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90.1 Scope
This article outlines the use and application, arrangement, and enforcement of this Code. It also explains the expression of mandatory, permissive, and nonmandatory text, provides guidance on equipment examination and wiring planning, and specifies the use and expression of measurements.
90.2 Use and Application
(A) Practical Safeguarding
The primary purpose of this Code is to ensure the practical safeguarding of persons and property from hazards arising from the use of electricity. It is not intended as a design specification or an instruction manual for untrained persons.
(B) Adequacy
This Code includes provisions deemed necessary for safety. Compliance and proper maintenance result in installations that are essentially free from hazards, though they may not necessarily be efficient, convenient, or adequate for good service or future expansion of electrical use.
Informational Note: Hazards often arise from overloading wiring systems due to methods or usage not conforming to this Code. This typically occurs because initial wiring did not account for increased electricity use. Adequate initial installation and reasonable provisions for system changes can accommodate future increases in electricity use.
(C) Installations Covered
This Code applies to the installation and removal of:
- Electrical conductors, equipment, and raceways
- Signaling and communications conductors, equipment, and raceways
- Optical fiber cables
Covered locations include:
- Public and private premises (e.g., buildings, structures, mobile homes, recreational vehicles, floating buildings)
- Yards, lots, parking lots, carnivals, and industrial substations
- Installations connecting to the electricity supply
- Installations used by electric utilities (e.g., office buildings, warehouses, garages, machine shops, recreational buildings) that are not part of a generating plant, substation, or control center
- Installations supplying shore power to ships and watercraft in marinas and boatyards, including leakage current monitoring
- Installations exporting electric power from vehicles to premises wiring or enabling bidirectional current flow
(D) Installations Not Covered
This Code does not apply to:
- Installations in ships, watercraft (excluding floating buildings), railway rolling stock, aircraft, or automotive vehicles (excluding mobile homes and recreational vehicles).
- Informational Note: Portions of this Code are incorporated by reference into Title 46, Code of Federal Regulations, Parts 110-113.
- Installations underground in mines and self-propelled mobile surface mining machinery with attendant electrical trailing cables.
- Railway installations for generation, transformation, transmission, energy storage, or power distribution used exclusively for rolling stock operation or signaling and communications.
- Communications equipment under the exclusive control of communications utilities located outdoors or in building spaces used exclusively for such installations.
- Installations under the exclusive control of an electric utility, including:
- Service drops or service laterals and associated metering
- Installations on property owned or leased by the electric utility for communications, metering, generation, control, transformation, transmission, energy storage, or distribution of electric energy
- Installations in legally established easements or rights-of-way
- Installations governed by written agreements designated or recognized by public service commissions, utility commissions, or other regulatory agencies. These agreements apply to federal lands, Native American reservations, military bases, lands controlled by port authorities, state agencies, and railroad-owned lands.
Informational Note to (4) and (5): Utilities may include entities recognized by governmental law or regulation for installing, operating, and maintaining electric supply or communications systems. These entities may be subject to compliance with codes and standards adopted under governmental law or regulation. For more information, consult relevant governmental bodies such as state regulatory commissions, the Federal Energy Regulatory Commission, and the Federal Communications Commission.
(E) Relation to Other International Standards
The requirements in this Code align with the fundamental principles of protection for safety outlined in Section 131 of IEC 60364-1 (Low-voltage Electrical Installations – Part 1: Fundamental Principles, Assessment of General Characteristics, Definitions).
Informational Note: IEC 60364-1 addresses protection against:
- Electric shock
- Thermal effects
- Overcurrent
- Fault currents
- Overvoltage
All these hazards are covered by the requirements in this Code.
(F) Special Permission
The authority having jurisdiction may grant exceptions for installing conductors and equipment not under the exclusive control of electric utilities. These installations must:
- Connect the electric utility supply system to the premises service conductors
- Be located outside a building or structure, or terminate inside at a readily accessible location nearest the point of entrance of the service conductors.