Texas - Journeyman Industrial Electrician

Key Concepts

Article 90 - Introduction and Scope

The National Electrical Code (NEC) Article 90 establishes the foundation for all electrical work. Know these critical points:

Purpose and Scope (90.2) - Primary purpose: practical safeguarding of persons and property from electrical hazards - NOT a design specification or instruction manual for untrained persons - Compliance ensures safety but not necessarily efficiency, convenience, or adequacy for future expansion

Installations Covered (90.2(C)) - Public and private premises, buildings, structures, mobile homes, recreational vehicles - Yards, lots, parking lots, carnivals, industrial substations - Conductors and equipment connecting to electrical supply - Electric utility installations (offices, warehouses, garages, machine shops) that are NOT integral parts of generating plants, substations, or control centers

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Service Definition and Scope (Article 230) - Article 230 covers service conductors and equipment for control and protection of services not over 1000V AC or 1500V DC nominal - Service conductors supply a building from the utility and terminate at the service disconnecting means

Number of Services (230.2) - Buildings shall be supplied by only ONE service unless specifically permitted - Additional services allowed for: fire pumps, emergency systems, legally required standby systems, optional standby systems, interconnected power production sources, and enhanced reliability systems - Special occupancies may have additional services by special permission (multiple-occupancy buildings without accessible service equipment space, or buildings large enough to require multiple services) - Additional services permitted when capacity exceeds 2000 amperes at 1000V or less

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Feeder Definition & Scope (Article 215) Feeders are circuit conductors between the service equipment and final branch-circuit overcurrent device. Article 215 covers installation requirements for feeders under 1000V AC or 1500V DC.

Minimum Conductor Sizing (215.2) Feeder conductors must meet BOTH requirements: - 215.2(A)(1): Continuous loads require 125% sizing: noncontinuous load + (125% × continuous load) - 215.2(A)(2): Account for ampacity adjustment/correction factors per 310.14

Critical Exceptions to 125% Rule: - Exception 1: Equipment listed for 100% operation allows 100% sizing - Exception 2: Separately installed pressure connections (110.14(C)(2)) allow 100% sizing - Exception 3: Grounded conductors not connected to overcurrent devices may be sized at 100%

Grounded Conductor Sizing (215.2(B)) Feeder grounded conductor cannot be smaller than the equipment grounding conductor required by 250.122.

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Grounded Conductor Identification Requirements (Article 200) - Scope: Article 200 covers identification of terminals, grounded conductors in premises wiring, and proper identification methods - Insulation Requirements (200.2(A)): Grounded conductors must have insulation rated the same as ungrounded conductors for systems ≤1000V, or ≥600V for solidly grounded neutral systems >1000V - Continuity (200.2(B)): Grounded conductor continuity cannot depend on connection to metal enclosure, raceway, or cable armor

Size-Based Identification Rules (200.6) - 6 AWG or smaller (200.6(A)): Must use continuous white/gray outer finish, three white/gray stripes on non-green insulation, or white/gray with colored tracer threads - 4 AWG or larger (200.6(B)): Same options as smaller conductors, plus field identification with distinctive white/gray marking at terminations that encircles the conductor - MI cable exception: Grounded conductors identified at terminations with distinctive white/gray marking encircling conductor insulation

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Article 300 Scope and Application (300.1) - Applies to ALL wiring installations unless specifically modified by other Chapter 3 articles - Does NOT apply to conductors integral to equipment (motors, controllers, factory-assembled equipment) - Use Table 300.1(C) for metric designator/trade size conversions (e.g., 21 = 3/4", 27 = 1", 41 = 1½")

Voltage and Temperature Limitations (300.2) - Chapter 3 wiring methods are for 1000V AC/1500V DC nominal or less - Higher voltages only where specifically permitted elsewhere in the Code - Temperature limitations per 310.14(A)(3)

Conductor Installation Requirements (300.3) - Single conductors from Table 310.4(1) only permitted as part of recognized Chapter 3 wiring methods - Exception: Separate overhead conductors per 225.6

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Article 404 - Switches (1000V and below) - Covers all switches, switching devices, and circuit breakers used as switches operating at 1000V and below - Does NOT cover wireless control equipment with no circuit conductors connected

Switch Connection Requirements (404.2) - Three-way and four-way switches: All switching must be done ONLY in the ungrounded (hot) conductor - Grounded conductors: Switches or circuit breakers SHALL NOT disconnect the grounded conductor, except when: - All circuit conductors are disconnected simultaneously, OR - Device is arranged so grounded conductor cannot be disconnected until all ungrounded conductors are disconnected first

Grounded Conductor at Switch Locations (404.2(C)) - Required at switch locations controlling lighting loads in: bathrooms, hallways, stairways, habitable rooms, and occupiable spaces - NOT required when: - Conductors enter through raceway large enough for grounded conductor - Snap switches with…

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Article 430 Coverage: Motors, motor circuits, and controllers fall under Article 430 per Table 240.3. This is your primary reference for motor-related overcurrent protection requirements.

Overcurrent Protection Philosophy: Per 240.1 Informational Note No. 1, overcurrent protection opens circuits when current reaches values causing excessive or dangerous temperatures in conductors or insulation. For motors, this involves both overload protection (prolonged overcurrent) and short-circuit/ground-fault protection (sudden high current).

Motor Protection Requirements: Motors require dual protection: - Overload protection: Protects against sustained overcurrent that would damage motor windings - Short-circuit and ground-fault protection: Protects against sudden high currents from faults

Conductor Protection: Per 240.4, motor circuit conductors must be protected according to their ampacities from 310.14, but motor circuits have special rules under Article 430 that modify standard conductor protection requirements.

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Service Disconnecting Means Requirements (Article 230) - Only one service per building permitted unless specific conditions met per 230.2(A)-(D) - Additional services allowed for: fire pumps, emergency systems, legally required standby systems, optional standby systems, and interconnected power production sources - Multiple services permitted when capacity exceeds 2000 amperes at ≤1000V or by special permission (230.2(C))

Service Conductor Installation Rules (230.6-230.10) - Conductors considered "outside building" when: under 2" concrete, in raceway with 2" concrete/brick encasement, in approved vault, in conduit under 18" of earth, or in RMC/IMC through eaves only - Service conductors cannot pass through interior of another building (230.3) - Other circuit conductors prohibited in same raceway as service conductors (230.7) - Vegetation cannot support overhead service conductors (230.10)

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Hazardous Location Classification System (Article 500) The NEC uses a three-class system based on the type of hazardous material present: - Class I: Flammable gases and vapors (gasoline, propane, acetylene) - Class II: Combustible dusts (grain, coal, metal powders) - Class III: Combustible fibers and flyings (cotton, wood shavings, textiles)

Each class has two divisions based on likelihood of hazardous concentrations: - Division 1: Hazardous materials present under normal conditions or frequent maintenance - Division 2: Hazardous materials present only under abnormal conditions or equipment failure

Scope and Coverage (500.1) Article 500 covers electrical equipment in Division 1 and Division 2 locations but specifically excludes: - Zone classification systems (Zone 0, 1, 2 for gases; Zone 20, 21, 22 for dusts) - Explosive/pyrotechnic locations - Pyrophoric material locations - Non-electrical ignition sources (mechanical equipment, hot surfaces)

Key Concepts

Purpose of the NEC (Article 90.2(A)) The National Electrical Code exists for the "practical safeguarding of persons and property from hazards arising from the use of electricity." This is the foundational safety principle that drives all electrical work.

Safety vs. Adequacy (Article 90.2(B)) The NEC provides provisions "considered necessary for safety" but compliance only results in an installation that is "essentially free from hazard" - not necessarily efficient or adequate for future expansion. Safety is the minimum standard, not optimal performance.

Scope of Coverage (Article 90.2(C)) The NEC covers electrical installations in: - Public and private premises (buildings, structures, mobile homes, RVs) - Yards, parking lots, carnivals, industrial substations - Shore power installations at marinas - Utility buildings (offices, warehouses) not integral to generating plants