Master Electrician Exam (NEC)Grounding and BondingMedium
A master electrician is installing a new 480V, 3-phase, 3-wire delta service for an industrial facility. The service entrance conductors are 300 kcmil copper. What is the minimum size copper grounding electrode conductor (GEC) required for this service?
- ANo. 2/0 AWG
- BNo. 2 AWG
- CNo. 4 AWG
- DNo. 1/0 AWG
Show answer & explanationAnswer & explanation
Correct answer: B. No. 2 AWG
According to NEC 250.66 and Table 250.66, the GEC is sized based on the largest ungrounded service-entrance conductor. For 300 kcmil copper service conductors, the minimum size copper GEC required is No. 2 AWG.
Why the other options are wrong
- A. This size is significantly larger than required.
- C. This size is too small for 300 kcmil service conductors.
- D. This size is larger than required.
GEC Sizing for Services
The grounding electrode conductor (GEC) for a service is sized based on the largest ungrounded service-entrance conductor, referencing NEC Table 250.66.
- Sized by largest ungrounded service conductor.
- Table 250.66 is the reference.
- Connects GES to service equipment.
Memory trick: GEC size, the service it ties.