Journeyman Electrician Exam (NEC)Grounding and BondingMedium
A technician is installing a new 200-ampere feeder to a subpanel in a commercial office. The feeder conductors are 3/0 AWG copper. The equipment grounding conductor (EGC) is run with the feeder. What is the minimum size copper EGC required for this feeder?
- A8 AWG copper
- B6 AWG copper
- C4 AWG copper
- D2 AWG copper
Show answer & explanationAnswer & explanation
Correct answer: B. 6 AWG copper
According to NEC Table 250.122, for a 200-ampere overcurrent protective device, the minimum size copper equipment grounding conductor is 6 AWG. The size of the feeder conductors (3/0 AWG) is used to determine the ampere rating of the overcurrent device if it were not already given.
Why the other options are wrong
- A. This size is too small for a 200-ampere circuit.
- C. This size is larger than required for a 200-ampere circuit.
- D. This size is significantly larger than required for a 200-ampere circuit.
EGC Sizing by OCPD
The equipment grounding conductor (EGC) is sized based on the rating of the overcurrent protective device (OCPD) in the circuit, as per NEC Table 250.122.
- Sized from NEC Table 250.122.
- Based on the ampere rating of the OCPD.
- Not directly on the circuit conductor size, but the OCPD protects the conductors.
Memory trick: EGC: OCPD's protector, Table 122's guide!