Journeyman Electrician Exam NEC Code Topics: Core Articles
Article 90 & 100: Introduction and Definitions
Understanding NEC definitions for test performance is the first hurdle in the examination process. Article 90 establishes the scope and purpose of the code, clarifying that the NEC is not an instruction manual but a set of enforceable safety standards. It introduces the concept of Mandatory Rules, characterized by the terms "shall" or "shall not," and Permissive Rules, which use "shall be permitted." Recognizing this distinction is vital for answering questions regarding code compliance versus best practices.
Article 100 is perhaps the most critical section for deciphering "trick" questions. For instance, the distinction between Accessible (as applied to equipment) and Readily Accessible often determines the legality of a disconnect location. A piece of equipment is accessible if it can be reached without damaging the building structure, but it is only readily accessible if it can be reached quickly without the use of tools or ladders. Exam questions frequently hinge on these nuances, especially regarding the placement of overcurrent protective devices. Furthermore, terms like Bonded (Bonding) and Grounded (Grounding) are often used interchangeably in the field but have distinct legal definitions in Article 100 that affect how you answer technical questions about fault current paths.
Article 110: General Requirements for Electrical Installations
Article 110 serves as the "catch-all" for installation standards that apply regardless of the specific wiring method used. One of the most tested concepts here is Working Space requirements (Section 110.26). You must be able to calculate the required clear distance in front of electrical equipment based on the nominal voltage to ground and the "Condition" of the workspace (Condition 1, 2, or 3). For example, a 480/277V system (Condition 3, where there are exposed live parts on both sides) requires a minimum of 4 feet of clearance, whereas a 120/240V system typically requires 3 feet.
Another high-frequency topic is Tightening Torque (110.14(D)). The code now mandates that where a tightening torque is indicated on the equipment, a calibrated tool must be used. Exam questions may ask about the requirements for terminal identification or the "Mechanical Execution of Work," which requires electrical equipment to be installed in a neat and workmanlike manner. Pay close attention to Section 110.16 regarding Arc-Flash Hazard Warning labels; the exam may ask which types of equipment require these markings in non-dwelling units to protect qualified persons during maintenance.
Article 210: Branch Circuits
Article 210 covers the provisions for branch circuits, and it is a cornerstone of the NEC code study guide electrician candidates rely on. You must master the requirements for Ground-Fault Circuit-Interrupter (GFCI) protection (210.8) and Arc-Fault Circuit-Interrupter (AFCI) protection (210.12). The exam will likely present scenarios asking which outlets in a dwelling unit—such as those in a crawl space, laundry area, or kitchen dishwasher—require GFCI protection. Note that the 2020 and 2023 NEC editions expanded these requirements significantly.
Required lighting outlets and receptacle placement (210.52) are also heavily tested. You should know the "6-foot rule" for dwelling unit walls, where no point along a floor line is more than 6 feet from a receptacle. Additionally, the Small-Appliance Branch Circuit rules for kitchens (requiring at least two 20-ampere circuits) and the specific requirements for bathroom and laundry circuits are standard exam fare. Understanding Multiwire Branch Circuits (210.4) is also essential, particularly the requirement for a means to simultaneously disconnect all ungrounded conductors at the point where the branch circuit originates to prevent accidental shock from neutral feedback.
Grounding and Bonding: Article 250 Deep Dive
System Grounding vs. Equipment Grounding
Article 250 is often cited as the most difficult section of the NEC, yet it is among the most tested NEC articles journeyman candidates face. You must distinguish between System Grounding, which connects the circuit conductor (usually the neutral) to the earth, and Equipment Grounding, which connects non-current-carrying metal parts of equipment to the system grounded conductor or the grounding electrode conductor. The primary purpose of system grounding is to limit the voltage imposed by lightning or line surges, while equipment grounding is designed to provide a low-impedance path for fault current to facilitate the operation of overcurrent devices.
On the exam, you will encounter the Main Bonding Jumper, which is the critical link between the equipment grounding conductor and the grounded conductor at the service. Knowing how to size this using Table 250.102(C)(1) is a mandatory skill. Candidates often fail because they confuse the requirements for a Grounded Conductor (the neutral) with the Grounding Conductor (the green wire). Remember that the grounded conductor is intended to carry current during normal operation, whereas the grounding conductor should only carry current during a fault condition.
Grounding Electrode System and Conductors
Section 250.50 requires all grounding electrodes present at a building to be bonded together to form the Grounding Electrode System. Common electrodes include metal underground water pipes, the metal frame of the building, and Concrete-Encased Electrodes (often called Ufer grounds). A frequent exam question involves the minimum length of a ground rod (8 feet) and the requirement that it must be driven to a depth of 8 feet. If rock bottom is encountered, the rod can be buried in a trench at least 30 inches deep.
Sizing the Grounding Electrode Conductor (GEC) is a core calculation task. You must use Table 250.66, which bases the GEC size on the area of the largest ungrounded service-entrance conductor. For instance, if you are using 3/0 copper service conductors, the table dictates a #4 AWG copper GEC. However, there are exceptions: if the GEC connects to a rod, pipe, or plate electrode, the portion of the conductor that is the sole connection to that electrode is not required to be larger than #6 copper. Misapplying these exceptions is a common way to lose points on the exam.
Bonding Jumpers and Continuity
Bonding ensures electrical continuity and the capacity to conduct safely any fault current likely to be imposed. Article 250, Part V focuses on bonding, especially around service equipment. Because service-entrance conductors lack overcurrent protection at their supply end, the bonding requirements are more stringent than for branch circuits. You may be asked about the Supply-Side Bonding Jumper, which must be sized according to Table 250.102(C)(1).
Continuity is also vital for raceways. If you are using non-metallic boxes with metal raceways, a Bonding Jumper must be used to maintain the grounding path. In "Special Occupancies" or for circuits over 250 volts to ground, standard locknuts aren't sufficient for bonding; you must use bonding bushings with jumpers or other approved means. Understanding the Effective Ground-Fault Current Path is the underlying principle here—it must be permanent, continuous, and have sufficiently low impedance to trip the circuit breaker immediately during a ground fault.
Wiring Methods and Materials Coverage
Chapter 3 Wiring Methods: Articles 300-392
Chapter 3 of the NEC provides the "how-to" for physical installations. Article 300 contains general requirements, such as protection against physical damage. You must know the Minimum Cover Requirements found in Table 300.5 for underground installations. For example, direct-buried cables for a 120V residential circuit protected by a 20A GFCI breaker generally require 12 inches of cover, whereas standard rigid metal conduit only requires 6 inches.
Articles 320 through 348 cover specific cable types like Type AC, Type MC, and Type NM (Romex). The exam will test your knowledge of support intervals—for example, NM cable must be secured within 12 inches of every box and at intervals not exceeding 4.5 feet. You must also understand where these cables are prohibited; NM cable cannot be used in commercial garages or as service-entrance cable. Article 314 is another high-priority section, covering the installation of outlet, device, and pull boxes. You must be able to calculate the maximum number of conductors allowed in a box using the volume allowances in Table 314.16(B).
Conductor Properties and Ampacity (Article 310)
Article 310 is the heart of electrical code calculations exam preparation. It defines conductor construction and, most importantly, allowable ampacities. You will spend a significant amount of time during the exam in Table 310.16 (formerly 310.15(B)(16)). This table lists the ampacity of insulated conductors based on their temperature rating (60°C, 75°C, or 90°C) and the material (copper or aluminum).
A critical rule to remember is the Terminal Temperature Limitation found in 110.14(C). Even if you use a 90°C rated conductor (like THHN), you must usually size the conductor based on the 75°C column if the equipment terminals are rated for 75°C. The 90°C rating is typically only used as a starting point for derating due to ambient temperature or conductor bundling. Failure to account for the "weakest link" in the circuit—the terminal temperature—is a frequent mistake on journeyman exams.
Cable and Raceway Installation Requirements
Beyond just sizing conductors, you must understand the rules for the raceways that contain them. This involves calculating Conduit Fill using Chapter 9, Table 1 and the various tables in Annex C. For a lead-in question, the exam might ask for the minimum size of Electrical Metallic Tubing (EMT) required to house four 1/0 THHN copper conductors. You would use Table 5 in Chapter 9 to find the square-inch area of a 1/0 THHN conductor and then refer to Table 4 to find the 40% fill capacity of different EMT sizes.
Bending rules are also essential. Most raceways, such as Rigid Metal Conduit (RMC) or PVC, are limited to a maximum of 360 degrees of bends between pull points (Article 344.26, 352.26). This is to prevent damage to the conductor insulation during wire pulling. You should also be familiar with Article 392 for Cable Trays, specifically how to calculate the allowable fill for both power and control cables. These requirements ensure that heat can dissipate and that the physical integrity of the wiring is maintained over time.
Equipment for General Use and Special Occupancies
Motors, Motor Circuits, and Controllers (Article 430)
Article 430 is notoriously complex because motor circuits do not follow the standard rules for branch circuits. Instead of sizing conductors at 125% and then choosing the next standard size fuse, motor circuits separate the Overload Protection from the Short-Circuit and Ground-Fault Protection. For the exam, you must use the Full-Load Current (FLC) tables (Tables 430.247 through 430.250) rather than the nameplate rating of the motor unless the nameplate is specifically mentioned for overload sizing.
To size the branch circuit conductors for a single motor, you multiply the FLC by 125% (430.22). However, to size the Breaker or Fuse, you refer to Table 430.52. For an inverted-time circuit breaker, you typically multiply the FLC by 250%. This allows the high inrush current of the motor to start the load without tripping the breaker, while the separate overload heaters (sized much closer to the actual nameplate current) protect the motor from burning out during a mechanical jam or prolonged use. Mastering this two-step calculation process is non-negotiable for passing the journeyman exam.
Article 450 covers the protection and installation of transformers. The most common exam questions involve sizing the Overcurrent Protection Device (OCPD) for the primary and secondary sides. Using Table 450.3(B), you must determine the maximum percentage allowed based on the transformer's voltage and impedance. For example, a transformer with a primary current of 9 amperes or more typically allows a primary OCPD set at 125% of the rated current.
In addition to OCPD sizing, you must understand the rules for Transformer Grounding (250.30) for Separately Derived Systems. This includes the installation of a System Bonding Jumper and the connection to a grounding electrode. You may also be tested on the physical installation requirements, such as the required ventilation for transformer vaults and the minimum distances from combustible materials. Remember that transformers are heat-producing devices, and the NEC focuses heavily on preventing them from becoming fire hazards.
Luminaires, Appliances, and HVAC Equipment
Article 410 (Luminaires), Article 422 (Appliances), and Article 440 (HVAC) cover the remaining equipment for general use. For luminaires, pay attention to the rules for installation in clothes closets (410.16) to prevent fire; for instance, incandescent luminaires with open lamps are strictly prohibited. For appliances, you must know the requirements for Disconnecting Means. If an appliance is over 300 volt-amperes or 1/8 horsepower, it generally requires a specific type of disconnect within sight or one that can be locked in the open position.
Article 440 for Air-Conditioning and Refrigerating Equipment is similar to Article 430 but has its own specific terminology, such as Rated-Load Current (RLC) and Branch-Circuit Selection Current. You must be able to size the conductors and the short-circuit protection for these units, which are often found on residential and commercial exam versions. Knowing how to read the manufacturer's data plate and applying it to the NEC requirements is a practical skill often simulated in exam questions.
Essential NEC Calculations for the Exam
Box Fill and Conduit Fill Calculations
Calculating Box Fill is a fundamental task that tests your attention to detail. Under Section 314.16, each item inside a box is assigned a "volume allowance." A 14 AWG conductor counts as 2.00 cubic inches, while a 12 AWG conductor counts as 2.25 cubic inches. Internal cable clamps, support fittings (like hickeys), and all grounding conductors (collectively) each count as a single volume allowance based on the largest conductor in the box. Switches and receptacles (devices) count as a double volume allowance based on the conductor connected to them.
Conduit Fill calculations are equally important and involve Chapter 9. When all conductors in a raceway are the same size and insulation type, you can use the tables in Annex C. However, if you have a mix of different wire sizes, you must calculate the total cross-sectional area of all wires using Table 5 and ensure it does not exceed the percentage of the internal cross-sectional area of the conduit provided in Table 4. For most installations with more than two conductors, the limit is 40% fill. Understanding these limits is crucial for preventing heat buildup and physical damage during wire pulls.
Conductor Ampacity Adjustments and Corrections
Once you find the base ampacity in Table 310.16, you must often apply Adjustment Factors and Correction Factors. Adjustment factors (found in Table 310.15(C)(1)) are required when there are more than three current-carrying conductors in a raceway or cable. For example, if you have 4 to 6 current-carrying conductors, you must reduce the allowable ampacity to 80% of its table value.
Correction Factors are applied based on the Ambient Temperature. If the temperature is higher than 30°C (86°F), you must use the multipliers found at the bottom of the ampacity table (or in Table 310.15(B)(1)). A common exam scenario involves a rooftop installation where the sun's heat or the proximity to the roof surface (though the "roof adder" was removed in recent NEC editions) requires significant derating. You must apply both adjustment and correction factors to the conductor's 90°C rating before comparing the result to the 75°C terminal limitation to ensure the final design is safe.
Feeder and Service Load Calculations
Article 220 provides the methods for calculating branch-circuit, feeder, and service loads. You must be familiar with both the Standard Method (Part III) and the Optional Method (Part IV) for dwelling units. The standard method involves adding the general lighting load (3 volt-amperes per square foot), the small-appliance circuits, the laundry circuit, and then applying Demand Factors from Table 220.42. For example, the first 3,000 VA is taken at 100%, while the next 117,000 VA is taken at 35%.
Service calculations also require accounting for fixed appliances, dryers, cooking equipment, and HVAC loads. You must understand the "non-coincident load" rule (220.60), which allows you to omit the smaller of two loads (like heating and air conditioning) if they are unlikely to run at the same time. These multi-step calculations are the most time-consuming part of the exam, and a single error in a demand factor can lead to the wrong answer. Practicing these "long-form" calculations is essential for National Electrical Code exam prep success.
Navigating the NEC Codebook Under Time Pressure
Effective Index and Table of Contents Use
Speed is as important as accuracy on the Journeyman Electrician exam. Most candidates have between 2.5 to 4 minutes per question. To succeed, you must master the Index at the back of the NEC. Instead of searching for "wire," look for "Conductors." Instead of "grounding," look for "Grounding" and then find the specific sub-heading like "Electrode System." The index is your fastest path to the correct article number.
The Table of Contents is also useful for broad searches. If you know a question is about a specific wiring method like EMT, you can quickly see that all raceway articles are in the 300s and find Article 358. Developing a "keyword" strategy—identifying the most specific noun in the question—will help you decide whether to go to the Index or the Table of Contents first. This prevents the "page-flipping" panic that often leads to lost time.
Many exam questions are answered directly within the Tables or the Informational Notes. However, you must read the "Notes to Tables" carefully. For instance, Chapter 9, Table 1 has several notes that explain how to handle conduit fill for multiconductor cables or for very short runs (nipples). An informational note is not an enforceable part of the code, but it provides vital context that can clarify a rule's intent or point you toward another relevant article.
When using tables like Table 250.66 or Table 310.16, always double-check the units. Are you looking at "Circular Mils" or "AWG"? Is the temperature in Celsius or Fahrenheit? Misreading a column header is a common mistake. Furthermore, be aware of the Exceptions listed under many code sections. The exam often tests the exception rather than the general rule, so always read the small print following a code paragraph to see if your specific scenario qualifies for a different requirement.
Practice Drills for Code Question Speed
To build the necessary muscle memory, you should engage in timed practice drills. Start by taking a set of 20 questions and giving yourself 60 minutes. As you improve, reduce the time to 45 minutes. The goal is to reach a point where you can identify the relevant NEC article within 30 seconds of reading the question. This leaves you enough time to perform any necessary calculations or to read the fine print of the section.
Focus your drills on the most tested NEC articles journeyman exams cover, but don't ignore the "Special Conditions" in Chapter 7 or the "Communication Systems" in Chapter 8. While less frequent, questions on Emergency Systems (Article 700) or Class 1, 2, and 3 Circuits (Article 725) often appear as "tie-breakers." By combining a deep understanding of electrical theory with a disciplined approach to the NEC, you will be well-prepared to pass the exam and earn your Journeyman Electrician license.