NEC (National Electrical Code)
The model code that sets how electrical wiring and equipment are installed in the US.
Quick Answer
The National Electrical Code (NEC), published as NFPA 70, is the model code for the safe installation of electrical wiring and equipment in the United States. States and local governments adopt it, often with amendments, and the edition in force varies by jurisdiction. Inspectors enforce it, and electrical drawings and bids are built to comply with it.
The Full Picture
The NEC is published by the National Fire Protection Association as NFPA 70 and is revised on a regular cycle through NFPA's standards development process. It is a model code, which means it has no force of law until a state, county or city adopts it. Jurisdictions commonly adopt it with local amendments, so the edition and amendments in force on a given project are determined by the authority having jurisdiction, not by the newest publication.
The NEC covers the installation of electrical conductors, equipment and raceways in buildings and other premises. It organizes requirements by topic, such as general requirements, wiring methods and materials, equipment for general use, and special occupancies and equipment. Related NFPA codes address different parts of life safety, including NFPA 1 (the Fire Code), NFPA 13 (sprinklers), NFPA 72 (fire alarm and signaling) and NFPA 101 (the Life Safety Code), and they cross-reference the NEC where electrical work is involved.
Listing and labeling are tied to the NEC's expectations. OSHA's electrical rules for general industry say that suitability of equipment for an identified purpose may be evidenced by listing or labeling for that purpose, and that listed or labeled equipment must be installed and used according to the instructions included in the listing or labeling. Electrical equipment on a project is therefore commonly specified as listed by a nationally recognized testing laboratory, a topic covered on the UL page.
For estimators and precon teams, the NEC matters through its effects on scope. Requirements for items such as ground-fault protection, arc-fault protection, working clearances, conductor sizing and equipment labeling can change the amount of material and labor an electrical contractor carries, and a change of adopted edition between design and permit can add items. Specifications often name the NEC edition the design is based on, and the electrical subcontractor is expected to comply with the edition the jurisdiction enforces. Questions about which requirement applies go to the engineer of record and the electrical inspector.
Real Examples
Common Misconceptions
People assume: The newest NEC edition applies on every project.
Actually: Only the edition adopted by the jurisdiction applies, and states and cities adopt on different timelines and often with amendments.
People assume: The NEC is a design manual that tells you how to engineer a system.
Actually: It states installation and safety requirements. Design decisions, such as load calculations and system layout, are made by the engineer within those requirements.
Frequently Asked Questions
What is the NEC?
The National Electrical Code is the US model code for the safe installation of electrical wiring and equipment. It is published by NFPA as NFPA 70.
Is the NEC a law?
Not by itself. It becomes law when a state or local government adopts it, usually with some amendments. Enforcement is by the local inspector.
Which NEC edition applies to my project?
The one adopted by the jurisdiction where the project is built, which may differ from the edition named in the specifications. Confirm with the authority having jurisdiction and resolve conflicts with an RFI.
How does the NEC differ from other NFPA codes?
The NEC covers electrical installations. NFPA 13 covers sprinklers, NFPA 72 fire alarm and signaling, and NFPA 101 life safety. They address different systems and reference each other.
How does the NEC affect an electrical estimate?
Its requirements influence material and labor, such as protection devices, clearances and equipment labeling. Estimators confirm the adopted edition and local amendments before pricing.