Use this calculator to avoid mistakes. Input source voltage from 1 pole. Then choose the amount of poles. Then the power that will run through it. Amps are calculated and ideal breaker amp size chosen. If the size doesn't exist you can verify the final safety factor. Exact amps will be calculated and the breaker size with at least 1.25x safety factor. Real Safety factor shown live and will be bright red if unsafe values are used. (I determined that smaller than 1.25 or greater than 3 isn't safe to use)