 by John E. Traister
- Revised & Updated by Bradford Maher
Chapter One
About the
NEC
All electrical installations must
conform to applicable National Electrical Code® (NEC) requirements, local
ordinances, and instructions provided by equipment and component
manufacturers. This chapter
explains the key terms and basic layout of the NEC.
Purpose and History of the
NEC
Owing to the potential fire and
explosion hazards caused by the improper handling and installation of
electrical wiring, certain rules in the selection of materials, quality of
workmanship, and precautions for safety must be followed. To standardize
and simplify these rules and provide a reliable guide for electrical
construction, the National Electrical Code (NEC) was developed. The
NEC, originally prepared in 1897, is frequently revised to meet
changing conditions, improved equipment and materials, and new fire
hazards. It is the result of the best efforts of electrical engineers,
manufacturers of electrical equipment, insurance underwriters, fire
fighters, and other concerned experts throughout the
country.
The NEC is now published by the
National Fire Protection Association (NFPA), Batterymarch Park, Quincy,
Massachusetts 02269. It contains specific rules and regulations intended
to help in the practical safeguarding of persons and property from hazards
arising from the use of electricity.
The NEC states, "This Code is
not intended as a design specification, but includes such provisions where
considered necessary for safety. It is not intended as an instruction
manual for untrained persons." However, it does provide a sound basis for
the study of electrical installation procedures - under the proper
guidance. The probable reason for the NEC's self-analysis is that the Code also states,
"This Code contains provisions considered necessary for safety. Compliance
therewith and proper maintenance will result in an installation
essentially free from hazard, but not necessarily efficient, convenient,
or adequate for good service or future expansion of electrical
use."
The NEC, however, has become the bible
of the electrical construction industry, and anyone involved in electrical
work, in any capacity, should obtain an up-to-date copy, keep it handy at
all times, and refer to it frequently.
NEC Terminology
There are two basic types of rules in
the NEC: mandatory rules and advisory rules. Here is how to recognize the
two types of rules and how they relate to all types of electrical
systems.
-
Mandatory rules - All
mandatory rules have the word shall in them. The word "shall"
means must. If a rule is mandatory, you must comply with
it.
-
Advisory rules - All advisory
rules have the word should in them. The word "should" in this
case means recommended but not necessarily required. If a rule is
advisory, compliance is discretionary.
Be alert to local amendments to the
NEC. Local ordinances may amend the language of the NEC, changing it from
should to shall. This means that you must do in that county or city
what may only be recommended in some other area. The office that issues
building permits will either sell you a copy of the code that's enforced
in that area or tell you where the code is sold. In rare instances, the
electrical inspector having jurisdiction may issue these regulations
verbally.
There are a few other "landmarks" that
you will encounter while looking through the NEC. These are summarized in
Figure 1-1, and a brief explanation of each follows:
Explanatory material.
Explanatory material
in the form of Fine Print Notes is designated (FPN). Where these appear,
the FPNs normally apply to the NEC Section or paragraph immediately
preceding the FPN.
Change bar. A change bar in the margins indicates
that a change in the NEC has been made since the last edition. When
becoming familiar with each new edition of the NEC, always review these
changes. There are also several illustrated publications on the market
that point out changes in the NEC with detailed explanations of each.
Such publications make excellent reference material.
Bullets: A filled-in circle called a "bullet"
indicates that something has been deleted from the last edition of the
NEC. Although not absolutely necessary, many electricians like to
compare the previous NEC edition to the most recent one when these
bullets are encountered, just to see what has been omitted from the
latest edition. The most probable reasons for the deletions are errors
in the previous edition, or obsolete items.
Extracted text:
Material identified
by the superscript letter x includes text extracted from other NFPA
documents as identified in Appendix A of the NEC. For example, “ . . .
516-6.x This section shall apply to processes in which combustible dry
powders . . .”
NEC Text Formats
As you open the NEC book, you will
notice several different styles of text used. Here is an explanation of
each.
-
Normal black letters: Basic
definitions and explanations of the NEC requirements.
-
Bold black letters: Used for
Article, Section and Subsection headings.
-
Exceptions: These explain the
situations when a specific rule does not apply. Exceptions are written
in italics under the Section or paragraph to which they
apply.
-
Tables: Tables are often
included when there is
more than one possible application of a requirement.
-
Diagrams: A few diagrams are scattered
throughout the NEC to illustrate certain NEC applications.
Learning the NEC
Layout
The NEC is divided into the
Introduction (Article 90) and nine chapters. Chapters 1, 2, 3, and 4 apply
generally; Chapters 5, 6, and 7 apply to special occupancies, special
equipment, or other special conditions. These latter chapters supplement
or modify the general rules. Chapters I through 4 apply except as amended
by Chapters 5, 6, and 7 for the particular conditions.
While looking through these NEC
chapters, if you should encounter a word or term that is unfamiliar,
look in Chapter 1, Article 100 - Definitions. Chances are, the term will
be found here. If not, look in the Index for the word and the NEC page
number. Many terms are included in Article 100, but others are scattered
throughout the book.
For definitions of terms not found in
the NEC, check the glossary in the back of this book or obtain a copy of
Illustrated Dictionary for Electrical Workers, available from
Delmar Publishers, Inc., Albany, New York.
Chapter 8 of the NEC covers
communications systems and is independent of the other chapters except
where they are specifically referenced therein.
Chapter 9 consists of tables and
examples.
There is also the NEC Contents
at the beginning of the book and a comprehensive index at the back. You
will find frequent use for both of these helpful "tools" when searching
for various installation requirements.
Each chapter is divided into one or
more Articles. For example, Chapter 1 contains Articles 100 and 110. These
Articles are subdivided into Sections. For example, Article 110 of Chapter
1 begins with Section 110 - 2 - Approval. Some sections may contain only
one sentence or a paragraph, while others may be further subdivided into
lettered or numbered paragraphs such as (a), (1), (2), and so
on.
Begin your study of the NEC with
Articles 90, 100 and 110. These three articles have the basic information
that will make the rest of the NEC easier to understand. Article
100 defines terms you will need to understand the code. Article 110 gives
the general requirements for electrical installations. Read these three
articles over several times until you are thoroughly familiar with all the
information they contain. It's time well spent. For example, Article 90
contains the following sections:
Once you are familiar with Articles 90,
100, and 110 you can move on to the rest of the NEC. There are
several key sections you will use often while installing and servicing
electrical systems. Let's discuss each of these important
sections.
Wiring Design and
Protection
Chapter 2 of the NEC discusses
wiring design and protection, the information electrical technicians need,
most often. It covers the use and identification of grounded conductors,
branch circuits, feeders, calculations, services, overcurrent protection
and grounding. This is essential information for any type of electrical
system, regardless of the type.
Chapter 2 is also a "how-to" chapter. It
explains how to provide proper spacing for conductor supports, how to
provide temporary wiring and how to size the proper grounding conductor or
electrode. If you run into a problem related to the design/installation of
a conventional electrical system, you can probably find a solution for it
in this chapter.
Wiring Methods and
Materials
Chapter 3 has the rules on wiring
methods and materials. The materials and procedures used on a particular
system depend on the type of building construction, the type of occupancy,
the location of the wiring in the building, the type of atmosphere in the
building or in the area surrounding the building, mechanical factors and
the relative costs of different wiring methods.
The provisions of this article apply to
all wiring installations unless specified otherwise in NEC Articles
and Sections.
Wiring Methods
There are four basic wiring methods
used in most modem electrical systems. Nearly all wiring methods are a
variation of one or more of these four basic methods:
-
Sheathed cables of two or more
conductors, such as nonmetallic-sheathed cable and armored cable
(Articles 330 through 339)
-
Raceway wiring systems, such as rigid
steel conduit and electrical metallic tubing (Articles 342 to
358)
-
Busways (Article 364)
-
Cabletray (Article 318)
Electrical Conductors
Article 310 in Chapter 3 gives a
complete description of all types of electrical conductors. Electrical
conductors come in a wide range of sizes and forms. Be sure to check the
working drawings and specifications to see what sizes and types of
conductors are required for a specific job. If conductor type and size are
not specified, choose the most appropriate type and size meeting standard
NEC requirements.
When workers have the choice of
selecting the wiring method to use, most will select the least expensive
method allowed by the NEC. However, in some cases, what appears to
be the least expensive method may not hold true in the final results. For
example, when rewiring existing buildings where much "fishing" of cable is
necessary, workers have found that Type AC armored cable (MC) is usually
easier to fish in concealed partitions than Type NM (Romex) cable.
Although MC cable is more expensive, the savings in labor usually offset
the cost.
Boxes, Cabinets, And
Enclosures
Articles 318 through 384 give rules for
raceways, boxes, cabinets and raceway fittings. Outlet boxes vary in size
and shape, depending on their use, the size of the raceway, the number of
conductors entering the box, the type of building construction and
atmospheric conditions of the areas. Chapter 3 should answer most
questions on the selection and use of these items.
The NEC does not describe in
detail all types and sizes of outlet boxes. But manufacturers of outlet
boxes have excellent catalogs showing all of their products. Collect these
catalogs. They are essential to your work.
Wiring Devices And Switchgear
Article 380 covers the switches,
pushbuttons, pilot lamps, receptacles and power outlets. Again, get the
manufacturers' catalogs on these items. They will provide you with
detailed descriptions of each.
Article 384 covers switchboards and
panelboards, including their location, installation methods, clearances,
grounding and overcurrent protection.
Equipment for General Use
Chapter 4 of the NEC begins with
the use and installation of flexible cords and cables, including the trade
name, type letter, wire size, number of conductors, conductor insulation,
outer covering and use of each. The chapter also includes fixture wires,
again giving the trade name, type letter and other important
details.
Article 410 on lighting fixtures is
especially important. It gives installation procedures for fixtures in
specific locations. For example, it covers fixtures near combustible
material and fixtures in closets. The NEC does not describe how
many fixtures will be needed in a given area to provide a certain amount
of illumination.
Article 430 covers electric motors,
including mounting the motor and making electrical connections to it.
Motor controls and overload protection are also covered.
Articles 440 through 460 cover air
conditioning and heating equipment, transformers and
capacitors.
Article 480 gives most requirements
related to battery-operated electrical systems. Storage batteries are
seldom thought of as part of a conventional electrical system, but they
often provide standby emergency lighting service. They may also supply
power to security systems that are separate from the main ac electrical
system.
Special Occupancies
Chapter 5 of the NEC covers
special occupancy areas. These are areas where the sparks generated by
electrical equipment may cause an explosion or fire. The hazard may
be due to the atmosphere of the area or just the presence of a volatile
material in the area. Commercial garages, aircraft hangers and service
stations are typical special occupancy locations.
Articles 500 - 501 cover the
different types of special occupancy atmospheres that are considered to be
hazardous areas. The atmospheric groups were established to make it easy
to test and approve equipment for various types of uses.
Articles 501-4, 502-4, and 503-3 cover
the installation of wiring in hazardous (Classified) locations.
Wiring in these areas must be designed to prevent the ignition of a
surrounding explosive atmosphere when arcing occurs within the electrical
system.
There are three main classes of special
occupancy locations:
-
Class I (Article 501): Areas
containing flammable gases or vapors in the air. Class I areas include
paint spray booths, dyeing plants where hazardous liquids are used and
gas generator rooms.
-
Class II (Article 502): Areas where
combustible dust is present, such as grain handling and storage plants,
dust and stock collector areas and sugar pulverizing plants. These are
areas where, under normal operating conditions, there may be enough
combustible dust in the air to produce explosive or ignitable
mixtures.
-
Class III (Article 503): Areas that
are hazardous because of the presence of easily ignitable fibers or
flyings in the air, although not in large enough quantity to produce
ignitable mixtures. Class III locations include cotton mills, rayon
mills, and clothing manufacturing plants.
Articles 511 and 514 regulate garages
and similar locations where volatile or flammable liquids are used. While
these areas are not always considered critically hazardous locations,
there may be enough danger to require special precautions in the
electrical installation. In these areas, the NEC requires that volatile
gases be confined to an area not more than 4 ft above the floor. So in
most cases, conventional raceway systems are permitted above this level.
If the area is judged critically hazardous, explosionproof wiring
(including seal-offs) may be required.
Article 520 regulates theaters and
similar occupancies where fire and panic can cause hazards to life and
property. Drive-in theaters do not present the same hazards as enclosed
auditoriums. But the projection rooms and adjacent areas must be properly
ventilated and wired for the protection of operating personnel and using
the area.
Chapter 5 also covers residential
storage garages, aircraft hangars, service stations, bulk storage plants,
health cake facilities, mobile homes and parks, and recreation vehicles
and parks.
When security technicians are
installing systems in hazardous locations, extreme caution must be used.
You may be working with only 12 or 24 V, but a spark caused by, say, an
improper connection can set off a violent explosion. You may have already
witnessed a low-voltage explosion in the common automotive battery.
Although only 12 V dc are present, if a spark occurs near the battery and
battery gases are leaking through the battery housing, chances are the
battery will explode with a report similar to a shotgun
firing.
When installing security systems in
Class I, Division 1 locations, explosionproof fittings are required and
most electrical wiring must be enclosed in rigid steel conduit
(pipe).
Special Equipment
Article 600 covers electric signs and
outline lighting. Article 610 applies to cranes and hoists. Article 620
covers the majority of the electrical work involved in the installation
and operation of elevators, dumb- waiters, escalators and moving walks.
The manufacturer is responsible for most of this work. The electrician
usually just furnishes a feeder terminating in a disconnect means in the
bottom of the elevator shaft. The electrician may also be responsible for
a lighting circuit to a junction box midway in the elevator shaft for
connecting the elevator cage lighting cable and exhaust fans. Articles in
Chapter 6 of the NEC give most of the requirements for these
installations.
Article 630 regulates electric welding
equipment. It is normally treated as a piece of industrial power equipment
requiring a special power outlet. But there are special conditions that
apply to the circuits supplying welding equipment. These are outlined in
detail in Chapter 6 of the NEC.
Article 640 covers wiring for
sound-recording and similar equipment. This type of equipment normally
requires low-voltage wiring. Special outlet boxes or cabinets are usually
provided with the equipment. But some items may be mounted in or on
standard outlet boxes. Some sound-recording electrical systems require
direct current, supplied from rectifying equipment, batteries or motor
generators. Low-voltage alternating current comes from relatively small
transformers connected on the primary side to a 120-V circuit within the
building.
Other items covered in Chapter 6 of the
NEC include: X-ray equipment (Article 660), induction and
dielectric heat-generating equipment (Article 665) and machine tools
(Article 670).
If you ever have work that
involves Chapter 6, study the chapter before work begins. That can save a
lot of installation time. Here is another way to cut down on labor hours
and prevent installation errors. Get a set of rough-in drawings of the
equipment being installed. It is easy to install the wrong outlet box or
to install the right box in the wrong place. Having a set of rough-in
drawings can prevent those simple but costly errors.
Special Conditions
In most commercial buildings, the
NEC and local ordinances require a means of lighting public rooms,
halls, stairways and entrances. There must be enough light to allow the
occupants to exit from the building if the general building lighting is
interrupted. Exit doors must be clearly indicated by illuminated exit
signs.
Chapter 7 of the NEC covers the
installation of emergency lighting systems. These circuits should be
arranged so that they can automatically transfer to an alternate source of
current, usually storage batteries or gasoline-driven generators. As an
alternative in some types of occupancies, you can connect them to the sup-
ply side of the main service so disconnecting the main service switch
would not disconnect the emergency circuits. See Article 700. NEC
Chapter 7 also covers a variety of other equipment, systems and
conditions that are not easily categorized elsewhere in the
NEC.
Chapter 8 is a special category for
wiring associated with electronic communications systems including
telephone and telegraph, radio and TV, fire and burglar alarms, and
community antenna systems.
Once you become familiar with the
NEC through repeated usage, you will generally know where to look
for a particular topic. While this chapter provides you with an initial
familiarization of the NEC layout, much additional usage experience
will be needed for you to feel comfortable with the NEC's
content.
The NEC is not an easy book to
read and under- stand at first. In fact, seasoned electrical workers and
technicians sometimes find it confusing. Basically, it is a reference book
written in a legal, contract-type language and its content does assume
prior knowledge of most subjects listed. Consequently, you will sometimes
find the NEC frustrating to use because terms aren't always defined, or
because of some unknown prerequisite knowledge.
Definitions
Many definitions of terms dealing with
the NEC may be found in NEC Article 100. However, other
definitions are scattered throughout the NEC under their
appropriate category. For example the term lighting track is not listed in
Article 100. The term is listed under NEC Section 410-100 and reads as
follows:
Lighting track is a manufactured
assembly designed to support and energize lighting fixtures that are
capable of being readily repositioned on the track. Its length may be
altered by the addition or subtraction of sections of
track.
Regardless of where the definition may
be located in Article 100 or under the appropriate NEC Section elsewhere
in the book - the best way to team and remember these definitions is to
form a mental picture of each item or device as you read the definition.
For example, turn to page 70-25 of the 1996 NEC and under Article
100 – Definitions, scan down the page until you come to the term
"Attachment Plug (Plug Cap) (Plug)." After reading the definition, you
will probably have already formed a mental picture of attachment
plugs.
Once again, scan through the
definitions until the term "Appliance" is found. Read the definition and
then try to form a mental picture of what appliances look like. They
should be familiar to everyone.
Each and every term listed in the
NEC should be understood. Know what the item looks like and how it
is used on the job. If a term is unfamiliar, try other reference books
such as manufacturers' catalogs for an illustration of the item. Then
research the item further to determine its purpose in electrical systems.
Once you are familiar with all the common terms and definitions found in
the NEC, navigating through the NEC (and understanding what you
read) will be much easier.
There are many definitions included in
Article 100. You should become familiar with the definitions. Since a copy
of the latest NEC is compulsory for any type of electrical wiring,
there is no need to duplicate them here. However, here are two definitions
that you should become especially familiar with:
-
Labeled - Equipment or
materials to which has been attached a label, symbol or other
identifying mark of an organization acceptable to the authority having
jurisdiction and concerned with product evaluation, that maintains
periodic inspection of production of labeled equipment or materials, and
by whose labeling the manufacturer indicates compliance with appropriate
standards or performance in a specified manner.
-
Listed - Equipment or
materials included in a list published by an organization acceptable to
the authority having jurisdiction and concerned with product evaluation,
that maintains periodic inspection of production of listed equipment or
materials, and whose listing states either that the equipment or
material meets appropriate designated standards or has been tested and
found suitable for use in a specified manner.
Testing Laboratories
Besides installation rules, you will
also have to be concerned with the type and quality of materials that are
used in electrical wiring systems. Nationally recognized testing
laboratories (Underwriters' Laboratories, Inc. is one) are product
safety-certification laboratories. They establish and operate product
safety certification programs to make sure that items produced under the
service are safeguarded against reasonable foreseeable risks. Some of
these organizations maintain a worldwide network of field representatives
who make unannounced visits to manufacturing facilities to countercheck
products bearing their "seal of approval." See Figure
1-2.
However, proper selection,
overall functional performance and reliability of a product are factors
that are not within the basic scope of UL activities.
To fully understand the NEC, it
is important to understand the organizations that govern it. The following
organizations will frequently be encountered and associated with materials
and equipment used on almost every electrical
installation.
Nationally Recognized Testing
Laboratory (NRTL)
Nationally Recognized Testing
Laboratories are product safety certification laboratories. They establish
and operate product safety certification programs to make sure that items
produced under the service are safeguarded against reasonable foreseeable
risks. An approved item, however, does not mean that the item is approved
for all uses; it is safe only for the purpose for which it is intended.
NRTL maintains a worldwide network of field representatives who make
unannounced visits to factories to countercheck products bearing the
safety mark.
National Electrical Manufacturers
Association (NEMA)
The National Electrical Manufacturers
Association was founded in 1926. It is made up of companies that
manufacture equipment used for generation, transmission, distribution,
control, and utilization of electric power. The objectives of NEMA are to
maintain and improve the quality and reliability of products; to ensure
safety standards in the manufacture and use of products; to develop
product standards covering such matters as naming, ratings, performance,
testing, and dimensions. NEMA participates in developing the NEC
and the National Electrical Safety Code and advocates their acceptance
by state and local authorities.
National Fire Protection Association
(NFPA)
The NFPA was founded in 1896. Its
membership is drawn from the fire service, business and industry,
health care, educational and other institutions, and individuals in the fields of insurance,
government, architecture, and engineering. The duties of the NFPA
include:
The Role Of Testing
Laboratories
Testing laboratories are an integral
part of the development of the code. The NFPA, NEMA, and NRTL all provide
testing laboratories to conduct research into electrical equipment and its
safety. These laboratories perform extensive testing of new products to
make sure they are built to code standards for electrical and fire safety.
These organizations receive statistics and reports from agencies all over
the United States concerning electrical shocks and fires and their causes.
Upon seeing trends developing concerning association of certain equipment
and dangerous situations or circumstances, this equipment will be
specifically targeted for research.
Major Changes to the 1999
NEC
The following summarize the major areas
of change to the 1999 NEC. As mentioned previously, when using the
NEC book itself, a change is readily identified by a vertical line
(change bar) in the margin. A bullet in the margin represents a
deletion.
Article 90 -
Introduction
-
Section 90-1. Purpose
-
Section 90-2. Scope
Article 100 -
Definitions
-
Bonding (Bonded)
-
Feeder
-
Festoon Lighting
-
Service Conductors
-
Service Equipment
Article 110 - Requirements for
Electrical Installations
-
Section 110-22. Identification of
Disconnecting Means
Part B. Over 600 volts, Nominal, or
Less
-
Section 110-31. Enclosures for
Electrical Installations
-
Section 110-34. Work Space and
Guarding
-
Section 110-36. Circuit
Conductors
Part D. Tunnel Installations Over 600
Volts, Nominal
-
Section 110-51.
General
-
Section 110-52. Overcurrent
Protection
-
Section 110-53.
Conductors
-
Section 110-54. Bonding and
Equipment, Grounding Conductors
-
Section 110-55. Transformers,
Switches, and Electric Equipment
-
Section 110-56. Energized
Parts
-
Section 110-57. Ventilation System
Controls
-
Section 110-58. Disconnecting
Means
-
Section 110-59.
Enclosures
Article 200 - Use and Identification of
Grounded Conductors
-
Section 200-2.
General
-
Section 200-6. Means of Identifying
Grounded Conductors
-
Section 200-7. Use of Insulation of
a White or Natural Gray Color or with Three Continuous White
Stripes
-
Section 200-10. Identification of
Terminals
Article 210 - Branch
Circuits
Part A. General
Provisions
-
Section 210-2. Other Articles for
Specific- Purpose Branch Circuits
-
Section 210-4. Multiwire Branch
Circuits
-
Section 210-5. Identification for
Branch Circuits
-
Section 210-8. Ground-Fault
Circuit-Interrupter Protection for Personnel
-
Section 210-11. Branch Circuits
Required
Part B. Branch-Circuit
Ratings
-
Section 210-19. Conductors -
Minimum Ampacity and Size
-
Section 210-20. Overcurrent
Protection
-
Section 210-23. Permissible
Loads
-
Section 210-24. Branch-Circuit
Requirements- Summary
Part C. Required
Outlets
-
Section 210-52. Dwelling Unit
Receptacle Outlets
-
Section 210-60. Guest
Rooms
-
Section 210-70. Lighting Outlets
Required
Article 215 -
Feeders
-
Section 215-1. Scope
-
Section 215-2. Minimum Size and
Rating
-
Section 215-3. Overcurrent
Protection
-
Section 215-10. Ground-Fault
Protection of Equipment
Article 220 - Branch-Circuit, Feeder,
and Service Calculations
Part A. General
-
Section 220-2.
Computations
-
Section 220-3. Computation of
Branch Circuit Loads
Part B. Feeders and
Services
-
Section 220-10.
General
-
Section 220-12. Show-Window and
Track Lighting
-
Section 220-13. Receptacle Loads
Nondwelling Units
-
Section 220-15. Fixed Electric
Space Heating
-
Section 220-16. Small Appliance and
Laundry Loads - Dwelling Unit
-
Section 220-18. Electric Clothes
Dryers Dwelling Unit(s)
Part D. Method for Computing Farm
Loads
-
Section 220-40. Farm Loads -
Buildings and Other Loads
Article 225 - Outside Branch Circuits
and Feeders
-
Section 225-6. Conductor Size and
Support
-
Section 225-9. Overcurrent
Protection
-
Section 225-19 Clearances from
Buildings for Conductors of Not Over 600 Volts, Nominal
Article 230 -
Services
Part B. Overhead Service-Drop
Conductors
Part D. Service-Entrance
Conductors
-
Section 230-40. - Number of Service
Entrance Conductor Sets
-
Section 230-42. - Minimum Size and
Rating
-
Section 230-46. - Spliced
Conductors
Part G. Service Equipment –
Overcurrent Protection
-
Section 230-91.
Location
-
Section 230-95. Ground-Fault
Protection of Equipment
Part H. Services Exceeding 600 Volts,
Nominal
-
Section 230-204. Isolating
Switches
-
Section 230-205. Disconnecting
Means
Article 240 - Overcurrent
Protection
Part A. General
-
Section 240-3. Protection of
Conductors
-
Section 240-4. Protection of
Flexible Cords and Fixture Wires
-
Section 240-6. Standard Ampere
Ratings
-
Section 240-8. Fuses or Circuit
Breakers in Parallel
-
Section 240-13. Ground-Fault
Protection of Equipment
Part B.
Location
-
Section 240-20. Ungrounded
Conductors
-
Section 240-21. Location in
Circuit
-
Section 240-24. Location in or on
Premises
Part C.
Enclosures
-
Section 240-33. Vertical
Position
Part F Cartridge Fuses and
Fuseholders
Part G. Circuit
Breakers
-
Section 240-83,
Marking
-
Section 240-86. Series
Ratings
Part H. Supervised Industrial
Installations
Part I. Overcurrent Protection Over
600 Volts, Nominal
Article 250 - Grounding (Entirely
rewritten)
Article 300 - Wiring Methods
Part A. General
Requirements
-
Section 300-3.
Conductors
-
Section 300-5. Underground
Installations
-
Section 300-11. Securing and
Supporting
-
Section 300-14. Length of Free
Conductors at Outlets, Junctions and Switch Points
-
Section 300-15. Boxes, Conduit
Bodies, or Fittings - Where Required
Part B. Requirements for Over 600
Volts, Nominal
-
Section 300-32. - Conductors of
Different Systems
-
Section 300-37. - Aboveground
Wiring Methods
-
Section 300-39. - Braid-Covered
Insulated Conductors - Open Installation
-
Section 300-40. - Insulation
Shielding
-
Section 300-42. - Moisture or
Mechanical Protection for Metal-Sheathed Cables
-
Section 300-50. - Underground
Installations
-
Table 300-50. - Minimum Cover
Requirements
Article 305 - Temporary Wiring
-
Section 305-4.
General
-
Section 305-6. Ground-Fault
Protection for Personnel
Article 310 - Conductors for General
Wiring
-
Section 310-8.
Locations
-
Section 310-11.
Marking
-
Section 310-12. Conductor
Identification
-
Section 310-15. Ampacities for
Conductors Rated 0-2000 Volts
-
Table 310-15(b)(2)(a). Adjustment
Factors for More Than Three Current-Carrying Conductors in a Raceway
or Cable
-
Table 310-15(b)(6). Conductor Types
and Sizes for 120/240-Volt, 3-Wire, Single-Phase Dwelling Services and
Feeders
-
Table 310-20. Ampacities of Two or
Three Single-Insulated Conductors, Rated 0 through 2000 Volts,
Supported on a Messenger, Based on Ambient Air Temperature of 40
degrees C (104 degrees F)
-
Table 310-21. Ampacities for Bare
or Covered Conductors, Based on 40 degrees C (104 degrees F) Ambient,
80 degrees C (176 degrees F) Total Conductor Temperature, 2 ft/sec (6
1 0 mm/sec) Wind Velocity
-
Section 310-60. Conductors Rated
2001 to 35,000 Volts
Article 318 - Cable Trays
-
Section 318-6.
Installation
Article 320 - Open Wiring on
Insulators
-
Section 320-5.
Conductors
-
Section 320-15. Unfinished Attics
and Roof Spaces
Article 333 - Armored Cable: Type
AC
-
Section 333-11. Exposed
Work
Article 336 - Nonmetallic-Sheathed
Cable- Types NM, NMC, and NMS
Article 362 - Metal Wireways and
Nonmetallic Wireways
Part A. Metal
Wireways
-
Section 362-2. Uses
-
Section 362-6. Deflected Insulated
Conductors
Part B. Nonmetallic
Wireways
-
Section 362-19. Number of
Conductors
Article 364 -
Busways
Part A. General
Requirements
-
Section 364-10. Rating of
Overcurrent Protection - Feeders
Article 365 -
Cablebus
-
Section 365-5. Overcurrent
Protection
Article 370 - Outlet, Device, Pull and
Junction Boxes, Conduit Bodies and Fittings
Part B.
Installation
Part D. Manholes and Other Electric
Enclosures Intended for
Personnel Entry
Article 373 - Cabinets, Cutout Boxes
and Meter Socket Enclosures
-
Section 373-5. Cabinets, Cutout
Boxes, and Meter Socket Enclosures
Article 384 - Switchboards and
Panelboards
Part C.
Panelboards
-
Section 384-14. Classification of
Panelboards
-
Section 384-(16)(b). Power
Panelboard Protection
Article 410 - Lighting Fixtures,
Lampholders, Lamps and Receptacles
Part G. Construction of
Fixtures
-
Section 410-42. Portable
Lamps
Part L. Receptacles, Cord Connectors,
and Attachment Plugs (Caps)
-
Section 410-56(g). Attachment
Plugs
-
Section 410-58(a). Grounding
Poles
Part M. Special Provisions for Flush
and Recessed Fixtures
-
Section 410-66(a).
Clearance
Part P Special Provisions for
Electric Discharge Lighting Systems of 1000 Volt or
Less
-
Section 410-73(f). High-Intensity
Discharge Fixtures
Part R. Lighting
Track
-
Section 410- 101(c). Locations Not
Permitted
Article 422 -
Appliances
Part A. General
-
Section 422-4. Live
Parts
Part B.
Installation
-
Section 422- 10. Branch-Circuit
Rating
-
Section 422-11. Overcurrent
Protection
-
Section 422-12. Central Heating
Equipment
-
Section 422-13. Storage-Type Water
Heaters
-
Section 422-14. Infrared Lamp
Industrial Heating Appliances
-
Section 422-15. Central Vacuum
Outlet Assemblies
-
Section 422-16. Flexible
Cords
-
Section 422-17. Protection of
Combustible Materials
-
Section 422-18. Support of
Ceiling-Suspended (Paddle) Fans
-
Section 422-20. Other Installation
Methods
Part C. Disconnecting
Means
-
Section 422-30.
General
-
Section 422-31. Disconnection of
Permanently Connected Appliances
-
Section 422-32. Disconnection of
Cord- and Plug-Connected Appliances
-
Section 422-33. Unit Switch(es) as
Disconnecting Means
-
Section 422-34. Switch and Circuit
Breaker to Be Indicating
-
Section 422-35. Disconnecting Means
for Motor-Driven Appliance
Part D.
Construction
-
Section 422-40. Polarity in Cord-
and Plug- Connected Appliances
-
Section 422-41. Cord- and
Plug-Connected Appliances Subject to Immersion
-
Section 422-42. Signals for Heated
Appliances
-
Section 422-43. Flexible
Cords
-
Section 422-44. Cord- and
Plug-Connected Immersion Heaters
-
Section 422-45. Stands for Cord-
and Plug- Connected Appliances
-
Section 422-46.
Flatirons
-
Section 422-47. Water Heater
Controls
-
Section 422-48. Infrared Lamp
Industrial Heating Appliances
-
Section 422-49. High-Pressure Spray
Washers
-
Section 422-50. Cord- and
Plug-Connected Pipe Heating Assemblies
Part E. Marking
-
Section 422-60.
Nameplate
-
Section 422-61. Marking of Heating
Elements
-
Section 422-62. Appliances
Consisting of Motors and Other Loads
Article 424 - Fixed Electric
Space-Heating Equipment
Part E. Electric Space-Heating
Cables
-
Section 424-44(g). Ground-Fault
Circuit- Interrupter Protection for Conductive Heated Floors of
Bathrooms, Hydromassage Bathtub, Spa, and Hot Tub
Locations
Article 430 - Motors, Motor Circuits,
and Controllers
Part A. General
-
Section 430-6. Ampacity and Motor
Rating Determination
Part B. Motor Circuit
Conductors
-
Section 430-22(b). Other than
Continuous Duty
Part D. Motor Branch-Circuit
Short-Circuit and Ground-Fault Protection
-
Section 430-52. Rating or Setting
for Individual Motor Circuit
Part G. Motor
Controllers
Part J. Disconnecting
Means
Article 445 -
Generators
-
Section 445-9. Generator Terminal
Housings
-
Section 445-10. Disconnecting Means
Required for Generators
Article 490 - Equipment, Over 600
Volts, Nominal (New)
Article 500 - Hazardous
(Classified) Locations, Classes I, II, and 111, Divisions 1 and 2
(Entirely rewritten)
Article 513 - Aircraft
Hangers
-
Section 513-1. Scope
-
Section 513-2.
Definitions
Mobile Equipment
Portable
Equipment
Article 514 - Gasoline Dispensing and
Service Stations
-
Section 514-5. Circuit
Disconnects
Article 517 - Health Care
Facilities
Part C. Essential Electrical
Systems
-
Section 517-30(b)(6). Hospital
power sources to serve essential electrical systems
Part D. Inhalation Anesthetizing
Locations
-
Section 517-63(a). Battery-Powered
Emergency Lighting Units
Part G. Isolated Power
Systems
-
Section 517-160(a)(5).
Identification of isolated circuit conductors
Article 518 - Places of
Assembly
-
Section 518-2. General
Classifications
-
Section 518-4. Wiring
Methods
Article 520 - Theaters, Audience Areas
of Motion Picture and Television Studios, and Similar
Locations
Part A. General
-
Section 520-5. Wiring
Methods
Part D. Portable Switchboards on
Stage
-
Section 520-53(h). Supply
Conductors
Part E. Portable Stage Equipment
Other than Switchboards
-
Section 520-68. Conductors for
Portables
Part F Dressing
Rooms
-
Section 520-73. Switches
Required
Article 525 - Carnivals, Circuses,
Fairs and Similar Events
Part A. General
Requirements
-
Section 525-3(c). Audio Signal
Processing, Amplification and Reproduction Equipment
Part B.
Installation
-
Section 525-10(b).
Services
-
Section 525-13(g). Inside Tents and
Concessions
-
Section 525-18. Ground-Fault
Circuit-Interrupter Protection for Personnel
Part D. Disconnecting
Means
-
Section 530-30. Type and
Location
Part E. Attractions Utilizing Pools,
Fountains and Similar Installations with Contained Volumes of
Water
-
Section 525-40. Wiring and
Equipment
Article 530 - Motion Picture and
Television Studios and Similar Locations
Part B. Stage or
Set
-
Section 530-12. Portable
Wiring
Article 547 - Agricultural
Building
-
Section 547-4. Wiring
methods
-
Section 547-8. Service Equipment,
Separately Derived Systems, Feeders, Disconnecting Means, and
Grounding
-
Section 547-9. Bonding and
Equipotential Plane
Article 550 - Mobile Homes,
Manufactured Homes and Mobile Home Parks
Part B. Mobile
Homes
-
Section 550-8(g) Pipe Heating Cable
Outlet
Article 551 - Recreational Vehicles and
Recreational Vehicle Parks
Part G. Recreational Vehicle
Parks
-
Section 551-72. Distribution
System
Article 552 - Park
Trailers
Part D. Nominal 120-Volt or 1201240
Volt Systems
-
Section 552-41(d). Pipe Heating
Cable Outlet
-
Section 552-43. Power
Supply
Article 555 - Marinas and
Boatyards
-
Section 555-6. Feeders and
Services
Article 600 - Electric Signs and
Outline Lighting
Part A. General
-
Section 600-6.
Disconnects
Part B. Field Installed Skeleton
Tubing
-
Section 600-32(j). Length of High
Voltage Cable
Article 604 - Manufactured Wiring
Systems
-
Section 604-5. Uses Not
Permitted
Article 610 - Cranes and Hoists
Part A. General
-
Section 610-2(b). Combustible
Materials
Part B. Wiring
-
Section 610-13(d) Conductors for
Class 1, Class 2, and Class 3
installation
Part E. Overcurrent
Protection
-
Section 610-41(b). More Than One
Feeder Circuit
Article 620 - Elevators, Dumbwaiters,
Escalators, Moving Walks, Wheelchair Lifts, and Stairway Chair
Lifts
Part C. Wiring
-
Section 620-22(a). Car Light
Source
Article 625 - Electric Vehicle Charging
System Equipment
Part A. General
-
Section 625-2.
Definitions
Electric Vehicle
Coupler
Part B. Wiring and
Methods
-
Section 625-9. Electric Vehicle
Coupler
Part C. Equipment
Construction
-
Section 625-13. Electric Vehicle
Supply Equipment
-
Section 625-15.
Markings
Part E. Electric Vehicle Supply
Equipment Location
-
Section 625-29. Indoor
Sites
Article 668 - Electrocytic
Cells
-
Section 668-2.
Definitions
Electrically
Connected
Article 680 - Swimming Pools, Fountains
and Similar Installations
Part A. General
-
Section 680-1. Scope
-
Section 680-4.
Definitions
Packaged Therapeutic Tub or
Hydrotherapeutic Tank Equipment Assembly
Self-Contained Therapeutic Tubs or
Hydrotherapeutic Tanks
-
Section 680-6. Receptacles,
Lighting Fixtures, Lighting Outlets, Switching Devices and Ceiling
Suspended (Paddle) Fans
Part B. Permanently Installed
Pools
-
Section 680-22.
Bonding
-
Section 680-25(c).
Motors
Part D. Spas and Hot
Tubs
-
Section 680-38. Emergency Switch
for Spas and Hot Tubs
-
Section 680-40. Outdoor
Installations
Part E.
Fountains
-
Section 680-57. Signs
Part G. Hydromassage
Bathtubs
-
Section 680-72.
Accessibility
Article 690 Solar Photovoltaic
Systems
Part A. General
-
Table 690- 1 (a). Identification of
solar photovoltaic system components
-
Table 690- 1 (b). Identification of
solar photovoltaic system components in common
configurations
-
Section 690-2.
Definitions
Alternating-Current Module (AC
Photovoltaic Module)
Charge Controller
Electrical Production and
Distribution Network Hybrid System
Interactive
System
System
Voltage
-
Section 690-3. Other
Articles
-
Section 690-4(c). Module Connection
Arrangement
-
Section 690-5. Ground-Fault
Protection
Part B. Circuit
Requirements
-
Section 690-7. Maximum
Voltage
-
Table 690-7. Voltage
Correction Factors for
-
Crystalline and Multi-Crystalline
Silicon Modules
-
Section 690-8. Circuit Sizing and
Current
Part H. Storage
Batteries
-
Section 690-72. Charge
Control
Part I. Systems Over 600
Volts
Article 695 - Fire
Pumps
-
Section 695-6. Power
Wiring
Article 700 - Emergency
Systems
Part B. Circuit
Wiring
-
Section 700-9. Wiring, Emergency
System
Part C. Sources of
Power
-
Section 700-12(c). Uninterruptible
Power Supplies
-
Section 700-12(d). Separate
Service
Part F. Overcurrent
Protection
Article 725. Class 1, Class 2, and
Class 3
Remote-Control, Signaling and Power-Limited
Circuits
Part C. Class 2 and Class 3
Circuits
-
Section 725-71(g). Class 3 Single
Conductors
Article 727 - Instrumentation Tray
Cable: Type ITC
Article 760 - Fire Alarm
Systems
Part A. General
-
Section 760-2.
Definitions
Fire Alarm Circuit Integrity (CI)
Cable
Part B. Nonpower-Limited Fire Alarm
(NPLFA) Circuits
-
Section 760-24. NPLFA Circuit
Overcurrent Device Location (Exception #3)
-
Section 760-31. Listing and Marking
of NPLFA Cables
Part C. Power Limited Fire Alarm
(PLFA) Circuits
-
Section 760-61. Applications of
Listed PLFA Cables
Article 770 - Optical Fiber Cables and
Raceways
Part A. General
-
Section 770-2.
Definitions
Article 800 - Communications
Circuits
Part A. General
-
Section 800-2.
Definitions
Exposed
Premises
Part E. Communications Wires and
Cables Within Buildings
-
Section 800-51(j). Plenum
Communications Raceway
-
Section 800-51 (k). Riser
Communications Raceway
-
Section 800-51 (l). General-Purpose
Communications Raceway
-
Section 800-53(f). Cable
Substitutions
-
Table 800-53. Cable Uses, and
Permitted Substitutions
Article 810 - Radio and Television
Equipment
Article 820 - Community Antenna
Television and Radio Distribution Systems
-
Section 820-2.
Definitions
Exposed
Premises
-
Section 820-3. Locations and Other
Articles
Article 830 - Networked-Powered Broadband Communications
Systems
Appendix D
Summary
The NEC specifies the minimum
provisions necessary for protecting people and property from hazards
arising from the use of electricity and electrical equipment. Anyone
involved in any phase of the electrical industry must be aware of how to
use and apply the code on the job. Using the NEC will help you to safely
install and maintain the electrical security equipment and systems that
you come into contact with.
The NEC is composed of the
following components:
Appendix: Appendix A includes material extracted
from other NFPA documents. Appendix B is not part of the requirements of
the NEC and contains additional material for informational purposes
only. Appendix C includes tables for the amount and type of cables allowed
in all the standard size conduits and tubings available. Appendix D
includes examples illustrating load computations for various types of
dwelling and electrical systems. These appendices are located at the back
of the code book.
Article: Beginning with Article 90 -
Introduction, and ending with Article 830 - Network Powered Broadband
Communication Systems, the NEC Articles are the main topics in the
code book.
Chapter: The NEC includes nine chapters. Chapter 1 -
General, Chapter 2 - Wiring and Protection Chapter 3 - Wiring Methods and
Materials, Chapter 4 - Equipment for General Use, Chapter 5 - Special
Occupancies, Chapter 6 - Special Equipment, Chapter 7 - Special
Conditions, Chapter 8 - Communications Systems and Chapter 9 - Tables and
Examples. The Chapters form the broad structure of the
NEC.
Contents: Located among the first pages of the
code book, the contents section provides a complete outline of the
Chapters, Articles, Parts, Tables, and Examples. The contents section,
used with the index, provides excellent direction for locating answers to
electrical problems and questions.
Diagrams and Figures: Diagrams and Figures appear in the
NEC to illustrate the relationship of Articles and Parts of the
NEC. For example, Diagram 230-1, Services, shows the relationship
of Articles and Parts relating to the installation of electric
services.
Examples: Service and feeder calculations for
various types of buildings.
Exceptions: Exceptions follow code sections and
allow alternative methods, to be used under specific conditions, to the
rule stated in the section.
FPN (Fine Print Note): A Fine Print Note is defined in NEC
Section 110-1; that is, explanatory material is in the form of Fine
Print Notes (FPN).
Notes: Notes typically follow tables and are
used to provide additional information to the tables or clarification of
tables.
Part: Certain Articles in the NEC are
divided into Parts. Article 220 - Branch Circuit, Feeder and Service
Calculations is divided into Part A, B, C, and D.
Section: Parts and Articles are divided into
Sections. A reference to a section will look like the
following:
300-19. Supporting Conductors in
Vertical Raceways.
NEC Sections provide more detailed
information within NEC Articles.
Tables: Tables are located within Chapters to
pro- vide more detailed information explaining code content. For example,
Table 310-16 lists ampacities for insulated conductors for copper,
aluminum, and copper-clad aluminum conductors with insulation types,
sizes, temperature ratings, and ampacity correction
factors.
See Figure 1-3 for a summary of NEC
installation requirements for various occupancies.
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