Texas - Journeyman Electrician - Calculations Portion

Key Concepts

Branch Circuit Scope (NEC 210.1) - Article 210 covers branch circuits not over 1000 volts AC or 1500 volts DC, nominal - For circuits over these voltages, refer to Article 235, Part II

Multiwire Branch Circuits (NEC 210.4) - A multiwire circuit can be considered as multiple circuits - All conductors must originate from the same equipment containing the overcurrent protective device - Critical requirement: Must have simultaneous disconnect of all ungrounded conductors at the point of origin - Line-to-neutral loads only, with specific exceptions for single equipment or simultaneous opening devices

Conductor Identification Requirements (NEC 210.5) - Grounded conductors: Follow NEC 200.6 - Equipment grounding conductors: Follow NEC 250.119 - Multiple voltage systems: Each ungrounded conductor must be identified by phase/line and voltage system at all termination, connection, and splice points - DC systems over 60V:…

Key Concepts

Load Calculation Framework (Article 220) - Article 220 provides the foundation for all service load calculations - Part I: General requirements for calculation methods - Part III and IV: Specific methods for feeder and service loads - Use nominal system voltages: 120, 120/240, 208Y/120, 240, 480Y/277, 480, 600Y/347, and 600V (220.5(A))

Service Load Calculation Components - Start with branch-circuit loads calculated per 220.14 (other loads - all occupancies) - Apply specific calculation methods from Table 220.3 for specialized equipment - Round calculations to nearest whole ampere; drop fractions less than 0.5 (220.5(B)) - Floor area calculations use outside building dimensions (220.5(C))

Key Concepts

Feeder Definition & Scope (NEC 215.1) - Feeders are circuits that distribute power from service equipment to branch circuit panelboards - Article 215 covers feeders not over 1000V AC or 1500V DC - Must comply with installation, overcurrent protection, and conductor sizing requirements

Minimum Conductor Sizing (NEC 215.2(A)) - Feeder conductors must meet the larger of two requirements: 1. Continuous/Noncontinuous Load Rule: Ampacity ≥ noncontinuous load + 125% of continuous load 2. Adjustment/Correction Factors: Ampacity after applying derating per NEC 310.14

Key Exceptions for 100% Rated Equipment (NEC 215.2(A) Exception 1) - If assembly and overcurrent devices are listed for 100% operation: Ampacity = continuous load + noncontinuous load (no 125% multiplier needed)

Key Concepts

Grounded Conductor Requirements (Article 200) - Grounded conductors must have insulation rated for any ungrounded conductor of the same circuit (systems ≤1000V) per 200.2(A) - Continuity cannot depend on connection to metal enclosure, raceway, or cable armor per 200.2(B) - Must be electrically connected to supply system grounded conductor to ensure continuous grounded system per 200.3

Grounded Conductor Identification (200.6) - 6 AWG or smaller: White outer finish, gray outer finish, or three continuous white/gray stripes on non-green insulation - 4 AWG or larger: Same options as smaller conductors, OR distinctive white/gray marking at terminations that encircles the conductor insulation - Flexible cords: White or gray outer finish or methods per 400.22 - Different voltage systems in same enclosure: Each system's grounded conductor must be uniquely identified and documented per 200.6(D)

Key Concepts

Article 300 Scope and Application - Article 300 covers general requirements for ALL wiring methods and materials unless specifically modified by other Chapter 3 articles - Requirements do NOT apply to conductors that are integral parts of equipment (motors, controllers, factory-assembled equipment) - Voltage limitations: Chapter 3 methods used for ≤1000V AC, ≤1500V DC unless specifically permitted elsewhere

Metric Designators and Trade Sizes (Table 300.1(C)) - Conduit sizing uses both metric designators and trade sizes for identification - Key sizes: 12mm = 3/8", 16mm = 1/2", 21mm = 3/4", 27mm = 1", 35mm = 1¼", 41mm = 1½", 53mm = 2" - These are identification purposes only, not actual dimensions

Key Concepts

Scope and Application (404.1) - Article 404 covers all switches, switching devices, and circuit breakers used as switches operating at 1000 volts and below - Does NOT cover wireless control equipment to which circuit conductors are not connected

Critical Switch Connection Rules (404.2) - Three-way and four-way switches: All switching must be done only in the ungrounded (hot) conductor - Grounded conductor protection: Switches or circuit breakers SHALL NOT disconnect the grounded conductor of a circuit - Exception: Permitted only when all circuit conductors are disconnected simultaneously, or the grounded conductor cannot be disconnected until all ungrounded conductors are disconnected first

Key Concepts

Motor Overcurrent Protection (Article 430) Motor circuits require multiple types of overcurrent protection, each serving different purposes: - Branch-circuit short-circuit and ground-fault protection - protects against short circuits and ground faults - Motor overload protection - protects the motor from overheating due to overload conditions - Motor branch-circuit conductor protection - ensures conductors are properly protected

Motor Circuit Components (Article 430) Every motor circuit consists of specific components that must be properly sized: - Motor branch-circuit conductors - Motor controller (starter) - Motor overload protection device - Branch-circuit short-circuit and ground-fault protective device - Disconnecting means

Key Concepts

Service Disconnect Requirements (Article 230) - Each service must have a readily accessible disconnecting means per NEC 230.70 - Service disconnecting means must be located at a readily accessible location either outside the building or inside nearest the point of conductor entry - Maximum of six service disconnects per service per 230.71(A) - Service disconnects must be permanently marked to identify the load served per 230.70(B)

Disconnect Location and Accessibility - "Readily accessible" means capable of being reached quickly without climbing over/removing obstacles or using portable ladders - Service equipment must be installed in accordance with 110.26 working space requirements - Emergency disconnects required for one- and two-family dwellings per 230.85 - must be outside building or inside nearest point of entrance

Key Concepts

Hazardous (Classified) Locations Classifications (Article 500)

The foundation of hazardous location electrical work is understanding the three main classification systems:

• Class I: Flammable gases, flammable liquid-produced vapors, or combustible liquid-produced vapors
• Class II: Combustible dusts
• Class III: Combustible fibers/flyings or ignitible fibers/flyings

Each class has two divisions: - Division 1: Hazardous substances are present under normal operating conditions - Division 2: Hazardous substances are present only under abnormal conditions

Documentation Requirements (500.4)

All hazardous location classifications must be documented on area classification drawings. This documentation must be available to the AHJ and authorized personnel who design, install, inspect, maintain, or operate electrical equipment. Without proper documentation, installations cannot be approved.

Individual Area Consideration (500.5(A)(1))

Key Concepts

Solar PV System Scope and Applications (Article 690) - Article 690 covers solar PV systems including array circuits, inverters, and controllers - Systems can be interactive with other power sources, stand-alone, or both - PV systems may have AC or DC output for utilization - Multiple PV systems are permitted on a single building/structure

Maximum Voltage Requirements (690.7) - Building-mounted systems: DC circuits cannot exceed 1000V within or originating from arrays on buildings - Residential systems: DC circuits cannot exceed 600V on one- and two-family dwellings - Maximum voltage determines conductor, equipment, and working space requirements - Use highest voltage between any two conductors or any conductor and ground