90.4 Enforcement. This Code is intended to be suitable for mandatory application by governmental bodies that exercise legal jurisdiction over electrical installations, including signaling and communications systems, and for use by insurance inspectors. The authority having jurisdiction for enforcement of the Code has the responsibility for making interpretations of the rules, for deciding on the approval of equipment and materials, and for granting the special permission contemplated in a number of the rules.
Some localities do not adopt the NEC, but even in those localities, installations that comply with the current Code are prima facie evidence that the electrical installation is safe.
Section 90.4 advises that all materials and equipment used under the requirements of the Code are subject to the approval of the authority having jurisdiction. The text of 90.7, 110.2, and 110.3, along with the definitions of the terms approved, identified (as applied to equipment), labeled, and listed, is intended to provide a basis for the authority having jurisdiction to make the judgments that fall within that particular area of responsibility.
The phrase ?including signaling and communication systems? emphasizes that, indeed, these systems are also subject to enforcement.
By special permission, the authority having jurisdiction may waive specific requirements in this Code or permit alternative methods where it is assured that equivalent objectives can be achieved by establishing and maintaining effective safety.
The authority having jurisdiction is responsible for interpreting the specific rules of the Code. This paragraph empowers the authority having jurisdiction, using special permission (written consent), to permit alternative methods where specific rules are not established in the Code. For example, the authority having jurisdiction may waive specific requirements in industrial occupancies, research and testing laboratories, and other occupancies where the specific type of installation is not covered in the Code.
This Code may require new products, constructions, or materials that may not yet be available at the time the Code is adopted. In such event, the authority having jurisdiction may permit the use of the products, constructions, or materials that comply with the most recent previous edition of this Code adopted by the jurisdiction.
The last paragraph of 90.4 permits the authority having jurisdiction to waive a new Code requirement during the interim period between acceptance of a new edition of the NEC and the availability of a new product, construction, or material redesigned to comply with the increased safety required by the latest edition. Establishing a viable future effective date in each section of the NEC is difficult because the time needed to change existing products and standards, as well as to develop new materials and test methods, usually is not known at the time the latest edition of the Code is adopted.
