NFPA
National Electrical Code (NFPA 70)
Published by National Fire Protection Association (NFPA) · written for United States
nfpa.org · checked 2026-09-23
Citing it here is not conformity with it, and this site holds no copy of its text.
- 28Calculators cite it
- 36Sections cited
- 4Editions listed
What it governs
The electrical installation code for the United States: how conductors are sized and protected, how circuits are grounded and bonded, and what has to be in place before a wiring installation can be energised. It governs the installation rather than the equipment — a device's own listing and construction sit with the testing laboratory that listed it, and the NEC says how a listed device may be used.
It is the most amended document on this list. Adoption is state by state and often city by city, several editions behind the newest, so a clause number that is right in one jurisdiction can be wrong in the next county.
What it is not is a design manual: it sets minimum safety requirements, and a circuit that satisfies it may still be a poor circuit for the load it serves — voltage drop across a long run being the usual example, since the NEC treats it as a recommendation rather than a requirement. Anything upstream of the service point belongs to the utility and is outside its scope entirely, which is why a question about the supply transformer cannot be answered from this document.
Obtained from National Fire Protection Association. What NFPA publishes
Editions
Published: 2023, 2020, 2017, 2014. A new edition every three years.
Adoption is not verified for your jurisdiction. A model document binds only where an authority adopted it, usually some editions behind and amended locally. Citing a clause is not conformance. No part of the text is reproduced here.