Texas - Residential Wireman Electrician

Key Concepts

Purpose of the NEC (Article 90.1–90.2) The NEC exists for the practical safeguarding of persons and property from hazards arising from the use of electricity. It is not a design specification or instruction manual for untrained persons. Compliance produces an installation that is essentially free from hazard — but not necessarily efficient, convenient, or adequate for future expansion.

What the NEC Covers (90.2(C)) - Public and private premises: buildings, structures, mobile homes, recreational vehicles, floating buildings - Yards, lots, parking lots, carnivals, industrial substations - Conductors/equipment connecting to the electricity supply - Electric utility office buildings, warehouses, garages, etc. (when NOT integral to a generating plant, substation, or control center) - Shore power to ships in marinas and boatyards - Vehicle-to-premises bidirectional power export

Texas Residential Wireman Exam — Study Brief

Key Concepts

Service Entrance Fundamentals (Article 230) - Services must be installed in accordance with NEC Article 230. The service drop or lateral connects utility power to the service entrance conductors. - Service entrance conductors must be insulated, except the grounded (neutral) conductor may be bare under specific conditions (230.41). - Only one service is permitted per building/structure, with limited exceptions (230.2). - Service conductors must not pass through the interior of another building (230.3).

Service Equipment (Article 230, Part VI) - Service equipment must be listed and rated for the calculated load (230.66). - The main disconnect must be located at a readily accessible location nearest the point of entrance of service conductors (230.70). It can consist of up to six switches or breakers (the "six-disconnect rule," 230.71). -…

Key Concepts

Article 215 governs feeders not exceeding 1000V AC or 1500V DC nominal (215.1).

Minimum Conductor Ampacity (215.2(A)(1)): Feeder conductors must have an ampacity not less than: - Noncontinuous load + 125% of the continuous load - Exception: If the assembly (including overcurrent devices) is listed for 100% operation, conductors may be sized at 100% of continuous + noncontinuous load. - Grounded conductors not connected to an overcurrent device may always be sized at 100% of combined load (Exception No. 3).

Ampacity Adjustment/Correction (215.2(A)(2)): Conductor size must also account for any adjustment or correction factors per 310.14 (temperature, conduit fill, etc.). Use the larger result from (A)(1) or (A)(2).

Texas Residential Wireman — Study Brief

Key Concepts

Branch Circuit Ratings (210.3 & 210.18) Branch circuits are rated by the ampere rating of the overcurrent protective device. Standard ratings: 15A, 20A, 30A, 40A, and 50A. The rating of the circuit determines the maximum cord-and-plug-connected load and the minimum conductor size allowed.

Conductor Sizing to Circuit Rating (210.19) Conductors must have an ampacity not less than the maximum load to be served, and not less than the branch circuit rating. Minimums: - 15A circuit → 14 AWG - 20A circuit → 12 AWG - 30A circuit → 10 AWG - 40A circuit → 8 AWG - 50A circuit → 6 AWG

Texas Residential Wireman Electrician Exam

Key Concepts

Scope (300.1): Article 300 covers general requirements for all wiring installations unless modified by other Chapter 3 articles. It does not apply to conductors that are integral parts of equipment (motors, controllers, factory-assembled equipment).

Conductors Must Stay Together (300.3(B)): All conductors of the same circuit — including the grounded conductor, equipment grounding conductors, and bonding conductors — must be contained within the same raceway, cable, conduit body, trench, or cord. This prevents inductive heating issues.

Conductors of Different Systems (300.3(C)): - AC and DC circuits rated 1000V AC / 1500V DC or less may share the same raceway or enclosure — but all conductors must be insulated for the highest voltage present. - Circuits over 1000V AC / 1500V DC must not share raceways or enclosures with lower-voltage conductors.

Key Concepts

Scope (404.1): Article 404 covers all switches, switching devices, and circuit breakers used as switches at 1000 volts and below. Does not cover wireless control equipment with no circuit conductors connected.

Switch Connections (404.2): - Three-way and four-way switches must switch only in the ungrounded conductor (404.2(A)) - Grounded conductors cannot be disconnected by a switch or circuit breaker — unless all circuit conductors are disconnected simultaneously, or ungrounded conductors disconnect first (404.2(B)) - Grounded conductor at switch locations (404.2(C)): Required at switch locations controlling lighting loads on grounded general-purpose branch circuits in bathrooms, hallways, stairways, and habitable/occupiable rooms - Exception: Not required where conductors enter via a raceway sized for an added grounded conductor, where snap switches with integral enclosures comply with 300.15(E), where lighting is controlled by automatic means, or where the switch controls a…

Key Concepts

Primary Code Reference: NEC Article 430 (Motors, Motor Circuits, and Controllers) and Article 445 (Generators)

Motors and generators are covered under separate articles but are grouped as a topic on this exam. As noted in NEC Table 240.3, motors and motor circuits defer to Article 430 for overcurrent protection requirements, and generators defer to Article 445.

Key Motor Principles (Article 430):

• Motor circuits require four levels of protection: branch-circuit short-circuit and ground-fault protection, motor overload protection, motor controller, and disconnecting means.
• Overload protection is sized based on the motor's full-load current (FLC) from NEC Tables 430.247–430.250 — not from the nameplate current — for conductor and overcurrent device sizing purposes. However, overload devices protecting the motor windings are based on nameplate current.
• Branch-circuit overcurrent protection (fuses or breakers) for motors is intentionally rated higher…

Texas Residential Wireman Electrician Exam — Study Brief

Key Concepts

Article 312 — Cabinets, Cutout Boxes, and Meter Socket Enclosures

• Scope (312.1): Covers installation and construction of cabinets, cutout boxes, and meter socket enclosures. Does not apply to equipment over 1000 volts unless specifically referenced.

• Damp/Wet Locations (312.2): Surface-type enclosures must prevent moisture from entering. Must be mounted with at least 1/4 in. (6 mm) airspace between the enclosure and the wall or supporting surface. Enclosures in wet locations must be weatherproof. Raceways or cables entering above uninsulated live parts must use fittings listed for wet locations.

• Exception: Nonmetallic enclosures may be installed without the airspace on concrete, masonry, tile, or similar surfaces.

Texas Residential Wireman Electrician Exam

Key Concepts

Hazardous (Classified) Locations — Article 500

Hazardous locations are classified based on what flammable/combustible material is present and how likely it is to be present. Each room, section, or area is evaluated individually (500.5(A)).

Three Classes: - Class I — Flammable gases, flammable liquid–produced vapors, or combustible liquid–produced vapors (e.g., gasoline, propane) - Class II — Combustible dusts (e.g., grain dust, coal dust, metal dust) - Class III — Ignitible fibers/flyings (e.g., cotton, sawdust — NOT suspended in air)

Two Divisions per Class: - Division 1 — Hazardous material is present under normal operating conditions - Division 2 — Hazardous material is present only under abnormal conditions (failure, accident, or faulty operation)

Key Concepts

Article 690 – Solar PV Systems Article 690 (NEC 2023) governs solar PV systems including arrays, inverters, and controllers. It covers both grid-interactive and stand-alone systems with AC or DC output.

DC Voltage Limits (690.7) - PV system DC circuits on or in one- and two-family dwellings: 600V maximum - PV system DC circuits on/attached to other buildings: 1000V maximum - Systems exceeding 1000V must comply with 690.31(G)

Equipment Listing Requirements (690.4(B)) All PV-specific equipment — including electronic power converters, PV modules, charge controllers, DC combiners, and rapid shutdown equipment — must be listed or evaluated for the application with a field label applied.

Qualified Personnel (690.4(C)) Installation of PV equipment, wiring, and interconnections must be performed only by qualified persons.

Prohibited Locations (690.4(E)) PV system equipment and disconnecting means shall not be installed in bathrooms.