What is the minimum size equipment-grounding conductor required for a branch circuit protected by a 40 ampere overcurrent device supplying a range receptacle rated at 50 amperes?

• A. 8 AWG copper
• B. 10 AWG copper
• C. 12 AWG copper
• D. 6 AWG copper

Answer: (B)

The key idea is that the size of the equipment-grounding conductor (EGC) is set by the overcurrent protection on the circuit. According to NEC 250.122, the EGC must be large enough to carry fault current for the circuit’s protection device to trip safely. For a branch circuit protected by a 40-ampere overcurrent device, the copper EGC required is 8 AWG. The rating of the range receptacle (50 A) does not change this sizing—the protection curve is driven by the 40 A breaker. So the minimum copper EGC you’d use here is 8 AWG. Larger sizes (like 6 AWG) would be acceptable but not required, and smaller sizes (such as 10 AWG or 12 AWG) would be undersized for a 40 A OCPD.