For a panel with a 175-A main breaker and service entrance conductors of 2/0 AWG, what is the smallest size permitted for the main bonding jumper?

For a panel with a 175-A main breaker and service entrance conductors of 2/0 AWG, what is the smallest size permitted for the main bonding jumper?

• A. 1 AWG
• B. 3 AWG
• C. 6 AWG
• D. 4 AWG

Answer: (D)

Sizing the main bonding jumper hinges on the service rating’s required equipment grounding conductor. The bonding jumper ties the neutral to the grounding path at the service equipment, so its size must be no smaller than the grounding conductor specified for that service rating. For a 175 A service disconnect, the minimum equipment grounding conductor size is 4 AWG copper. The service entrance conductors being 2/0 AWG are larger, so the smallest permissible size for the main bonding jumper is 4 AWG copper. This ensures an adequate fault path without over- or under-sizing the bonding jumper.

Sizing the main bonding jumper hinges on the service rating’s required equipment grounding conductor. The bonding jumper ties the neutral to the grounding path at the service equipment, so its size must be no smaller than the grounding conductor specified for that service rating.

For a 175 A service disconnect, the minimum equipment grounding conductor size is 4 AWG copper. The service entrance conductors being 2/0 AWG are larger, so the smallest permissible size for the main bonding jumper is 4 AWG copper. This ensures an adequate fault path without over- or under-sizing the bonding jumper.