ICC T16 Master Electrician Exam (2020 NEC)

Key Concepts

Article 90 — Scope, structure, enforcement - 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: underground mine installations, railway installations used exclusively for rolling stock operation/signaling, communications utility installations, and certain utility-controlled installations (90.2(B)(2)–(5)). - Covered (90.2(A)): public and private premises including buildings, structures, mobile homes, recreational vehicles, floating buildings; yards, lots, parking lots, carnivals, industrial substations; shore power installations in marinas. - Enforcement (90.4): "The authority having jurisdiction for enforcement of the Code has the responsibility for making interpretations of the rules, for deciding on the approval of equipment and materials, and for granting the special permission contemplated in a number of the rules." By special permission the AHJ may waive requirements or permit alternative methods. - Arrangement (90.3): Chapters 1–4 apply generally; Chapters 5, 6, 7 supplement or modify Chapters…

Key Concepts

Service load calculations (Article 220). - Optional dwelling method: the general calculated load is 100% of the first 10 kVA plus 40% of the remainder — NEC 220.82(B). Heating/AC uses the largest of six selections, including 100% of heat pump compressor + 65% of supplemental electric heating (220.82(C)(3)), 65% for fewer than four separately controlled electric space-heating units (220.82(C)(4)), and 40% for four or more (220.82(C)(5)). - Existing dwelling: where no additional AC or space heating is added, first 8 kVA at 100%, remainder at 40% — 220.83(A). Where additional AC/heat is added, AC and central electric space heating are at 100% — 220.83(B). - Existing installations by actual maximum demand: permitted only under 220.87 conditions, including that maximum demand at 125% plus the new load does not exceed the feeder ampacity or service rating; demand data must cover a 1-year period, and the method is not permitted where renewable energy systems…

Key Concepts

Feeder conductor sizing (215.2). Feeder conductors must 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 applying adjustment or correction factors per 310.14 — and must comply with 110.14(C) [215.2(A)(1)]. The feeder grounded conductor shall not be smaller than required by 250.122 [215.2(A)(2)]. Where feeder conductors carry the total load supplied by service conductors with an ampacity of 55 amperes or less, the feeder ampacity shall not be less than that of the service conductors [215.2(A)(3)].

Overcurrent protection (215.3). Feeders are protected per Part I of Article 240; with continuous loads the OCPD rating shall not be less than the noncontinuous load plus 125 percent of the continuous load. Exception: assemblies listed for operation at 100 percent of rating may be sized at continuous plus noncontinuous load.

2020 NEC

Key Concepts

Conductor identification & color coding - Insulated grounded conductor 6 AWG or smaller: continuous white outer finish, continuous gray outer finish, or three continuous white or gray stripes on other than green insulation — 200.6(A). 4 AWG or larger may also be identified by distinctive white or gray marking at terminations — 200.6(B). - Grounded terminal on receptacles, plugs, connectors: metal or metal coating substantially white or silver, or the word "white" or letter "W" adjacent to the terminal — 200.10(B)(1). - 120/240-V, single-phase, three-wire: neutral white or gray; line 1 black, line 2 red. 277/480-V, three-phase, four-wire wye: C phase yellow. 120/208-V wye: 120 V phase-to-neutral, 208 V between phases — Ugly's, Common Electrical Distribution Systems.

Based on the 2020 NEC (NFPA 70)

Key Concepts

Bending radii (inner edge of bend). - Type AC cable: not less than five times the diameter of the cable — 320.24 - Types NM and NMC: not less than five times the diameter, during or after installation — 334.24 - Types USE and SE: not less than five times the diameter, during or after installation — 338.24 - Type UF: not less than five times the diameter — 340.24 - Type MC with interlocked armor or corrugated sheath: seven times the external diameter of the metallic sheath — 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 metallic sheath — 332.24(2) - Over 1000 V: 8 times overall diameter nonshielded; 12 times shielded or lead-covered — 300.34

Key Concepts

Luminaire locations. In bathtub/shower areas, no parts of cord-connected luminaires, chain-, cable-, or cord-suspended luminaires, lighting track, pendants, or ceiling-suspended (paddle) fans may be within a zone 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 in wet locations must be marked "Suitable for Wet Locations"; damp locations, "Suitable for Wet Locations" or "Suitable for Damp Locations" (410.10(A)).

Clothes closets. Surface-mounted incandescent or LED luminaires with completely enclosed light sources need 300 mm (12 in.) clearance to the nearest point of storage space (410.16(C)(1)). Recessed fluorescent luminaires in wall or ceiling need 150 mm (6 in.) (410.16(C)(4)).

2020 NEC — Article 430 Parts VI, VII and IX; Articles 404, 409 and 725

Key Concepts

Controllers (NEC 430.83) - Controllers generally must have a horsepower rating at the application voltage not lower than the motor's horsepower rating. - 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 may serve as controller if its ampere rating is 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 such small stationary motors, with the motor load limited to 80 percent of the switch rating.

Key Concepts

• Use table FLC, not nameplate, for circuit sizing. Values in Table 430.247, Table 430.248, Table 430.249 and Table 430.250 are used to determine conductor ampacity, switch ratings and branch-circuit short-circuit/ground-fault protection instead of nameplate current (430.6(A)(1)). Separate overload protection, however, is based on the motor nameplate current rating (430.6(A)(2)). Ugly's "General Motor Rules" states the same (Ugly's page 41).
• Single motor branch-circuit conductors: not less than 125 percent of motor FLC (430.22).
• Special conductor percentages: wye-start, delta-run conductors between controller and motor — 72 percent of FLC (58% × 1.25) (430.22(C)); DC motor on a single-phase, half-wave rectifier — conductors between rectifier field wiring output terminals and motor at 190 percent of FLC (430.22(A)); wound-rotor secondary, continuous duty — 125 percent of full-load secondary current (430.23(A)).
• Feeder conductors: 125 percent of the highest-rated motor's FLC plus the sum of the FLCs of all other motors in the group,…

Key Concepts

Hazardous location classification (Art. 500/505/506) - Class III = easily ignitible fibers/flyings handled, manufactured, or used, but not likely in suspension in ignitible quantities — 500.5(D). - Group E = combustible metal dusts (aluminum, magnesium, commercial alloys); Group F = carbonaceous; Group G = flour, grain, wood, plastic; Group A = acetylene — 500.6(B)(1). Zone Group IIIC (combustible metal dust) is equivalent to Class II, Group E — 506.6(A). - NPT-threaded entries into explosionproof equipment: at least five threads fully engaged (exception: 4½ for listed equipment with factory-threaded NPT entries) — 500.8(E)(1). - Div. 1 seals: within 450 mm (18 in.) of the enclosure or as marked — 501.15(A)(1). Conductor/optical fiber tube fill in a seal ≤ 25 percent of an RMC of the same trade size — 501.15(C)(6). - Div. 1 motors may be totally enclosed with positive-pressure ventilation only if arranged to prevent energizing until purged with **at least 10…