Dedicated Neutrals

[jaggedben]

I don't see how a "dedicated neutral conductor" can be anything but a neutral for every circuit meaning no MWBC's. Not the best choice of words but the meaning is there. If MWBC's were permitted then the wording would not be needed.

A couple thoughts:

1) It could be to nix any thoughts of using a common neutral for multiple circuits, like jpflex is raising (I think). The NEC prohibits that for branch circuits, but not feeders. Plus some newbs don't understand it.

2) It could require a neutral to be pulled with all circuits even if they only have L-L loads.

I'll stick with "you're probably right but I'm not 100% sure". It moght be clearer in context.

 

[wwhitney]

Ignoring the NEC definition, a neutral can only exist in a MWBC, two conductor circuits are simply series circuits.

It's not so cut and dried. Certainly a two conductor circuit has no conductor at a neutral point of the circuit.

But if you just say "neutral" or "neutral conductor," absent any definitions there's no particular reason to decide the terminology refers to the role of the conductor at a particular point of the circuit, vs the point on the supply system to which the conductor is connected. The NEC definition clarifies this to the latter choice.

Cheers, Wayne

 

[roger]

The NEC definition clarifies this to the latter choice.

Cheers, Wayne

And the NEC definition is just an attempt to give the conductor a name which I understand is necessary but it is not factual. As I alluded to earlier, the same is the case with the NEC's usage of the word "ground".

Now, the point is that the note in the OP can actually be a MWBC neutral which is more accurate than thinking it means a two wire circuit conductor.

 

[Jpflex]

And the NEC definition is just an attempt to give the conductor a name which I understand is necessary but it is not factual. As I alluded to earlier, the same is the case with the NEC's usage of the word "ground".

Now, the point is that the note in the OP can actually be a MWBC neutral which is more accurate than thinking it means a two wire circuit conductor.

So would daisy chaining multiple receptacles from one circuit breaker 1 hot and 1 neutral feeding all be a code violation as it’s worded because each circuit clearly would not have its own “designated” neutral? This has confused me regarding the necs requirement for circuits to have their own neutral?

I’m sure two single pole breakers must have their own designated neutral return wire

 

[roger]

So would daisy chaining multiple receptacles from one circuit breaker 1 hot and 1 neutral feeding all be a code violation as it’s worded because each circuit clearly would not have its own “designated” neutral? This has confused me regarding the necs requirement for circuits to have their own neutral?

No, you have a single circuit, doesn't matter how many devices are in the circuit.

 

[roger]

I’m sure two single pole breakers must have their own designated neutral return wire

That would be a MWBC (one circuit) if the two breakers are on opposing phases. If they are on the same phase you would need two conductors per circuit.

 

[wwhitney]

And the NEC definition is just an attempt to give the conductor a name which I understand is necessary but it is not factual.

Both possible meanings of the phrase "neutral conductor" are equally factual. It's purely a linguistic or terminological choice.

Cheers, Wayne

 

[roger]

Both possible meanings of the phrase "neutral conductor" are equally factual. It's purely a linguistic or terminological choice.

Cheers, Wayne

No they're not, one is a made up term looking for a name, the other is a real item.

Linguistic or terminological are not the same thing either, you can choose either but they have different meanings.

Once again, the OP note can very well mean a MWBC don't you agree?


A designer needs to be articulate in expressing what they want, and an MWBC is a single circuit .

 

[Buddyboy]

That would be a MWBC (one circuit) if the two breakers are on opposing phases. If they are on the same phase you would need two conductors per circuit.

 

[wwhitney]

No they're not, one is a made up term looking for a name, the other is a real item.

You've totally lost me. Without the NEC definition, there's no good reason to pick between two possible meanings of the term "neutral conductor": (a) a conductor connected to the neutral point of the voltage system or (b) a conductor at the neutral point of the other accompanying circuit conductors. They are both equally real.

Even if (b) were somehow more "real", the NEC definition specifies (a), so that's the usage that's most appropriate for this forum.

Once again, the OP note can very well mean a MWBC don't you agree?

I think I agree with jaggedben: taken literally the note in the OP permits MWBC home runs to supply two wire loads. But then it's also an unnecessary duplication of NEC 200.4(A), as I'm not aware of any allowance in the NEC for neutral conductors to be shared between branch circuits. So the intention is likely to prohibit MWBC home runs from supplying two wire loads.

Cheers, Wayne

 

[roger]

Wayne, the NEC correctly recognizes a MWBC as a single circuit so answer this question.
Can a dedicated neutral be the neutral conductor associated with a single MWBC?

That is the gist of the thread.

 

[wwhitney]

Wayne, the NEC correctly recognizes a MWBC as a single circuit so answer this question.
Can a dedicated neutral be the neutral conductor associated with a single MWBC?

Didn't I just do that in the second half of my previous post:

"I think I agree with jaggedben: taken literally the note in the OP permits MWBC home runs to supply two wire loads. But then it's also an unnecessary duplication of NEC 200.4(A), as I'm not aware of any allowance in the NEC for neutral conductors to be shared between branch circuits. So the intention is likely to prohibit MWBC home runs from supplying two wire loads."

BTW, as an aside, I guess on a corner-grounded system you can share the grounded conductor between multiple branch circuits, since 200.4(A) only applies to neutral conductors.

Cheers, Wayne

 

[Jpflex]

That would be a MWBC (one circuit) if the two breakers are on opposing phases. If they are on the same phase you would need two conductors per circuit.

Which brings the subject of using a single unit tied 2 pole breaker vs two single phase breakers without tied handle for a MWBC, does the code detail on this specifically the tied aspect?

 

[roger]

Which brings the subject of using a single unit tied 2 pole breaker vs two single phase breakers without tied handle for a MWBC, does the code detail on this specifically the tied aspect?

Ye it does

 

[Fred B]

A homerun pipe with several circuits only needs to have ONE EGC, if not using the conduit as a EGC?

Sizing to the Largest overcurrent device.
250.122(C) Multiple Circuits.
A single equipment grounding conductor shall be permitted to be installed for multiple circuits that are installed in the same raceway, cable, trench, or cable tray. It shall be sized from Table 250.122 for the largest overcurrent device protecting circuit conductors in the raceway, cable, trench, or cable tray. Equipment grounding conductors installed in cable trays shall meet the minimum requirements of 392.10(B)(1)(c).

 

[HEYDOG]

Huh? Can you explain a little better?
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Ignoring the NEC definition, a neutral can only exist in a MWBC, two conductor circuits are simply series circuits.

This is the way that I always understood it to be! if you have a single two wire 120 volt circuit you have a ungrounded conductor and a grounded conductor…..not a neutral!

 

[Strathead]

We can be soooooooooooo anal here. I have seen that, or a similar statement on most higher end commercial, institutional, industrial plans I have seen in the last 5 years. It means no multiwire branch circuits to be used on the project and I think we all know it.

 

[wwhitney]

This is the way that I always understood it to be! if you have a single two wire 120 volt circuit you have a ungrounded conductor and a grounded conductor…..not a neutral!

The NEC definition says the name is based on what the conductor is connected to, not what other conductors may or may not be nearby.

Cheers, Wayne

 

[jaggedben]

The NEC definition says the name is based on what the conductor is connected to, not what other conductors may or may not be nearby.

I agree for all typical cases.

The interesting exception are those rare instances of a 2-wire 120V service. It's a bit unclear if the NEC considers at all what kind of 'system' exists outside its jurisdiction, or if the conductors provided at the service define the 'system' for NEC purposes. Compare the beginning of 250.26 to the definition of a neutral.