ICC T17 Journeyman Electrician Exam (2020 NEC)

Key Concepts

Article 90 — Purpose, Scope, Arrangement, Enforcement - Purpose (90.1(A)): 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. - Covered (90.2(A)): public and private premises including buildings, structures, mobile homes, recreational vehicles, and floating buildings; yards, lots, parking lots, carnivals, industrial substations; conductors/equipment connecting to the supply of electricity; shore power to ships and watercraft in marinas and boatyards. - Not Covered (90.2(B)(1)): installations in ships, watercraft other than floating buildings, railway rolling stock, aircraft, or automotive vehicles other than mobile homes and recreational vehicles. Also not covered: mines and self-propelled mobile surface mining machinery (B)(2); railway installations used exclusively for rolling stock operation or signaling (B)(3); communications utility installations under exclusive control (B)(4); and certain electric utility installations (B)(5). - Code Arrangement (90.3): Chapters 1–4 apply generally; Chapters 5, 6, 7 cover…

Key Concepts

Service-entrance conductor sizing. Service-entrance conductors shall have an ampacity not less than the sum of the noncontinuous loads plus 125 percent of continuous loads — 230.42(A)(1).

Service conductor identification. On a 4-wire, delta-connected service where the midpoint of one phase winding is grounded, the conductor with the higher phase voltage to ground must be durably and permanently marked orange, or by other effective means, at each termination or junction point — 230.56.

Dwelling load calculations. - Optional method: general calculated load = 100% of the first 10 kVA + 40% of the remainder of the listed loads — 220.82(B); general lighting/receptacles at 3 VA/ft², and 1500 VA for each 2-wire 20-A small-appliance and each laundry circuit — 220.82(B)(1), (2). - Standard method: 1500 VA per 2-wire small-appliance branch circuit — 220.52(A); the same 1500 VA for each 2-wire laundry circuit — 220.52(B). - Existing dwelling, no added A/C or electric space heating:…

Key Concepts

Feeder minimum ampacity (215.2(A)(1)). Feeder conductors shall have an ampacity not less than the larger of (a) the noncontinuous load plus 125 percent of the continuous load, or (b) the maximum load to be served after adjustment/correction factors per 310.14, and shall comply with 110.14(C). Exception No. 1: if the assembly, including the feeder overcurrent devices, is listed for operation at 100 percent of its rating, the ampacity may be the sum of continuous plus noncontinuous load.

Feeder overcurrent protection (215.3). Where a feeder supplies continuous loads or a combination, the rating of the overcurrent device shall not be less than the noncontinuous load plus 125 percent of the continuous load.

Key Concepts

Conductor identification. An insulated grounded conductor 6 AWG or smaller is identified by a continuous white outer finish, a continuous gray outer finish, or three continuous white or gray stripes on other than green insulation (200.6(A)). On receptacles, plugs, and connectors, the grounded-conductor terminal is identified by metal or a metal coating substantially white or silver in color, or by the word "white" or the letter "W" (200.10(B)(1)). A neutral conductor shall not be used for more than one branch circuit, more than one multiwire branch circuit, or more than one set of ungrounded feeder conductors (200.4(A)).

System color conventions (Ugly's, Common Electrical Distribution Systems). 120/240-V, 1φ, 3-wire: neutral white or gray, line 1 black, line 2 red. 277/480-V, 3φ, 4-wire wye: C phase yellow. 120/208-V wye: 120 V phase-to-neutral, 208 V phase-to-phase.

Key Concepts

Bending radii (inner edge of bend). - Type AC: not less than five times the cable diameter — NEC 320.24. - Types NM and NMC: five times the cable diameter, during or after installation — NEC 334.24. - Types USE and SE: five times the cable diameter — NEC 338.24. - Type MC, interlocked armor or corrugated sheath: seven times the external diameter of the metallic sheath — NEC 330.24(B). - Type MI over 19 mm (¾ in.) but not more than 25 mm (1 in.) external diameter: ten times the external diameter of the sheath — NEC 332.24(2). - Conductors over 1000 V: 8 times the overall diameter (nonshielded); 12 times for shielded or lead-covered — NEC 300.34.

Key Concepts

Luminaires (Article 410) - Bathtub/shower zone: no cord-connected luminaires, chain-, cable-, or cord-suspended luminaires, lighting track, pendants, or ceiling-suspended (paddle) fans within 900 mm (3 ft) horizontally and 2.5 m (8 ft) vertically from the top of the bathtub rim or shower stall threshold — 410.10(D)(1). Luminaires within the tub/shower outside dimension to 2.5 m (8 ft) must be marked suitable for damp (or wet) locations; where subject to shower spray, wet — 410.10(D)(2). - Clothes closet clearances from the nearest point of storage space: 300 mm (12 in.) for surface-mounted incandescent or LED luminaires with completely enclosed light sources — 410.16(C)(1); 150 mm (6 in.) for recessed fluorescent luminaires in the wall or ceiling — 410.16(C)(4). - Recessed luminaires: non-Type IC units must have all recessed parts spaced not less than 13 mm (½ in.) from combustible materials — 410.116(A)(1); thermal insulation shall not be installed above, or within **75 mm…

2020 NEC — Motor controllers, control circuits, and disconnecting means

Key Concepts

Controllers (NEC 430.83) - Controllers generally must have a horsepower rating at the application voltage not lower than the horsepower rating of the motor. - A branch-circuit inverse time circuit breaker rated in amperes is permitted as a controller for all motors — 430.83(A)(2). A molded case switch rated in amperes is likewise permitted — 430.83(A)(3). - For stationary motors rated 2 hp or less and 300 volts or less, a general-use switch is permitted as controller if rated not less than twice the motor full-load current — 430.83(C)(1). - 430.83(C)(2) permits an ac-only general-use snap switch (not ac–dc types) as controller for these small stationary motors, with the motor load limited to 80 percent of the switch rating.

Key Concepts

Motor FLC determination. Use the table values (Table 430.247–430.250), not the nameplate, to size conductors, switches, and branch-circuit short-circuit/ground-fault protection [430.6(A)(1)]. Separate overload protection is based on the nameplate current rating [430.6(A)(2)]. Ugly's "General Motor Rules" (Book Page 41) restates this: "Use full-load current from tables instead of nameplate."

Branch-circuit conductors. Conductors supplying a single continuous-duty motor must have an ampacity of at least 125% of the motor FLC [430.22]. Special multipliers: - Wye-start, delta-run: conductors between controller and motor ≥ 72% of FLC (58% × 1.25) [430.22(C)]. - DC motor from a single-phase, half-wave rectifier: conductors between rectifier output terminals and motor ≥ 190% of FLC [430.22(A)]; input conductors to the rectifier ≥ 125% of rated input current. - Wound-rotor secondary, continuous duty: 125% of full-load secondary current [430.23(A)].

Key Concepts

Hazardous location classification basics - Class I, Division 1 = ignitable gas/vapor normally present under normal conditions — NEC 500.5(B)(1). - Group IIIC combustible dusts (combustible metal dust) are equivalent to Class II, Group E — NEC 506.6(A). - In Zone 20, 21, and 22 locations, locknut-bushing and double-locknut type contacts shall not be depended on for bonding; bonding jumpers with proper fittings or other approved means must be used — NEC 506.25(A).

Commercial garages (Article 511) - Unventilated pit, below-grade work area, or subfloor work area = Class I, Division 1 — Table 511.3(C). - Areas adjacent to classified locations (stock rooms, switchboard rooms, etc.) are unclassified where mechanically ventilated at four or more air changes per hour, designed with positive air pressure, or effectively cut off by walls/partitions — 511.3(E)(1). - Fuel-dispensing units within buildings: Article 514 governs; where mechanical ventilation is provided, the control must be interlocked so the…