NEC · NFPA 70

The National Electrical Code (NEC), Explained

The NEC is the foundation of every journeyman exam — a code book you are allowed to bring into the test room and look things up in. Knowing what the book is and how it is organized is the first skill you need.

NEC 2017 2020 2023 Last updated 2026-06-27

What the NEC is

The National Electrical Code (NEC) is NFPA 70, a model electrical installation code published by the National Fire Protection Association (NFPA), a nonprofit standards organization. It sets minimum requirements for the safe installation of electrical wiring and equipment in the United States. The NFPA does not enforce the code — enforcement is left to the authority having jurisdiction (AHJ), typically a local building department or electrical inspector. The NEC becomes legally binding only after a state, county, or city adopts it by reference into local law.

The goal of the NEC is the practical safeguarding of persons and property from hazards arising from the use of electricity. It is not a design manual and it is not a wiring specification — it describes the minimums that an installation must meet, not the only way to do the work. Engineers, designers, and electricians are free to exceed the NEC's requirements; they cannot fall below them.

How the NEC is organized

The NEC is divided into nine chapters, with articles, parts, sections, and tables nested inside. Understanding this hierarchy lets you find a rule in seconds during an open-book exam.

Chapter Articles Subject matter
Chapter 1 90–110 General — scope, definitions, installations, equipment
Chapter 2 200–285 Wiring and protection — branch circuits, feeders, OCPD, grounding
Chapter 3 300–398 Wiring methods and materials — raceways, cables, boxes
Chapter 4 400–490 Equipment for general use — cords, switches, panels, motors
Chapter 5 500–590 Special occupancies — hazardous locations, healthcare, temporary power
Chapter 6 600–695 Special equipment — signs, elevators, solar PV, generators
Chapter 7 700–770 Special conditions — emergency systems, fire alarm, optical fiber
Chapter 8 800–830 Communications systems — independent of Chapters 1–7
Chapter 9 Tables Conduit fill, conductor properties, dimensions, and more

After Chapter 9 come Annexes A through I in the 2017 edition (A through J in the 2020 and 2023 editions) — informational material that includes example calculations, commonly used formulas, and cross-reference tables. Annexes are not enforceable requirements; they support understanding.

Within each chapter, articles are further divided into parts (labeled Part I, Part II, and so on) and then into numbered sections. A section reference like "250.122" means Article 250, Section 122. Within a section you may find lettered subsections — 250.122(B) — and further numbered exceptions.

One navigation shortcut: the first digit or two of an article number tells you its chapter. Article 210 is in Chapter 2; Article 330 is in Chapter 3; Article 430 is in Chapter 4. Once you recognize this pattern, you can open the book to the right chapter even before you reach for the index.

The 3-year revision cycle and state adoption

The NFPA publishes a new edition of the NEC every three years. Recent editions are 2017, 2020, and 2023; the next edition is expected in 2026. Each cycle incorporates proposals and comments submitted by the public, reviewed by technical committees, and voted on at the NFPA annual meeting.

Because states, counties, and cities adopt the NEC independently, the edition in force varies by jurisdiction and often lags the current publication by one or two cycles. As of 2026, many jurisdictions are on the 2017 or 2020 NEC; some have adopted 2023. A handful of states use locally amended versions. Check your state electrical licensing board's current requirements to confirm which edition governs your journeyman exam — this matters because table values, section numbers, and specific installation requirements do change between editions, even when the underlying concept stays the same.

The NEC as an open-book exam tool

The journeyman electrical exam is an open-book test. You are allowed to bring the current adopted edition of the NEC into the exam room and reference it during the test. This changes what the exam is actually measuring: it is not primarily a test of memorization — it is a test of how quickly and accurately you can find a rule and apply it to a scenario.

That means your primary study skill is lookup speed, not rote memorization. You need to know the code well enough to go straight to the right article when you read a question, find the relevant section in under a minute, and apply the rule correctly. A candidate who has tabbed their book, practiced finding rules under time pressure, and knows how the chapters relate to each other will consistently outperform someone who only read the code passively.

The most effective preparation combines both: understand the concepts so you can recognize what chapter a question belongs to, and practice navigating so you can confirm the exact value or exception quickly. The articles that appear most often on journeyman exams come from Chapters 1 through 4 — general rules, wiring design, wiring methods, and common equipment — with significant coverage of grounding and bonding (Article 250), branch circuits (Article 210), conductors (Article 310), boxes (Article 314), services (Article 230), and motors (Article 430).

Key topics to navigate confidently:

  • Grounding and bonding — Article 250 and its sub-articles on grounding electrode systems, conductor sizing, and bonding jumpers
  • Conductors and ampacity — Article 310 and Table 310.16, the most-referenced table on the exam
  • Box fill — Section 314.16 and Table 314.16(B)
  • Load calculations — Articles 220 and 230 for dwelling and service sizing
  • Motors — Article 430, especially the FLC tables and OCPD sizing
  • Conduit fill — Chapter 9 tables and the 40-percent fill rule
  • Voltage drop — an Annex concept, not a hard code requirement in most cases, but a frequent calculation question

The NEC is a large book and no one learns it all at once. The most productive approach is to build familiarity with the structure first — know which chapter handles what — and then work through the high-frequency articles with practice questions that send you back to the book to verify the answer. Over time, you stop needing to look up the answers you have seen many times and get faster at finding the ones you have not.

Practice questions on this rule

Real journeyman-exam practice questions from Loomi's bank — answer first, then reveal the explanation.

Q1 NEC 90.4(C)

Under 90.4(C), on what basis may the AHJ waive a specific Code requirement or permit an alternative method?

  1. A When the local building department has no jurisdiction over the requirement
  2. B When the alternative method costs less to install than the Code-required method
  3. C When it is assured that equivalent objectives can be achieved by establishing and maintaining effective safety
  4. D When the installing contractor submits a written request for a variance
Show answer & explanation

Correct: C — When it is assured that equivalent objectives can be achieved by establishing and maintaining effective safety

90.4(C) permits a waiver or alternative method only when the AHJ is assured that equivalent objectives can be achieved by establishing and maintaining effective safety. A written request, lower cost, or lack of local jurisdiction are not the standard the section sets.

Q2 NEC 90.3

Which statement correctly describes Chapter 8 of the NEC?

  1. A It must comply with all requirements in Chapters 1 through 7 as if fully incorporated
  2. B It applies only to hazardous locations and special equipment
  3. C It modifies Chapters 1 through 4 the same way Chapters 5, 6, and 7 do
  4. D It covers communications systems and is not subject to Chapters 1 through 7 except where specifically referenced
Show answer & explanation

Correct: D — It covers communications systems and is not subject to Chapters 1 through 7 except where specifically referenced

Per 90.3, Chapter 8 covers communications systems and is not subject to the requirements of Chapters 1 through 7 except where those requirements are specifically referenced in Chapter 8 — a different, more independent relationship than the supplement-or-modify role Chapters 5, 6, and 7 have. It is not tied to hazardous locations.

Q3 NEC 90.3

According to 90.3, what is the status of the NEC's informative annexes?

  1. A They are not part of the Code's requirements and are included for informational purposes only
  2. B They are enforceable once adopted by the authority having jurisdiction as local amendments
  3. C They carry the same enforceable weight as the Chapter 9 tables
  4. D They are enforceable only when referenced by Chapter 8
Show answer & explanation

Correct: A — They are not part of the Code's requirements and are included for informational purposes only

90.3 explicitly says informative annexes are not part of the requirements of the Code but are included for informational purposes only. This is a blanket statement in the Code text itself, not something contingent on AHJ adoption, Chapter 9 status, or a Chapter 8 reference.

Q4 NEC 90.5(A)

A code sentence reads, "Type NM cable shall be permitted to be installed in..." How should an electrician read this?

  1. A Type NM cable is prohibited in that situation
  2. B Type NM cable is one allowed option, not a requirement
  3. C Type NM cable must be used in that situation
  4. D Type NM cable is the only method allowed in that situation
Show answer & explanation

Correct: B — Type NM cable is one allowed option, not a requirement

90.5(B) defines "shall be permitted" as permissive language describing an allowed option or alternative method — it does not make that method mandatory or exclusive, and it certainly doesn't prohibit it.

More practice questions: General

Frequently asked questions

Is the NEC a federal law?
No. The NEC is a model code published by the National Fire Protection Association (NFPA), a private nonprofit. It has no legal force on its own. It becomes law only when a state, county, or municipality adopts it by reference into their statutes or regulations. Because each jurisdiction adopts on its own schedule, the legally enforceable edition varies by location.
Which edition of the NEC should I study for my journeyman exam?
Study the edition your state has adopted. Most states are currently on the 2017, 2020, or 2023 NEC. Check your state electrical licensing board's website for the adopted edition — that is the book that governs your exam. The core concepts are consistent across editions, but table values, section numbers, and specific requirements can differ.
Why is Chapter 8 treated differently from the rest of the NEC?
Chapter 8 covers communications systems — telephone, data, cable TV, and similar low-voltage wiring — and the NEC explicitly states that Chapter 8 is not subject to the requirements of Chapters 1 through 7 except where those chapters are specifically referenced in Chapter 8. This means you cannot automatically apply a general Chapter 1 rule to a Chapter 8 installation unless Chapter 8 says to.
Related articles
Grounding & Bonding Article 250 — one of the most tested sections of the NEC. Working Space (110.26) Chapter 1 general rules that apply everywhere in the code. Branch Circuits Article 210 — a cornerstone of Chapter 2. Overcurrent Protection Article 240 and how it threads through every chapter.
Loomi · NEC exam prep

Practice the NEC concepts in this article.

Loomi turns NEC content into 12,934 spaced-repetition exam questions built for the journeyman test. Try everything free for 3 days.

Get launch access