MWBC & 208v

[scwirenut]

I know on a single phase system the neutral carries the unbalanced load, but how does the neutral function in a 3 phase 120/208? I want to use MWBC's but not sure how to on this system, also , we are under 2005 NEC so I assume Im still safe using sp breakers without handle ties.

 

[iwire]

I know on a single phase system the neutral carries the unbalanced load, but how does the neutral function in a 3 phase 120/208? I want to use MWBC's but not sure how to on this system, also , we are under 2005 NEC so I assume Im still safe using sp breakers without handle ties.

As long as you run A, B, and C phases the current on the neutral will only be the unbalanced current of the others.

If you use only two phases of the three phase system the neutral current will be roughly the same as the current on either ungrounded conductors.

 

[jim dungar]

If you use only two phases of the three phase system the neutral current will be roughly the same as the current on either ungrounded conductors.

But mathematically that is still the unbalanced current.
And if I had a chance, I personally would reword your statement as using two lines or two hots, rather than two phases.