Question: What size equipment grounding conductor (EGC) is required for a feeder tap supplying a 60A breaker consisting of 8 ft of No. 6 THWN copper conductors tapped from a feeder supplied by a 400A circuit breaker?
See the answer below.
Answer: No. 6
Explanation: Section 250.122(G) requires the equipment grounding conductor (EGC) run with tap conductors to be sized in accordance with Table 250.122 based on the rating of the overcurrent device ahead of the feeder but not larger than the tap conductors. The 400A circuit breaker would normally require a No. 3 but a No. 6 is the largest EGC required to be run with the No. 6 tap conductors.
Lupacchino is a senior design engineer with Gaylor Electric, Inc. in Noblesville, Ind. and serves as an alternate on NEC Code-Making Panel No. 3. He is currently licensed in more than 80 jurisdictions. He can be reached at [email protected].