Journeyman Electrician NEC Study Guide

Quick Facts

Why the NEC Is the Exam

Journeyman electrician exams differ from state to state in length, format and passing score, but almost all of them test the National Electrical Code. The NEC is published by the National Fire Protection Association as NFPA 70 and revised every three years. Your state or city adopts an edition, sometimes with local amendments, and the testing vendor writes questions from that edition. The candidate information bulletin tells you which one.

That means two things. First, your code book is your main study tool. Second, speed matters as much as knowledge. A typical exam gives you a few minutes per question. If you know where a rule lives, you find it in seconds. If you have to search the index every time, you run out of time.

This guide uses the 2023 NEC. If your exam uses a different edition, the ideas are the same, but check section numbers in your own book.

How the Code Is Organised

Section 90.3 explains the arrangement of the code, and it is worth reading once with care.

Chapters 1 to 4 apply to all installations. Chapters 5, 6 and 7 can add to or change those general rules for particular places or equipment, such as hazardous locations, swimming pools or emergency systems. Chapter 8 stands mostly on its own. When a question mentions a special location, go to that article first, then back to the general rules.

Chapter 1: Definitions and Working Space

Article 100 defines the terms the rest of the code depends on. Exam questions often turn on a definition: the difference between “accessible” and “readily accessible”, between a “branch circuit” and a “feeder”, or what counts as “continuous load” (a load where the maximum current is expected to continue for three hours or more).

Article 110 holds the general rules. Two areas come up often:

• 110.14(C), termination temperature limits. For circuits rated 100 A or less, or conductors 14 AWG to 1 AWG, use the 60°C ampacity column unless the equipment is listed and marked for 75°C. Above 100 A, use 75°C unless marked otherwise. This rule decides which ampacity column you may use, even if the insulation is rated 90°C.
• 110.26, working space. Table 110.26(A)(1) sets the depth of clear working space by voltage to ground and condition. For 0 to 150 V to ground, the minimum depth is 3 ft in all three conditions. The width must be at least 30 in or the width of the equipment, whichever is greater, and the headroom at least 6½ ft.

Chapter 2: The Heaviest-Weighted Chapter

Most exam outlines give Chapter 2 more questions than any other.

Article 210, branch circuits. Learn the dwelling receptacle rules in 210.52: the 6 ft rule along the floor line in habitable rooms, the 24 in rule along countertop wall spaces, and the required small-appliance, laundry and bathroom circuits in 210.11(C). Learn the GFCI locations in 210.8 and the AFCI rules in 210.12. Know 210.20(A): overcurrent devices for continuous loads must be rated at least 125% of the continuous load plus the noncontinuous load. Know 210.23(A)(1): on a 15 A or 20 A circuit, a single cord-and-plug item not fastened in place may not exceed 80% of the circuit rating.

Article 220, load calculations. This is the most common calculation topic. In the 2023 edition the article was reorganised, so section numbers changed from 2020. The core values did not: 3 VA per square foot for dwelling general lighting, 1,500 VA per small-appliance circuit and laundry circuit, the dryer minimum of 5,000 W, and the demand factors for general lighting and for ranges in Table 220.55. Our Journeyman Electrician Exam Calculations works through these step by step.

Article 230, services. Know the service-drop clearances in 230.24 (for example, 12 ft over residential driveways for 300 V or less to ground) and the minimum service disconnect rating of 100 A for a one-family dwelling in 230.79(C).

Article 240, overcurrent protection. The small-conductor rule in 240.4(D) limits 14 AWG copper to 15 A, 12 AWG to 20 A and 10 AWG to 30 A, unless another article such as 430 or 440 permits otherwise. The standard ampere ratings are in 240.6(A). Section 240.4(B) allows the next higher standard size in some cases, up to 800 A.

Article 250, grounding and bonding. Grounding is one of the hardest topics because it has its own vocabulary. Know these tables and sections:

• Table 250.66: sizes the grounding electrode conductor based on the largest service-entrance conductor.
• Table 250.122: sizes the equipment grounding conductor based on the overcurrent device rating.
• 250.52 and 250.53: types of grounding electrodes, the 8 ft rod length, the 6 ft spacing between rods, and the supplemental electrode needed unless one rod has 25 ohms or less resistance.
• 250.24 and 250.142: where the neutral is bonded to the grounding system (at the service) and why it must not be bonded again downstream.

Chapter 3: Wiring Methods and Boxes

Article 300, general rules. Table 300.5 sets minimum cover depths for underground wiring. Section 300.4 protects cables from nails and screws, for example with a steel plate at least 1/16 in thick where a bored hole is closer than 1¼ in to the edge of a stud.

Article 310, conductors. Table 310.16 is the most used table in the book. Learn to read it: three temperature columns for copper and three for aluminum. Then apply the corrections in 310.15: Table 310.15(B)(1) for ambient temperature and Table 310.15(C)(1) for more than three current-carrying conductors in a raceway or cable.

Article 314, boxes. Box-fill questions are almost guaranteed. Table 314.16(B) gives the volume per conductor by size. Section 314.16(B) explains how to count: each conductor that enters and leaves, a double allowance for each device yoke, a single allowance for all equipment grounding conductors together, and a single allowance for internal cable clamps.

Raceway articles. Each wiring method has its own article with uses permitted, supports and bends. For example, Article 358 for EMT requires support within 3 ft of each box and every 10 ft, and limits bends between pull points to 360°. Article 334 requires NM cable to be secured within 12 in of boxes and at intervals no more than 4½ ft.

Chapter 4 and the Motor Article

Article 430 is long and has its own logic. The most tested steps are:

1. Use the full-load current from Tables 430.248 (single-phase) or 430.250 (three-phase), not the nameplate, to size conductors and short-circuit protection (430.6(A)(1)).
2. Size branch-circuit conductors at 125% of that full-load current (430.22).
3. Size overload protection from the nameplate current, generally 125% for motors with a service factor of 1.15 or more, and 115% for others (430.32).
4. Size short-circuit and ground-fault protection using the percentages in Table 430.52.

Article 422 (appliances) and Article 424 (fixed electric space heating) are smaller but appear on many outlines. For example, 422.13 treats a fixed storage water heater of 120 gallons or less as a continuous load.

Chapter 9 Tables

Table 1 in Chapter 9 sets maximum raceway fill: 53% for one conductor, 31% for two and 40% for more than two. Note 4 allows 60% in nipples 24 in long or less. Tables 4 and 5 give raceway areas and conductor areas so you can calculate fill. Annex C has ready-made tables for conductors of the same size, which are faster when the question allows them.

A Four-Week Study Plan

Adjust this to your own schedule.

• Week 1: Read Article 90, then skim Articles 100 and 110. Practise finding ten definitions a day. Learn the layout until you can open the book to any chapter quickly.
• Week 2: Chapter 2. Work through 210, 220 and 240. Do a few load calculations every day.
• Week 3: Article 250 and Chapter 3. Practise box fill, conduit fill and ampacity corrections.
• Week 4: Article 430 and special occupancies. Take a full timed practice exam every other day, and review every missed question in the code book.

Use our Journeyman Electrician Practice Test (NEC 2023) to check progress. Every answer gives the NEC reference, so look each one up even when you get it right. Our NEC Exam Tips for Electricians cover tabbing and time management.

Common Mistakes

• Using the 90°C column for terminations. The insulation may be 90°C, but 110.14(C) usually limits you to the 60°C or 75°C value.
• Forgetting the small-conductor rule. A 12 AWG copper conductor has a 25 A rating at 75°C, but 240.4(D) still caps protection at 20 A.
• Counting each ground separately in box fill. All equipment grounding conductors together count as one allowance.
• Using the motor nameplate to size conductors. Use the table full-load current.
• Studying the wrong edition. Check the bulletin before you buy a code book.

Before Test Day

Read your candidate bulletin again in the final week. Confirm the edition, what reference materials and calculators are allowed, and whether permanent tabs or highlighting are permitted. Get a good night’s sleep, arrive early, and work through the easy questions first, flagging any that need a long lookup.