What is the NEC minimum wire size for primary power to an electrical device?

What is the NEC minimum wire size for primary power to an electrical device?

• A. #14 gauge
• B. #16 gauge
• C. #12 gauge
• D. #10 gauge

Answer: (C)

Wire sizing hinges on the circuit’s overcurrent protection. The NEC requires the conductor’s ampacity to be at least the rating of the protection device feeding it. For a typical primary power feed to a device on a standard branch circuit, that protection is usually 20 amps. The smallest copper conductor permitted on a 20-amp circuit is 12 AWG, so the minimum wire size for the primary feed in this scenario is 12 AWG. Using smaller conductors, like 14 AWG, would only be allowed if the circuit is protected at 15 amps, while larger conductors like 10 AWG are used for higher protection levels (e.g., 30 amps). Always check the device’s input current and any manufacturer requirements, but with a common 20-amp feed, 12 AWG is the NEC minimum.

Wire sizing hinges on the circuit’s overcurrent protection. The NEC requires the conductor’s ampacity to be at least the rating of the protection device feeding it. For a typical primary power feed to a device on a standard branch circuit, that protection is usually 20 amps. The smallest copper conductor permitted on a 20-amp circuit is 12 AWG, so the minimum wire size for the primary feed in this scenario is 12 AWG. Using smaller conductors, like 14 AWG, would only be allowed if the circuit is protected at 15 amps, while larger conductors like 10 AWG are used for higher protection levels (e.g., 30 amps). Always check the device’s input current and any manufacturer requirements, but with a common 20-amp feed, 12 AWG is the NEC minimum.