State Master/Journeyman Electrician License — Study Guide

State Master/Journeyman Electrician License — Study Guide

Credential: State Master / Journeyman Electrician License (trade license) Issuing body: State electrical boards (e.g., Colorado State Electrical Board); some states delegate licensing to counties/municipalities Jurisdiction: United States — state by state. A few states have no statewide license (licensing is local). Level: Trade license: Apprentice → Journeyman → Master → (Electrical Contractor, a separate business endorsement in most states) Prerequisites (example — Colorado, verified via Colorado DPO pages): Journeyman = 8,000 hours of verified wiring experience over 4+ years (including 2,000 hours commercial/industrial) + 288 classroom hours + written exam. Master = 10,000 hours over 5+ years (or EE degree + 2,000 construction hours) + written exam. Requirements vary substantially by state — verify with your state board before scheduling. Renewal: State cycles, commonly 1–3 years, with continuing-education hours tied to code-update training (varies by state).

Scope boundary that candidates must internalize: this is the electrician scope — installation, wiring, and construction work performed for hire. It is distinct from the PE engineer scope — design, analysis, and stamping. A licensed PE is not automatically licensed to wire for hire, and a licensed electrician is not automatically entitled to design or stamp plans. The two scopes overlap on the NEC but diverge on what the credential authorizes you to sign.

1. Pathway — how the license is earned

1. Register as an apprentice. Most states require an apprentice card to log hours legally. Keep meticulous hour logs — boards audit hours against employer attestations.
2. Accumulate verified experience. The archetypal journeyman threshold is 4 years / 8,000 hours (Colorado verified); the master threshold is 5 years / 10,000 hours (Colorado verified). Apprenticeship programs (IBEW, IEC, ABC) combine this with classroom instruction (e.g., 288 classroom hours in Colorado).
3. Pass the written exam. Most state exams are open-book NEC examinations: typically ~80 multiple-choice questions in ~4 hours with a 70% pass mark. The dominant source is the current NEC edition plus state-specific amendments. Exam format is state-dependent — this guide covers the knowledge, but confirm question count, timing, pass mark, and allowed references with your board.
4. Maintain with continuing education. Renewal cycles (commonly 1–3 years) require code-update CE hours. Boards retire stale NEC editions; many states adopt a new NEC within 12–36 months of publication, and the exam follows the adopted edition — study the edition your state currently uses.

2. Exam format and timing

Public exam facts (verify with your state board — these are the industry norms, not a single uniform standard):

• Open book: you bring the NEC (paperback, tabbed). The exam tests retrieval + application, not memorization.
• Roughly 80 multiple-choice questions, ~4 hours, ~70% to pass (state-specific; some states use fewer questions and different pass marks).
• Question mix: NEC article questions (locate the rule), calculation questions (load, conductor size, box fill, conduit fill, voltage drop, motor sizing), and safety/scope questions (who may do what, OSHA basics, 70E concepts).
• No formula sheet is provided; the NEC's tables are your formula sheet. You must know which table to open and which note governs.

Strategy is covered in section 7, but internalize this now: the exam is won in the index, table of contents, and Chapter 9 tables, not in the article text. Tab every frequently used article (210, 215, 220, 230, 240, 250, 300, 310, 314, 404, 408, 430, 440, 680, 690, 700, 701, 702, Chapter 9 Tables, Annex C).

3. Knowledge domains — the theory that makes the NEC make sense

Domain A — NEC structure and philosophy (how to navigate the Code)

The NEC is NFPA 70, adopted by most US jurisdictions as law. Its nine chapters:

• Chapters 1–4: general rules that apply everywhere. Ch.1 General (Art. 100 definitions, Art. 110 requirements for electrical installations), Ch.2 Wiring and Protection (200–280), Ch.3 Wiring Methods and Materials (300–392), Ch.4 Equipment for General Use (400–490).
• Chapters 5–7: special cases that MODIFY or SUPPLEMENT Chapters 1–4. Ch.5 Special Occupancies (500–590), Ch.6 Special Equipment (600–695), Ch.7 Special Conditions (700–770).
• Chapter 8: Communications Systems (800–830) — stands largely independent.
• Chapter 9: Tables — conductor properties, conduit fill. Annexes A–J: informational (not enforceable) except where the Code specifically references them — Annex C conduit-fill tables are enforceable via Art. 300 notes.

The critical navigation rule: later, more specific chapters override earlier general ones (90.3). A rule in Art. 430 (motors) beats a rule in Art. 210 (branch circuits). Always check whether a special-occupancy or special-equipment article governs before applying the general rule.

Domain B — Electrical fundamentals and load calculations

Ohm's law and power (the entire Code is applied physics):

• V = I·R (V volts, I amps, R ohms). Power: P = V·I (W, watts) for DC and single-phase resistive loads. For AC: P = V·I·cos(θ) where cos(θ) is the power factor.
• Three-phase power: P = √3·V_L·I_L·cos(θ), with V_L in line-to-line volts and I_L in line amps. Current: I_L = P / (√3·V_L·cos θ).
• Energy: E = P·t, in watt-hours (kWh for billing). The Code deals in volt-amperes (VA), not watts, for load calculations — VA is the conservative apparent power, S = V·I. Use VA everywhere in Art. 220 work.

Why VA, not watts, governs sizing: conductors and overcurrent devices respond to actual current, which is determined by apparent power (S = V·I). A 10 kW load at 0.8 power factor draws 12.5 kVA — sizing by watts would undersize the conductor by 20%. The Code forces VA so the physics is right regardless of power factor.

Continuous vs. noncontinuous loads (Art. 100): a continuous load is one where the maximum current is expected to continue for 3 hours or more. Branch-circuit conductors and overcurrent devices serving continuous loads are sized at 125% of the continuous load (210.19(A), 210.20(A)). This 125% is thermal protection for enclosed devices, not a safety factor on the physics — breakers in hot enclosures trip below nameplate, and sustained current at 100% rating overheats terminals. Exams hammer this: lighting in commercial buildings is continuous; size accordingly.

Domain C — Branch circuits, feeders, services (Art. 210, 215, 220, 230)

• Branch circuit (Art. 210): the circuit conductors between the final overcurrent device and the outlet(s). Minimums: 210.52 gives dwelling-unit receptacle spacing rules; 210.8 gives GFCI requirements; 210.11 requires branch-circuit counts for lighting and appliance loads.
• Feeder (Art. 215): all circuit conductors between the service equipment and the final branch-circuit overcurrent device.
• Service (Art. 230): the conductors and equipment for delivering energy from the serving utility to the premises wiring system. Service point, service conductors, service equipment, service disconnect.

Article 220 load-calculation theory: Art. 220 has two methods — the standard method (Part III) and the optional method (Part IV, for dwellings). Both exist because diversity matters: not every load runs simultaneously. Demand factors (220.42 lighting demand, 220.53 appliance demand at 75% for 4+ fixed appliances, 220.54/220.55 dryer/range demand tables) are engineering approximations of coincident demand. Understand that demand factors <100% are justified only when the Code explicitly grants them — never invent diversity.

Neutral sizing (220.61): the feeder/service neutral may be reduced per 220.61 demand factors (200 A or less at 100%, next 200 A at 70%, remainder at 60%... with limits) because unbalanced neutral current in a 3-wire/4-wire system is statistically less than phase current — but never smaller than 250.24(C) grounding requirements, and in nonlinear-load environments (harmonics) reduction is unsafe practice.

Domain D — Overcurrent protection (Art. 240)

• Purpose: protect conductors and equipment from excessive current, not people. Overcurrent = overload + short circuit + ground fault.
• Standard ratings (240.6): 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, 6000 A.
• 240.4(B) "round up" rule: if the conductor ampacity doesn't match a standard OCPD rating, you may use the next higher standard rating — only for 800 A or less and only when the calculated load doesn't exceed the conductor ampacity. This is the single most-tested exception in the Code; know its conditions cold (it does NOT apply to 240.4(D) small-conductor limits or to specific equipment articles like 430/440).
• 240.4(D) small conductor rule: 14 AWG → 15 A max, 12 AWG → 20 A max, 10 AWG → 25 A max protection, regardless of what 90°C ampacity says. The 60°C column (110.14(C)) usually governs terminations anyway.

Domain E — Grounding and bonding (Art. 250) — theory, not just rules

Why grounding exists (physics): (1) limit voltage imposed by lightning/line surges/unintentional contact with higher-voltage lines; (2) stabilize voltage to earth during normal operation; (3) facilitate overcurrent device operation during a ground fault — the equipment grounding conductor provides the low-impedance fault path that lets hundreds of amps flow so the breaker trips in milliseconds instead of leaving the enclosure energized.

The trap concept: grounding (connection to earth) ≠ bonding (connection of conductive parts together to establish electrical continuity). Equipment grounding conductors are bonding conductors — their job is a low-impedance path back to the source, not a path to dirt. Earth is a poor, high-resistance conductor; it cannot clear faults. Exams test this distinction constantly.

Key sizing: equipment grounding conductors per Table 250.122 (indexed by OCPD rating); grounding electrode conductors per Table 250.66 (indexed by largest service-entrance conductor); main bonding jumper per 250.28.

Domain F — Wiring methods and box/conduit fill (Art. 300–392, 314)

• 314.16 box fill: every conductor counts as one volume unit (based on largest conductor in the box, Table 314.16(B)); device yokes count as 2 units each; internal clamps count as 1; ground wires collectively count as 1 (the largest ground). Volume required vs. box volume (Table 314.16(A)). The theory: heat dissipation and physical protection of insulation from abrasion.
• Chapter 9 conduit fill: 53% for one conductor, 31% for two, 40% for three or more (Table 1). Use Table 4 (conduit dimensions) and Table 5 (conductor areas). Annex C pre-computed tables are the fast path — know they exist.
• 310.15(B)(3)(a) adjustment (derating): more than 3 current-carrying conductors in a raceway → apply adjustment factors (4–6 CCC: 80%; 7–9: 70%; 10–20: 50%; etc.). Heat is the enemy: bundled conductors can't shed heat, so ampacity drops. Neutral counts as CCC when it carries unbalanced current of nonlinear loads.

Domain G — Motors (Art. 430) — the exam's calculation engine

Art. 430 is a complete separate sizing system that overrides general rules:

• 430.6: use the motor full-load current (FLC) from Tables 430.247–250, NOT the nameplate FLA, for sizing conductors, disconnects, and short-circuit/ground-fault protection. Nameplate FLA is used only for overload protection sizing. Why: the tables represent the worst-case motor the rating could be, so protection is conservative; nameplate is the specific motor's actual draw, so overload (thermal) protection must match the real motor.
• Branch-circuit conductors: 125% of FLC (430.22).
• Short-circuit/ground-fault protection: sized from Table 430.52 as a percentage of FLC (e.g., inverse-time breaker 250%, nontime-delay fuse 300%, time-delay fuse 175%) — then 430.52(C)(1) Exception allows stepping up to the next standard size if the calculated value doesn't correspond, and Exception 2 allows up to 400%/225% if needed for starting. The philosophy: SC/GF protection need only clear faults, NOT protect against overload — overload protection is separate (430.32).
• Overload protection: 115–125% of nameplate FLA (430.32), because overloads are thermal and must track the actual motor.
• Disconnecting means: 115% of FLC (430.110).

Worked example in section 5. Memorize the architecture: conductors 125% FLC-table, SC/GF from 430.52 percentages, overload from nameplate.

Domain H — Special equipment and conditions (exam high-yield)

• Art. 440 (Air conditioning/refrigeration): similar dual system to motors — branch-circuit conductors 125% of rated-load current (or branch-circuit selection current, whichever is greater); SC/GF protection max 175% (225% if needed for starting).
• Art. 680 (Pools): equipotential bonding (680.26) — the theory is eliminating voltage gradients in the water/deck zone, not grounding to earth.
• Art. 690 (PV): 690.8 continuous-duty 125% rules; rapid shutdown (690.12); labeling.
• Art. 700/701/702: emergency (700, 10-second transfer), legally required standby (701), optional standby (702).
• GFCI (210.8) vs AFCI (210.12): GFCI = ground-fault (5 mA personnel) protection; AFCI = arc-fault fire protection. Different physics, different articles, different required locations.

4. Key equations (units + assumptions)

5. Worked examples

Example 1 — Dwelling branch-circuit load (Art. 220, 210). A dwelling has 1,500 ft² of living area. General lighting load = 1,500 × 3 VA/ft² = 4,500 VA (220.12). Small-appliance circuits: 2 × 1,500 = 3,000 VA; laundry: 1,500 VA. Total = 9,000 VA. First 3,000 VA at 100% + remainder (6,000) at 35% (220.42 demand) = 3,000 + 2,100 = 5,100 VA. At 240/120 V single-phase, the lighting/appliance feeder contribution = 5,100 / 240 = 21.25 A. Note the demand factor collapsing 9,000 VA to 5,100 VA — diversity is doing real work, and the exam tests whether you apply Table 220.42 before sizing.

Example 2 — Motor circuit (Art. 430). A 25-hp, 460-V, 3-phase motor. Table 430.250 FLC = 34 A.

• Branch-circuit conductors: 34 × 1.25 = 42.5 A → 8 AWG THHN (55 A at 90°C, but check 75°C termination column = 50 A; 8 AWG OK either way) per 430.22.
• SC/GF with inverse-time breaker: 34 × 2.50 = 85 A → next standard size up per 430.52(C)(1) Ex.1 = 90 A breaker.
• Disconnect: 34 × 1.15 = 39.1 A → 60 A disconnect (next standard size ≥ 39.1).
• Overload: from the motor NAMEPLATE (say 33 FLA): 33 × 1.15 = 37.95 A heater selection per 430.32 (service factor ≥1.15). The exam's favorite trap: using nameplate FLA for conductor sizing. Conductors/disconnect/SC-GF use the table FLC; only overloads use nameplate.

Example 3 — Box fill (314.16). A 4-in. square × 2-1/8-in. deep box (30.3 in³ per Table 314.16(A)) contains: four 12 AWG current-carrying conductors, two 12 AWG grounds, one duplex receptacle (counts as 2 units at the largest conductor). Unit volume for 12 AWG = 2.25 in³ (Table 314.16(B)). Units = 4 (conductors) + 1 (all grounds together) + 2 (device) = 7 units. Required = 7 × 2.25 = 15.75 in³ ≤ 30.3 in³. Compliant — with room to spare. (Clamps internal to the box would add 1 unit.)

Example 4 — Conduit fill (Chapter 9). Six 10 AWG THHN conductors (0.0211 in² each, Table 5) in EMT. Total area = 6 × 0.0211 = 0.1266 in². 40% fill of 1/2-in. EMT = 0.122 in² (Table 4) — too small. 3/4-in. EMT at 40% = 0.213 in² — compliant. Exam shortcut: Annex C, Table C.1 gives the max count directly — 6 × 10 AWG THHN fits in 3/4-in. EMT (max 10).

Example 5 — Voltage drop (design check). A 120-V, 20-A branch circuit runs 100 ft one-way in 12 AWG copper (K = 12.9, CM = 6,530). VD = 2 × 12.9 × 20 × 100 / 6,530 = 7.9 V = 6.6% of 120 V. The informational note recommends ≤3% on the branch circuit — this run is a design problem (upsizing to 10 AWG gives 4.96 V ≈ 4.1%, still over; the run should be split or upsized further). The exam tests that you know the 3%/5% figures are recommendations (informational notes), not enforceable — but a good designer fixes it anyway.

6. Standards/regulations cross-reference

7. Pitfalls, trap patterns, exam strategy

Trap patterns:

1. Table FLC vs. nameplate FLA (Art. 430). Conductors, disconnects, SC/GF protection → table FLC. Overloads → nameplate. The exam will give you both numbers and watch which you reach for.
2. 240.4(B) round-up abuse. Round up to the next standard OCPD only if ≤800 A, the load doesn't exceed conductor ampacity, and no specific article (430, 440) or 240.4(D) overrides. If the question gives you 14 AWG, the answer is 15 A — full stop.
3. Continuous-load 125%. Commercial lighting, EVSE, PV — if it's 3+ hours, multiply by 1.25 before touching any table. Forgetting this is the #1 calculation error.
4. The neutral as CCC. In derating (310.15(B)(3)(a)), the neutral counts when nonlinear loads make it current-carrying. Questions love a "4-wire wye with nonlinear loads" setup.
5. Grounding vs. bonding language. If an answer choice says the earth "clears the fault," it's wrong. The EGC (bonding path) clears the fault.
6. Enforceable vs. informational. Informational notes (voltage drop 3%/5%) are not requirements. Annexes are not enforceable unless referenced — except Annex C via Chapter 9.
7. Motor SC/GF exceptions. 430.52 exceptions let you size UP when the motor won't start — the exam tests the exception order, not just the base percentage.

Exam strategy:

• Time management: ~3 minutes per question on an 80-question/4-hour exam. Calculation questions (motors, fill, VD) get 4–5 minutes; lookup questions get 90 seconds. Flag and move on — open-book exams punish perfectionists.
• Memorize vs. derive: Memorize the architecture (which article, which table, the 125% rules, standard OCPD sizes, the 40% fill rule). Look up the numbers (exact ampacities, box volumes, demand factors). Deriving on the fly wastes time; memorizing tables wastes memory.
• Allowed references: the NEC itself (tabbed), and sometimes a state law booklet. No phones. Practice with your tabs — the exam is a retrieval race.
• Read the exception chain: NEC questions are written so the obvious answer is in the base rule and the correct answer is in Exception 2. Always scan the full article section.

8. Practice problems (answers at end)

1. A commercial occupancy has 40 A of continuous lighting load on a 120/208-V branch circuit. What is the minimum branch-circuit rating and conductor sizing current?
2. A 10-hp, 230-V, 3-phase motor has a nameplate FLA of 27 A. Size (a) the branch-circuit conductors, (b) the inverse-time circuit breaker for SC/GF protection, (c) the overload protection.
3. A box contains five 12 AWG conductors, one 12 AWG ground, two internal cable clamps, and one single-pole switch. What is the minimum box volume in cubic inches?
4. How many 12 AWG THHN conductors are permitted in 3/4-in. EMT? (Use the Annex C approach.)
5. A 50-A OCPD protects a feeder. What is the minimum equipment grounding conductor size (copper)?
6. A feeder serves 150 A of noncontinuous load plus 60 A of continuous load. What is the minimum feeder ampacity?
7. True/false with one-line justification: "The grounding electrode conductor is the conductor that clears ground faults."

Answers:

1. 40 × 1.25 = 50 A minimum → 50-A circuit; conductor ampacity ≥ 50 A (210.19(A), 210.20(A)).
2. Table 430.250 FLC for 10 hp/230 V = 28 A. (a) Conductors: 28 × 1.25 = 35 A → 8 AWG (50 A at 75°C). (b) Breaker: 28 × 2.50 = 70 A → 70 A standard (no round-up needed; if it didn't land on standard, 430.52(C)(1) Ex.1 permits next size up). (c) Overload: nameplate 27 × 1.15 = 31.05 A.
3. Units: 5 (conductors) + 1 (grounds) + 1 (clamps) + 2 (device) = 9 units × 2.25 in³ = 20.25 in³ minimum.
4. Annex C Table C.1: 3/4-in. EMT, 12 AWG THHN → 16 conductors max.
5. Table 250.122: 50-A OCPD → 10 AWG copper EGC.
6. 150 + (60 × 1.25) = 150 + 75 = 225 A minimum feeder ampacity (215.2(A)).
7. False — the equipment grounding conductor (bonding path back to the source) clears ground faults; the grounding electrode conductor connects the system to earth for lightning/surge/voltage stabilization, not fault clearing.

Original ETS reference writing, verified against public sources on 2026-09-30. Thin sourcing is flagged inline. Not legal advice — confirm current editions with the issuing body.