Grounded Conductor - Right or Wrong

MarkDavis

Member
Location
Albany GA
Although the attached drawing is not exactly like that represented in exhibit 250.15, is it wrong? Is there any technical reason why it could not be configured as such?
 

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LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Although the attached drawing is not exactly like that represented in exhibit 250.15, is it wrong? Is there any technical reason why it could not be configured as such?
Looks fine, as long as the grounding bus and conductor are sized to the greatest need. Remember to not re-bond the neutral downstream.
 

victor.cherkashi

Senior Member
Location
NYC, NY
I don't see something wrong, but picture has missing information/wires if you compare with exhibit 250.15 from NEC handbook 2017

Sent from my ONEPLUS A6013 using Tapatalk
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Many of us do not have the handbook so what is different about the graphic you've posted? This is from the 2011 NECH, not sure if it's the same as the one you're referencing. The word ground in your graphic should say SSBJ.

Delta WyeTransformer Grounding.jpg
 

MrJLH

Senior Member
Location
CO
Many of us do not have the handbook so what is different about the graphic you've posted? This is from the 2011 NECH, not sure if it's the same as the one you're referencing. The word ground in your graphic should say SSBJ.

View attachment 23088
This figured changed a little bit around in the latest edition of the handbook.
 

kwired

Electron manager
Location
NE Nebraska
Although the attached drawing is not exactly like that represented in exhibit 250.15, is it wrong? Is there any technical reason why it could not be configured as such?
Location of the "ground bus"?

The EGC to the panelboard should be routed with the feeder conductors. If the "ground bus" is in immediate vicinity of the transformer this is less of a problem than if it is not near the transformer.
 

keefeowen

Member
I have a similar question about Exhibit 250.15 in the 2017 NEC Handbook (NECH). The "Neutral" bar in the 2011 NECH Exhibit 250.13 has been changed to a "Terminal bar" in the 2017 NECH Exhibit 250.15. To me, this "Terminal bar" is the termination bar required per 450.10, which I'm guessing will be sized like a ground bus and not rated for neutral current. For example: For a K-Rated transformer with a 200% neutral, I doubt the termination bar will be rated 200% to support the neutral current. Shouldn't the neutral be connected as shown in the 2017 NECH Exhibit 250.16, such that the neutral connections are the same for either exhibit?
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
I have a similar question about Exhibit 250.15 in the 2017 NEC Handbook (NECH). The "Neutral" bar in the 2011 NECH Exhibit 250.13 has been changed to a "Terminal bar" in the 2017 NECH Exhibit 250.15. To me, this "Terminal bar" is the termination bar required per 450.10, which I'm guessing will be sized like a ground bus and not rated for neutral current. For example: For a K-Rated transformer with a 200% neutral, I doubt the termination bar will be rated 200% to support the neutral current. Shouldn't the neutral be connected as shown in the 2017 NECH Exhibit 250.16, such that the neutral connections are the same for either exhibit?
Can you post a photo of the 2017 graphic?
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Due to copyright restrictions, I can't. Please refer to page 184 in the 2017 NECH.
Most of us do not have the 2017 NECH. It's generally accepted here that under Fair Use of copyrighted material you would be permitted to post the graphic.
 

keefeowen

Member
Adding to my 10/22/19 question... As you can see from these two exhibits (2017 NECH Exhibit 250.15 & 250.16), the System Bonding Jumper (SBJ) in Exhibit 250.15 is now part of the neutral current return path. Thus, the SBJ and Terminal Bar would need to be sized for the neutral current. In Exhibit 250.16, the SBJ and Terminal Bar do not carry neutral neutral current. If the "white" wire in Exhibit 250.15 was moved from the Terminal Bar to the transformer X0 terminal, the SBJ and Terminal Bar would not carry neutral current and could be sized similar to Exhibit 250.16. Looking back at the 1st entry of this thread on 6/10/19, the attached file shows a similar configuration of what I think Exhibit 250.15 should be changed to show.
 

keefeowen

Member
Just to clarify, I was calling the "black" wire between the transformer X0 and Terminal Bar in Exhibit 250.15 as the SBJ even though it's not identified as such in the exhibit. If the Terminal Bar needs to accept equipment ground conductors (EGC's), then the Terminal Bar should be treated as a ground bar and not a neutral bar.
 

Attachments

ActionDave

Moderator
Staff member
Location
Durango, CO, 10 h 20 min without traffic from wing
Occupation
wire pulling grunt
Just to clarify, I was calling the "black" wire between the transformer X0 and Terminal Bar in Exhibit 250.15 as the SBJ even though it's not identified as such in the exhibit. If the Terminal Bar needs to accept equipment ground conductors (EGC's), then the Terminal Bar should be treated as a ground bar and not a neutral bar.
You can bond the neutral of a transformer secondary at the transformer or in the first disconnect. This has been the way this way as long as I have been alive, it is not unique to the 2017 NEC. If you bond at the first disconnect then there is no reason to separate the neutrals and equipment grounds.
 

ActionDave

Moderator
Staff member
Location
Durango, CO, 10 h 20 min without traffic from wing
Occupation
wire pulling grunt
Adding to my 10/22/19 question... As you can see from these two exhibits (2017 NECH Exhibit 250.15 & 250.16), the System Bonding Jumper (SBJ) in Exhibit 250.15 is now part of the neutral current return path.
No, it's part of the fault current path.

Thus, the SBJ and Terminal Bar would need to be sized for the neutral current. In Exhibit 250.16, the SBJ and Terminal Bar do not carry neutral neutral current. If the "white" wire in Exhibit 250.15 was moved from the Terminal Bar to the transformer X0 terminal, the SBJ and Terminal Bar would not carry neutral current and could be sized similar to Exhibit 250.16. Looking back at the 1st entry of this thread on 6/10/19, the attached file shows a similar configuration of what I think Exhibit 250.15 should be changed to show.
[/img]
 
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