The smallest grounded or neutral conductor for an electric service using 1100 kcmil copper conductors is which?

• A. 2/0 copper
• B. 3/0 copper
• C. 1/0 copper
• D. No. 4 AWG copper

Answer: (A)

The idea here is how the neutral (grounded) conductor is sized for a service with very large feeders. The neutral must be able to carry the imbalance current that could occur between the hot conductors, and the NEC provides minimum sizes for the grounded conductor based on the size of the service conductors. For a service using 1100 kcmil copper conductors, the code specifies that the smallest allowable grounded (neutral) conductor is 2/0 copper. This ensures the neutral is big enough to handle normal and fault conditions and to coordinate properly with protection and grounding requirements. Although larger neutral sizes like 3/0 or 1/0 are permissible, they aren’t the minimum; 2/0 copper is the smallest allowed in this scenario. A much smaller conductor, such as No. 4 AWG copper, would not meet the code for this level of service.