elcome to this course on the  National Electrical Code as it applies to Motor Control circuits, Class 1, Class 2 and Class 3 circuits.  This Guide was written specifically to address the needs of mechanical and electrical persons doing control work that install work subject to the rules in the National Electrical Code.

Brief History:

he NEC has been around for about 100 years, the first edition being no more than a pamphlet.  As early as 1881, the first Electrical Code was a one page document written by the New York Board of Fire Underwriters, then later in 1911 by the National Fire Protection Association.  Today's 2002 NEC is over 1000 pages long and contains over 100 articles.  Thousands of individuals and organizations have contributed to writing the NEC.   The NEC is the most widely adopted electrical code in the world and is adopted as law by many States and local jurisdictions in the USA.

The Purpose of the NEC.

he purpose of the NEC is the practical safeguarding of persons and property from the hazards arising from the use of electricity.  Many persons doing control wiring ask, "What are the hazards associated with low voltage control work?"  For most common low voltage circuits there are minimal hazards from electrical shock or fire in a normal dry and nonhazardous environment.  However, if the wiring is not done correctly and to the rules in the NEC, the installation may become a source of ignition when there are flammable gases and vapors present.  Also use of  incorrect insulations may become a hazard in a fire by spreading toxic products of combustion and by helping accelerate the fire.  Many additional installation rules apply to special locations where flammable gases, vapors, combustible dusts, or ignitable filings are present.

The General Organization of the NEC

here are a set of rules that must be followed when reading and studying the NEC, or interpretations can become vague and contradictory leading to many arguments.  The first rule is to recognize the general organization of the NEC.  Chapters 1 through 4 apply generally except as modified or amended by Chapters 5 through 8.  When a chapter is divided into parts, Part 1 - General applies to all the other parts that are independent of each other.  When sections are referenced always read the title to the section.  The section rules apply within the scope of the heading or subheading only.   Also, exceptions apply only to the subsection that they follow.  Article 110, Requirements for electrical installations applies to all other Articles in the NEC.  Fine Print Notes (FPN) are explanations only and are not mandatory rules.  Mandatory rules are worded with "Shall."  Where the word "May" is used the authority having jurisdiction may or may not grant special permission.