Study Guides
Free in-depth guides covering electrical theory, NEC code articles, HVAC fundamentals, and exam concepts — with fully worked examples.
Plain-English breakdowns of the NEC articles tested most on licensing exams, with worked examples.
A deep, worked-example-driven guide to Article 250 — the grounding electrode system, GEC and EGC sizing logic, bonding jumpers, separately derived systems, and why ground rods alone never clear a fault.
A deep guide to NEC Article 210 branch circuits — circuit classifications, the 80% continuous-load rule with worked examples, multiwire branch circuits, dwelling outlet spacing, and dedicated appliance circuits.
A step-by-step walkthrough of NEC Article 220 dwelling and commercial load calculations, with six fully worked examples covering small, mid-size, and large homes plus a simplified commercial building.
A deep, plain-English walkthrough of NEC Article 240 — how fuses and breakers actually interrupt current, why conductors (not loads) get protected, standard device sizes, tap rules, panel schedules, and selective coordination, with worked examples for the exam.
A deep, plain-English breakdown of how GFCI and AFCI devices actually work inside, where each type of protection is required, and how to troubleshoot nuisance trips — with worked examples for the exam and the field.
A clear, from-first-principles explanation of how electrical service works — overhead vs underground, the six-disconnect rule, grounding at the service, and worked examples sizing both a residential and a commercial service.
A deep, plain-English walkthrough of NEC Article 300 — the general wiring method rules that govern every conduit run and cable installation, plus how EMT, IMC, RMC, PVC, NM, MC, AC, and UF actually compare in the field.
A deep, plain-English walkthrough of NEC Article 430 motor circuit rules — why motors need special sizing math, and how to size branch circuit conductors, short-circuit/ground-fault protection, and overload protection with fully worked examples.
A plain-English walkthrough of NEC Article 408 -- panelboard vs. switchboard vs. switchgear, overcurrent protection of panelboards, the position-2/lighting-and-appliance-panel rules, working space, and five worked examples.
A plain-English walkthrough of NEC hazardous location rules -- the Class/Division system, the newer Zone system, why standard equipment can't be used in these areas, common protection techniques, and five realistic scenarios covering fuel dispensing, spray booths, and grain handling.
A plain-English walkthrough of NEC Article 215 feeder rules -- how a feeder differs from a branch circuit and a service conductor, the 125% continuous-load sizing rule, feeder overcurrent protection, voltage drop considerations, and five worked examples.
A deep, plain-English walkthrough of how transformers work -- turns ratio, the inverse primary/secondary current relationship -- plus NEC Article 450 overcurrent protection rules, overcurrent protection located on the primary side vs. both sides, and five fully worked examples.
A plain-English walkthrough of NEC Article 110 -- approval and listing of equipment, the three working-space conditions and their required depths, headroom and width requirements, dedicated equipment space, and five worked examples.
A plain-English walkthrough of NEC Article 410 -- clothes closet luminaire clearance rules, recessed fixture thermal protection and IC vs. non-IC ratings, damp/wet location listing, outlet box support, and five worked examples.
A plain-English walkthrough of NEC Article 680 -- why water and electricity around pools demand extra protection, equipotential bonding, GFCI requirements, receptacle and overhead-line setback distances, and five realistic scenarios.
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