ICC T18 Residential Electrician Exam (2020 NEC)

Key Concepts

NEC Purpose, Scope, and Arrangement (Article 90) - Purpose: "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" (90.1(A)). - 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." Mobile homes, recreational vehicles, and floating buildings are covered (90.2(A)(1)). - Enforcement/interpretations (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 specific requirements or permit alternative methods. - Code arrangement (90.3): Chapters 1–4 apply generally; Chapters 5, 6, and 7 apply to special occupancies, special equipment, or other special conditions and may supplement or modify Chapters 1 through 7. Chapter 8 (communications systems) is not subject to Chapters 1–7 except where specifically referenced. Chapter 9 consists of tables applicable as referenced. Informative annexes are informational only. - Mandatory vs. permissive (90.5):…

2020 NEC

Key Concepts

Service load calculations (standard method, Article 220 Part III) - Dwelling unit minimum unit load is 3 volt-amperes/ft² for general lighting and general-use receptacles (220.14(J)); floor area excludes open porches, garages, and unused/unfinished spaces not adaptable for future use (220.11). - Each 2-wire small-appliance branch circuit is calculated at 1500 volt-amperes (220.52(A)); each 2-wire laundry branch circuit is not less than 1500 volt-amperes (220.52(B)). - Table 220.42 demand factors for dwelling units: first 3000 VA at 100%, 3001–120,000 VA at 35%, remainder over 120,000 VA at 25%. - Four or more fastened-in-place appliances rated ½ hp or 500 watts or greater, served by the same feeder/service in a dwelling, may take a 75% demand factor — but not cooking equipment, clothes dryers, space heating, or air-conditioning equipment (220.53). - Fixed electric space heating is calculated at 100% of connected load (220.51). Noncoincident loads: only the largest load(s) used at one time need be counted (220.60).

Key Concepts

Feeder minimum size and ampacity (Article 215) - Feeder conductors must have ampacity not less than the larger of 215.2(A)(1)(a) or (b). Where a feeder supplies continuous loads or any combination of continuous and noncontinuous loads, the minimum size shall have an ampacity not less than the noncontinuous load plus 125 percent of the continuous load — 215.2(A)(1)(a). - The feeder overcurrent device rating likewise shall not be less than the noncontinuous load plus 125 percent of the continuous load — 215.3. - Up to three sets of 3-wire feeders or two sets of 4-wire or 5-wire feeders may use a common neutral — 215.4(A). In a metal raceway or enclosure, all conductors of feeders sharing a common neutral must be in the same raceway or enclosure — 215.4(B). - Feeder grounded conductor: not smaller than required by 250.122 — 215.2(A)(2). - GFPE: each feeder disconnect rated 1000 amperes or more on solidly grounded wye systems of more than 150 volts to ground but not exceeding 600 volts phase-to-phase requires ground-fault protection of equipment per 230.95 — 215.10. - Identification: grounded conductor per 200.6 — 215.12(A); equipment grounding conductor per 250.119 — 215.12(B); ungrounded conductors per 215.12(C)(1)…

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)); 4 AWG or larger may also be identified by distinctive white or gray marking at terminations (200.6(B)). Receptacle/plug terminals for the grounded conductor are 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)). In a 120/240-volt, single-phase, three-wire system, line one is black, line two is red, and the grounded neutral is white or gray (Ugly's, Common Electrical Distribution Systems). Neutral conductors shall not serve more than one branch circuit, more than one multiwire branch circuit, or more than one set of ungrounded feeder conductors (200.4(A)).

Branch circuits. Two or more 20-ampere small-appliance branch circuits are required in dwellings (210.11(C)(1)). Ranges rated 8¾ kW or more require a minimum 40-ampere branch circuit (210.19(A)(3)). Branch-circuit ratings other than individual circuits are 15, 20, 30, 40, and 50 amperes (210.18). OCPD rating ≥ noncontinuous load + 125% of continuous load (210.20(A)). One cord-and-plug utilization equipment not fastened in place…

Key Concepts

Cable wiring methods - Types NM and NMC: the radius of the curve of the inner edge of any bend, during or after installation, shall not be less than five times the diameter of the cable (NEC 334.24). The same five-times rule applies to Types USE and SE (NEC 338.24) and to Type UF (340.24). - Type NM must be supported and secured at intervals not exceeding 1.4 m (4½ ft) and within 300 mm (12 in.) of every cable entry into enclosures (NEC 334.30). - Type SE used for interior wiring must comply with the installation requirements of Part II of Article 334, excluding 334.80 (338.10(B)(4)(a)). For Type SE with ungrounded conductors 10 AWG and smaller in contact with thermal insulation, ampacity is based on the 60°C (140°F) rating (338.10(B)(4)(a)(3)). - Type UF ampacity is that of 60°C (140°F) conductors in accordance with 310.14 (340.80). Type UF shall not be used as service-entrance cable (340.12(1)); it is permitted underground/direct burial, in wet, dry, or corrosive locations, and as nonheating leads for heating cables. - Cables/raceways through bored holes in wood members: the edge of the hole must be not less than 32 mm (1¼ in.) from…

Key Concepts

Luminaires in specific locations (Art. 410, Part II) - Bathtub/shower zone: no cord-connected luminaires, chain-, cable-, or cord-suspended luminaires, lighting track, pendants, or ceiling-suspended (paddle) fans 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; the zone includes the space directly over the tub or stall — 410.10(D)(1). Luminaires within the actual outside dimension of the tub/shower up to 2.5 m (8 ft) must be marked suitable for damp (or wet) locations — 410.10(D)(2). - Wet-location luminaires must be marked "Suitable for Wet Locations"; damp-location luminaires marked for wet or damp locations — 410.10(A). - Luminaires 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 luminaire — 410.10(F). - Combustible material may not be subjected to temperatures over 90°C (194°F) — 410.11.

Key Concepts

Pools — receptacles and clearances (Art. 680, Part I & II) - At least one 125-volt, 15- or 20-ampere receptacle on a general-purpose branch circuit shall be not less than 1.83 m (6 ft) from and not more than 6.0 m (20 ft) from the inside wall of a permanently installed pool, and not more than 2.0 m (6 ft 6 in.) above the floor [680.22(A)(1)]. Circulation/sanitation receptacles and "other" receptacles are also at least 1.83 m (6 ft) [680.22(A)(2), (A)(3)]. - All 15- and 20-ampere, single-phase, 125-volt receptacles within 6.0 m (20 ft) of the inside walls of a pool require Class A GFCI protection [680.22(A)(4)]. - Storable pool, storable spa, or storable hot tub: receptacles shall not be located less than 1.83 m (6 ft) from the inside walls [680.34]. - Outdoor luminaires, lighting outlets, and ceiling-suspended (paddle) fans above the pool or within 1.5 m (5 ft) horizontally must be not less than 3.7 m (12 ft) above maximum water level [680.22(B)(1)]. Indoors with GFCI protection, totally enclosed luminaires and identified paddle fans may be at 2.3 m (7 ft 6 in.) [680.22(B)(2)]. Between 1.5 m (5 ft) and 3.0 m (10 ft) horizontally,…