Texas Journeyman Electrician NEC Knowledge Portion

Key Concepts

Article 90 - Introduction is the foundation of the NEC and establishes critical principles for electrical installations.

Purpose and Scope (90.1-90.2): The NEC's primary purpose is the practical safeguarding of persons and property from electrical hazards (90.2(A)). This is NOT a design manual or instruction guide for untrained persons. The Code provides minimum safety requirements - compliance results in installations "essentially free from hazard but not necessarily efficient, convenient, or adequate for good service" (90.2(B)).

Installations Covered (90.2(C)): The NEC covers electrical installations in: - Public and private premises (buildings, mobile homes, RVs, floating buildings) - Yards, parking lots, carnivals, industrial substations - Shore power installations for ships/watercraft - Electric utility buildings (offices, warehouses) that aren't integral to generation plants

Key Concepts

Service Load Calculations (Article 220) are fundamental to sizing electrical services properly. Article 220 provides comprehensive requirements for calculating branch-circuit, feeder, and service loads across different occupancy types.

Voltage Standards (220.5(A)) - Unless otherwise specified, use these nominal system voltages for calculations: 120V, 120/240V, 208Y/120V, 240V, 347V, 480Y/277V, 480V, 600Y/347V, and 600V.

Calculation Precision (220.5(B)) - Round calculations to the nearest whole ampere, dropping decimal fractions smaller than 0.5.

Floor Area Calculations (220.5(C)) - Calculate from outside dimensions of the building. For dwelling units, exclude open porches and unfinished areas not adaptable for future habitable use.

Key Concepts

Article 215 scope and application: Covers feeders not over 1000V AC or 1500V DC nominal. This article is your primary reference for feeder installation, sizing, and protection requirements.

Feeder conductor sizing (215.2(A)): Conductors must have ampacity not less than the larger of: 1. Continuous/noncontinuous load calculation: Noncontinuous load + 125% of continuous load 2. After applying adjustment/correction factors per 310.14

Key exceptions to 125% rule (215.2(A)(1)): - Exception 1: Equipment listed for 100% operation allows sizing at 100% of total load - Exception 2: Separately installed pressure connections allow 100% sizing - Exception 3: Grounded conductors not connected to overcurrent devices can be sized at 100%

Overcurrent protection (215.3): Must protect against overcurrent per Article 240. Rating must be at least noncontinuous load + 125% continuous load, with same 100% exception as conductor sizing.

Key Concepts

Grounded Conductor Requirements (Article 200.1-200.3) - Grounded conductors must have insulation rated for any ungrounded conductor of the same circuit (≤1000V) or rated ≥600V for systems >1000V - Continuity cannot depend on connection to metal enclosure, raceway, or cable armor (200.2(B)) - Must be electrically connected to supply system grounded conductor for continuous grounded system (200.3)

Neutral Conductor Installation (200.4) - Neutrals cannot be used for more than one branch circuit, multiwire branch circuit, or feeder set unless specifically permitted - Multiple neutral conductors in same enclosure must be identified/grouped to correspond with ungrounded conductors using wire markers, cable ties, or similar means

Grounded Conductor Identification by Size:

Key Concepts

Article 300 Scope and Application (300.1) - Article 300 applies to ALL wiring installations unless specifically modified by other Chapter 3 articles - Does NOT apply to conductors that are integral parts of equipment (motors, controllers, factory-assembled equipment) - Metric designators and trade sizes follow Table 300.1(C) - know that these are for identification only, not actual dimensions

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)

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

Key Concepts

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

Critical Switch Connection Requirements (404.2) - Three-way and four-way switches: All switching must be done only in the ungrounded conductor. When using metal raceways or metal-armored cables, follow 300.20(A) requirements - Grounded conductor rule: Switches/circuit breakers SHALL NOT disconnect the grounded conductor unless ALL conductors disconnect simultaneously or the grounded conductor cannot be disconnected until all ungrounded conductors disconnect first - Lighting switch locations (404.2(C)): Grounded conductors must be installed at switch locations controlling lighting in bathrooms, hallways, stairways, and habitable rooms. Exception allows up to 5 electronic switches per branch circuit and 25 per feeder

Key Concepts

Article 430 - Motors, Motor Circuits, and Controllers is the primary code section governing motor installations. While the provided reference material focuses on overcurrent protection (Article 240), motors have special overcurrent protection requirements that differ from standard branch circuits.

Overcurrent Protection Hierarchy: Motors require multiple levels of protection: - Branch circuit short-circuit and ground-fault protection (at the panel) - Motor overload protection (typically at or in the motor) - Motor circuit conductor protection

Table 240.3 Reference: Motors, motor circuits, and controllers are specifically covered under Article 430, not the general overcurrent protection rules of Article 240. This is a critical distinction - motor circuits have specialized protection requirements.

Key Concepts

Service Disconnecting Means Requirements (Article 230) - Services must have a readily accessible disconnecting means located at a readily accessible location either outside the building or inside nearest the point of entrance (230.70) - Maximum of six switches or circuit breakers permitted as the service disconnecting means (230.71) - Each service disconnect must be permanently marked to identify the load served (230.66)

Service Equipment Location and Access - Service equipment must be installed in accordance with 110.26 for working space requirements - Service disconnects must be grouped together and cannot be located in bathrooms (230.70) - Emergency disconnects may be required by local jurisdiction at readily accessible outdoor locations

Key Concepts

Article 500 Scope and Coverage: Article 500 covers area classification and general requirements for electrical equipment where fire or explosion hazards exist due to flammable gases, vapors, dusts, or fibers. Specifically covers Class I, II, and III, Divisions 1 and 2 locations.

What's NOT Covered by Article 500: - Zone 0, 1, 2 hazardous locations (covered by other articles) - Zone 20, 21, 22 hazardous locations - Explosive/pyrotechnic locations - Pyrophoric materials - Non-electrical ignition sources (pumps, engines, etc.)

Classification System: - Class I: Flammable gases and vapors from flammable/combustible liquids - Class II: Combustible dusts - Class III: Combustible fibers and flyings - Division 1: Hazardous materials present under normal conditions - Division 2: Hazardous materials present only under abnormal conditions

Key Concepts

Solar PV System Scope (Article 690): - Covers solar photovoltaic systems including array circuits, inverters, and controllers - Applies to interactive systems (grid-tied) and stand-alone systems - Does NOT cover large-scale PV electric supply stations (covered by Article 691) - Systems may have AC or DC output for utilization

Equipment Requirements (690.4(B)): - ALL PV system equipment must be listed or evaluated for the application - Required equipment includes: electronic power converters, motor generators, PV modules, AC modules, DC combiners, PV rapid shutdown equipment (PVRSE), PV hazard control equipment (PVHCE), and charge controllers - Equipment must have field label applied