National Electrical Code Summary: Article 90 -- Introduction

Based on the 2023 NEC

by Mark Lamendola

NEC Article 90 draws boundaries around the National Electrical Code—boundaries many people fail to understand. For example, Article 90 has long made it clear the NEC is not intended as design specification or instruction manual. The National Electrical Code has one purpose only. Logically, Article 90 belongs in Chapter 1 (along with Article 80) .

90.1 covers the scope of Article 90, not the scope of the NEC.

90.2 describes the scope of the Code—what it covers and what it does not cover. It has has six subdivisions:

• (A) says the purpose of the NEC is the practical safeguarding of people and property "from hazards arising from the use of electricity."
• (B) distinguishes from the adequacy concept (provisions necessary for safety) and other concepts. The Code is a minimum standard. Further effort may be required for an installation to be efficient, convenient, or adequate for good service or future expansion. This is a fundamental concept upon which many Code disagreements arise. The Code is not a target you’d like to hit. It is the minimum you can do.
• (C) clearly states the Code is not intended to be a design specification or instruction manual.
• (D) ties the Code to international standards. The Code-making panels do have members who are in countries other than the USA. The intention is to draw on the collective wisdom of the international community. Many people who make the Code what it is are also members of the IEEE. Standards published by the IEEE frequently get review from people who serve on NEC committees and vice-versa.
• (E) its relation to other intenational standards.
• (F) Special permission.

It is worth noting that in many industrial faclities, management has an attitude (and sometimes explicity expresses the sentiment) of "We are not under the NEC." That is because their facility doesn't undergo inspections by the typical Authority Having Jurisdiction (state licensed electrical inspector). What they neglect to consider, however, is there are other AHJs. These include the insurer (who will insist on Code compliance and will dispute a claime where Code compliance failure has contributed to the outcome for which a claim is filed), the local fire chief (who can order cessation of operations if there is sufficient evidence the facility's Code violations make it a fire hazard), and the electric utility (which can disconnect service until specific Code violations are resolved).

90.3 explains how the Code is arranged. Please note the influence of the international and engineering communities. For example, the Code uses the "dot" system of enumeration and the "Appendices" are called "Annexes." Note also what it says about the interaction/interplay of Chapters 1 through 7, Chapter 8, and Chapter 9. Figure 90.3 is helpful for understanding this.

90.4 gives the Authority Having Jurisdiction (AHJ) some flexibility in enforcement.

90.5 distinguishes between mandatory rules, permissive rules, and explanatory material. These often get confused. An example is a Fine Protection Note (FPN) that discusses voltage drop. The Code does not require addressing voltage drop—it merely explains that it is an additional consideration and gives a "rule of thumb." Unfortunately, many people have over-engineered to get "the Code-required drop" or have under-engineered because they were "within the Code requirements." The Code does not give voltage drop requirements.

90.6 discusses formal interpretations.

90.7 adds a dose of common sense regarding equipment inspections. For example, a product that is Listed (e.g., by U.L.) can be assumed to be adequate for the stated purpose and need not be inspected again (except for alterations or damage).

90.8 alerts the user to allow for expansion and to know that the Code does specify various restrictions on the number of wires and circuits in a given enclosure.

90.9 discusses units of measurement.