Article 90 of the National Electrical Code (NEC) serves as the foundational framework that establishes the scope, purpose, and practical use of the code. It sets the stage for the comprehensive guidelines and safety measures outlined in the subsequent chapters and articles. Below is a detailed overview of the key elements covered in Article 90:
90.1 Purpose
The primary purpose of the NEC is to ensure the practical safeguarding of persons and property from electrical hazards. The code achieves this by providing a standard for the installation of electrical wiring and equipment in various locations. The key objectives include:
- Safety: Protecting people and property from electrical hazards such as electric shock, fires, and explosions.
- Practicality: Offering guidelines that are both practical and enforceable.
- Maintenance: Facilitating the maintenance and preservation of a safe electrical system over time.
90.2 Scope
Article 90 outlines the scope of the NEC, which includes the following areas:
- Covered: The installation of electrical conductors, equipment, and raceways; signaling and communication conductors, equipment, and raceways; and optical fiber cables and raceways.
- Not Covered: Installations in ships, aircraft, automotive vehicles, underground mines, and certain utilities that fall under the exclusive control of an electric utility (e.g., transmission lines).
90.3 Code Arrangement
This section provides a roadmap for the structure of the NEC. It explains that the code is divided into chapters, which are further divided into articles, and those articles are organized into parts. The chapters are categorized as follows:
- Chapters 1-4: General rules applicable to all electrical installations.
- Chapters 5-7: Special occupancies, special equipment, and special conditions that supplement or modify the general rules.
- Chapter 8: Communication systems.
- Chapter 9: Tables containing numerical data necessary for the application of the rules.
90.4 Enforcement
The NEC is intended to be enforced by an authority having jurisdiction (AHJ), typically a local building department or electrical inspector. This section empowers the AHJ to interpret the code and approve alternative methods that ensure equivalent safety.
90.5 Mandatory and Permissive Rules
Article 90 clarifies the language used within the code:
- Mandatory Rules: These are requirements that must be followed and are typically indicated by terms like “shall” or “shall not.”
- Permissive Rules: These allow for flexibility and are indicated by terms like “shall be permitted.”
90.6 Formal Interpretations
This section explains the process for obtaining formal interpretations of the code. The National Fire Protection Association (NFPA) is responsible for issuing these interpretations, which help clarify code requirements and resolve disputes.
90.7 Examination of Equipment for Safety
Equipment must be examined for safety before installation. This section emphasizes the importance of listing and labeling by recognized testing laboratories to ensure compliance with the NEC.
90.8 Wiring Planning
This section encourages the planning of electrical wiring installations to allow for future expansion and to accommodate advances in technology.
Conclusion
Article 90 serves as the introductory framework for the NEC, outlining its purpose, scope, structure, enforcement, and interpretative guidelines. It is essential for ensuring that electrical installations are safe, practical, and capable of evolving with technological advancements.
For further information, you can refer to the NFPA’s official NEC Handbook and other resources from the NFPA.