Idaho Journeyman Electrician Exam

Key Concepts

Purpose and limits of the Code. The purpose of the Code is "the practical safeguarding of persons and property from hazards arising from the use of electricity," and the Code "is not intended as a design specification or an instruction manual for untrained persons" (verified questions cite NEC 90.1(A); the reference text prints this under 90.2(A) Practical Safeguarding). Compliance plus proper maintenance yields an installation "essentially free from hazard but not necessarily efficient, convenient, or adequate for good service or future expansion" — 90.2(B).

Installations covered — 90.2(C). 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; utility office buildings, warehouses, garages, machine shops and recreational buildings not integral to a generating plant, substation or control center; shore power to ships and watercraft in marinas and boatyards; power export from vehicles.

Key Concepts

• Protection through/along framing (300.4). Bored holes must keep the hole edge at least 32 mm (1 1/4 in.) from the edges of the wood member; where that cannot be maintained, protect with a steel plate — NEC 300.4(A)(1). Cables/raceways in notches must be protected by a steel plate at least 1.6 mm (1/16 in.) thick — 300.4(A)(2). Runs parallel to framing members need the same 32 mm (1 1/4 in.) clearance, or steel plate/sleeve protection — 300.4(D). Raceways containing 4 AWG or larger insulated conductors entering a cabinet, box, enclosure, or raceway require an identified fitting providing a smoothly rounded insulating surface (or the other listed options) — 300.4(G).
• Underground (300.5). Minimum cover per Table 300.5(A): direct burial 600 mm (24 in.); RMC/IMC 150 mm (6 in.) in "all locations not specified"; residential 120 V GFCI-protected branch circuits with max 20 A OCPD 300 mm (12 in.); one- and two-family dwelling driveways 450 mm (18 in.); under streets/highways/alleys/parking lots 600 mm (24 in.) for all methods. Cables emerging from grade get enclosures/raceways to at least 2.5 m (8 ft) above finished grade — 300.5(D)(1). Service conductors buried 450 mm (18 in.) or more and not…

Key Concepts

Conductors (Article 310) - Minimum size for voltage ratings up to and including 2000 volts: 14 AWG copper or 12 AWG aluminum/copper-clad aluminum, except as permitted elsewhere — 310.3(A). - Solid aluminum 8, 10, and 12 AWG and stranded aluminum 8 AWG–1000 kcmil marked RHH, RHW, XHHW, THHN, THWN, etc., must be AA-8000 series alloy — 310.3(B). - Conductors 8 AWG and larger in raceways shall be stranded, unless permitted or required to be solid — 310.3(C). - Parallel conductors permitted only in 1/0 AWG and larger — 310.10(G)(1). - Type THHN: 90°C (194°F) in dry and damp locations — Table 310.4(1). - AWG size marking repeated at intervals not exceeding 610 mm (24 in.); other markings not exceeding 1.0 m (40 in.) — 310.8(B)(1). - Ampacity tables 310.16 and 310.17 are based on a 30°C (86°F) ambient — 310.16, 310.17; correct with Table 310.15(B)(1)(1). - Rooftop raceways/cables in direct sunlight less than 19 mm (¾ in.) above the roof: add 33°C (60°F) to outdoor temperature — 310.15(B)(2). - Grounding/bonding conductors are not counted for adjustment factors — 310.15(F). - Where more than one ampacity applies to a circuit length, use the lowest value (exception: lower-ampacity portion…

Key Concepts

Fixture wires (Article 402) - Fixture wires shall not be smaller than 18 AWG (402.6). - Ampacity comes from Table 402.5; maximum operating temperature from Table 402.3 (e.g., Type RFHH-2 and Type TFN are both 90°C (194°F)). - Fixture wires are permitted in luminaires and for connecting luminaires to branch-circuit conductors, but not as branch-circuit conductors except where permitted elsewhere (402.10, 402.12).

Flexible cords (Article 400) - Cords shall not be used as a substitute for the fixed wiring of a structure (400.12(1)). - Cord not smaller than 18 AWG is considered protected against overcurrent in accordance with 240.5 (400.16). - Ampacity: Table 400.5(A)(1) (Column A = three current-carrying conductors); derating for more than three current-carrying conductors: Table 400.5(A)(3).

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 (404.8(A)). - Switches/CBs shall not disconnect the grounded conductor except where all conductors are disconnected simultaneously or the grounded conductor cannot be disconnected until all ungrounded conductors are (404.2(B)). - Grounded circuit conductor must be installed where switches control lighting loads on a grounded general-purpose branch circuit serving bathrooms, hallways, stairways, and habitable…

Key Concepts

Hazardous location classification (Art. 500) - Class I locations are those in which flammable gases, flammable liquid–produced vapors, or combustible liquid–produced vapors are or may be present in air in quantities sufficient to produce explosive or ignitible mixtures (500.5(B)). - Areas designated hazardous (classified) or determined to be unclassified must be documented on an area classification drawing available to the AHJ (500.4).

Class I sealing and wiring (Art. 501) - Conduit seals entering an explosionproof enclosure shall be installed within 450 mm (18 in.) of the enclosure or as required by the enclosure marking; only threaded couplings or explosionproof fittings (unions, reducers, elbows, capped elbows) not larger than the conduit trade size are permitted between the sealing fitting and the enclosure (501.15(A)(1)). - Two or more explosionproof enclosures connected by nipples/conduit not more than 900 mm (36 in.) long: one seal is sufficient if located not more than 450 mm (18 in.) from either enclosure (501.15(A)(3)). - Division 1 and Division 2 boundary seals may be on either side, within 3.05 m (10 ft) of the boundary (501.15(A)(4), 501.15(B)(2)). - Optical fiber cables (OFNP, OFCP, OFNR, OFCR, OFNG, OFCG, OFN, OFC) may be installed in raceways in…

Key Concepts

Cranes and hoists (Article 610) - Conductors external to motors and controls: not smaller than 16 AWG; 18 AWG permitted in multiconductor cord for control circuits not exceeding 7 amperes; not smaller than 20 AWG for electronic circuits — 610.14(C). - Wiring method: raceway, Type AC (with insulated EGC), MC, or MI cable, unless otherwise permitted; contact conductors are not required to be enclosed in raceways — 610.11 and 610.11(A). Short exposed lengths at resistors and collectors also exempt — 610.11(B). - Runway contact conductor supports: insulating supports at intervals not exceeding 6.0 m (20 ft), separation not less than 150 mm (6 in.) (75 mm/3 in. for monorail hoists); intervals may increase to 12 m (40 ft) with proportionally increased separation — 610.21(C). - Bridge contact conductors: at least 65 mm (2½ in.) apart; where the span exceeds 25 m (80 ft), insulating saddles at intervals not exceeding 15 m (50 ft) — 610.21(D). Rigid conductors: supports not more than 80 times the vertical dimension of the conductor, never more than 4.5 m (15 ft) — 610.21(E). - Disconnect rating: not less than 50 percent of the combined short-time ampere rating of the motors, or **75…

Key Concepts

PV maximum voltage (690.7) - PV system dc circuits shall not exceed 1000 volts within or originating from arrays located on or attached to buildings, and for PV system dc circuits inside buildings. - PV system dc circuits shall not exceed 600 volts on or in one- and two-family dwellings. - Circuits exceeding 1000 volts shall comply with 690.31(G). - Maximum voltage is the highest voltage between any two conductors, or any conductor and ground [690.7]. - A permanent, readily visible label showing the highest maximum dc voltage must be provided at the dc PV disconnecting means, the PV electronic power conversion equipment, or associated distribution equipment [690.7(D)].

PV arc-fault protection (690.11) — Systems with PV dc circuits operating at 80 volts dc or greater between any two conductors must be protected by a listed PV arc-fault circuit interrupter (or equivalent listed components). Exception: metal-clad cable, metal raceway, enclosed metal cable tray, or underground circuits, if not installed in or on buildings, or located in/on detached structures whose sole purpose is to support or contain PV equipment.