Charles R. Miller

Code Contributor

Charles R. Miller, owner of Lighthouse Educational Services, teaches classes and seminars on the electrical industry. He is the author of “Illustrated Guide to the National Electrical Code” and NFPA’s “Electrical Reference.” He can be reached at 615.333.3336, or

Articles by Charles R. Miller

March 2015
The National Electrical Code (NEC) is divided into an introduction and nine chapters with 10 informational annexes. As specified in 90.5(D), the informative annexes are not part of the NEC’s enforceable requirements but are included for informational purposes only. Like annexes, informational notes are not enforceable. 
February 2015
There have been countless changes, both in the electrical industry and in the National Electrical Code (NEC), since the first edition in 1897. While a lot has changed, the reason and purpose of the Code have remained constant. As stated in 90.1(A), the purpose of the Code is the practical safeguarding of persons and property from hazards arising from electricity use. READ MORE
January 2015
Article 210 in the National Electrical Code (NEC) covers branch circuits, with the exception of circuits that supply motor loads only. Article 430 covers these branch circuits, and Part II covers motor-circuit conductors. As stated in 430.21, Part II specifies ampacities of conductors that are capable of carrying the motor current without overheating under the conditions specified. READ MORE
December 2014
Article 430 of the National Electrical Code (NEC) covers motors, motor branch-circuit and feeder conductors, motor branch-circuit and feeder protection, motor-overload protection, motor-control circuits, motor controllers, and motor-control centers. Many factors must be considered when sizing conductors for motors. READ MORE
November 2014
Most of Article 240 in the National Electrical Code (NEC) provides general requirements for overcurrent protection and overcurrent protective devices not more than 1,000 volts (V), nominal. As a general rule, the overcurrent device rating shall not exceed the ampacity of a conductor. READ MORE
October 2014
Article 310 in the National Electrical Code (NEC) covers general requirements for conductors and their type designations, insulations, markings, mechanical strengths, ampacity ratings and uses. READ MORE
September 2014
Article 210 in the National Electrical Code (NEC) covers branch circuits, except when they supply only motor loads, which Article 430 covers. When sizing conductors for branch circuits, it is necessary to comply with the provisions in Article 210. It may also be necessary to check for applicable provisions in other articles. READ MORE
August 2014
Article 100 of the National Electrical Code (NEC) defines “equipment” as a general term, including fittings, devices, appliances, luminaires, apparatus, machinery and the like, used as a part of, or in connection with, an electrical installation. READ MORE
July 2014
Selecting the correct size conductor is not difficult, but it involves more than selecting a conductor based solely on the ampacity shown in Table 310.15(B)(16) in the National Electrical Code (NEC). READ MORE