Texas Journeyman Electrician NEC Knowledge Portion

Key Concepts

Purpose and scope. "The purpose of this Code is the practical safeguarding of persons and property from hazards arising from the use of electricity. This Code is not intended as a design specification or an instruction manual for untrained persons" (90.2(A)). Article 90 itself "covers use and application, arrangement, and enforcement of this Code," plus mandatory/permissive/nonmandatory text, equipment examination, wiring planning, and measurements (90.1).

Adequacy. Compliance and proper maintenance "result in an installation that is essentially free from hazard but not necessarily efficient, convenient, or adequate for good service or future expansion of electrical use" (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, and industrial substations; conductors and equipment that connect to the supply of electricity; utility-used buildings (office buildings, warehouses, garages,…

Key Concepts

Service conductor clearances (230.24) - 230.24(B) minimum vertical clearances from final grade for overhead service conductors not over 1000 volts: - 3.0 m (10 ft) — at the service entrance, at the lowest point of the drip loop, and above areas/sidewalks accessible only to pedestrians, only for conductors supported on and cabled together with a grounded bare messenger where the voltage does not exceed 150 volts to ground. - 3.7 m (12 ft) — over residential property and driveways, and commercial areas not subject to truck traffic, where voltage does not exceed 300 volts to ground. - 4.5 m (15 ft) — the same areas where voltage exceeds 300 volts to ground. - 5.5 m (18 ft) — public streets, alleys, roads, parking areas subject to truck traffic, driveways on other than residential property, and cultivated, grazing,…

Key Concepts

• Minimum feeder conductor ampacity (125% rule). 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 (NEC 215.4(A)(1); 2023 text at 215.2(A)(1)). 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 conductors may be sized at the sum of the continuous plus noncontinuous load.
• Feeder OCPD rating. Where a feeder supplies continuous loads or any combination of continuous and noncontinuous loads, the rating of the overcurrent device shall not be less than the noncontinuous load plus 125 percent of the continuous load (NEC 215.3; NEC 2026, Section 215.5). Same 100%-rated-assembly exception applies.
• **Common…

Key Concepts

Branch-circuit ratings and permissible loads - Ratings for other than individual branch circuits: 10, 15, 20, 30, 40, and 50 amperes (NEC 210.18). Branch circuits rated 10 amperes shall not supply receptacle outlets (210.18 Exception No. 2; Table 210.24(1), note 2). - 10-ampere multiple-outlet circuits are limited to lighting outlets or dwelling unit exhaust fans on bathroom and laundry room lighting circuits (210.23(A)). - On 15- and 20-ampere circuits: any one cord-and-plug-connected utilization equipment not fastened in place ≤ 80 percent of the circuit rating (210.23(B)(1)); total utilization equipment fastened in place (other than luminaires) ≤ 50 percent where lighting units or portable equipment are also supplied (210.23(B)(2)). - 30-ampere circuits may supply fixed lighting units with heavy-duty lampholders in other than dwelling units (210.23(C)); lampholders on circuits over 20 amperes must be heavy-duty (210.21(A), Table 210.24(1)).…

Key Concepts

General limitations - Wiring methods in Chapter 3 are used for 1000 volts ac, 1500 volts dc, nominal, or less where not specifically limited elsewhere in Chapter 3 (300.2(A)). - All conductors of the same circuit, the grounded conductor, and all equipment grounding conductors shall be contained within the same raceway, conduit body, auxiliary gutter, cable tray, cablebus assembly, trench, cable, or cord (300.3(B)). - AC conductors in ferrous metal enclosures/raceways: all phase conductors, the grounded conductor, and all EGCs shall be grouped together to avoid induction heating (300.20(A)). - Multiwire branch circuits: continuity of the grounded conductor shall not depend on device connections such as lampholders or receptacles (300.15(B)).

Key Concepts

Switches and wiring devices - An AC/DC general-use snap switch may control tungsten-filament lamp loads not exceeding its ampere rating at the applied voltage only if the switch is T-rated — 406.46(B)(3). - General-use dimmer switches and electronic control switches (timing switches, occupancy sensors) shall control only permanently connected loads, such as incandescent luminaires, unless listed for other loads — 406.46(D). - Devices that directly terminate aluminum conductors must be marked CO/ALR; devices not so marked shall not directly terminate aluminum — 406.10(1) and 406.10(2). - Screwless push-in terminals: permitted only on branch circuits not greater than 15 amperes and with 14 AWG solid copper only — 406.10(3). - Reconditioned knife switches, butt-contact switches, and bolted pressure contact switches are permitted — 404.3(A). Reconditioned molded-case switches (and lighting, dimmer, and electronics control switches that are not wiring…

Based on NEC Articles 240, 250, 430, 440, and 445

Key Concepts

Determining the current to use. For general motor applications, the values in Table 430.247, Table 430.248, Table 430.249, and Table 430.250 are used instead of the nameplate current to determine ampacity of conductors, current ratings of switches, and current ratings of branch-circuit short-circuit and ground-fault protection [430.6(A)(1)]. Single-phase AC motor full-load currents come from Table 430.248. By contrast, the motor nameplate current rating is used for separate motor overload protection [430.6(A)(2), 430.32(A)(1)].

Branch-circuit conductors — single motor. Conductors supplying a single motor in a continuous duty application shall have an ampacity of not less than 125 percent of the motor full-load current rating as determined by 430.6(A)(1) [430.22, 430.22(A)].

NEC Knowledge Portion

Key Concepts

Service disconnecting means - Each service disconnect shall simultaneously disconnect all ungrounded service conductors that it controls from the premises wiring system — 230.74. - Each service shall have only one service disconnect unless the requirements of 230.71(B) are met — 230.71. The two to six disconnects, if permitted in 230.71, shall be grouped, and each disconnect shall be marked to indicate the load served — 230.72(A). - Service disconnects shall be marked "SERVICE DISCONNECT"; enclosures for one- and two-family dwellings shall be marked "EMERGENCY DISCONNECT," on the outside front of the enclosure, red background with white text, letters at least 13 mm (½ in.) high — 230.70(B)(1) and 230.70(B)(2). - For one- and two-family dwellings, service disconnects shall be installed in a readily accessible outdoor location on the dwelling unit or within sight…

Key Concepts

Classification of locations (500.5) - Class I, Division 1 — ignitible concentrations of flammable gases, flammable liquid–produced vapors, or combustible liquid–produced vapors can exist under normal operating conditions [500.5(B)(1)]. - Class I, Division 2 — those liquids, gases, or vapors are normally confined within closed containers or closed systems, escaping only on accidental rupture or breakdown [500.5(B)(2)]. - Metal combustible fibers/flyings locations are classified Class II, Division 1, Group E — not Class III [500.5(D)(1)(b)]. Nonmetal combustible fibers/flyings and ignitible fibers/flyings fall under Class III, Division 1. - Ammonia refrigerant machinery rooms may be classified unclassified where mechanical ventilation runs continuously or is initiated by a detection system at a concentration not exceeding 150 ppm [500.5(A)(2)].

Key Concepts

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

Source-circuit voltage calculation (690.7(A)). Sum the series-connected module rated open-circuit voltages, corrected for the lowest expected ambient temperature by (1) the module's listed temperature coefficients, (2) Table 690.7(A) for crystalline/multicrystalline silicon modules, or (3) a stamped design by a licensed…