Branch circuit neutrals

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dgs

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I hope someone can help resolve this discussion.

First:
Consider a 208/120Y 3 phase breaker panel with 120v single phase branch circuits (1 pole breakers) for receptacles and audio amplifiers (over 1000 watts each with switching type power supplies and are therefore non linear loads).

Second:
Same 208/120Y panel with 2 pole breakers powering SCR phase fired type light dimmers where each leg powers 4 single phase lamp loads (again 1 pole breakersfor branch circuits).

Is it acceptable to share a neutral conductor with multiple branch circuits or is it necessary to pull a separate neutral with each branch circuit.



Thanks
 
It is Code permissible to "shate" the neutrals. Under the '08 Code the circuits would be required to have a disconnecting means that turned off all nonghrounded conductors simultaneously.
Being non linear loads, good practice would call for an oversized neutral, but I don't know that it is Code mandated.
 
You can share neutrals if you so choose. IMO it's unlikely to have that much of an effect on a MWBC.
 
infinity said:
You can share neutrals if you so choose. IMO it's unlikely to have that much of an effect on a MWBC.
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Agreed. Remember that, with a balanced load, the neutral carries no 'normal' current, so any harmonics-caused current would be the only current.

Even with neutral current, the harmonics would have to be very high to be an issue. IMHO, the oversized neutral is overrated.
 
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