Neutral Question

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Daniel_Mack

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Hello All- I am new to the forum and have a question that was asked of me and I am not sure exactly how to answer it. It came up in a discussion with a friend who is not an electrician. The question I was asked regards as to why the grounded conductor is referred to as the neutral. I found it difficult to explain why it is referred to as 'neutral'. Understanding that it is bonded to the ground at the service was not the issue, it was the use of the term neutral...because I couldn't define it is really bugging me. TIA!
 
Since it is tied to a zero voltage point (i.e., dirt), all other voltages are referenced to it. On a single phase system, for example, at the moment when the Phase A voltage is at its positive peak, the Phase B voltage is at its negative peak, and the voltage at the "grounded" conductor is still zero. That is the essence of it. However, why use the word "neutral" to describe this situation? My response is, "what's in a name?" (with apologies to William Shakespeare). Don't try too hard to correlate the "common, conversational English" meaning of that word with the language of our profession. You might as well ask,
  • Why do we calculate voltage drop using "load flow" software, when the load itself is not flowing?
  • Why do we park in the driveway but drive on the parkway?
  • Why do we buckle up our "seat belt" before driving, when that device touches our lap and torso, not our seat?
  • Why is material sent by ship called "cargo," when the same material sent by car is called "shipment"?
  • Why is a large factory called a "manufacturing" facility, when the word "manufacture" is derived from Latin words meaning "made by hand"?
 
I'll take a stab at this.

As I understand, the term comes from the early days of AC power supply. The neutral is the common point of the system, and also the center-point of a tapped transformer winding or series-connected generators/dynamos is often called the "neutral point" (American Electricians Handbook 2nd ed, 1921).

Also turn the question around- the neutral wire is often used as the grounded conductor, but just grounding a lead doesn't make it a neutral (as in a corner-grounded 3-phase system).
 
Daniel_Mack said:
Hello All- I am new to the forum and have a question that was asked of me and I am not sure exactly how to answer it. It came up in a discussion with a friend who is not an electrician. The question I was asked regards as to why the grounded conductor is referred to as the neutral. I found it difficult to explain why it is referred to as 'neutral'. Understanding that it is bonded to the ground at the service was not the issue, it was the use of the term neutral...because I couldn't define it is really bugging me. TIA!
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It has to do with the fact that when all L-N loads are balanced in a 3 phase wye, the current returning to the transformer via neutral is zero- and if one was to cut the neutral at that point, the voltage across the cut would be zero even if the neutral was totally ungrounded through out the system. Same in single phase, same electrical properties. Neutral refers to the properties of the conductor- and the natural symmetry of split phase and 3 phase power at a hypothetical center point between phases or two sets of phases in the case of single phase or 4 wire delta.
 
charlie b said:
Since it is tied to a zero voltage point (i.e., dirt), all other voltages are referenced to it. On a single phase system, for example, at the moment when the Phase A voltage is at its positive peak, the Phase B voltage is at its negative peak, and the voltage at the "grounded" conductor is still zero.
Click to expand...


Zero to what, though?

That is the essence of it. However, why use the word "neutral" to describe this situation? My response is, "what's in a name?" (with apologies to William Shakespeare). Don't try too hard to correlate the "common, conversational English" meaning of that word with the language of our profession. You might as well ask,
Click to expand...

  • Why do we calculate voltage drop using "load flow" software, when the load itself is not flowing?
  • Why do we park in the driveway but drive on the parkway?
  • Why do we buckle up our "seat belt" before driving, when that device touches our lap and torso, not our seat?
  • Why is material sent by ship called "cargo," when the same material sent by car is called "shipment"?
  • Why is a large factory called a "manufacturing" facility, when the word "manufacture" is derived from Latin words meaning "made by hand"?
Click to expand...

If I had a B phase grounded wye, the center point would still be a neutral, and its wire leading out would still be a neutral.
 
Thanks you for the response guys! Yeah, I admit I was probably over thinking it a bit, but have never had to answer as to when/where the term"neutral" derived from... I checked out a copy of the AEH but it was the 10th Edition and didn't really address it as the 1920's version quoted did, but it made sense. I wanted to say that it was due to being electrically connected to the point in an electrical system with a 'neutral' charge but wasn't sure if that was technically appropriate statement.

Would I be accurate in saying that the neutral is called that "due to the fact that it is electrically connected to a neutral point in the electrical system that is bonded to earth and provides a path for current to flow back to the source of power"? That seems to be the answer I have derived from blowing off the dust of my electrical theory books that have been sitting on the shelf and reading your response. LOL
 
In broad terms yes.

Two things:

1. Reason I say that is a phase conductor can also provide that return path. Remember that a neutral is a return, but technically only for what is left over after all the loads have balanced to the best that symmetry allows.


Meaning if you had a 10amps load on phase A, 11 on B and 10 on C, everything would balance out, and that 1 amp that can not- goes through the neutral to get back to the source (transformer).



2. At the single phase 120 volt circuit branch circuit level the return is always the neutral- and you can still call it that because it originates from the center point of the system.


One could also argue that because the neutral is normally no more than a few volts to ground at worse, its not active and therefore "neutral".
 
Daniel_Mack said:
Just found this article in ECM that gives a pretty good definition-

https://www.ecmag.com/section/codes-standards/neutral-or-not
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NEC knows the difference well. Historically the NEC has avoided the term neutral, choosing instead to use the term "grounded conductor" Reason being that not all conductors connected to earth are neutral. Two examples:

1. A corner grounded delta. Here a phase is grounded down. Its far from a center point, but code wants it to be treated like a neutral, ie unfused- and if run through a disconnect or OCPD, it must simultaneously open the hots.

2. A 120 volt only transformer. Technically there is no neutral, just two ends of a single winding. IF feeding outlets or light sockets, code wants one end grounded. Hence grounded conductor- treated and identified like you would with a typical neutral conductor.


Only recently has the NEC decided to use the term neutral, and when it does its only in applications where an actual center point is involved, ie sizing the grounded conductor on a 3 phase or split phase service, not counting the grounded conductor on a MWBC in derating ,ect- stuff that you know only applies to imbalance current.
 
The original basic definition of the neutral is that it differs in voltage by exactly the same magnitude when measured to each of the (2 or 3 or even 4) "hot" conductors. It is the center point of a balanced set of voltage vectors (phasors actually).
If you have a three phase wye source and you ground the outer end of one of the wye windings you still have a neutral conductor at the wye point, but it is not grounded.
(Although the NEC in most cases requires that the neutral of a wye be used as the grounded conductor if there is one.)
 
My thoughts are similar as what was mentioned in last few posts.

Neutral is a "mid point" that is equal in potential to the other points involved. It may or may not be grounded, though if the system is going to be grounded NEC typically requires neutral (if system has a neutral) to be the conductor that is grounded.

Also been mentioned NEC never used to use the term neutral or had very limited use of that term, but more recently they do call the grounded conductor of a high leg delta system a neutral conductor even though it is not really a "true neutral" to the system in a way like the neutral of a wye system is.
 
kwired said:
M
Also been mentioned NEC never used to use the term neutral or had very limited use of that term, but more recently they do call the grounded conductor of a high leg delta system a neutral conductor even though it is not really a "true neutral" to the system in a way like the neutral of a wye system is.
Click to expand...
I suspect part of the reasoning for the acceptance of the "neutral" designation for high leg was to simplify the definitions with respect to CCC count.
 
Sometimes the grounded conductor is actually being used as a neutral, only conducting unbalanced current for feeders or a multi-wire branch circuit (MWBC).

In normal branch circuits, it's usually not actually a neutral, and is simply the grounded conductor.

It's just easier to always call it a neutral.
 
MAC702 said:
Sometimes the grounded conductor is actually being used as a neutral, only conducting unbalanced current for feeders or a multi-wire branch circuit (MWBC).

In normal branch circuits, it's usually not actually a neutral, and is simply the grounded conductor.

It's just easier to always call it a neutral.
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A multi wire branch circuit is about as normal as you can get.
 
GoldDigger said:
Although not quite as much anymore between the handle tie and ACFI rules. :(
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I hate 210.4(B) so much it's one of the few code sections I know by heart. One of the worst code changes ever.

MAC702 said:
I'd say they are maybe 5% here. Most are single breakers and 12/2 cable.
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I never knew a day of wiring without MWBC in both resi and commercial.
 
Gentlemen,

I'd be most appreciative if i may use this opportunity to interject a particular query posed of me

Quite some time ago, conversing with a UK spark , i was asked

"Why do you lot have neutrals at all"??

I'm still at a loss......

~RJ~
 
romex jockey said:
Gentlemen,

I'd be most appreciative if i may use this opportunity to interject a particular query posed of me

Quite some time ago, conversing with a UK spark , i was asked

"Why do you lot have neutrals at all"??

I'm still at a loss......

~RJ~
Click to expand...

You need to explain the position of said UK spark since most systems in UK utilize a grounded wye with a center point neutral.

Resi is one phase and a noodle at ~215-230V.

So I am unclear on the issue: they use a neutral.
 
What they do not use is a balanced single phase two wires with respect to that neutral.
One answer is that it gives us the ability to run both 120V and 240V loads from the same service without adding another transformer.

Sent from my XT1585 using Tapatalk
 
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