On my jobsite there is talk of a fairly new code that requires the three ungrounded(when working with a three phase system) to trip together when they are sharing a common neutral. I am referring to three seperate circuits that may supply three seperate receptacles. This would require installing a handle tie (if this is acceptable) across the three circuit breakers or using one three pole circuit breaker.
The suggested solution to this is to simply use a seperate neutral for each circuit and continue to use seperate single pole circuit breakers.
I am aware of a requirement that would require all ungrounded conductors to trip together when terminating at a common piece of equiptment, such as a multi pole disconnect switch or when terminating on a common yoke such as a duplex receptacle where the top half would be the black circuit and the bottom half would be the red circuit.
Is anyone aware of this new requiremment. It seems silly for two circuits to trip when there is a overload on just one circuit just because they a sharing the same neutral and if seperat neutrals had to be used there would be much more wire being used plus the size of the raceway would also need to be considered.