If a 2 or 3 pull 20 amp breaker has 12 amps on each phase, how is the total amp per phase not added up?
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Trace the path
Take a 2 pole 20A breaker. If you put a 15A load on it that’s just wired across the phases then when Phase A is positive relative to ground you’ll have current flowing from Phase A into Phase B, then the next half cycle the current flows from Phase B back into Phase A. The sine wave peaks at 21.2A (15A RMS) each time
Each phase has a current equivalent to 15A RMS in this scenario so it doesn’t trip the breaker. Current flows up one phase and down the other then down one and up the other, but matched currents
The total power is increased but its better to think of that as a result of the increased voltage. A single phase 120V 15A load is 1,800W. The split phase(technically not two phase) 240V 15A load on the 2 pole breaker is 3,600W
Its actually important that we increase the voltage to increase the delivered power because double the current requires a wire that’s over twice the area to stay a safe temperature
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