Journeyman Electrician Exam (NEC)Wiring Methods and MaterialsMedium
A residential electrician is installing a new 200-amp, 120/240-volt single-phase service entrance. The grounding electrode conductor (GEC) will connect to a ground rod. What is the minimum size for the GEC when connected to a ground rod, assuming the service conductors are 3/0 AWG copper?
- A8 AWG copper
- B6 AWG copper
- C4 AWG copper
- D2 AWG copper
Show answer & explanationAnswer & explanation
Correct answer: B. 6 AWG copper
NEC Section 250.66(A) specifies that a grounding electrode conductor connected to a ground rod, pipe, or plate electrode shall not be required to be larger than 6 AWG copper. The size of the service conductor (3/0 AWG) would normally suggest a larger GEC, but the ground rod electrode limits the GEC size to 6 AWG.
Why the other options are wrong
- A. This is smaller than the minimum required size.
- C. This is larger than the minimum required size for a ground rod electrode.
- D. This is larger than the minimum required size for a ground rod electrode.
GEC Sizing (Ground Rod Exception)
The specific minimum size for a grounding electrode conductor when connected to a ground rod, irrespective of the service entrance conductor size.
- Overrides standard GEC sizing tables.
- Applies specifically to ground rod, pipe, or plate electrodes.
- Ensures adequate fault current path to the electrode.
Memory trick: Six gauge copper, for the ground rod's cover.