Dedicated or Shared Neutrals

[Alwayslearningelec]

A lot of my specs read to use dedicated neutrals but if shared neutrals are used all circuits must be disconnected simultaneously.

Anyone ever do they analysis whether a MWBC using handle ties it a multi pole breaker would cost less than running dedicated neutrals? I'd say, since copper is expensive, and dedicated neutrals can add A LOT of copper depending on the job size that it would always be cheaper to use MWBC. Thoughts?

Any code retrictions on using handle ties in lieu of mutiple pole breaker? Thanks.

 

[roger]

MWBC's savings are more than material, such as voltage drop and I2R losses.

As long as all ungrounded conductors can be disconnected simultaneously it doesn't matter if multi-pole breakers or handle ties are used.
See 210.4(B)

 

[infinity]

Using MWBC's with handle ties will save money. For example a simple 4-wire MWBC in EMT to a home run box will end up with one EMT in and three MC cables out. That's 4 splices (EGC's are the same) one for each hot and one for the neutral. Run the same three circuits in the EMT home run and that's six splices one for each hot and neutral. So you saved the two wire nuts, the labor for two splices and the two extra wires.

 

[augie47]

It's not all positive, however, the simultaneous requirement can take out a lot of lighting when 1 ballast or driver decides to short.

 

[roger]

It's not all positive, however, the simultaneous requirement can take out a lot of lighting when 1 ballast or driver decides to short.

Not advocating skirting NEC requirements but I remember in some large areas we would put three switches above the ceiling where we could isolate the lighting circuit for repairs.

 

[LarryFine]

It also depends on the wiring method. If three-conductor NM costs twice as much as two-conductor NM, there's no saving, even labor, and can actually cost more with the extra joints required.

 

[Jpflex]

A lot of my specs read to use dedicated neutrals but if shared neutrals are used all circuits must be disconnected simultaneously.

Anyone ever do they analysis whether a MWBC using handle ties it a multi pole breaker would cost less than running dedicated neutrals? I'd say, since copper is expensive, and dedicated neutrals can add A LOT of copper depending on the job size that it would always be cheaper to use MWBC. Thoughts?

Any code retrictions on using handle ties in lieu of mutiple pole breaker? Thanks.

When the code requires dedicated neutrals, it means (excluding MWBC) separate branch circuits which originates with its own breaker must return with its own neutral.

However, some time ago this made me confused as to whether the code was no longer allowing additional loads to be paralleled (daisy chain) on this beach circuit while sharing or returning on the same neutral. I’m pretty sure that’s not what they meant but NEC code can be ambiguous at times

 

[don_resqcapt19]

When the code requires dedicated neutrals, it means (excluding MWBC) separate branch circuits which originates with its own breaker must return with its own neutral.

However, some time ago this made me confused as to whether the code was no longer allowing additional loads to be paralleled (daisy chain) on this beach circuit while sharing or returning on the same neutral. I’m pretty sure that’s not what they meant but NEC code can be ambiguous at times

What code section requires a dedicated neutral?