Journeyman Electrician Exam (NEC)Services, Feeders, and Branch CircuitsMedium
A technician is installing a 200-ampere, 120/240V, single-phase service for a new dwelling unit. What is the minimum size grounding electrode conductor (GEC) required if it connects to a ground rod?
- ANo. 8 AWG copper
- BNo. 6 AWG copper
- CNo. 4 AWG copper
- DNo. 2 AWG copper
Show answer & explanationAnswer & explanation
Correct answer: B. No. 6 AWG copper
According to NEC 250.66(A), a grounding electrode conductor that connects to a ground rod (a made electrode) does not need to be larger than No. 6 AWG copper, regardless of the service size. If it were connected to a concrete-encased electrode, it would not need to be larger than No. 4 AWG copper per NEC 250.66(B). If it connected to a metal water pipe, it would be sized by NEC 250.66 based on the service entrance conductors.
Why the other options are wrong
- A. No. 8 AWG copper is the minimum size for a GEC to a ground rod that is protected from physical damage, but No. 6 AWG is typically used for general ground rod connections.
- C. No. 4 AWG copper is the minimum size for a GEC connected to a concrete-encased electrode, not a ground rod.
- D. No. 2 AWG copper would be oversized for this application and is not the minimum requirement for a ground rod connection.
GEC Sizing for Ground Rods
When a grounding electrode conductor (GEC) connects to a ground rod (a made electrode), its minimum size is not required to be larger than No. 6 AWG copper, regardless of the service entrance conductor size.
- Applies to made electrodes like ground rods.
- Maximum required size is No. 6 AWG copper.
- Different rules apply for other electrode types.
Memory trick: Grounding Rod is Six, Concrete is Four, Pipe is Service.