Grounded Conductor

Status
Not open for further replies.

raider1

Senior Member
Staff member
Location
Logan, Utah
No, the grounded conductor of a corner grounded delta system would not be a neutral conductor.

Here are a couple of new terms from Article 100 of the 2008 NEC.

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.

FPN: 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.

Chris
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
A true neutral carries the unbalance load from the ungrounded conductors. Only a perfectly balanced system would have not current flow on the neutral.


I thought to be called a neutral it had to be perfectly balanced. I was under the impression that's why there was a push to called it the grounded conductor. Guess I was wrong....:smile:-- so what's new.
 

raider1

Senior Member
Staff member
Location
Logan, Utah
A true neutral carries the unbalance load from the ungrounded conductors. Only a perfectly balanced system would have not current flow on the neutral.

Agreed, under normal conditions the neutral will have some current flow on it. The amount of current flow would be the imbalanced current from the loads on the ungrounded conductors.

Chris
 

480sparky

Senior Member
Location
Iowegia
I thought to be called a neutral it had to be perfectly balanced. I was under the impression that's why there was a push to called it the grounded conductor. Guess I was wrong....:smile:-- so what's new.

If you had a perfectly balanced system, then why would you need the grounded? I think it's called the neutral because it has no potential to ground as it is grounded.

"Neutral" conductors are covered in 310.15(B)(4).
 
Last edited:

raider1

Senior Member
Staff member
Location
Logan, Utah
If you had a perfectly balanced system, then why would you need the grounded? I think it's called the neutral because it has no potential to ground as it is grounded.

"Neutral" conductors are covered in 310.15(B)(4).

310.15(B)(4) covers when a neutral conductor is to be counted as a current carrying conductor for the ampacity adjustments of 310.15(B)(2)(a).

Chris
 

raider1

Senior Member
Staff member
Location
Logan, Utah
To me the neutral is the wire going back to the center tap of the transformer.You can have a neutral without it being grounded.

What about 250.20(B)(2) & (3). This requires systems with a neutral that is used as a circuit conductor to be grounded.

Chris
 

raider1

Senior Member
Staff member
Location
Logan, Utah
The grounded conductor of a 2 wire branch circuit is not a neutral conductor.

Not according to the definition of neutral conductor in Article 100.

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

Also take a look at the definition of neutral point:

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.

According to the NEC definition, if the grounded conductor connects to the neutral point of the system it is a neutral conductor.

Chris
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
Not according to the definition of neutral conductor in Article 100.



Also take a look at the definition of neutral point:



According to the NEC definition, if the grounded conductor connects to the neutral point of the system it is a neutral conductor.

Chris
Chris,

If all you have is a 2-wire system, like from a door bell or HVAC transformer, you do not have a neutral point per the 100 definition therefore you do not have a neutral conductor. Not all voltage sytems start as 120/240 1ph 3W.
 

raider1

Senior Member
Staff member
Location
Logan, Utah
Chris,

If all you have is a 2-wire system, like from a door bell or HVAC transformer, you do not have a neutral point per the 100 definition therefore you do not have a neutral conductor. Not all voltage sytems start as 120/240 1ph 3W.

Your right Jim,

I had assumed that Pierre was talking about a 2 wire circuit from either a single phase 120/240 volt system or a 2 wire circuit from either a 277/480 or 120/208 3 phase Y system.

Chris
 
Status
Not open for further replies.
Top