V DC nominal. This new article also includes all general requirements previously contained in the earlier parts of Article 250, based on the requirements in the NEC Style Manual. 

That said, Section 270.4 contains all the performance requirements for electrical grounding and bonding and describes what is intended and required to be accomplished. A new Section 270.5 has been added that addresses supervised installations and permits grounding and bonding requirements to be determined by qualified people under engineering supervision. 

Supervised installations shall be considered as either (1) under engineering supervision or (2) where qualified people with documented training and experience in systems over 1,000V AC or 1,500V DC install and maintain, monitor and service these systems.

With the understanding that 270.4 provides the performance requirements for grounding and bonding detailed in subdivisions (A) for grounded systems and (B) for ungrounded systems, it can be effectively applied to field installations. Two vitally important requirements in 250.4 apply to either the effective ground-fault current path for grounded systems or the ground-fault current path for ungrounded systems. Either of these paths typically includes an EGC, which could be any of the types provided in 270.118, including a wire-type conductor as indicated in 270.118(A)(1). If a wire-type EGC is used, proper sizing is critical for meeting the performance criteria for an effective ground-fault current path and is mandatory as indicated in the last sentence to 270.122(A). 

Here is a significant change: sizing EGCs of the wire type is based on the size of the largest ungrounded circuit conductor (either feeder or branch circuit). This is a totally new method of sizing and different from the previous editions of the NEC, where the rating of the circuit overcurrent protective device (OCPD) establishes the minimum size of a wire-type EGC. Keep in mind that Section 250.122 and Table 250.122 continue to be required for sizing wire-type EGCs based on the OCPD rating. It’s different now for over-1,000V applications. 

Sizing EGCs

With that understanding, the new method of sizing wire-type EGCs for these systems and circuits must be applied. The sizing is not based on OCPD ratings as indicated in Table 250.122. New NEC tables in Article 270 are based on established criteria that exist in applicable UL standards. The sizing is now based on the minimum sizes provided in Table 270.122(B)(1), based on UL 1277, Table 8.1 and Table 8.2; Table 270.122(B)(2), based on UL 1072, Table 23.1; or Table 270.122(B)(3), based on UL 1027, Table 23.2. 

So as an example, if a 5-kilovolt, 200A feeder is installed with three 4/0 copper conductors in a 2½-inch PVC conduit, a wire-type EGC must be installed. The minimum size copper EGC required based on Table 270.122(B)(2) would be 3 AWG copper. 

It is interesting that the table used for sizing separately installed wire-type EGCs (in conduit for example) is triggered by the titles of each of these three new tables. This means that each of these tables applies to multiple conductor cable assemblies (MV-90 or MV-105) or to two or more individual insulated conductors that might be installed in a conduit system. 

Section 270.122 continues to indicate that wire-type EGCs shall not be required to be sized any larger than the circuit conductors. Also, wire-type EGCs that are not an integral part of a cable assembly shall not be smaller than 6 AWG copper or 4 AWG aluminum or copper-clad aluminum. The exception allowing qualified people to size wire-type EGCs in compliance with sections 270.4(A)(5) or 270.4(B)(4) is now provided in 270.122 and continues to be included in Section 250.122 as in the previous edition.

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