INTRODUCTION

70-3 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. 90-5. Mandatory Rules and Explanatory Material. Mandatory rules of this Code are characterized by the use of the word "shall." Explanatory material is in the form of Fine Print Notes (FPN). 90-6. Formal Interpretations. To promote uniformity of interpretation and application of the provisions of this Code, Formal Interpretation procedures have been established. (FPN): These procedures may be found in the "NFPA Regulations Governing Committee Projects." 90-7. Examination of Equipment for Safety. For specific items of equipment and materials referred to in this Code, examinations for safety made under standard conditions will provide a basis for approval where the record is made generally available through promulgation by organizations properly equipped and qualified for experimental testing, inspections of the run of goods at factories, and service-value determination through field inspections. This avoids the necessity for repetition of examinations by different examiners, frequently with inadequate facilities for such work, and the confusion that would result from conflicting reports as to the suitability of devices and materials examined for a given purpose. It is the intent of this Code that factory-installed internal wiring or the construction of equipment need not be inspected at the time of installation of the equipment, except to detect alterations or damage, if the equipment has been listed by a qualified electrical testing laboratory that is recognized as having the facilities described above and that requires suitability for installation in accordance with this Code. (FPN No. 1): See Examination, Identification, Installation, and Use of Equip- I ment, Section 110-3. (FPN No. 2): See definition of "Listed," Article 100. 90-8. Wiring Planning. (a) Future Expansion and Convenience. Plans and specifications that provide ample space in raceways, spare raceways, and additional spaces will allow for future increases in the use of electricity. Distribution centers located in readily accessible locations will provide convenience and safety of operation. See Sections 110-16 and 240-24 for clearances and accessibility. (b) Number of Circuits in Enclosures. It is elsewhere provided in this Code that the number of wires and circuits confined in a single enclosure be varyingly restricted. Limiting the number of circuits in a single enclosure will minimize the effects from a short-circuit or ground fault in one circuit. 90-9. Metric Units of Measurement. For the purpose of this Code, metric units of measurement are in accordance with the modernized metric system known as the International System of Units (SI). Values of measurement in the Code text will be followed by an approximate equivalent value in SI units. Tables will have a footnote for SI conversion units used in the table. 70-4 NATIONAL ELECTRICAL CODE Conduit size, wire size, horsepower designation for motors, and trade sizes that do not reflect actual measurements, e.g., box sizes, will not be assigned dual designation SI units. (FPN): For metric conversion practices, see Standard for Metric Practice, ANSI/ASTM E380-1984. 70-5 Chapter 1. General