SDS 480Y to 208 Y Transformer Grounding

Saturn_Europa

Senior Member
Location
Raleigh, NC USA
I have a 35 Kw, NEMA 3R, 480 Y to 208 Y transformer at my plant. X0 has a bonding jumper attached to the ground lug on the case of the transformer, the grounding electrode conductor is also attached to a ground lug on the case of the transformer then to some building steel. Five feet from the transformer is the 208 panel board. It has a system bonding jumper connected to the neutral bus bar. There is also a EGC from the panel board to the case of the transformer.

My question is: Doesnt this set up a parallel path to the source? Should I lift the system bonding jumper at the panel board?
 

Smart $

Esteemed Member
Location
Ohio
...
My question is: Doesnt this set up a parallel path to the source? Should I lift the system bonding jumper at the panel board?
Yes, it establishes a parallel path... and yes, remove the N-G jumper in the panelboard. The N-G jumper must be in the same enclosure as the GEC connection.
 

ptonsparky

Senior Member
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
Electrical Contractor
I have a 35 Kw, NEMA 3R, 480 Y to 208 Y transformer at my plant. X0 has a bonding jumper attached to the ground lug on the case of the transformer, the grounding electrode conductor is also attached to a ground lug on the case of the transformer then to some building steel. Five feet from the transformer is the 208 panel board. It has a system bonding jumper connected to the neutral bus bar. There is also a EGC from the panel board to the case of the transformer.

My question is: Doesnt this set up a parallel path to the source? Should I lift the system bonding jumper at the panel board?
Yes it does.

Yes. Remove any EGs from the neutral bus bar and give them their own bar bonded to the can. I think you have it figured out already.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
I have a 35 Kw, NEMA 3R, 480 Y to 208 Y transformer at my plant. X0 has a bonding jumper attached to the ground lug on the case of the transformer, the grounding electrode conductor is also attached to a ground lug on the case of the transformer then to some building steel. Five feet from the transformer is the 208 panel board. It has a system bonding jumper connected to the neutral bus bar. There is also a EGC from the panel board to the case of the transformer.

This would actually be considered a SSBJ (supply side bonding jumper) not an EGC, there is a distinction between to the two because sizing them is different.

As others have stated you'll need to remove the jumper in the panel because the neutral current is now flowing on the SSBJ and any metal between the panel and the transformer including metallic raceways if used.
 

iwire

Moderator
Staff member
Location
Massachusetts
Beautiful pics Augie. Are we allowed to know what tool you are using to create such fine drawings???
Those are oil paintings on canvas that Gus creates. After that he just takes a picture of them and posts them here.

He sells signed originals on the side.
 

Smart $

Esteemed Member
Location
Ohio
Beautiful pics Augie. Are we allowed to know what tool you are using to create such fine drawings???
I recommend you disregard the two previous posts. I apologize on their behalf. They could not contain the wise cracker side of their personalities. :lol:
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Beautiful pics Augie. Are we allowed to know what tool you are using to create such fine drawings???
Mike Holt has hundreds of those graphics in pdf form that you can view for free on the Internet. Just type a code section into Google and click on the images tab in the search results. At one time they were not all pdf's but actually images which allowed you to easily insert them into a post. For some reason the newer ones are now pdf's.
 

Smart $

Esteemed Member
Location
Ohio
Mike Holt has hundreds of those graphics in pdf form that you can view for free on the Internet. Just type a code section into Google and click on the images tab in the search results. At one time they were not all pdf's but actually images which allowed you to easily insert them into a post. For some reason the newer ones are now pdf's.
Hmmm.... not sure where you are getting the pdf's. Google's image tab does not display pdf's.
 

iwire

Moderator
Staff member
Location
Massachusetts
Beautiful pics Augie. Are we allowed to know what tool you are using to create such fine drawings???
You may not know but that image is one of Mike Holt's. I do not know who the graphic artist is, or if it is Mike himself.

Using Google image search as Rob mentioned is a good way to find them. Another great place to go is the Mike Holt free resources page.


Check it out, lots of great stuff there. Mike Holt Free Resources
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector
You may not know but that image is one of Mike Holt's. I do not know who the graphic artist is, or if it is Mike himself.

Using Google image search as Rob mentioned is a good way to find them. Another great place to go is the Mike Holt free resources page.


Check it out, lots of great stuff there. Mike Holt Free Resources
That is the origin of the pic i posted.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Hmmm.... not sure where you are getting the pdf's. Google's image tab does not display pdf's.
There was a time when the image was simply a thumbnail and when you went to copy it the only option was a pdf. I see now that's been changed and they're available as .png files which is helpful when adding them to a post.
 

tadavidson

Senior Member
Is the conduit used between the Main and the xmfr sufficient for the egc or is a separate conductor required?
 

roger

Moderator
Staff member
Location
Fl
Occupation
Electrician
I think one reason the MH graphics have disappeared from the free stuff section is people were posting them all over the internet and using them with out Mike Holt's permission.

Roger
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
You may not know but that image is one of Mike Holt's. I do not know who the graphic artist is, or if it is Mike himself.

Using Google image search as Rob mentioned is a good way to find them. Another great place to go is the Mike Holt free resources page.


Check it out, lots of great stuff there. Mike Holt Free Resources
Mike Culbreath does all of the graphics for Mike Holt. He is an electrician, but I believe that he works full time for Mike Holt now.
 
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