Master Electrician Exam (NEC)Grounding and BondingMedium
A master electrician is installing a new 100A, 240V, single-phase motor in an industrial facility. The motor is supplied by a 1-inch rigid nonmetallic conduit (RNC) containing 3 AWG copper ungrounded conductors. What is the minimum size copper equipment grounding conductor (EGC) required for this motor circuit?
- ANo. 4 AWG
- BNo. 8 AWG
- CNo. 6 AWG
- DNo. 10 AWG
Show answer & explanationAnswer & explanation
Correct answer: B. No. 8 AWG
According to NEC 250.122(B) and Table 250.122, the minimum size EGC is based on the rating of the overcurrent protective device. For a 100A circuit, the minimum size copper EGC is No. 8 AWG.
Why the other options are wrong
- A. This size is significantly larger than required for a 100A circuit.
- C. This size is larger than required for a 100A circuit.
- D. This size is too small for a 100A circuit.
Equipment Grounding Conductor Sizing
Equipment grounding conductors (EGCs) are sized based on the rating of the overcurrent protective device for the circuit, as per NEC Table 250.122.
- Sized by overcurrent device rating.
- Table 250.122 is the reference.
- Ensures fault current path.
Memory trick: EGC size, fault current's demise.