Code Quiz of Day

Proper Size Grounding Electrode Conductor

Dec. 4, 2014

Grounding electrode conductor sizes for use in AC systems

The largest size grounding electrode conductor required is _____ copper.

a) 6 AWG
b) 1/0 AWG
c) 3/0 AWG
d) 250kcmil

See answer and applicable Code reference

The correct answer is: c) 3/0 AWG

Article 250 covers general bonding and grounding requirements. As noted in Sec. 250.66, the size of the grounding electrode conductor at the service, at each building or structure where supplied by a feeder or branch circuit, or at a separately derived system of a grounded or ungrounded AC system shall not be less than given in Table 250.66, except as permitted in 250.66(A) through (C). Looking at Table 250.66, we see that the largest size copper grounding conductor is 3/0 AWG.

About the Author

Mike Holt

Mike Holt is the owner of Mike Holt Enterprises (www.MikeHolt.com), one of the largest electrical publishers in the United States. He earned a master's degree in the Business Administration Program (MBA) from the University of Miami. He earned his reputation as a National Electrical Code (NEC) expert by working his way up through the electrical trade. Formally a construction editor for two different trade publications, Mike started his career as an apprentice electrician and eventually became a master electrician, an electrical inspector, a contractor, and an educator. Mike has taught more than 1,000 classes on 30 different electrical-related subjects — ranging from alarm installations to exam preparation and voltage drop calculations. He continues to produce seminars, videos, books, and online training for the trade as well as contribute monthly Code content to EC&M magazine.