National Electrical Code

The NEC, decoded for the journeyman exam.

The exam isn't about memorizing the code — it's about finding and applying the right article fast. Browse the NEC by exam topic, by reference table, or by the individual concepts that show up most.

NEC 2017 2020 2023

Browse the NEC

By exam topic, reference table, or individual code concept.

Article 250
Grounding & Bonding
Article 250 is the highest-volume topic on the journeyman exam, covering grounding electrode systems, equipment grounding conductors, bonding jumpers, and conductor sizing tables.
Open →Article 430
Motors
Article 430 requires candidates to size motor branch-circuit conductors, select short-circuit protection, and calculate overload protection—multi-step problems that appear on nearly every journeyman exam.
Open →Article 220
Load Calculations
Article 220 drives service and feeder sizing for dwelling and commercial occupancies, making it one of the most heavily tested multi-step calculation areas on the journeyman exam.
Open →Article 314
Boxes & Box Fill
Article 314 box fill calculations test whether candidates can size junction and device boxes based on conductor count, device allowances, and clamp allowances per NEC 314.16.
Open →Article 310
Conductors & Ampacity
Article 310 and Table 310.16 govern conductor ampacity and temperature-correction derating—foundational knowledge required to size any circuit correctly on the journeyman exam.
Open →Ch. 9 / 210.19 / 215.2
Voltage Drop
Voltage drop calculations span Chapter 9, 210.19, and 215.2, testing whether candidates can upsize conductors to keep voltage loss within recommended limits for branch circuits and feeders.
Open →Chapter 9
Conduit & Raceway Fill
Chapter 9 Tables 1, 4, and 5 define the fill percentages and conduit dimensions used to determine how many conductors fit in a given raceway—a frequent exam calculation.
Open →Article 230
Services
Article 230 specifies service entrance conductor sizing, clearances, number of disconnecting means, and the 2020-edition outdoor emergency disconnect added at 230.85.
Open →Reference
NEC Tables
Ampacity, conduit fill, grounding and motor tables — the lookups the exam expects you to find fast.
Open → 250.122
EGC Sizing — Table 250.122
Table 250.122 sets the minimum size of the equipment grounding conductor based on the rating of the overcurrent device protecting the circuit.
Open →250.66
GEC Sizing — Table 250.66
Table 250.66 determines the minimum size of the grounding electrode conductor based on the largest service-entrance conductor or equivalent area.
Open →Article 250
Grounding Electrode System
The grounding electrode system connects the electrical system to earth using electrodes such as ground rods, metal water pipe, and concrete-encased electrodes as required by Article 250.
Open →Articles 200 / 250
Neutral vs. Ground
The grounded (neutral) conductor carries return current under normal operation, while the equipment grounding conductor provides a fault-current path—NEC Articles 200 and 250 define each role.
Open →310.15
Conductor Ampacity & Derating
Ampacity is the maximum current a conductor can carry continuously; NEC 310.15 and Table 310.16 require correction factors for ambient temperature and bundling adjustments.
Open →Articles 344 / 358 / 352
Conduit Types
RMC (344), EMT (358), and PVC (352) differ in wall thickness, permitted uses, support spacing, and installation restrictions—all commonly tested on the journeyman exam.
Open →314.16
Box Fill Calculations
NEC 314.16 calculates the required cubic-inch capacity of an outlet or device box by assigning allowances for conductors, clamps, support fittings, and devices.
Open →Article 430
Motor Full-Load Current
Tables 430.248 and 430.250 list the NEC nameplate full-load current values used to size motor branch-circuit conductors and overcurrent devices regardless of the actual motor nameplate.
Open →Article 240
Overcurrent Protection
Article 240 covers the selection and rating of fuses and circuit breakers, including the next-size-up rule at 240.4(B) and the standard OCPD sizes listed in Table 240.6(A).
Open →110.26
Electrical Working Space
NEC 110.26 specifies the minimum depth, width, and headroom of clear working space that must be maintained in front of electrical equipment to allow safe operation and maintenance.
Open →210.19 / 210.20
Continuous Loads
A continuous load—expected to operate for three hours or more—must have its branch-circuit conductor and OCPD rated at 125% of the load per NEC 210.19 and 210.20.
Open →Article 210
Branch Circuits
Article 210 governs branch-circuit ratings, conductor sizing, receptacle placement, and GFCI/AFCI protection requirements that apply throughout dwelling and commercial installations.
Open →210.12
Arc-Fault Circuit Interrupters (AFCI)
NEC 210.12 requires AFCI protection in nearly all dwelling-unit areas in the 2020 and 2023 editions, with required locations expanding in each code cycle.
Open →210 / 406
Ground-Fault Circuit Interrupters (GFCI)
GFCI protection requirements have expanded across NEC editions to cover kitchens, bathrooms, garages, outdoors, basements, and HVAC outlets in dwelling and non-dwelling occupancies.
Open →406.12
Tamper-Resistant Receptacles
NEC 406.12 requires tamper-resistant receptacles throughout all areas of dwelling units in the 2020 and 2023 editions, not just in rooms accessible to children.
Open →Article 230
Service Disconnecting Means
Article 230 limits the number of service disconnects to six and, in the 2020 NEC, added 230.85 requiring an outdoor emergency disconnect for one- and two-family dwellings.
Open →Article 215
Feeders
Article 215 governs the sizing of feeder conductors from the service equipment to branch-circuit panelboards, including minimum ampacity and voltage-drop recommendations.
Open →Article 334
NM Cable (Romex)
Article 334 permits nonmetallic-sheathed cable in dry residential locations but prohibits it in hazardous locations, concrete, masonry, or any area requiring a raceway.
Open →Article 330
MC Cable
Article 330 covers metal-clad cable installation, support spacing, and permitted uses, distinguishing it from AC cable (Article 320) by its full-size equipment grounding conductor.
Open →300.5
Direct Burial Wiring
NEC 300.5 and Table 300.5 specify the minimum burial depths for cables and conduit based on wiring method, voltage, and whether the location is under a building, pavement, or open ground.
Open →210.52
Receptacle Placement Rules
NEC 210.52 requires receptacles in dwelling units to be spaced so no point along any wall is more than 6 feet from an outlet, with additional rules for kitchens, baths, and outdoor areas.
Open →NEC Overview
National Electrical Code — Overview
The NEC is a model electrical safety standard published by NFPA on a three-year cycle; understanding its chapter structure and article numbering system is essential for navigating exam questions efficiently.
Open →

The big point-getters on the journeyman exam cluster into a handful of NEC areas — Article 250 grounding and bonding, Article 430 motors, Article 220 load calculations, Article 314 box fill, and Article 310 conductor ampacity make up the bulk of the test. The topic hubs above pull each area's rules, calculations, and practice questions into one place.

Most NEC concepts don't change between editions, so Loomi covers the 2017, 2020, and 2023 codes together and flags the rules that actually differ by year — like emergency disconnects, GFCI/AFCI expansion, and the Table 310.16 renumber — so you study the version your state's exam uses.

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