Breaker sizing for MWBC

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JOEE

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When running (2) 12/3 feeders for a kitchen. One feeder is for the SA receptacles, both 20A breakers. The other feeder is one leg for lighting and the other leg for the dishwasher. My question is if lighting gets a 15A breaker, can a 20A breaker be used for the dishwasher leg or do both breakers have to be the same amperage rating. Like 15A for both? I read through 210.4 but can't find it in there.
 
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Do you really mean to say "feeders" or are you discussing "branch circuits"? Precise definitions will yield you better answers. :smile:
 
You can size the overcurrent protective device separate for each leg of the multiwire branch circuit. So you could have a 15 amp breaker on one leg and a 20 amp breaker on the other leg. Keep in mind that if you are under the 2008 NEC you must have a simultaneous means to disconnect all ungrounded conductors of the multiwire branch circuit, this can be a common trip 2 pole breaker or 2 single pole breakers with a common handle tie.

On a side note, if you are running a 12/3 NM cable why would you need to have a 15 amp breaker for the lighting circuit?

Chris
 
ok thanks for the clarification on the two breaker sizing. As for the breakers, they meet 2008 code. As for the lighting circuit, it's just force of habit.
 
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