Journeyman Electrician Exam (NEC)Wiring Methods and MaterialsMedium
A technician is installing a new 200-amp, 240-volt single-phase feeder to a detached garage. The feeder conductors are 3/0 AWG THWN copper. What is the minimum size copper equipment grounding conductor (EGC) required for this feeder?
- A8 AWG
- B4 AWG
- C2 AWG
- D6 AWG
Show answer & explanationAnswer & explanation
Correct answer: D. 6 AWG
According to NEC Table 250.122, for an overcurrent protective device rating of 200 amps, the minimum size copper equipment grounding conductor is 6 AWG. This ensures the EGC can safely carry fault current to facilitate the operation of the overcurrent device.
Why the other options are wrong
- A. 8 AWG is too small for a 200-amp overcurrent device.
- B. 4 AWG is larger than required but acceptable, not the minimum.
- C. 2 AWG is significantly oversized and not the minimum.
Equipment Grounding Conductor Sizing
The process of determining the minimum size of the equipment grounding conductor (EGC) based on the rating of the overcurrent protective device, as specified in NEC Table 250.122.
- Sized based on the overcurrent protective device, not the load.
- Ensures effective clearing of ground faults.
- Table 250.122 is the primary reference.
Memory trick: Grounding conductor size is for fault protection, not load, check the 'OCPD shield'.