NEC(R) Overview 231

"NEC Overview" provides information on the contents, purpose, history, and applications of the National Electrical Code. The NEC is written for experienced electrical workers. The NEC(R) is the essential standard on minimum safe installations. While safe practices are encouraged when working with electrical systems and the NEC(R) offers them, the code is not the law unless it is adopted by local government. However, the NEC(R), in some form, is the law for minimum electrical installations in all states. Using and understanding the National Electrical Code is essential for anyone who works with electrical systems. This course assists readers in navigating the NEC(R) and understanding its function. After completing this course, users will be able to describe the structure of the National Electric Code(R), as well as its major guidelines that impact electrical maintenance in production facilities.

Class Details

Class Name:
NEC(R) Overview 231
Number of Lessons:
Related 1.0 Class:
NEC Overview 150

Class Outline

  • What Is the NEC(R)?
  • The History of the Code
  • The NFPA
  • NFPA 70E(R) and OSHA
  • How the Code Is Developed
  • Code Development and History Review
  • How the Code Becomes Law
  • Code Scope
  • Code Structure
  • How to Read the Code
  • Code Definitions
  • Code Details Review
  • Code Abbreviations
  • Code Measurements
  • Code Tables
  • Changes to the Code
  • Nationally Recognized Testing Laboratories
  • Code Information and Organizations Review


  • Describe the National Electrical Code(R).
  • Describe the history of the Code.
  • Describe the NFPA.
  • Describe the relationship between NFPA 70E and OSHA.
  • Describe how the Code is developed.
  • Explain how the Code becomes law.
  • Describe the scope of the Code.
  • Describe the structure of the Code.
  • Describe the ways to read the Code.
  • Explain how the Code defines terms.
  • Explain how the Code uses abbreviations.
  • Explain how the Code uses measurements.
  • Describe the tables in the Code.
  • Describe how changes to the Code are communicated.
  • Describe Nationally Recognized Testing Laboratories.

Job Roles



Vocabulary Term Definition
accessible A product or system whose wiring can be maintained and used without damaging a structure. As defined by the NEC(R), even a 20-foot ceiling fan is accessible.
adoption by reference A method of entering the NEC(R) into law. Adoption by reference creates laws that point to specific sections of the NEC(R).
adoption by transcription A method of entering the NEC(R) into law. Adoption by transcription reproduces the NEC(R) standards as law.
AFCI Arc fault circuit interrupter. An AFCI is a device that de-energizes a circuit. AFCIs de-energize circuits when arc faults are detected.
ampacity The allowable current-carrying capacity of a conductor measured in amps. Maximum safe ampacities are listed for each wire gauge in NEC(R) tables.
annexes Sections of a book that provide readers with supplemental material. In the NEC(R), Annexes A-F provide readers with additional helpful information.
Article 100 The first article of Chapter 1 of the NEC(R). Article 100 provides the NEC(R) definitions of the key terms used throughout the text.
Article 110.3 An article in the NEC(R) that calls for electrical devices and equipment to be labeled or listed. Article 110.3 requires that nationally recognized testing laboratories certify electrical items as safe for use.
Article 110.6 A section of the NEC(R) that includes standards regarding employee training in safety measures. Article 110.6 covers safety training in CPR and other certifications.
Article 80 A model local ordinance for the administration and enforcement of the NEC(R). Article 80 is located in Annex H of the 2014 NEC(R).
Article 90.2 An article of the NEC(R) that states what is and is not covered in the Code. Article 90.2 is a section of Article 90.
Article 90.5 A section of Article 90 that explains rules in the NEC(R). Article 90.5 specifically details mandatory and permissive rules.
Article 90.9 A section of Article 90 that explains the NEC(R) rules for units of measurement. Article 90.9 lists both permissive and mandatory rules.
AWG American Wire Gauge. AWG are units used to express conductor sizes, required in Article 110.6 of the NEC(R). AWG is represented by kcmils.
Canadian Standards Association CSA. The major Canadian listing agency. CSA usually certifies a device based on UL testing.
Chapter 9 The final chapter of the NEC(R). Chapter 9 contains various tables with a collection of important information.
Code The standard for minimum safe electrical installations. The Code, or the NEC(R), is adopted in some form as law in all 50 states.
conductor A material that allows the free movement of electrons and electricity. Most conductors are metals.
consumers A person who purchases products or services that are affected by the NEC(R). Consumers provide input to the NEC(R) online.
enforcing authorities Member of an organization who is in charge of enforcing the NEC(R). Enforcing authorities may issue citations to facilities that do not comply with NEC(R) standards.
FPN Fine-print notes. Supplements to article rules. FPNs are not requirements and exist for information purposes only.
General Duty Clause A statement contained within OSHA's standards that requires employers offer employment free from health and safety hazards. The General Duty Clause covers situations for which there are no specific standards.
GFCI Ground fault circuit interrupter. A GFCI is a device that de-energizes a circuit. GFCIs de-energize circuits when a dangerous current fault occurs.
hazard A source of danger or possible injury. Hazards can pose risks to physical well-being or health.
inch-pound A system of measurement based on the pound, gallon, and inch. The inch-pound system is also known as the English system, as it is used in only a few English-speaking countries.
index An alphabetized list with the page numbers of subjects discussed in the NEC. The index is more helpful when trying to locate specific information in the Code than its table of contents.
installers/maintainers People in the business of installing and maintaining electrical products or systems. Installers/maintainers must follow NEC(R) guidelines to keep users safe.
insurance People associated with the insurance industry. Insurance members work to financially protect facilities when damage from electrical products and systems occurs.
insurers Members of insurance companies. Insurers work to financially protect facilities when damage from electrical products and systems occurs.
Intertek Testing Services The NRTL that uses the ETL listing mark. Intertek Testing Services also uses CE listing marks.
kcmil Thousands of circular mils. A unit of measurement for electrical conductors. Kcmils are used to express large conductor sizes.
labor A person who is involved with increasing and maintaining workplace safety. Labor members are often part of unions or other organizations devoted to improving working conditions.
lockout/tagout A safety method that involves the locking and labeling of machines. Lockout/tagout protects employees from accidental machine startup.
mandatory rule A rule in the NEC(R) that uses the words "shall" and "shall not." Mandatory rules must always be followed by users.
manufacturers A person or organization that makes an electrical product or system. Manufacturers will often provide guides to use their products.
Maryland electrical testing laboratories MET labs. The first listing organization to pass the OSHA NRTL process. MET laboratory markings are accepted everywhere in the United States.
metric system A standard international system of measurement based on the gram, liter, and meter. The metric system is also known as the SI (standard international) system.
mil A linear unit of diameter that is equal to 0.001 of an inch. The mil is used as a unit of measurement because of the small size of wire diameters.
National Electrical Code NEC(R). The standard for minimum safe electrical installations. The NEC(R) 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 NFPA was originally formed to develop standards for sprinkler systems.
nationally recognized testing laboratory NRTL. A listing organization that has passed the OSHA recognition process. NRTLs certify the safety of devices through listing and labeling.
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. NFPA 70(R) is the National Fire Protection Association's technical name for the National Electrical Code(R).
NFPA 70E(R) A corollary to the NEC(R) known as the standard for electrical safety in the workplace. The NFPA 70E(R) is used by OSHA to establish work safety guidelines.
Occupational Safety and Health Administration OSHA. A government agency that sets the standards for working conditions in the United States. OSHA ensures that employees work in safe and healthy environments.
optical cables A conductor that contains fibers that carry light. Optical cables are covered by the NEC(R).
OSHA recognition process A thorough, formal process to certify listing organizations as qualified to deem devices safe for use. The OSHA recognition process ensures that electrical products provide protection against known safety risks.
permissive rule A rule in the NEC(R) that uses the words "shall be permitted" and "shall not be permitted." Permissive rules are typically found in lists of the different ways a project can be completed.
research/testing A member of an independent lab that tests electrical products and systems. Research/testing members help develop the Code to include advancements in and new types of electrical equipment and systems.
short circuits A circuit where current takes a shorter, unintended path between two conductors. Short circuits can occur when the insulation of two conductors is worn or damaged.
special experts A person with expertise in a specific area of the NEC(R). Special experts ensure that the different areas of the NEC(R) contain accurate, updated information.
Standard International system SI system. A system of measurement based on the gram, liter, and meter. The standard international system is known as the metric system.
standards 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.
table of contents A sequentially ordered list found in the front of a book. The table of contents shows where general topics can be found in a book.
trade size A phrase used to distinguish between actual size and industry standard approximation for that size. A trade size of 1/2 in. may have the actual size of up to .7 in. depending on the situation.
Underwriters Laboratories UL. One of the most recognized NRTLs dedicated to product safety testing and certification. UL wrote many standards for safe devices before OSHA formalized the process.
union A group that workers form in order to protect their positions and rights in the workplace. In the electrical industry, unions often work to increase worker safety.
users Any person who uses the NEC(R) on a regular basis. Users may need guidelines or other assistance to use the NEC(R) effectively.
utility company An entity recognized by governmental law that installs, operates, and maintains electric supply. Most utility company installations are not covered under the scope of the NEC(R).
wire gauge The size of the diameter of a wire conductor. Wire gauges come in a series of standard sizes.