Electical Contractor

When sizing conductors, more is involved than just selecting a copper or aluminum conductor with the right ampacity from Table 310.15(B)(16) (formerly Table 310.16) in the National Electrical Code (NEC).

A good client summoned me to investigate an accident that occurred when a maintenance electrician was replacing a 30-ampere (A), bolt-in circuit breaker. An electrical arc developed while the electrician was changing out the circuit breaker.

Lately, I have received questions about the number of disconnects permitted for a building or structure. In one query, an inspection found more than six disconnects were present in an oil and gas refinery building, and it took more than six throws of the hand to disconnect incoming power supplies.

From marking equipment and conductors at the factory to field-marking with signs where electrical hazards exist, there are hundreds, if not thousands, of marking requirements in the National Electrical Code (NEC).

Motor-control circuits may be very low voltage; they may be in the 12- to 24-volt (V) alternating current (AC) or direct current (DC) range or as high as 600V.

If you have a problem related to the National Electrical Code (NEC), are experiencing difficulty in understanding a Code requirement, or are wondering why or if such a requirement exists, ask Charlie, and he will let the Code decide. Questions can be sent to codefaqs@earthlink.net.

The 2014 National Electrical Code (NEC) development process is in full swing with the NEC technical committees acting on 3,745 proposed new articles and revisions. New and improving technologies and industry advances are driving changes into the electrical industry at an accelerated pace.

Through the years, I have instructed many seminars for folks using NFPA 70E, the Standard for Electrical Safety in the Workplace. Participants often ask the same questions. Here are the most frequently asked questions about NFPA 70E. Does 70E apply to personnel performing electrical installations?

Table 310.15(B)(16) in the National Electrical Code (NEC) provides allowable or maximum ampacities for insulated conductors rated up to and including 2,000 volts (V).