The National Electric Code (NEC) defines the Equipment Grounding Conductor (EGC) as the conductive path or paths that provides a route for ground-fault current. This connects any non-current carrying metal parts of equipment together and to the system ground conductor or to the ground electrode conductor or both.
Grounding and Bonding is discussed in Article 250 and the sizing of equipment grounding conductors in 250.122. The calculation is based on Table 250.122 which defines the minimum size equipment grounding conductor necessary.
These are summaries or definitions from the NEC. To see the actual NEC text visit NFPA.org. You can purchase a copy of the standard or utilize the free access as shown at the NFPA website.
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