ICC R16 Master Electrician Exam (2023 NEC)
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Questions per topic, out of 100Topics
General Knowledge
2023 NEC
Key Concepts
NEC Article 90 — scope, arrangement, enforcement - Purpose is "the practical safeguarding of persons and property from hazards arising from the use of electricity." The Code "is not intended as a design specification or an instruction manual for untrained persons" — 90.2(A) / NEC 90.1(A). - Not covered: installations in ships, watercraft other than floating buildings, railway rolling stock, aircraft, or automotive vehicles other than mobile homes and recreational vehicles — 90.2(D). - The Code is divided into the introduction and nine chapters. Chapters 1, 2, 3, and 4 apply generally; Chapters 5, 6, and 7 apply to special occupancies, special equipment, or other special conditions and may supplement or modify requirements; Chapter 8 (communications systems) is not subject to Chapters 1 through 7 except where specifically referenced; Chapter 9 consists of tables — 90.3. - The authority having jurisdiction for enforcement has responsibility for making interpretations, deciding on…
Services and Service Equipment
Key Concepts
Number and sizing of services. A building shall be supplied by only one service unless permitted for special conditions (fire pumps, emergency systems), special occupancies (by special permission), capacity requirements, or different characteristics (230.2). A one-family dwelling service disconnecting means shall be rated not less than 100 amperes, 3-wire (230.79(C)). Overhead and underground service conductors shall not be smaller than 8 AWG copper or 6 AWG aluminum (230.23(B), 230.31(B)). Service-entrance conductors supplying continuous loads shall be sized at the noncontinuous load plus 125 percent of continuous load (230.42(A)(1)).
Clearances. Overhead service conductors need 2.6 m (8 ft 6 in.) above a roof (230.24(A)); Exception No. 2 reduces this to 900 mm (3 ft) where voltage between conductors does not exceed 300 and roof slope is 4 in 12 or greater. From final grade (230.24(B)): 3.7 m (12 ft) over residential property and driveways ≤300 V to ground; 4.5 m (15 ft) where…
Feeders
2023 NEC — Feeders
Key Concepts
Minimum feeder conductor ampacity — 215.2(A)(1). Where a feeder supplies continuous loads or any combination of continuous and noncontinuous loads, the minimum feeder conductor size shall have an ampacity not less than the noncontinuous load plus 125 percent of the continuous load. Exception No. 1: if the assembly, including the overcurrent devices protecting the feeder(s), is listed for operation at 100 percent of its rating, the conductor ampacity may be not less than the sum of the continuous plus noncontinuous load. Exception No. 3: grounded conductors not connected to an overcurrent device may be sized at 100 percent of both loads.
Adjustment/correction — 215.2(A)(2). Feeder conductors must have an ampacity not less than the larger of 215.2(A)(1) or (A)(2), and comply with 110.14(C). (A)(2) requires ampacity not less than the maximum load served after any adjustment or correction factors per 310.14.
Branch Circuits and Conductors
Key Concepts
Conductors (Article 310) - Minimum size for voltage ratings up to 2000 volts: 14 AWG copper or 12 AWG aluminum/copper-clad aluminum (310.3(A)). - Conductors 8 AWG and larger installed in raceways shall be stranded (310.3(C)). - Conductors may be paralleled only in sizes 1/0 AWG and larger (310.10(G)(1)). - The AWG size or circular mil area must be repeated on the surface at intervals not exceeding 610 mm (24 in.); other markings at intervals not exceeding 1.0 m (40 in.) (310.8(B)(1)). - Insulation: THHN = 90°C, dry and damp only; THWN is permitted in wet locations (Table 310.4(1); 310.10(C)). Type UF = 60°C (140°F), ampacity limited per 340.80. - Table 310.16 ampacities are based on a 30°C (86°F) ambient (310.16), with correction factors from Table 310.15(B)(1)(1). - Rooftop: raceways/cables in direct sunlight less than 19 mm (¾ in.) above the roof get a 33°C (60°F) adder; Type XHHW-2 is excepted (310.15(B)(2) and…
Wiring Methods and Materials
Key Concepts
Protection against physical damage (Art. 300) - Bored holes in wood members: edge of hole not less than 32 mm (1¼ in.) from the edge of the member; otherwise protect with a steel plate — 300.4(A)(1). - Notches in wood members: steel plate at least 1.6 mm (1/16 in.) thick — 300.4(A)(2). - Parallel to framing members: nearest outside surface not less than 32 mm (1¼ in.) from the edge; otherwise steel plate or sleeve — 300.4(D). - Under metal-corrugated sheet roof decking: not less than 38 mm (1½ in.) from the lowest surface of the decking to the top of the cable, raceway, or box — 300.4(E). - Indoor wet locations / frequently washed walls: at least 6 mm (¼ in.) airspace behind exposed wiring systems — 300.6(D).
Equipment and Devices
Key Concepts
Fixture wires (Article 402) - Fixture wires shall not be smaller than 18 AWG (402.6). - Ampacity comes from Table 402.5: 18 AWG = 6 A, 16 AWG = 8 A, 14 AWG = 17 A, 12 AWG = 23 A, 10 AWG = 28 A. - Table 402.3 gives types and maximum operating temperatures — e.g., RFHH-2 = 90°C (194°F), TFN/TFFN = 90°C, TF/TFF = 60°C, KF-1/KF-2 = 200°C. - Uses permitted: in luminaires and similar enclosed/protected equipment, or to connect luminaires to branch-circuit conductors (402.10); not as branch-circuit conductors (402.12).
Switches (Article 404) - Operating handle in its highest position: not more than 2.0 m (6 ft 7 in.) above the floor or working platform, and operable from a readily accessible place (404.8(A)). - AC general-use snap switch may control tungsten-filament lamp loads not exceeding the switch ampere rating at 120 volts (404.14(A)); an AC-DC general-use snap switch may control…
Control Devices
2023 NEC — Articles 404, 409, and 430
Key Concepts
Switches (Art. 404) - An ac general-use snap switch may control motor loads not exceeding 80 percent of the switch's ampere rating at its rated voltage; it also controls resistive/inductive loads up to the switch rating [404.14(A)]. - An ac–dc general-use snap switch may control inductive loads not exceeding 50 percent of its ampere rating; switches rated in horsepower are suitable for motor loads within their rating [404.14(B)]. - Switches shall be listed and marked with their ratings [404.14]; marking includes current, voltage, and, if horsepower rated, the maximum rating [404.20(A)].
Disconnecting means (Art. 430 Part IX) - For motor circuits 1000 V, nominal, or less, the disconnecting means must have a current rating not less than 115 percent of the motor full-load current rating [430.110(A)]. - An individual disconnecting means is required for each motor controller, located **in sight from the motor controller…
Motors and Generators
2023 NEC — Article 430 (Motors, Motor Circuits, and Controllers), Article 445 (Generators), Article 455, Article 460, and Ugly's Electrical References
Key Concepts
Which current to use. For general motor applications, use the table values (Table 430.247, 430.248, 430.249, 430.250) instead of nameplate current to determine conductor ampacity, switch ratings, and branch-circuit short-circuit/ground-fault (BCSCGF) protection ratings [430.6(A)(1)]. Nameplate current is used for separate motor overload protection [430.6(A)(2)]. Ugly's "General Motor Rules" (Page 41) repeats: use full-load current from tables instead of nameplate.
Branch-circuit conductors — single motor. Not less than 125% of motor FLC as determined by 430.6(A)(1) [430.22, 430.22(A)].
Special conductor percentages under 430.22: - DC motor, rectified single-phase half-wave: 190%; full-wave: 150% [430.22(A)] - Wye-start, delta-run, controller-to-motor: 72% (58% × 1.25) [430.22(C)] - Part-winding, controller-to-motor: 62.5% (50% × 1.25) [430.22(D)] - Other than continuous duty: Table 430.22(E) — intermittent duty, 30- & 60-minute rated = 90% of nameplate - 18 AWG copper…
Special Occupancies, Equipment, and Conditions
Key Concepts
Hazardous location classification - Class I, Division 1 = ignitable gas/vapor normally present (500.5(B)(1)). Locations where ignitible fibers/flyings are handled, manufactured, or used are Class III, Division 1 — cotton and other textile mills (500.5(D)(1)(b)). - Group A = acetylene; Group B = MESG ≤ 0.45 mm or MIC ratio ≤ 0.40 (hydrogen); Group C = MESG > 0.45 mm and ≤ 0.75 mm, or MIC > 0.40 and ≤ 0.80 (ethylene); Group D = MESG > 0.75 mm or MIC > 0.80 (propane) — 500.6(A)(1)–(4). - Class II dusts: Group E = combustible metal dusts including aluminum, magnesium and their commercial alloys; Group F = carbonaceous dusts over 8% volatiles; Group G = flour, grain, wood, plastic, chemicals (500.6(B)(1)–(3)). Zone system: Group IIIC = combustible metal dust including metal fibers/flyings (506.6). - Seals: within 450 mm (18 in.) of the explosionproof enclosure, with only threaded couplings or explosionproof fittings between (501.15(A)(1));…