2.2 Public Information: Terminology, Listing & Labeling (0102)

Article 100 vs. Article 90

• Article 100 — Definitions. The 2023 NEC consolidated every definition in the Code into Article 100. Definitions that used to live at the front of an individual article (for example, the pool definitions formerly in 680.2) were relocated here, and each entry carries a scope indicator telling you whether it applies throughout the Code or only within a named article or part. Terms not defined in Article 100 take their common, everyday dictionary meaning.
• Article 90 — Introduction. Establishes what the NEC covers and, critically, what it does not cover. 90.2 sets the scope and lists the exclusions: installations under the exclusive control of an electric utility for generation, transmission, and distribution; installations in mines, ships, aircraft, and railway rolling stock; and similar. An E2 inspector working on commercial property should recognize that conductors on the utility side of the service point are usually utility-controlled and outside NEC enforcement.

Mandatory vs. Permissive Language

90.5 defines the Code's own language, and the exam tests it:

• "Shall" identifies a mandatory rule (90.5(A)).
• "Shall be permitted" and "shall not be required" identify permissive rules — allowances and options, not obligations (90.5(B)).
• Informational Notes are explanatory material and are not enforceable as requirements (90.5(C)). A contractor cannot be cited for a violation of an Informational Note.
• Informative Annexes (Annex A through Annex J, including the Annex C fill tables and the Annex D calculation examples) are likewise not part of the enforceable requirements — they are reference material. Annex C is safe to use as a shortcut, but the enforceable rule is the Chapter 9 fill calculation it was derived from.

An inspector writing a correction notice must cite a mandatory rule ("shall"), not a recommendation or an Informational Note.

The Four Listing Terms

These four words appear constantly on the exam and are frequently confused. Each has a specific meaning in Article 100:

The quick distinction: listed/labeled come from a testing laboratory; approved comes from the AHJ; identified is a recognition of suitability for a specific use. A breaker can be listed but not identified for a current-limiting application; a material can be approved by the AHJ under 90.4 even when not listed, if equivalent safety is assured.

A Practical Example

A molded-case circuit breaker is listed by UL (it appears in UL's list and bears the UL label). That makes it both listed and labeled. However, the same breaker may not be identified (recognized as suitable) for use as a current-limiting device unless the listing specifically states that function. If a specifier needs a current-limiting function, the inspector verifies the listing covers that specific application — "listed" alone is not enough. Separately, the AHJ may approve an unlisted equipment enclosure made of a specific material if the AHJ judges it provides equivalent safety (90.4), though this is the exception, not the routine path.

NEC 110.3(B): Listing and Labeling Make Instructions Enforceable

110.3(B) is the bridge between listing and enforcement. It requires that listed or labeled equipment be installed and used in accordance with any instructions included in the listing or labeling. This means:

• Torque values stamped on a breaker terminal are enforceable as code, and 110.14(D) requires that those tightening torque values be applied with a calibrated torque tool.
• A luminaire's listing limitation ("maximum 60°C supply conductor") is enforceable.
• A panelboard's maximum OCPD rating is enforceable.
• A raceway's listed application (e.g., EMT for exposed/concealed work, not direct burial) is enforceable.

If a product is listed, the instructions inside the box are part of the code.

Communicating Code Intent

An inspector communicates compliance determinations with two obligations: (1) cite the specific NEC article violated, and (2) state what compliance looks like. For example, instead of "this splice is wrong," the inspector writes: "Splice outside a box — violation of 300.15; install a listed junction box accessible per 314.29." This specificity:

• Gives the contractor an actionable correction.
• Supports the correction notice if appealed.
• Ties the violation to an enforceable article rather than a preference.

When answering general compliance or material-suitability questions from the public, the inspector should:

1. Answer using defined NEC terminology ("listed," not "approved by UL").
2. Distinguish "code minimum" from "best practice."
3. Defer product equivalency and approval to the AHJ per 90.4.

The Role of the AHJ

Authority Having Jurisdiction (AHJ) (Article 100) is the organization, office, or individual responsible for enforcing the code. Under 90.4, the AHJ:

• Is responsible for interpreting and enforcing the code.
• May grant approval for equipment and materials, but must ensure equivalent safety.
• May waive specific requirements where the AHJ judges the alternative provides equivalent safety.
• Is the final arbiter when listing, manufacturer instructions, and code text appear to conflict.

For the E2 exam, the AHJ is the correct answer when a question asks who resolves ambiguity, grants material approval for an unlisted product, or interprets an unclear installation.