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Article 90 Introduction 90.1 Scope. This article covers use and application, arrangement, and enforcement of this Code. It also covers the expression of mandatory, permissive, and nonmandatory text, provides guidance on the examination of equipment and on wiring planning, and specifies the use and e...

Article 90 Introduction 90.1 Scope. This article covers use and application, arrangement, and enforcement of this Code. It also covers the expression of mandatory, permissive, and nonmandatory text, provides guidance on the examination of equipment and on wiring planning, and specifies the use and expression of measurements. 90.2 Use and Application. (A) Practical Safeguarding. The purpose of this Code is the practical safeguarding of persons and property from hazards arising from the use of electricity. This Code is not intended as a design specification or an instruction manual for untrained persons. ENHANCED CONTENT Collapse The National Electrical Code® (NEC®) is prepared by the National Electrical Code Committee, which consists of a correlating committee and 18 code-making panels. The code-making panels have specific technical responsibilities. The scope of the committee is as follows: This committee shall have primary responsibility for documents on minimizing the risk of electricity as a source of electric shock and as a potential ignition source of fires and explosions. It shall also be responsible for text to minimize the propagation of fire and explosions due to electrical installations. In addition to its overall responsibility for the NEC, the Correlating Committee on National Electrical Code is responsible for correlation of the following documents: NFPA 70B, Recommended Practice for Electrical Equipment Maintenance NFPA 70E®, Standard for Electrical Safety in the Workplace® NFPA 73, Standard for Electrical Inspections for Existing Dwellings NFPA 79, Electrical Standard for Industrial Machinery NFPA 110, Standard for Emergency and Standby Power Systems NFPA 111, Standard on Stored Electrical Energy Emergency and Standby Power Systems NFPA 790, Standard for Competency of Third-Party Field Evaluation Bodies NFPA 791, Recommended Practice and Procedures for Unlabeled Electrical Equipment Evaluation (B) Adequacy. This Code contains provisions that are considered necessary for safety. Compliance therewith and proper maintenance result in an installation that is essentially free from hazard but not necessarily efficient, convenient, or adequate for good service or future expansion of electrical use. Informational Note: Hazards often occur because of overloading of wiring systems by methods or usage not in conformity with this Code. This occurs because initial wiring did not provide for increases in the use of electricity. An initial adequate installation and reasonable provisions for system changes provide for future increases in the use of electricity. (C) Installations Covered. This Code covers the installation and removal of electrical conductors, equipment, and raceways; signaling and communications conductors, equipment, and raceways; and optical fiber cables for the following: (1) Public and private premises, including buildings, structures, mobile homes, recreational vehicles, and floating buildings Yards, lots, parking lots, carnivals, and industrial substations Installations of conductors and equipment that connect to the supply of electricity Installations used by the electric utility, such as office buildings, warehouses, garages, machine shops, and recreational buildings, that are not an integral part of a generating plant, substation, or control center Installations supplying shore power to ships and watercraft in marinas and boatyards, including monitoring of leakage current Installations used to export electric power from vehicles to premises wiring or for bidirectional current flow ENHANCED CONTENT Collapse Often, the source of supply is the serving electric utility. The point of connection from a premises wiring system to a serving electric utility system is referred to as the service point. The conductors on the premises side of the service point are referred to as service conductors. See Article 100 for definitions. The source might be a stand-alone system, such as a generator, a battery system, a photovoltaic system, a fuel cell, a wind turbine, an electric vehicle, or a combination of those sources. Conductors from stand-alone systems are not service conductors, they are feeders. Service conductors are supplied only by a utility source. The following articles can be referred to for specific sources: Article 230 for service conductor and service equipment requirements if the only source of supply of electricity is from a utility Article 625 if the source is an electric vehicle arranged for bidirectional current flow Article 705 if the source of supply includes a utility source(s) in combination with alternate energy sources The exhibit below helps to illustrate the distinction between electric utility facilities subject to the NEC and those not subject to the NEC. The electrical equipment in the generating plant is not governed by the rules of the NEC. Office buildings and warehouses of electric utilities are functionally like the facilities owned by other commercial entities. Although the warehouse is owned by the utility, it is a typical commercial facility in which the electrical installation would be governed by the rules of the NEC. Industrial and multibuilding complexes and campus-style complexes often include substations and other installations that employ construction and wiring similar to those of electric utility installations. Because these installations are on the load side of the service point, they are within the purview of the NEC. At an increasing number of industrial, institutional, and other campus style distribution systems, the service point is at an owner maintained substation, and the conductors extending from that substation to the campus facilities are feeders (see Article 100). NEC requirements cover these distribution systems in 235.360 and 235.361 and in Article 395. The overhead conductor and live parts clearance requirements in the NEC correlate with those in ANSI C2, National Electrical Safety Code® (NESC®), for overhead conductors under the control of an electric utility. The NEC also addresses removal of equipment, such as abandoned conductors. Abandoned conductors and cables from several generations of equipment can increase the fire loading in a building. Abandoned cable is commonly found where communications systems or computer networks have been upgraded. Several places in the NEC specify where abandoned cable is required to be removed. Installations Not Covered. This Code does not cover the following: Installations in ships, watercraft other than floating buildings, railway rolling stock, aircraft, or automotive vehicles other than mobile homes and recreational vehicles Informational Note: Although the scope of this Code indicates that the Code does not cover installations in ships, 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 and its attendant electrical trailing cable Installations of railways for generation, transformation, transmission, energy storage, or distribution of power used exclusively for operation of rolling stock or installations used exclusively for signaling and communications purposes Installations of 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 where such installations Consist of service drops or service laterals, and associated metering, or Are on property owned or leased by the electric utility for the purpose of communications, metering, generation, control, transformation, transmission, energy storage, or distribution of electric energy, or Are located in legally established easements or rights-of-way, or Are located by other written agreements either designated by or recognized by public service commissions, utility commissions, or other regulatory agencies having jurisdiction for such installations. These written agreements shall be limited to installations for the purpose of communications, metering, generation, control, transformation, transmission, energy storage, or distribution of electric energy where legally established easements or rights-of-way cannot be obtained. These installations shall be limited to federal lands, Native American reservations through the U.S. Department of the Interior Bureau of Indian Affairs, military bases, lands controlled by port authorities and state agencies and departments, and lands owned by railroads. Informational Note to (4) and (5): Examples of utilities may include those entities that are typically designated or recognized by governmental law or regulation by public service/utility commissions and that install, operate, and maintain electric supply (such as generation, transmission, or distribution systems) or communications systems (such as telephone, CATV, Internet, satellite, or data services). Utilities may be subject to compliance with codes and standards covering their regulated activities as adopted under governmental law or regulation. Additional information can be found through consultation with the appropriate governmental bodies, such as state regulatory commissions, the Federal Energy Regulatory Commission, and the Federal Communications Commission. ENHANCED CONTENT Collapse Section 90.2(B)(5) is not intended to prevent the NEC from being used as an installation regulatory document for these types of installations. The NEC is fully capable of being utilized for electrical installations in most cases. Rather, 90.2(B)(5) lists specific areas where the nature of the installation requires specialized rules or where other installation rules, standards, and guidelines have been developed for specific uses and industries. For example, the electric utility industry uses ANSI C2, National Electrical Safety Code (NESC), as its primary requirement in the generation, transmission, distribution, and metering of electric energy. In most cases, utility-owned installations are on legally established easements or rights of way. Easements or rights of way might not be available on federally owned lands, Native American reservations, military bases, lands controlled by port authorities or state agencies or departments, and lands owned by railroads. In those limited applications, a written agreement complying with this section can be used to establish the extent of the utility installation. Utility installations of energy storage are outside the scope of the NEC. Utility-owned energy storage would be covered by the NESC. Energy storage that is not under the exclusive control of an electric utility is governed by Article 706 of the NEC. Relation to Other International Standards. The requirements in this Code address the fundamental principles of protection for safety contained in Section 131 of International Electrotechnical Commission Standard 60364-1, Low-voltage Electrical Installations – Part 1: Fundamental Principles, Assessment of General Characteristics, Definitions. Informational Note: See IEC 60364-1, Low-voltage Electrical Installations – Part 1: Fundamental Principles, Assessment of General Characteristics, Definitions, Section 131, for fundamental principles of protection for safety that encompass protection against electric shock, protection against thermal effects, protection against overcurrent, protection against fault currents, and protection against overvoltage. All of these potential hazards are addressed by the requirements in this Code. ENHANCED CONTENT Collapse In addition to being an essential part of the safety system of the Americas and the most widely adopted code for the built environment in the United States, the NEC has been adopted and is used extensively in many other countries. The NEC is compatible with international safety principles, and installations meeting the requirements of the NEC are also in compliance with the fundamental principles outlined in International Electrotechnical Commission (IEC) 60364-1, Electrical Installations of Buildings, Section 131. Countries that do not have formalized rules for electrical installations can adopt the NEC and be fully compatible with the safety principles of IEC 60364-1, Section 131. Special Permission. The authority having jurisdiction for enforcing this Code may grant exception for the installation of conductors and equipment that are not under the exclusive control of the electric utilities and are used to connect the electric utility supply system to the service conductors of the premises served, provided such installations are outside a building or structure, or terminate inside at a readily accessible location nearest the point of entrance of the service conductors. 90.3 Code Arrangement. This Code is divided into the introduction and nine chapters, as shown in Figure 90.3. Chapters 1, 2, 3, and 4 apply generally. Chapters 5, 6, and 7 apply to special occupancies, special equipment, or other special conditions and may supplement or modify the requirements in Chapters 1 through 7. Chapter 8 covers communications systems and is not subject to the requirements of Chapters 1 through 7 except where the requirements are specifically referenced in Chapter 8. Chapter 9 consists of tables that are applicable as referenced. Informative annexes are not part of the requirements of this Code but are included for informational purposes only. code book image: 8e1b81dc-aa9c-11ec-a46d-e9dd887336cb Figure 90.3 Code Arrangement. ENHANCED CONTENT Collapse An example of how the general rules of Chapter 3 are modified is 300.22, which is modified by 725.3(B) and 760.3(B) and is specifically referenced in 800.3(C) and (D). Figure 90.3 is a graphic explanation of the NEC arrangement. The requirements in Chapters 5 through 7 can modify the requirements in Chapters 1 through 7. Prior to the 2017 edition, Chapters 5 through 7 could modify only the requirements in Chapters 1 through 4. 90.4 Enforcement. Application. 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. ENHANCED CONTENT Collapse All materials and equipment used under the requirements of the NEC are subject to the approval of the AHJ. Sections 90.7, 110.2, and 110.3 — along with the definitions of the terms approved, identified (as applied to equipment), labeled, and listed — are intended to provide a basis for the AHJ to make judgments about the approval of an installation. The phrase “including signaling and communications systems” emphasizes that those systems are also subject to enforcement. Some localities do not adopt the most current version of the NEC, but in those that do there is sufficient evidence that compliance with the current edition serves as a reference for a safe installation. Interpretations. 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. Specific Requirements and Alternative Methods. 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. ENHANCED CONTENT Collapse The AHJ is responsible for interpreting the NEC. Using special permission (written consent), the AHJ may permit alternative methods where specific rules are not established in the NEC. For example, the AHJ 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 NEC. New Products, Constructions, or Materials. 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. Informational Note: See Informative Annex H, Administration and Enforcement, for a model of guidelines that can be used to create an electrical inspection and enforcement program and to adopt NFPA 70, National Electrical Code. ENHANCED CONTENT Collapse The AHJ may waive a new NEC 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 level of 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 or to develop new materials and test methods usually is not known at the time the latest edition is adopted. 90.5 Mandatory Rules, Permissive Rules, and Explanatory Material. (A) Mandatory Rules. Mandatory rules of this Code are those that identify actions that are specifically required or prohibited and are characterized by the use of the terms shall or shall not. Permissive Rules. Permissive rules of this Code are those that identify actions that are allowed but not required, are normally used to describe options or alternative methods, and are characterized by the use of the terms shall be permitted or shall not be required. ENHANCED CONTENT Collapse Permissive rules are options or alternative methods of achieving equivalent safety — they are not requirements. Permissive rules are often misinterpreted. For example, the frequently used permissive term shall be permitted can be mistaken for a requirement. Substituting “the inspector must allow [item A or method A]” for “[item A or method A] shall be permitted” generally clarifies the interpretation. Explanatory Material. Explanatory material, such as references to other standards, references to related sections of this Code, or information related to a Code rule, is included in this Code in the form of informational notes or an informative annex. Unless the standard reference includes a date, the reference is to be considered as the latest edition of the standard. Such notes are informational only and are not enforceable as requirements of this Code. Brackets containing section references to another NFPA document are for informational purposes only and are provided as a guide to indicate the source of the extracted text. These bracketed references immediately follow the extracted text. Informational Note: The format and language used in this Code follows guidelines established by NFPA and published in the NEC Style Manual. Copies of this manual can be obtained from NFPA. ENHANCED CONTENT Collapse Several requirements in the NEC have been extracted from other NFPA codes and standards. Although NEC requirements based on extracted material are under the jurisdiction of the technical committee responsible for the document from which the material was extracted, 90.5(C) clarifies that the NEC requirements stand on their own as part of the NEC. The extracted material with bracketed references does not indicate that other NFPA documents are adopted through reference. Articles that make use of extracted text include Articles 500, 511, 514, 515, 516, 517, and 695. The NEC contains numerous informational notes. Prior to the 2011 edition, these notes were referred to as fine print notes, or FPNs. They were renamed informational notes to clarify that they do not contain requirements, statements of intent, or recommendations. They present additional supplementary material that aids in the application of the requirement they follow. Because informational notes are not requirements of the NEC, they are not enforceable. Footnotes to tables, although also in fine print, are not explanatory material unless they are identified as informational notes. Table footnotes are part of the tables and are necessary for proper use of the tables. Therefore, they are mandatory and enforceable. Additional explanatory material is in the informative annexes. The term informative annex clarifies that the annexes contain additional information and do not contain recommendations or requirements. The National Electrical Code® Style Manual can be accessed at nfpa.org/70 by selecting the Current & Prior Editions tab and scrolling down to Additional Information. Informative Annexes. Nonmandatory information relative to the use of the NEC is provided in informative annexes. Informative annexes are not part of the enforceable requirements of the NEC, but are included for information purposes only. 90.6 Formal Interpretations. To promote uniformity of interpretation and application of this Code, formal interpretation procedures have been established and are found in the Regulations Governing the Development of NFPA Standards. ENHANCED CONTENT Collapse The procedures for Formal Interpretati