? Neutral ? Why do they call it that?

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jaggedben

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Nor does the NEC, who seem to throw physics under the theory bus as well......:)
~RJ~

I would disagree with the part about the NEC not dictating the zero. You should read the informational note that goes with the definition.

I think the million dollar question is: what is the definition of neutral?

Not really worth a million dollars when any of us can look it up in the NEC. :p

Neutral Point. The common point on a wye-connection in a polyphase system or midpoint on a single-phase, 3-wire system, or midpoint of a single-phase portion of a 3-phase delta system, or a midpoint of a 3-wire, direct current system.

(Why did no one quote it already?)

The informational note makes the point that the nominal vector sums are zero among conductors which 'utilize' the neutral, which is true even in a high leg delta.

My question to you: in a 2 phase 3 wire system (see this: http://electrical-engineering-portal...-3-wire-system), is the midpoint conductor a neutral conductor?

Under the NEC definition, no. But if I'm talking to my helper in the field, well then, yeah, maybe?

Now I'm curious, is the common conductor in those old systems in Philly grounded? If so I'd just call it the 'white' wire. :D
 

kwired

Electron manager
Location
NE Nebraska
What year was it that the NEC changed the definition of a neutral?
I believe either 2005 or 2008.

Now I'm curious, is the common conductor in those old systems in Philly grounded? If so I'd just call it the 'white' wire. :D
If you are going to ground the system why wouldn't you prefer this common conductor over any other conductor of the system, is all I have to say about it.
 

kwired

Electron manager
Location
NE Nebraska
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Originally Posted by kwired


You have to have a multiwire source to have a neutral. .


According to who Mr Kwired?

~RJ~

What is "neutral" about anything with a two wire source? Either side can be grounded. Grounded conductors don't have to be neutral but neutral conductors are frequently grounded and per NEC usually required to be the one that is grounded.
 

romex jockey

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What is "neutral" about anything with a two wire source? Either side can be grounded. Grounded conductors don't have to be neutral but neutral conductors are frequently grounded and per NEC usually required to be the one that is grounded.

Wouldn't an Earthed conductor in a 'two wire source'{figure a} theoretically be at zero potential, as well as vectoral sum of all phases?

single-phase-2-wire-system.png


~RJ~
 

mbrooke

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I would disagree with the part about the NEC not dictating the zero. You should read the informational note that goes with the definition.



Not really worth a million dollars when any of us can look it up in the NEC. :p



(Why did no one quote it already?)

The informational note makes the point that the nominal vector sums are zero among conductors which 'utilize' the neutral, which is true even in a high leg delta.



Under the NEC definition, no. But if I'm talking to my helper in the field, well then, yeah, maybe?

Now I'm curious, is the common conductor in those old systems in Philly grounded? If so I'd just call it the 'white' wire. :D




Correct in the NEC, however in the links RJ posted it seems like all grounded conductors are being called neutrals.
 

mbrooke

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I believe either 2005 or 2008.

If you are going to ground the system why wouldn't you prefer this common conductor over any other conductor of the system, is all I have to say about it.

My 1999 does not even seem to have neutral in it?
 

romex jockey

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Location
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electrician
My 1999 does not even seem to have neutral in it?

'Neutral' was trade slang for almost a century.

The debates on this burnt big holes in the ascii-sphere , today's NEC reading as >>>>

Neutral Conductor. The conductor connected to the neu-
tral point of a system that is intended to carry current under
normal conditions.

Neutral Point. The common point on a wye-connection in a
polyphase system or midpoint on a single-phase, 3-wire sys-
tem, or midpoint of a single-phase portion of a 3-phase delta
system, or a midpoint of a 3-wire, direct-current system.

Informational Note: At the neutral point of the system, the
vectorial sum of the nominal voltages from all other phases
within the system that utilize the neutral, with respect to the
neutral point, is zero potential.


Said debates become relevant when one realizes it could be considered exclusive to our wiring and grounding system(s)

It could further be stated that any parallel path involved essentially disqualifies the vectoral sum passage of the definition

not exactly worth a million imho....



and thank you for the link Mr MBrooke :)
 

Besoeker

Senior Member
Location
UK
Because hot makes sense.

Or is this another in the list of things Besoeker has determined the US does wrong?:lol:
Not wrongly. Just differently. Except SI units. You really need to catch up with the rest of the world on that. Or get left behind in the Burmese jungles.

:p
 
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romex jockey

Senior Member
Location
Vermont
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electrician
Not wrongly. Just differently.

There have been many here who have tried to make changes , earthing vs. bonding being one i recall .....



Except SI units. You really need to catch up with the rest of the world on that. Or get left behind in the Burmese jungles.

:p

Indeed it's not marketable , yet in our defense you lot started it.......:)

English Peasant > "we demand a couple of acres"
Queen of England imparts foot to crotch....:lol:

~R(omnino rudes responsa)J~
 

kwired

Electron manager
Location
NE Nebraska
Wouldn't an Earthed conductor in a 'two wire source'{figure a} theoretically be at zero potential, as well as vectoral sum of all phases?

single-phase-2-wire-system.png


~RJ~
Zero potential to earth, but is nothing "neutral" about it's relationship to the other side of the source. You can always lift the earth bond and apply it to the other side and you still have one conductor of the system that is earthed.

But a multiwire source with a true midpoint tap somewhere in that source is same voltage to all other usable points regardless of where the system is grounded. Just so happens NEC generally requires us to bond this "neutral" point to ground so that is what is usually earthed/grounded.

With a two wire system or a three phase three wire system there is no neutral, and NEC allows us to ground any conductor we want to in those systems. Common practice is to ground the B phase in the three phase systems, but that can still be any one of the three depending on where you decide to start calling them A,B, and C.
 

jaggedben

Senior Member
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Solar and Energy Storage Installer
Wouldn't an Earthed conductor in a 'two wire source'{figure a} theoretically be at zero potential, as well as vectoral sum of all phases?

The vectoral sum would not be zero. It would be whatever the circuit voltage is. This goes to the heart of the original question. We call a conductor a neutral because of its midpoint characteristic (aka nominal vectoral sum) , not because of its lack of potential to ground.

In US power wiring we hardly ever have a neutral that isn't a grounded conductor. But we do occasionally have grounded conductors that aren't a neutral. Examples would be 120V systems, grounded (non-bipolar) DC systems, and corner grounded deltas.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
If you are going to ground the system why wouldn't you prefer this common conductor over any other conductor of the system, is all I have to say about it.

I'm sure you would, and I'm guessing they do. However my curiosity was whether they actually do, based on the 2014 code not covering the situation. (See below). However, now I'm sure they do, because looking back at the 2011 code, 250.26(3) reads as follows:

...conductor to be grounded...: (3) Multiphase systems having one wire common to all phases - the common conductor.

But curiously enough, in 2014 they changed one word:

...conductor to be grounded...: (3) Multiphase systems having one wire common to all phases - the neutral conductor.

Guess they forgot about Philly. :lol:
 

kwired

Electron manager
Location
NE Nebraska
I'm sure you would, and I'm guessing they do. However my curiosity was whether they actually do, based on the 2014 code not covering the situation. (See below). However, now I'm sure they do, because looking back at the 2011 code, 250.26(3) reads as follows:



But curiously enough, in 2014 they changed one word:



Guess they forgot about Philly. :lol:
Not all that well educated on two phase systems, but doesn't that common wire to all phases usually also meet definition of neutral?

I guess you may be able to look at two phase three wire similar to how you look at corner grounded delta and maybe not call it a neutral.
 
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