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(ecmag.com) The National Electrical Code (NEC) contains the minimum requirements for a safe installation. One must do at least that much when installing electrical equipment and systems. This means understanding how to size electrical conductors of circuits, including the equipment grounding conductors (EGCs).
For circuits to operate or perform effectively, conductor sizing must by addressed in longer runs of feeders and branch circuits. Increasing conductor sizes from the minimum required sizes of current-carrying conductors reduces circuit impedance, because there is more wire to do the necessary work. EGCs of the wire type must also be increased to effectively perform during a ground-fault or short-circuit event.
Section 250.4(A)(5) indicates that electrical equipment, wiring and other electrically conductive material likely to become energized shall be installed in a manner that creates a low-impedance circuit facilitating the operation of the overcurrent device or ground detector for high-impedance grounded systems. It shall be capable of safely carrying the maximum ground-fault current likely to be imposed on it from any point on the wiring system where a ground fault may occur to the electrical supply source.
This performance requirement addresses installing electrical materials that form part or all of an effective ground-fault current path. An important aspect of this requirement is that it is related to the manner in which the materials are installed. Because the effective ground-fault current path is intentionally installed, its effectiveness is measurable based on NEC meeting minimum requirements and being installed in workmanlike fashion.
Wire-type EGCs must meet specific criteria directly related to performance and be of the lowest possible impedance. This will vary because of different lengths, sizes and other installation characteristics of branch circuits and feeders. Read full article: http://www.ecmag.com/section/codes-s...ing-conductors
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