What Is the NEC?

The National Electrical Code (NEC), also known as NFPA 70, is the benchmark for safe electrical design, installation, and inspection in the United States. Published by the National Fire Protection Association (NFPA) and updated every three years, it covers everything from residential wiring to industrial power systems.

The NEC is not federal law by itself — instead, states and municipalities adopt it (sometimes with local amendments) as part of their building codes. Most jurisdictions are currently enforcing the 2020 or 2023 edition.

How the NEC Is Organized

The NEC is divided into Articles, each covering a specific topic:

  • Articles 90–110 — General provisions, definitions, and examination of equipment
  • Articles 200–285 — Wiring and protection (grounding, overcurrent, surge protection)
  • Articles 300–399 — Wiring methods and materials (conduit, cable types)
  • Articles 400–490 — Equipment for general use (switchboards, motors, appliances)
  • Articles 500–590 — Special occupancies (hazardous locations, healthcare facilities)
  • Articles 600–695 — Special equipment (signs, EV chargers, solar PV systems)
  • Articles 700–770 — Special conditions (emergency systems, fire alarms, optical fiber)
  • Articles 800–840 — Communications systems (telephone, network, coax)

Key Articles Every Electrician Should Know

Article 110 — Requirements for Electrical Installations covers working space clearances around equipment, examination and approval of equipment, and connection of terminals. The 36-inch (or more) working clearance in front of electrical panels (Article 110.26) is one of the most cited code sections during inspections.

Article 210 — Branch Circuits defines circuit ratings, required outlets, and GFCI/AFCI protection rules. Most residential kitchens and bathrooms now require GFCI protection on all receptacles.

Article 220 — Branch-Circuit, Feeder, and Service Calculations is essential for sizing conductors and panels. Engineers use the demand factors and calculation methods here to determine the total load for a building.

Article 250 — Grounding and Bonding is one of the most complex articles in the NEC. It specifies how systems must be grounded, the size of grounding conductors, and how to bond metal parts to prevent shock hazards.

Common NEC Violations to Avoid

  • Insufficient working clearance in front of electrical panels
  • Missing GFCI protection in wet locations (bathrooms, kitchens, outdoors)
  • Oversized circuit breakers (overcurrent protection that doesn't match conductor ampacity)
  • Improper wire splices — all splices must be in accessible junction boxes
  • Using the wrong wire type for the location (e.g., NM cable where conduit is required)

Using the NEC on Your iPhone

The NEC is over 900 pages long — searching it during an inspection or design session is slow. Apps like NEC Engineer and NEC Illustrated make it fast to look up code requirements, see illustrated diagrams, and run quick load calculations right from your phone.