What wire do I need for 220V 30 amp?
10-2A 30 Amp circuit is needed for most 220V tools. You will need to run a 10-2 to the outlet. 10-2 copper wire is usually good for up to 40 Amps on start loads and 35 Amps on constant load.
Can you use 12-gauge wire on a 30-amp breaker?
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. This higher current can damage the thinner wire, melt the insulation, cause short circuits, fire, and even lethal shock.