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, charles@charlesRmiller.com or www.charlsRmiller.com

Articles by Charles R. Miller

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
June 2014
Article 450 in the National Electrical Code (NEC) covers requirements for transformers. The scope of Article 450, located in 450.1, states that it covers the installation of all transformers, but there are eight exceptions. READ MORE
May 2014
Rules for transformer secondary conductors are in Section 240.21 of the National Electrical Code (NEC). Many electricians and electrical engineers are familiar with 240.21 because it contains tap rules. Rules for transformer secondary conductors follow the feeder tap rules because transformer secondary conductors are similar to feeder taps. READ MORE
April 2014
Transformer secondary conductor rules are similar to the rules for tap conductors. Rules for transformer secondary conductors and tap conductors are even in the same section of the National Electrical Code (NEC). READ MORE
March 2014
Article 240, in the National Electrical Code (NEC), provides general requirements for overcurrent protection and overcurrent protective devices. Also covered in Article 240 are overcurrent protection requirements for supervised industrial installations operating at voltages of not more than 1,000 volts (V), nominal. READ MORE

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