Oklahoma Residential Electrical Journeyman

Key Concepts

Purpose of the NEC (Article 90.2(A)) The NEC's purpose is the practical safeguarding of persons and property from hazards arising from the use of electricity. It is not a design specification or instruction manual for untrained persons. Compliance produces an installation that is essentially free from hazard — but not necessarily efficient, convenient, or adequate for future expansion.

NEC Chapter Organization (Article 90.3) The NEC contains an introduction (Article 90) plus nine chapters: - Chapters 1–4: Apply generally to all installations - Chapters 5–7: Special occupancies, special equipment, special conditions — these supplement or modify Chapters 1–4 - Chapter 8: Communications systems — independent of Chapters 1–7 unless specifically referenced - Chapter 9: Tables, applicable only as…

Key Concepts

Ohm's Law & Power Formulas The foundation of all circuit calculations. Every relationship between P (watts), E (volts), I (amps), and R (ohms) derives from two base equations: E = IR and P = EI. Combine them to get P = I²R and P = E²/R. Know all 12 variations of the PIE/PIR wheel cold.

Series vs. Parallel Circuits - Series: Total resistance = R₁ + R₂ + R₃; current is the same throughout; voltage divides across loads. - Parallel: 1/Rₜ = 1/R₁ + 1/R₂ + 1/R₃; voltage is the same across all branches; current divides. - Combination circuits: Solve by reducing parallel groups to equivalent resistance first, then treat as series.

Key Concepts

Physical Protection of Cables Through Framing (NEC 300.4) - Bored holes in wood members: edge of hole must be ≥ 1¼ in. (32 mm) from the nearest edge of the wood member. - If that distance can't be maintained, install a steel plate ≥ 1/16 in. (1.6 mm) thick to protect against nail/screw penetration. - Steel plates are not required for RMC, IMC, rigid PVC, RTRC, or EMT. - Cables laid in notches also require the 1/16 in. steel plate, installed before finish is applied. - NM cable through metal framing members requires listed bushings or grommets to protect the cable sheath.

Oklahoma Residential Electrical Journeyman | 10 Questions (12%)

Key Concepts

Branch Circuit Ratings (Article 210) - Standard branch circuit ratings: 15A, 20A, 30A, 40A, 50A - 15A circuits require 14 AWG minimum; 20A circuits require 12 AWG minimum; 30A require 10 AWG - Multiwire branch circuits (210.4) must simultaneously disconnect all ungrounded conductors and may only supply line-to-neutral loads unless an exception applies - GFCI protection required in bathrooms, garages, outdoors, crawl spaces, unfinished basements, kitchens (within 6 ft of sink), boathouses, and near pools/spas (210.8) - AFCI protection required for all 120V, 15A and 20A branch circuits supplying outlets in dwelling unit bedrooms, living rooms, parlors, libraries, dens, sunrooms, recreation rooms, closets, hallways, laundry areas, and…

Key Concepts

Conductor Protection (NEC 240.4) Conductors must be protected per their ampacity from NEC 310.14. Small conductor maximums are fixed: 14 AWG copper = 15A, 12 AWG copper = 20A, 10 AWG copper = 30A. When ampacity doesn't match a standard rating, the next higher standard rating is permitted — but only if the OCPD is 800A or less (240.4(B)). If over 800A, conductor ampacity must equal or exceed the device rating (240.4(C)).

Standard Ampere Ratings (NEC 240.6(A)) Standard fuse/breaker ratings: 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 125, 150, 175, 200, 225, 250, 300, 350, 400, 450, 500, 600, 700, 800, 1000, 1200, 1600, 2000, 2500, 3000, 4000, 5000, 6000A.…

Key Concepts

Grounding Electrode System (NEC 250.50–250.54) All grounding electrodes present at a building must be bonded together to form the grounding electrode system. Required electrodes include metal underground water pipe (≥10 ft in contact with earth), metal building frame, concrete-encased electrode (Ufer), ground ring, rod/pipe/plate electrodes, and other listed electrodes. If none of the "preferred" electrodes exist, you must install a made electrode (rod, pipe, or plate) per 250.52(A)(4)–(A)(8).

Grounding Electrode Conductor (GEC) — 250.62–250.66 GECs must be copper, aluminum, or copper-clad aluminum — solid or stranded, insulated, covered, or bare. They must be installed in one continuous length without splices (exception: splicing with irreversible compression connectors or exothermic welding is permitted). Sizing is based on the size…

Key Concepts

Minimum Conductor Size (310.3(A)) - Copper: 14 AWG minimum - Aluminum or copper-clad aluminum: 12 AWG minimum

Stranding Requirement (310.3(C)) - Conductors 8 AWG and larger installed in raceways must be stranded (unless specifically permitted to be solid)

Aluminum Alloy Material (310.3(B)) - Solid aluminum 8, 10, and 12 AWG must be AA-8000 series alloy - Stranded aluminum 8 AWG–1000 kcmil marked as THHN, THWN, XHHW, RHW, THW, SE Style U/R, etc., must also be AA-8000 series

Common Insulation Types and Ratings (Table 310.4(1))

Key Concepts

Box Fill Calculations (Article 314.16) Each conductor, device, and fitting takes up space measured in cubic inches. Volume allowances are assigned by AWG size per Table 314.16(B). Count every conductor entering the box, plus deductions for devices, clamps, and equipment grounds. Conductors that originate and terminate in the box count as one conductor each. Conductors that pass through count as one. Equipment grounding conductors together count as one conductor at the largest EGC size present.

Conduit Fill (Chapter 9, Table 1 & Tables 4–5) - 1 conductor: 53% fill - 2 conductors: 31% fill - 3+ conductors: 40% fill

Oklahoma Residential Electrical Journeyman Exam | 8 Questions (10%)

Key Concepts

Hazardous Location Classification (Article 500)

• Class I — Flammable gases or vapors (e.g., gasoline, propane). Class II — Combustible dusts (e.g., grain, coal). Class III — Ignitible fibers/flyings (e.g., sawdust, textile fibers).
• Division 1 — Hazardous material is present under normal operating conditions.
• Division 2 — Hazardous material is present only under abnormal conditions (failure, accident).
• Groups A–D = Class I gases. Groups E–G = Class II dusts. (Group A = most dangerous; acetylene. Group D = propane, gasoline.)
• Sealing fittings required in Class I locations at conduit entries to enclosures and where conduit passes between divisions (Article 501).

Oklahoma Residential Electrical Journeyman Exam Study Brief

Key Concepts

Fire Alarm Circuit Types (Article 760)

• NPLFA (Non-Power-Limited Fire Alarm): Powered by standard electrical sources complying with Chapters 1–4. Higher voltage/current potential — must follow stricter wiring methods.
• PLFA (Power-Limited Fire Alarm): Powered by listed, power-limited sources. More flexible installation options with dedicated cable types.
• Branch circuit requirement: Fire alarm control panels require a dedicated branch circuit. The disconnect must be identified in red and marked "FIRE ALARM CIRCUIT." It shall be accessible only to qualified personnel.
• Separation rule (760.136): PLFA cables must be separated from electric light/power conductors by at least 50 mm (2 in.) unless in a raceway or separated by…

Key Concepts

Luminaire Location Requirements (Article 410)

• Wet locations: Luminaires must be listed and marked for wet locations.
• Damp locations: Luminaires must be listed for damp or wet locations.
• Bathtub/shower zones: No luminaires permitted within a zone 3 ft horizontally and 8 ft vertically from the top of the bathtub rim or shower stall threshold unless listed for damp/wet locations (410.10(D)).
• Clothes closets: Only listed surface-mounted or recessed incandescent luminaires with completely enclosed light sources, surface-mounted or recessed LED luminaires, or surface-mounted fluorescent/LED luminaires are permitted. Must maintain minimum clearances from storage areas (410.16).

2 questions | 2% of exam

Key Concepts

Lockout/Tagout & Electrically Safe Work Condition

• Before working on energized or de-energized equipment, an electrically safe work condition must be established: open disconnecting means, lock/tag out, release stored energy, verify absence of voltage with a rated test instrument.
• OSHA 29 CFR 1926.417 requires that controls be locked or tagged out before work begins on equipment that could be unexpectedly energized.
• Tags alone (tagout) are not as reliable as locks — if a lock cannot be applied, a tag must explain why and what it means.