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

November 2011
Safety is the main reason for the existence of the National Electrical Code (NEC). Its purpose is the practical safeguarding of persons and property from hazards arising from the use of electricity [90.1(A)]. Ensuring conductors and overcurrent protective devices are sized correctly is one aspect of practical safeguarding. READ MORE
October 2011
The National Electrical Code (NEC) is revised every three years. The renumbering of Table 310.16 to Table 310.15(B)(16) was a significant change in the 2011 edition. READ MORE
September 2011
Sizing conductors is not a difficult task, but more is involved than referencing just one section, one article or even one chapter in the National Electrical Code (NEC). To select the correct conductor size, it is necessary to reference several sections throughout the Code. Before referencing the NEC, certain information is needed. Gather it by answering some key questions. READ MORE
August 2011
Whether conductors are supplying power to branch circuits, feeders or services, the ampacity must not be less than the load. The load can be an actual load, or it can be calculated in accordance with the requirements in Article 220 of the National Electrical Code (NEC). READ MORE
July 2011
Many factors are involved when sizing conductors. Specifications for sizing conductors are not just in one section or even one article of the National Electrical Code (NEC). Although the maximum allowable ampacities for conductors are listed in Table 310.15(B)(16) (formerly Table 310.16), other provisions must be considered. Section 110.14(C) must be acknowledged when sizing conductors. READ MORE
June 2011
Selecting the correct size conductor involves referencing more than one section and more than one chapter in the National Electrical Code (NEC). The following questions must be answered before selecting conductors. What is the lowest temperature rating of any connected termination, conductor or device? What is the connected load, or what is the calculated load in accordance with Article 220? READ MORE
May 2011
Article 220 of the National Electrical Code (NEC) provides requirements for calculating branch-circuit, feeder and service loads and is divided into five parts. Part I provides general requirements for calculation methods. Part II covers requirements for branch-circuit load calculations. READ MORE
April 2011
Last month’s article concluded with calculation requirements for new restaurants in accordance with the optional method. This month, the discussion continues with calculating farm loads in accordance with Article 220 in the National Electrical Code (NEC). READ MORE
March 2011
The National Board of Fire Underwriters, which is now the American Insurance Association, published the first edition of the National Electrical Code (NEC) in 1897. In 1911, the National Fire Protection Association (NFPA) assumed sponsorship and control of the NEC. READ MORE