10-gauge wire“Twelve-gauge wire is good for 20 amps, 10-gauge wire is good for 30 amps, 8-gauge is good for 40 amps, and 6-gauge is good for 55 amps,” and “The circuit breaker or fuse is always sized to protect the conductor [wire].”
Can You Use a 30-Amp Breaker On 12-Gauge Wire? You should not use a 30-amp circuit breaker on a 12-gauge wire. The circuit breaker installed on a circuit is of a specific size to protect a certain wire gauge. A larger breaker on a thinner wire will allow more current over the wire before tripping.