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Electrical Systems

NEC(R) Overview 231

This class provides information on the contents, purpose, history, and applications of the National Electrical Code(R). The NEC is the essential standard on minimum safe electrical installations and is intended for use by experienced electrical technicians. While the NEC establishes safe practices for working with electrical systems, the Code is not the law unless it is adopted by local government. However, some form of the NEC is adopted as law in all 50 states.

Using and understanding the National Electrical Code is essential for anyone who works with electrical systems. After completing this course, users will be able to navigate the National Electric Code and understand its scope and function.

  • Difficulty Intermediate

  • Format Online

  • Number of Lessons 19

  • Language English

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Course Outline
  • The NEC(R)
  • The History of the Code
  • The NFPA
  • NFPA 70E(R) and OSHA
  • Electrical Standards and Organizations Review
  • Code Structure
  • Code Scope
  • Reading the Code
  • Code Introduction Review
  • Code Definitions
  • Code Measurements
  • Code Tables
  • Nationally Recognized Testing Laboratories
  • Code Details Review
  • The Code Development Process
  • Committee Members
  • Changes to the Code
  • How the Code Becomes Law
  • Final Review
Objectives
  • Describe the National Electrical Code®.
  • Describe the history of the Code.
  • Describe the NFPA.
  • Describe the relationship between NFPA 70E® and OSHA.
  • Describe the structure of the Code.
  • Describe the scope of the Code.
  • Describe how to read the Code.
  • Explain how the Code defines terms.
  • Explain how the Code uses measurements.
  • Describe the tables in the Code.
  • Describe nationally recognized testing laboratories.
  • Describe how the Code is developed.
  • Identify the classifications for Code committee members.
  • Describe how changes to the Code are communicated.
  • Explain how the Code becomes law.
Glossary
Vocabulary Term
Definition

adoption by reference

A method of entering the NEC into law by creating laws that point to specific sections of the NEC. Adoption by reference is the only method currently supported by the NEC.

adoption by transcription

adoption by transcription | A method of entering the NEC into law by reproducing the text of the NEC standard as law. Adoption by transcription is no longer supported by the NEC.

American Wire Gauge

AWG. A measurement system that expresses conductor thickness with whole numbers. The American Wire Gauge system assigns numbers to conductors that decrease in value as the thickness of conductors increases.

ampacity

The allowable current-carrying capacity of a conductor, measured in amperes. Maximum safe ampacities are listed for each wire gauge in NEC tables.

annexes

A section of a book or document that provides readers with supplemental material. Annexes A-K in the NEC provide readers with additional helpful information that is not part of the official requirements.

Applied Research/Testing Laboratory

R/T. An NEC committee classification used to identify representatives of independent organizations that assess electrical products and systems and promote and/or enforce standards based on their evaluation. Applied Research/Testing Laboratory members help develop the Code to include advancements in and new types of electrical equipment and systems.

Article 100

An article of Chapter 1 that provides definitions of technical terms used throughout the NEC. Article 100 provides technical definitions, which may differ from what a term means in common usage.

Article 110.3

A section of Article 110 that calls for electrical devices and equipment to be labeled and/or listed to certify them as safe for use. The requirements in Article 110.3 are fulfilled by nationally recognized testing laboratories that have completed the OSHA recognition process.

Article 110.6

A section of Article 110 that states that conductor sizes are expressed in American Wire Gauge (AWG) or circular mils (cmils). Although Article 110.6 specifies circular mils, most conductor sizes are actually given in thousands of circular mils (kcmils).

Article 80

An article in Annex H that provides a model local ordinance for the administration and enforcement of the NEC. Article 80 is not a requirement but an example to help governments adopt the Code as law.

Article 90.2

A section of Article 90 that states what is and is not covered in the NEC. Article 90.2 also states that special permission may allow the Code to be used for installations that are listed as not covered.

Article 90.5

A section of Article 90 that describes the types of rules and material in the NEC. Article 90.5 explains the difference between mandatory and permissive rules.

Article 90.9

A section of Article 90 that explains the rules for units of measurement in the NEC. Article 90.9 states that the International System of Units (SI) measurements should appear first and inch-pound, or English, units should appear afterwards in parentheses.

box fill

The volume inside an electrical box that is taken up by conductors, devices, and fittings. Box fill calculations can be made using information found in tables in the NEC.

circular mils

cmils. A unit of measurement that is equal to the area of a circle with a diameter of one mil, or one thousandth of an inch (0.0254 mm). Circular mils are used to measure the cross-sectional area of wire conductors.

Code

The standard for minimum safe electrical installations in the United States. The Code, also referred to as the National Electrical Code or by the technical name NFPA 70, is adopted in some form as law in all 50 states.

conductor

A material that allows the free movement of electrons and acts as a path for electricity. Most conductors, such as electrical wires, are made of metals.

conduit fill

The amount of volume inside a conduit that is taken up by wires and cables. Conduit fill is usually given as a percentage of the conduit's total internal volume.

Consumer

C. An NEC committee classification used to identify individuals or representatives of organizations that use finished products regulated by the NEC. Consumer members are separate from User members, who represent organizations that follow the Code.

control center

The location from which an electrical distribution system is monitored and controlled. Control centers collect and process data from the various parts of the system.

CSA Group

The major Canadian nationally recognized testing laboratory (NRTL). The CSA Group, formerly known as the Canadian Standards Association, usually certifies a device based on UL testing.

distribution system

An electrical circuit that provides power from the utility to specific end destinations. A distribution system uses generators, power lines, and transformers to deliver electric power to buildings and other structures.

electrical metallic tubing

EMT. A cylindrical enclosure made of metal that is used to route electrical wires and cables together. Electrical metallic tubing is durable and protects conductors from moisture, impact, and chemicals.

Enforcing Authority

E. An NEC committee classification used to identify representatives of organizations that are responsible for ensuring proper adherence to the NEC. Enforcing Authority organizations may issue citations to facilities that do not comply with NEC standards.

English system

A system of measurement based on the pound, gallon, and inch. The English system, also known as the inch-pound system, is used in only a few English-speaking countries.

General Duty Clause

A statement contained within OSHA's standards that requires employers to offer employment free from health and safety hazards. The General Duty Clause covers situations for which there are no specific standards.

generating station

A building where a utility company houses large, linked AC generators. Generating stations can create large amounts of power for widespread use throughout an electrical distribution system.

ground-fault circuit interrupter

GFCI. A protective device that de-energizes a circuit when a dangerous fault current occurs. Ground-fault circuit interrupters should be used whenever there is a chance for electricity to come into contact with water.

hazards

A source of danger or possible injury. Hazards can pose risks to physical well-being or health.

inch-pound system

A system of measurement based on the pound, gallon, and inch. The inch-pound system, also known as the English system, is used in only a few English-speaking countries.

index

An alphabetized list of keywords that provides the locations where different subjects are discussed in a book or document. The index can be more helpful than the table of contents when trying to locate specific information in the NEC.

Installer/Maintainer

I/M. An NEC committee classification used to identify representatives of organizations that install and/or maintain products and systems regulated by the Code. Installer/Maintainer organizations are responsible for the proper connection and upkeep of electrical products and systems.

Insurance

I. An NEC committee classification used to identify representatives of organizations that financially protect facilities when damage occurs. Insurance organizations specialize in the risks associated with damage caused by electrical products and systems.

insurers

A representative of an organization that works to financially protect facilities when damage occurs. Insurers originally formed the National Fire Protection Association (NFPA) in 1896 to improve fire prevention methods.

International System of Units

SI. An internationally recognized standard system of measurement based on the gram, liter, and meter. The International System of Units is also known as the metric system.

Intertek Testing Services

The nationally recognized testing laboratory (NRTL) that uses the ETL listing mark in the United States. Intertek Testing Services also uses the CE listing mark internationally.

Labor

L. An NEC committee classification used to identify individuals or representatives of organizations concerned with increasing and maintaining workplace safety. Labor members are often part of unions or other organizations devoted to improving working conditions.

lockout/tagout

A method of protecting employees from accidental machine startup through proper locking and labeling of machines. Lockout/tagout is an essential practice for the safe repair of machines.

mandatory rule

A rule in the NEC that must always be followed. A mandatory rule uses the words "shall" or "shall not."

Manufacturer

M. An NEC committee classification used to identify representatives of organizations that make products regulated by the Code. Manufacturer organizations produce electrical devices and systems.

MET Laboratories

The first electrical testing organization to become a nationally recognized testing laboratory (NRTL). MET Laboratories markings are accepted in the United States and Canada.

metric system

An internationally recognized standard system of measurement based on the gram, liter, and meter. The metric system is also known as the International System of Units (SI).

National Electrical Code

NEC. The standard for minimum safe electrical installations in the United States. The National Electrical Code, also referred to as the Code or by the technical name NFPA 70, is adopted in some form as law in all 50 states.

National Fire Protection Association

NFPA. A non-profit organization that maintains standards of public safety and fire prevention. The National Fire Protection Association was originally formed to develop standards for sprinkler systems.

nationally recognized testing laboratory

NRTL. An organization that certifies the safety of devices through listing and labeling. Nationally recognized testing laboratories must pass the OSHA recognition process before they can certify devices.

NEC

National Electrical Code. The standard for minimum safe electrical installations in the United States. The NEC, also referred to as the Code or by the technical name NFPA 70, is adopted in some form as law in all 50 states.

NFPA

National Fire Protection Association. A non-profit organization that maintains standards of public safety and fire prevention. The NFPA was originally formed to develop standards for sprinkler systems.

NFPA 70

The standard for minimum safe electrical installations in the United States. NFPA 70, also referred to as the National Electrical Code or the Code, is adopted in some form as law in all 50 states.

NFPA 70E

The standard for electrical safety in the workplace. NFPA 70E is a corollary to the NEC that OSHA uses to establish electrical work safety guidelines.

Occupational Safety and Health Administration

OSHA. A government agency that sets the standards for working conditions in the United States. The Occupational Safety and Health Administration ensures that employees work in safe and healthy environments.

optical cables

A conductor that contains fibers that carry light. Optical cables do not carry electricity, but they are covered by the NEC because they depend on electrical systems to function.

OSHA

Occupational Safety and Health Administration. A government agency that sets the standards for working conditions in the United States. OSHA ensures that employees work in safe and healthy environments.

OSHA recognition process

A thorough, formal process used to certify listing organizations as qualified to deem devices safe for use. The OSHA recognition process enables organizations to ensure that electrical products provide protection against known safety risks.

OSHA standards

An OSHA policy on a particular practice or method. OSHA standards have the same power as law, and non-compliance can result in fines or other penalties.

permissive rule

A rule in the NEC that is acceptable but not necessary. A permissive rule uses the words "shall be permitted" or "shall not be required."

Special Expert

SE. An NEC committee classification used to identify individuals who are extremely knowledgeable about the Code and do not represent one of the other categories. Special Expert members ensure that their specific areas of expertise in the NEC reflect accurate and up-to-date information.

special purpose ground-fault circuit interrupter

SPGFCI. A protective device used in circuits with a voltage to ground greater than 150 volts that de-energizes the circuit when a dangerous fault current occurs. Special purpose ground-fault circuit interrupters are activated at higher fault currents than typical ground-fault circuit interrupters.

substations

Any grouping of switchgears and transformers located near a source or destination being powered. Substations alter voltage levels and provide a point of control in electrical distribution systems.

table of contents

A sequentially ordered list of topics found in the front of a book or document. The table of contents shows the pages where each chapter, article, and part can be found in the NEC.

trade size

An industry-standard approximation for a given size. A trade size of 1/2 in. may have an actual measurement of up to 0.7 in. depending on the situation.

Underwriters Laboratories

UL. A widely recognized nationally recognized testing laboratory (NRTL) whose mark is widely accepted. Underwriters Laboratories wrote many standards for safe devices before OSHA formalized the NRTL recognition process.

Union

A group that employees form in order to protect their positions and rights in the workplace. In the electrical industry, unions often strive to increase employee safety.

User

U. An NEC committee classification used to identify representatives of organizations that follow the Code. User members represent organizations that are required to follow the Code as well as organizations that follow it voluntarily.

Utility

UT. An NEC committee classification used to identify representatives of organizations that install, operate, and maintain electrical distribution systems. Utility members are included in the NEC committee even though most utility company installations are not covered under the scope of the Code.

utility companies

An entity recognized by governmental law that installs, operates, and maintains electrical distribution systems. Most utility company installations are not covered under the scope of the NEC.