Which phrase indicates a mandatory requirement in NEC terminology?

In NEC (National Electrical Code) terminology, "Shall" and "Shall Not" establish mandatory requirements that must be followed in electrical installations and systems. The use of "Shall" indicates a provision that is compulsory, meaning that it must be adhered to without exception. This language conveys a clear expectation that the stated action or condition is required for compliance with the code.

When applied in the context of electrical safety standards, "Shall" and "Shall Not" ensure that there are no ambiguities in what is required of electricians and contractors. This clarity is critical for maintaining safety, consistency, and compliance in electrical practices. The other options, such as "Should be," "May not," and "Should consider," imply recommendations or suggest best practices rather than impose mandatory requirements. These terms do not carry the same weight as "Shall" and "Shall Not," which are explicitly designed to enforce compliance within the regulatory framework of the NEC.