bonding a separatley derived system

[bob52]

I am working in an old mill on the fouth floor with no building steel or water piping available to bond the neutral conductor at a 75kva 480 delta to 120/208 wye system. can I use the EGC from the primary to bond the grounded conductor at my transformer?

 

[packersparky]

I am working in an old mill on the fouth floor with no building steel or water piping available to bond the neutral conductor at a 75kva 480 delta to 120/208 wye system. can I use the EGC from the primary to bond the grounded conductor at my transformer?

250.121 Use of Equipment Grounding Conductors. An equipmentgrounding conductor shall not be used as a grounding electrode conductor.


Exception: A wire-type equipment grounding conductor installed in
compliance with 250.6(A) and the applicable requirements for both the
equipment grounding conductor and the grounding electrode conductor
in Parts II, III, and VI of this article shall be permitted to serve as both
an equipment grounding conductor and a grounding electrode conductor.

 

[augie47]

I can't speak for bob but I have no clue what that is saying

 

[LarryFine]

I can't speak for bob but I have no clue what that is saying

As long as it's a wire (as opposed to conduit) and meets requirements for both, it may serve as both.

 

[texie]

250.121 Use of Equipment Grounding Conductors. An equipmentgrounding conductor shall not be used as a grounding electrode conductor.


Exception: A wire-type equipment grounding conductor installed in
compliance with 250.6(A) and the applicable requirements for both the
equipment grounding conductor and the grounding electrode conductor
in Parts II, III, and VI of this article shall be permitted to serve as both
an equipment grounding conductor and a grounding electrode conductor.

As you probably know there is some history on this starting, I think, in the 2011 edition. So, yes, one can exercise this Exception but as a practical matter in many cases I'm not sure if you could be fully compliant.

 

[david]

I am working in an old mill on the fouth floor with no building steel or water piping available to bond the neutral conductor at a 75kva 480 delta to 120/208 wye system. can I use the EGC from the primary to bond the grounded conductor at my transformer?

it seems unlikely that the primary equipment ground would be sized for, to comply with the grounding electrode conductor, sized for the secondary conductors