NEC Article 100 — The Definitions Every NJ Electrician Should Memorize

NEC Article 100 is the dictionary — every term used elsewhere in the code is defined here. Most electricians skip it, then get tripped up by interpretation disputes with AHJs. The definitions below come up most often in NJ residential reviews:

Branch Circuit: the circuit conductors between the FINAL overcurrent device protecting the circuit and the outlet(s). Translation: from the breaker in the panel out to the receptacle, switch, or hardwired load.

Feeder: the conductors between the service equipment and the FINAL branch-circuit overcurrent device. Translation: the conductors between the main panel and a sub-panel.

Service: the conductors and equipment delivering electric energy from the utility supply to the wiring system of the premises served. The "service" stops at the main breaker; everything beyond is feeder or branch.

Dwelling Unit: a single unit providing complete and independent living facilities — permanent provisions for living, sleeping, cooking, and sanitation. Two-family dwellings have two dwelling units; an in-law suite with a kitchenette and bath qualifies as a separate dwelling unit and triggers separate service-rating rules.

Readily Accessible: capable of being reached quickly without climbing over or removing obstacles or resorting to portable ladders. The main breaker must be readily accessible; a panel behind a workbench or above a finished ceiling fails this test.

Qualified Person: someone who has skills and knowledge related to the construction and operation of the electrical equipment AND has received safety training to recognize and avoid the hazards involved. Used throughout NEC 110 — only qualified persons can work on energized equipment.

In Sight From: visible AND not more than 50 ft distant from each other. The disconnect for an HVAC condenser must be "in sight from" the condenser per NEC 440.14 — meaning visible and within 50 ft.

Bonded: connected to establish electrical continuity and conductivity. Different from "grounded." Bonding ties metal parts together so they share a potential; grounding connects to earth.

When an inspector challenges your install, more often than not the disagreement comes down to one of these definitions. Read Article 100 once, keep a bookmark.