NFPA 70: National Electrical Code (NEC)
The National Electrical Code is the standard for safe installation of electrical wiring and equipment in the U.S. It’s updated every three years and adopted by states and cities as law.
- Electrical
- Construction
What it covers
- Wiring methods, conductor sizing, overcurrent protection and grounding
- Where GFCI and AFCI protection are required
- Working space around electrical equipment (NEC 110.26). See Panel Clearance.
- Temporary power on construction sites (Article 590)
- Special equipment like solar (Article 690), EV chargers and generators
NEC vs. NFPA 70E vs. OSHA
| Document | Purpose | Enforced by |
|---|---|---|
| NEC (NFPA 70) | How electrical systems are installed | Local and state electrical inspectors |
| NFPA 70E | How workers stay safe working on or near electrical equipment | Voluntary, but used by OSHA and employers as the recognized practice |
| OSHA electrical standards | Workplace electrical safety requirements | OSHA or state plan |
Which edition of the NEC applies depends on what your state or city has adopted. Electrical work generally requires a licensed electrician and a permit and inspection.
How the NEC is organized
- Chapters 1 to 4: general rules, wiring and protection, wiring methods and materials, and equipment. These apply everywhere.
- Chapters 5 to 7: special occupancies (like hazardous locations and health care), special equipment (like solar, EV chargers and signs) and special conditions (like emergency systems and energy storage). These add to or change Chapters 1 to 4.
- Chapter 8: communications systems.
- Chapter 9: tables, such as conduit fill.
Articles you’ll hear about
| Article | Topic |
|---|---|
| 110.26 | Working space around equipment |
| 210.8 | GFCI protection for personnel. See GFCI |
| 210.12 | Arc-fault (AFCI) protection |
| 250 | Grounding and bonding |
| 445 | Generators |
| 590 | Temporary installations. See Temporary Power |
| 625 | Electric vehicle charging |
| 690 and 706 | Solar photovoltaic systems and energy storage |
Listed and labeled equipment
The NEC generally requires equipment to be listed by a recognized testing laboratory (like UL, CSA or ETL) and installed according to its listing. That’s why the mark on cords, tools, panels and fixtures matters. OSHA has a similar requirement for equipment used at work.
For homeowners: some places allow homeowners to do electrical work on their own homes with a permit, and others don’t. Check with your local building department first. See Home Electrical Safety.
Standards & references
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