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

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
August 2013
Section 240.21 in the National Electrical Code (NEC) contains feeder tap rules. As defined in 240.2, a tap conductor 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. READ MORE
July 2013
Table 310.15(B)(16) is one of the most referenced tables in the National Electrical Code (NEC). It contains allowable (or maximum) ampacities for insulated conductors rated up to and including 2,000 volts (V). The ampacities listed in this table are based on specific conditions.
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