Mandatory and permissive rules are defined in which section of the NEC?

Mandatory and permissive rules are defined in NEC Article 90, which serves as the introduction to the National Electrical Code (NEC). This article establishes the purpose of the code, which includes providing a standard for electrical installations that enhance safety. Within this context, mandatory rules are those that must be followed, while permissive rules provide additional options or alternatives. Understanding these distinctions is essential for compliance with the NEC and ensures that electrical systems are installed safely and effectively.

The importance of Article 90 lies in its conceptual framework for interpreting the rest of the code, setting the stage for how to approach both mandatory and permissive requirements throughout subsequent articles.