What is the minimum size copper equipment grounding conductor for an 80-amp branch circuit?

What is the minimum size copper equipment grounding conductor for an 80-amp branch circuit?

• A. #8 AWG
• B. #6 AWG
• C. #10 AWG
• D. #12 AWG

Answer: (A)

Sizing the equipment grounding conductor depends on the size of the overcurrent protective device (OCPD). For copper conductors, NEC 250.122 provides a table that maps the OCPD rating to the minimum EGC size. If there isn’t an exact row for the OCPD value, you use the next lower rating shown in the table and take the corresponding conductor size. For a circuit protected at 80 amps, there isn’t an 80-amp line item. The next lower rated OCPD is 70 amps, which requires a copper equipment grounding conductor of 4 AWG. That ensures a low enough impedance path to allow fault current to trip the protection device promptly. A smaller conductor, like 8 AWG, would not meet the minimum required size for this protection level. If the circuit were protected by 100 amps, the minimum copper EGC would be larger (2 AWG), and larger or smaller OCPD ratings would shift the required EGC accordingly. If aluminum were used instead of copper, the required size would be larger still per the applicable table.

Sizing the equipment grounding conductor depends on the size of the overcurrent protective device (OCPD). For copper conductors, NEC 250.122 provides a table that maps the OCPD rating to the minimum EGC size. If there isn’t an exact row for the OCPD value, you use the next lower rating shown in the table and take the corresponding conductor size.

For a circuit protected at 80 amps, there isn’t an 80-amp line item. The next lower rated OCPD is 70 amps, which requires a copper equipment grounding conductor of 4 AWG. That ensures a low enough impedance path to allow fault current to trip the protection device promptly. A smaller conductor, like 8 AWG, would not meet the minimum required size for this protection level.

If the circuit were protected by 100 amps, the minimum copper EGC would be larger (2 AWG), and larger or smaller OCPD ratings would shift the required EGC accordingly. If aluminum were used instead of copper, the required size would be larger still per the applicable table.