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

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
February 2011
The National Electrical Code (NEC) contains nine chapters. The second chapter, Wiring and Protection, is one of four that apply generally to all electrical installations. Some of the articles in Chapter 2 include Article 200—Use and Identification of Grounded Conductors, Article 210—Branch Circuits, Article 230—Services, Article 240—Overcurrent Protection and Article 250—Grounding and Bonding. READ MORE
January 2011
Every three years, the National Electrical Code (NEC) is revised, but the Code has only been on a three-year cycle since 1975. During the NEC’s 114-year existance, revision cycles have ranged from one year to four years. The first edition of the Code book was published in 1897. The newest NEC, the 2011 edition, is the 52nd edition. READ MORE
December 2010
This month, Code in Focus covers an optional feeder and service load calculation for two dwelling units that are supplied by a single feeder. There are two methods for calculating services and feeders for one-family dwellings and multifamily dwellings, and either is permissible. In Article 220, the procedures are covered in Part III for the standard method and in Part IV for the optional method. READ MORE
November 2010
Last month’s Code in Focus covered multifamily-dwelling house loads as calculated in accordance with the optional method. This month, the discussion continues with the connected loads for multifamily dwellings as specified in 220.84(C)(4) of the National Electrical Code (NEC). READ MORE