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.

Brief History:

he first NEC was little more than a pamphlet started by the insurance and related  industries in 1897.   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 2005 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 according to the rules in the NEC that require separation of low power control wiring from power and lighting wiring, the installation may become a source of ignition and shock.   The use of  incorrect insulations is also important.  Cable insulations found in the NEC have extensive listing and substitution rules to prevent the spread of fire and toxic products of combustion.  There are also extensive rules covering  special locations where flammable gases, vapors, combustible dusts, or ignitable filings are present.  In these locations low power control circuits act as a source of ignition and raceways and cable sheaths  can act as a conduit for flammable gases and vapors.

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.