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

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
February 2014
The first seven parts of Article 240 in the National Electrical Code (NEC) provide the general requirements for overcurrent protection and overcurrent protective devices not more than 1,000 volts (V), nominal. The scope of Article 240 (located in 240.1) describes the items covered in all nine parts. READ MORE
December 2013
Tap conductor rules are located in Article 240 in the National Electrical Code (NEC). A tap conductor (as used in Article 240) has overcurrent protection ahead of its point of supply that exceeds the value permitted for similar conductors that are protected as described elsewhere in 240.4 [240.2]. Also, service conductors are not tap conductors.
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November 2013
transformer secondary conductor rules are similar to tap conductor rules. Article 240.21 of the National Electrical Code (NEC) covers the location and sizing requirements of overcurrent protection for tap conductors and transformer secondary conductors. READ MORE
October 2013
Article 240 in the National Electrical Code (NEC) is titled “Overcurrent Protection.” While this term is not defined, Article 100 defines overcurrent. Overcurrent is any current in excess of the rated current of equipment or the ampacity of a conductor. The definition also states overcurrent may result from overload, short circuit or ground fault. READ MORE
September 2013
There is more to sizing a conductor than just selecting a conductor from Table 310.15(B)(16) (formerly Table 310.16) in the National Electrical Code (NEC). READ MORE

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