For a Level II EVSE rated 32 amperes, what is the minimum overcurrent protective device size required by NEC 250.122?

For a Level II EVSE rated 32 amperes, what is the minimum overcurrent protective device size required by NEC 250.122?

• A. 30 A
• B. 32 A
• C. 40 A
• D. 50 A

Answer: (C)

The key idea is that the overcurrent protection for an EVSE circuit on a continuous load must be 125% of the EVSE’s rated current. A Level II EVSE rated at 32 A can draw significant current for hours during charging, so you multiply 32 A by 1.25 to get 40 A. The smallest standard overcurrent protection device that meets or exceeds that value is 40 A, so the minimum OCPD is 40 A. This also implies the conductors in the circuit must be sized to carry at least 40 A. Using a 32 A or smaller device would undersize protection for the continuous charging load, while a 50 A device would be larger than necessary for the minimum requirement.

The key idea is that the overcurrent protection for an EVSE circuit on a continuous load must be 125% of the EVSE’s rated current. A Level II EVSE rated at 32 A can draw significant current for hours during charging, so you multiply 32 A by 1.25 to get 40 A. The smallest standard overcurrent protection device that meets or exceeds that value is 40 A, so the minimum OCPD is 40 A. This also implies the conductors in the circuit must be sized to carry at least 40 A. Using a 32 A or smaller device would undersize protection for the continuous charging load, while a 50 A device would be larger than necessary for the minimum requirement.