A 27-chapter interactive guide to electrical power systems — Ohm's law and circuit theory fundamentals, utility distribution from the substation to the service drop, service entrance and riser diagrams for residential, multi-family, commercial, and office facilities, panel and load distribution with panel schedule and load calculation forms, grounding/bonding/ground-fault protection, and motor circuits (NEC 430/620), low-voltage Class 1/2/3 circuits (NEC 725), and solar/backup generator power. Every reference drawing gets its own full-size slide so schedules, tables, and labels stay legible.
Chapters 1–4 build the foundation: Ohm's law, Kirchhoff's laws, and AC fundamentals, then the physical path power takes from a utility substation through a pole-mounted transformer to a building. Chapters 5–12 cover service entrance and riser diagrams — overhead service one-line drawings, clearance requirements, single- and three-phase service and distribution configurations, and full riser diagrams for commercial, multi-family, and office-complex buildings. Chapters 13–16 cover panel and load distribution — residential subpanels, panelboard schedule and load calculation forms, a power/lighting floor plan, and the conductor ampacity and sizing flowchart. Chapters 17–23 cover grounding, bonding, and ground-fault protection — the grounding electrode system, grounding vs. bonding, intersystem bonding, the ground-fault return path, GFCI detection circuits, and lightning protection. Chapters 24–27 cover motor circuits under NEC Articles 430 and 620, low-voltage Class 1/2/3 circuits under NEC Article 725, and a combined solar/backup generator power system.
Use the Prev / Next buttons at the bottom, or press the arrow keys on your keyboard. Click the ☰ menu button in the top-right to open the table of contents and jump to any of the 27 chapters. Each chapter's text explanation is immediately followed by its own dedicated, full-size figure slide, so every diagram, riser, schedule, and table can be read at full legibility before moving to the next chapter.
Electrical engineers and designers who want a structured visual reference spanning fundamentals through full system design; electrical contractors and licensed electricians reviewing riser diagrams, panel schedules, and grounding requirements; and PE/FE exam candidates and apprentices building foundational knowledge of power distribution, load calculations, motor protection, and grounding/bonding concepts referenced throughout the NEC.
Ohm's law states V = I × R (voltage equals current times resistance). Combined with the power equation P = V × I, this produces twelve interchangeable formulas for solving voltage, current, resistance, or power from any two known values — the basis for every ampacity, voltage-drop, and load calculation covered later in the guide.
Read a riser diagram top to bottom, following the same three-layer pattern at every level: service equipment (or a distribution panel) feeds a feeder, which feeds the next panelboard, which fans out into individually protected branch circuits. A larger building simply nests more panelboard-to-panelboard feeder hops between the service equipment and the branch circuits than a single dwelling does.
A panel schedule records every circuit number, description, breaker size, and number of poles in that panel, matching the circuit directory NEC 408.4 requires posted at the panel itself. A load calculation worksheet totals general lighting, small-appliance and laundry circuits, kitchen equipment, HVAC, and other fixed appliances into one total connected load in VA, following the method in NEC Article 220.
Grounding connects the electrical system and equipment to the earth itself, mainly to stabilize system voltage and drain surges like lightning strikes. Bonding connects all the normally non-current-carrying metal parts — panel enclosures, equipment frames — into one low-impedance network, which is what actually provides the fault-current path needed to trip a breaker per NEC 250.4(A)(5).
Full-load current (FLA) comes from NEC tables, not the nameplate. Branch-circuit conductors are generally sized at 1.25× FLA per NEC 430.22, overload protection is sized to protect the motor itself per 430.32, and branch-circuit short-circuit/ground-fault protection is selected from NEC Table 430.52's percentage-of-FLA ratings — deliberately larger than the overload device so it rides through the motor's starting inrush without nuisance tripping. NEC Article 620 layers additional requirements on top of Article 430 specifically for elevator motor circuits.
Disclaimer: This guide summarizes general electrical engineering concepts and illustrative reference drawings for educational purposes only. All projects, facilities, and equipment depicted are illustrative examples, not as-built or permit-ready documents. Always consult a licensed electrical engineer or electrician and the applicable edition of the National Electrical Code (NEC) and local jurisdiction requirements for actual project design and installation.