Master Electrician Exam (NEC)Services, Feeders, and Branch CircuitsMedium
A master electrician is installing a 30A, 120/240V, single-phase branch circuit for an electric clothes dryer in a dwelling unit. The circuit conductors are 10 AWG copper with 75°C insulation. What is the minimum size required for the equipment grounding conductor (EGC) for this circuit?
- A10 AWG copper
- B12 AWG copper
- C8 AWG copper
- D14 AWG copper
Show answer & explanationAnswer & explanation
Correct answer: A. 10 AWG copper
According to NEC Table 250.122, for a branch circuit protected by a 30A overcurrent device, the minimum size copper equipment grounding conductor is 10 AWG.
Why the other options are wrong
- B. 12 AWG copper is for 20A circuits, not 30A.
- C. 8 AWG copper is larger than required for a 30A circuit.
- D. 14 AWG copper is too small for a 30A circuit.
Branch Circuit Equipment Grounding Conductor Sizing
The equipment grounding conductor (EGC) for a branch circuit provides a low-impedance path for ground-fault current from the appliance or equipment to the branch-circuit overcurrent device, ensuring rapid clearing of faults.
- Sized based on the branch-circuit overcurrent protective device rating.
- Referenced in NEC Table 250.122.
- Must be copper, aluminum, or copper-clad aluminum.
Memory trick: Branch EGC: The safety wire, matching the breaker's power.