Grounded/Neutral Conductor

[mstrlucky74]

I am bit confused by an excerpt in one of Mike Holts Code books I am reading.

" Since a neutral conductor can only be from a 3 or 4 wire system, the white wire of a 2 wire system, 120v, single phase or 4 wire, 120/240v, three phase high-leg delta system is not a neutral conductor- it's a grounded condutor."

Aren't they contradicting themselves as they say a neutral conductor can only be from a 4 wire but then they mention a 4 wire again saying it can't be a neutral? Thanks.

 

[al hildenbrand]

Go to Article 100 Definitions and spend a little time with the definitions of the terms "Neutral Conductor" and "Neutral Point".

 

[Volta]

I am bit confused by an excerpt in one of Mike Holts Code books I am reading.

" Since a neutral conductor can only be from a 3 or 4 wire system, the white wire of a 2 wire system, 120v, single phase or 4 wire, 120/240v, three phase high-leg delta system is not a neutral conductor- it's a grounded condutor."

Aren't they contradicting themselves as they say a neutral conductor can only be from a 4 wire but then they mention a 4 wire again saying it can't be a neutral? Thanks.

Well, yes and no. In the first part of the sentence the 4-wire system would be a wye: 3 secondaries / phases connected in a star configuration, with one end of each winding connected together to form the neutral point.

In the second, they are pushing it a bit. The white wire of the 4-wire, high-leg delta (regardless of the voltage is a neutral to the single-phase portion (the midpoint of the 120/240, but is not a neutral in relation to the high-leg.

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.

 

[GoldDigger]

Well, yes and no. In the first part of the sentence the 4-wire system would be a wye: 3 secondaries / phases connected in a star configuration, with one end of each winding connected together to form the neutral point.

In the second, they are pushing it a bit. The white wire of the 4-wire, high-leg delta (regardless of the voltage is a neutral to the single-phase portion (the midpoint of the 120/240, but is not a neutral in relation to the high-leg.

Even more simply stated: The fact that you can only have a neutral in a three or four wire system does not mean that all three and four wires systems will have a neutral. The second sentence just gives an example of one four wire system without a neutral.
A simple example of a three wire system without a neutral is a three wire delta. Grounding one corner of the delta does not make the grounded wire a neutral either.

 

[don_resqcapt19]

I am bit confused by an excerpt in one of Mike Holts Code books I am reading.

" Since a neutral conductor can only be from a 3 or 4 wire system, the white wire of a 2 wire system, 120v, single phase or 4 wire, 120/240v, three phase high-leg delta system is not a neutral conductor- it's a grounded conductor."

Aren't they contradicting themselves as they say a neutral conductor can only be from a 4 wire but then they mention a 4 wire again saying it can't be a neutral? Thanks.

I am not sure when Mike wrote that. There has been some changes in the past couple of code cycles on the definitions. Based on the 2011 code, there is no question that the grounded conductor of a high leg system is a neutral.

Neutral Conductor. The conductor connected to the neutral 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 system, or midpoint of a single-phase portion of a 3-phase delta system, or a midpoint of a 3-wire, direct-current system.

 

[jumper]

I think someone once said :

"All neutrals are grounded conductors, but not all grounded conductors are neutrals."

Someone will now post the exceptions.

 

[GoldDigger]

I think someone once said :

"All neutrals are grounded conductors, but not all grounded conductors are neutrals."

Someone will now post the exceptions.

Happy to oblige, although I am getting a cramp from stretching so far.....
If any conductor is grounded, in a wide variety of situations, it must be the neutral conductor. (2011: 250.26)
However, it is also permitted to have an ungrounded wye system, with a neutral conductor. (Not that I am aware of any in the wild.)
2011: 250.20(B) gives conditions under which the neutral MUST be grounded. But if a wye system does not use the neutral as a circuit conductor AND the voltage from phase to neutral is more than 150 volts, then the system can be operated ungrounded.
(Think of it as an ungrounded delta that happens to have a neutral nearby.)

PS: And I am willing to yield to any objections that a neutral which is not a circuit conductor is not a neutral conductor. But you did not say neutral conductor.:angel:

 

[jumper]

PS: And I am willing to yield to any objections that a neutral which is not a circuit conductor is not a neutral conductor. But you did not say neutral conductor.:angel:

What the hay?:? Ya wanna rewrite this or is it me?

 

[kwired]

What the hay?:? Ya wanna rewrite this or is it me?

It's not just you, I'm not really sure what he meant either.

 

[GoldDigger]

It's not just you, I'm not really sure what he meant either.

Allow me to rephrase that with a bit more logic and attention to detail, rather than trying to do a poor imitation of Ulysses.

Your quote (clay pigeon) was that "All neutrals are grounded conductors."
I took exception with that statement to the extent that some neutral points (as long as not used as circuit conductors) were not required by NEC to be grounded.
I was admitting in advance that a small rewording of your quote, namely "All neutral conductors are grounded conductors" would not necessarily be contradicted by my example.

Logical, yes. Clear, no.

 

[jumper]

Allow me to rephrase that with a bit more logic and attention to detail, rather than trying to do a poor imitation of Ulysses.

Your quote (clay pigeon) was that "All neutrals are grounded conductors."
I took exception with that statement to the extent that some neutral points (as long as not used as circuit conductors) were not required by NEC to be grounded.
I was admitting in advance that a small rewording of your quote, namely "All neutral conductors are grounded conductors" would not necessarily be contradicted by my example.

Logical, yes. Clear, no.

You quoted kwired as saying what I did.

I am tired and about done for the night; remind me to ban you later this weekend.

 

[kwired]

Allow me to rephrase that with a bit more logic and attention to detail, rather than trying to do a poor imitation of Ulysses.

Your quote (clay pigeon) was that "All neutrals are grounded conductors."
I took exception with that statement to the extent that some neutral points (as long as not used as circuit conductors) were not required by NEC to be grounded.
I was admitting in advance that a small rewording of your quote, namely "All neutral conductors are grounded conductors" would not necessarily be contradicted by my example.

Logical, yes. Clear, no.

The muddy water has been strained some. But I didn't say anything other than I did not understand what you meant

 

[Besoeker]

My two pence worth:

This is the manufacturer's specification for a transformer we used recently:

Primary: 3300V
Tappings: Nil
No of phases: 3
Frequency: 50Hz
Secondary: 668V
Rating: 85kVA
Vector group: Dyn11


Delta connected HV winding, star (wye) connected LV winding with neutral brought out.
The star point is called neutral - whether grounded or not.

Grounded and neutral are not the same thing.

 

[GoldDigger]

My two pence worth:

This is the manufacturer's specification for a transformer we used recently:

Primary: 3300V
Tappings: Nil
No of phases: 3
Frequency: 50Hz
Secondary: 668V
Rating: 85kVA
Vector group: Dyn11


Delta connected HV winding, star (wye) connected LV winding with neutral brought out.
The star point is called neutral - whether grounded or not.

Grounded and neutral are not the same thing.

But under the NEC, almost all systems that contain a neutral point must have that neutral point grounded. At least if any current flows into or out of it under normal conditions.

 

[Besoeker]

But under the NEC, almost all systems that contain a neutral point must have that neutral point grounded. At least if any current flows into or out of it under normal conditions.

Doesn't negate my point.
Grounded and neutral are not the same thing. And I think it's important to understand the difference.

 

[kwired]

Doesn't negate my point.
Grounded and neutral are not the same thing. And I think it's important to understand the difference.

Exactly why many balk at corner grounded systems, they seem to associate neutral with grounded and when a phase conductor happens to be the grounded conductor they can't understand why there isn't a fault there.

A two wire secondary has no neutral, yet many call the side that is grounded the neutral. Reality is you can ground either side, but it is not a neutral, just a system conductor that has been grounded.

 

[mstrlucky74]

I am not sure when Mike wrote that. There has been some changes in the past couple of code cycles on the definitions. Based on the 2011 code, there is no question that the grounded conductor of a high leg system is a neutral.

It is his 2005 code book

 

[don_resqcapt19]

It is his 2005 code book

The terms "neutral" and "neutral point" were not defined in Article 100 in the 2005 code.