Master Electrician Exam (NEC)Services, Feeders, and Branch CircuitsMedium
A commercial kitchen is being wired with a 480Y/277V, 3-phase, 4-wire service. The service entrance conductors are 500 kcmil copper per phase. What is the minimum size copper bonding jumper required to bond the service raceway to the service equipment enclosure?
- A3/0 AWG copper
- B1/0 AWG copper
- C2/0 AWG copper
- D4/0 AWG copper
Show answer & explanationAnswer & explanation
Correct answer: B. 1/0 AWG copper
According to NEC Table 250.102(C)(1), for service-entrance conductors with an area of 500 kcmil copper, the minimum size required for the supply-side bonding jumper is 1/0 AWG copper. This table specifies the sizing of bonding jumpers based on the size of the ungrounded service conductors.
Why the other options are wrong
- A. 3/0 AWG copper is larger than required, leading to unnecessary cost.
- C. 2/0 AWG copper is larger than required, leading to unnecessary cost.
- D. 4/0 AWG copper is significantly larger than required, leading to unnecessary cost.
Supply-Side Bonding Jumper Sizing
The supply-side bonding jumper connects the service raceway or enclosure to the service equipment enclosure, and its size is determined by the largest ungrounded service-entrance conductors, per NEC Table 250.102(C)(1).
- Used for bonding raceways and enclosures at the service.
- Sized based on ungrounded service conductors.
- Referenced in NEC Table 250.102(C)(1).
- Ensures continuity of the equipment grounding path.
Memory trick: Bonding's Strength: Service conductor size sets the jumper's length.