Neutrals

[Alwayslearningelec]

Do this make any sense to limit a MWBC to 3 circuits within a conduit?

 

[roger]

There is no MWBC that would have more than 3 phases sharing a single neutral. They're just wasting ink the way they worded it.

 

[Alwayslearningelec]

There is no MWBC that would have more than 3 phases sharing a single neutral.

True but the limit to 3 circuits is what I believe is unnecessary

 

[roger]

True but the limit to 3 circuits is what I believe is unnecessary

They should have said "only one MWBC per conduit" that would include single phase and three phase MWBC's

 

[LarryFine]

You could also take it to mean no more than three circuits per neutral.

 

[Elect117]

I think they are alluding to possible derating of conductor?

3 phases + neutral of a MWBC means no derating (under normal circumstances).

6 phases + 2 neutrals of a MWBC means derating.

1 phase + one neutral of a circuit with 3 Phases + neutral of a MWBC is 5 conductors and need derating.

Really wierd language though. Seems like they could have been more clear if they are trying to limit the number of CCCs in a conduit or limit the number of phases per MWBC.

True but the limit to 3 circuits is what I believe is unnecessary

There is no compliant way to have 4 phases and 1 neutral of a multi wire branch circuit. A, B, C, + neutral is 3 phases plus neutral. If you tried to make it 4 phases, for example, you would end up with a neutral carrying A phase twice and that would no longer be a compliant MWBC.

 

[jaggedben]

Without more context I'd assume that they are just restating what any electrician who deals with 208/120 ought to know. The last bit about underfloor electrification systems sounds weird though.

 

[infinity]

It means that if there are more than 3 circuits they cannot be MWBC's.

 

[roger]

You could also take it to mean no more than three circuits per neutral.

No such thing as far as MWBC's are concerned.