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:
Tip #3 Code Arrangement [90-3]
- 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
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
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,
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
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, 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
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).