First published in 1897, the National Electric Code is a standard for the safe installation of electrical wiring and equipment in the United States. It is published by the National Fire Protection Association (NFPA), a private trade association.
Despite the use of the term “national”, it is not a federal law; rather it is typically adopted by states and municipalities in an effort to standardize their enforcement of safe electrical practices. In some cases, the NEC is amended, altered and may even be rejected in lieu of regional regulations as voted on by local governing bodies.
Standards relevant to electric signs are located in Article 600 “Electric Signs and Outline Lighting”. These standards are updated every three years. The current 2017 edition was released in August 2016; 2020 edition will be released in 2019.