NEC Code Tips

Article 90 - Introduction

Tip #1 Purpose of NEC [90-1]

The purpose of the NEC is the protection of persons and property by minimizing the risks caused by the use of electricity. It’s intended for the application of safety. When the rules of the NEC are complied with, an installation is expected to be essentially free from hazards, but this does not mean that the electrical system will be efficient, convenient, adequate for good service, or that it will work properly.

CAUTION:  The NEC does not contain any rule that requires consideration for future expansion of electrical use. The NEC is concerned solely with safety; but the electrical designer must be concerned with safety, efficiency, convenience, good service, and future expansion. Often, electrical systems are designed and installed that exceed NEC requirements. However, the inspector does not have the authority to require installations to exceed the NEC requirements, unless additional requirements have been adopted by local ordinance.

Tip # 2 Scope of the NEC [90-2]

Covered The National Electrical Code is not intended to apply to all electrical installations, but it does apply to most buildings, mobile homes, recreational vehicles, floating buildings, yards, carnivals, parking and other lots, and private industrial substations. Also covered are conductors and equipment that connect to the supply of electricity, conductors and equipment outside on the premises, and the installation of fiber optic cable.

Not Covered.  The Code is not intended to apply to:

  • Electrical wiring for cars, trucks, boats, ships, planes, electric trains, or underground mines.
  • Self-propelled mobile surface mining machinery and their attendant electrical trailing cables.
  • Railway power, signaling and communications wiring.
  • Communications equipment under the exclusive control of a communication utility located outdoors or in building spaces used exclusively for such installations.
  • Wiring under the exclusive control of electric utilities for the purpose of power generation, distribution, control, transformation, and transmission
  Tip #3 Code Arrangement [90-3]

The Code is divided into an Introduction and nine chapters. These chapters are divided as follows:

General Rules. The Introduction and Chapters 1 through 4 apply in general to all installations, which represents the scope of this book.

Special Rules. Chapters 5 through 7 apply to special occupancies, equipment, or conditions, and may modify the general rules of Chapters 1 through 4. Examples include: aircraft hangers, health care facilities, x-ray equipment, etc.

Communications Systems.  Chapter 8 contains the requirements for communication circuits such as telephones, satellite dishes, TV antennas, and CATV systems. The requirements within Chapter 8 are independent of Chapter 1 through 7 requirements, unless a specific reference in Chapter 8 is made to a requirement in those Chapters. Chapter 8 covers communications.

Tables. Chapter 9 consists of tables that are used for raceway sizing and conductor fill and voltage drop.

  Tip #4 Enforcement [90-4]

The NEC, while purely advisory, is intended to be a document that can be adopted by governmental bodies and other inspection departments. It is up to these bodies, states, counties, cities, etc., to adopt the NEC as a legal requirement for electrical installations.

The enforcement of complying with the NEC falls under the authority having jurisdiction. Generally, the electrical inspector is employed by some government agency and is responsible to an advisory council or board for his or her decisions or rulings. An inspector's authority and responsibilities include:

Interpretation of the NEC Rules. The inspector is responsible to interpret the NEC rules. This means that the inspector must have a specific rule upon which to base his/her interpretations. If an inspector rejects your installation, you have the right to know the specific NEC rule that you violated.

Note. The art of getting along with the electrical inspector, is knowing the Code and when to battle.

Approval of Equipment and Materials. The electrical inspector is the person who decides the approval of equipment. However, equipment listed by a qualified electrical testing laboratory, does not need the internal wiring reinspected at the time of installation [90-7].

Waiver of Rules. When an installation does not comply with normal NEC rules, the inspector may waive specific requirements of the Code or permit alternate methods. This is permitted only where it is ensured that equivalent electrical safety can be achieved.

Waiver of New Code Requirements. If the Code requires materials, products, or construction that are not yet available, the inspector may allow materials, products, and construction methods that were acceptable in the previous Code.

Note. It takes time for manufacturers to redesign, manufacture, and distribute new products to meet new Code requirements.

Equipment Installation. It is the inspector's responsibility to ensure that the electrical equipment is installed to the equipment listing or labeling instructions. The inspector is also responsible for detecting any field modification of equipment. Listed equipment may not be modified in the field without the approval of the listing agency or the electrical inspector [90-7, 110-3(b)].

Tip #5 Mandatory Rules and Explanatory Material [90-5]

Mandatory Rules. Rules that identify actions that are specifically required or prohibited are characterized by the use of the terms “shall” or “shall not.”

Permissive Rules. Rules, which identify actions that are allowed but not required, such as options or alternative methods, are characterized by the use of the terms “shall be permitted” or “shall not be required.” A “permissive rule” is often an exception to the general requirement.

Explanatory Material. Explanatory material, such as references to other standards, references to related Sections of the Code, or information related to a Code rule is included in the form of a Fine Print Note (FPN). Fine Print Notes are informational only and are not to be enforced. Most FPN's contain a reference to another related Code Section.

Tip # 6 Examination of Equipment for Product Safety [90-7]

Product safety evaluation is done by nationally recognized independent testing laboratories that publish lists of equipment that meet nationally recognized test standards. Products and materials that are listed, labeled, or are identified by a responsible and respected organizations, is usually the basis of approval by the electrical inspector. National testing laboratories decrease the need for inspectors to reinspect or evaluate the electrical equipment at the time of installation.

The above tips were extracted from the book Understanding the 1999 National Electrical Code written by Mike Holt. This book can be ordered over the Internet or by calling Mike Holt Enterprises, Inc., 1-888 NEC CODE (632-2633).

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