Is there a better way??

[Alwayslearningelec]

So each floor we have two electrical closets and (6) tenant spaces. Each tenant space is feed from a tenant distribution board in main closet to trough/equipment as you see below. For the grounding( see below) they are asking us to run 1-1/2" and 4/0(note not shown below) from ground bar in electrical closet to each tenant space. Not even sure where we would land in the tenants space( only shows the line/arrow below). Maybe at the transformer or another ground bar?

1. Do you thin this is require from ground bar to each tenant space( the 1-1/4 & 4/0?
2. Is do where could the ground land at the tenant space? Somewhere at the distribution equipment or xfrmr or a ground bar?
3. Anyway this run might not be needed? Thanks

 

[don_resqcapt19]

Are the transformers in the electrical rooms? If so that would be a common grounding electrode for multiple separately derived systems. Each transformer requires a connection to a GEC. It is only required to be 3/0 and if the conduit is ferrous, you will need a 3/0 bonding jumper between the conductor in the raceway and the conduit at each end.

 

[augie47]

It looks as if each tenant space has a transformer and 250.30(A)(6) allows a 3/0 to be used as a common grounding electrode conductor.
Unless you have a point in the system such as a large transformer there would be no need for a 4/0.

 

[Alwayslearningelec]

Are the transformers in the electrical rooms? If so that would be a common grounding electrode for multiple separately derived systems. Each transformer requires a connection to a GEC. It is only required to be 3/0 and if the conduit is ferrous, you will need a 3/0 bonding jumper between the conductor in the raceway and the conduit at each end.

The transformers you see on my pics are in the tenants spaces? Are you asking if there are also transformers in the electrical room feeding the tenant spaces to the electrical rooms with the ground bars?

 

[Alwayslearningelec]

It looks as if each tenant space has a transformer and 250.30(A)(6) allows a 3/0 to be used as a common grounding electrode conductor.
Unless you have a point in the system such as a large transformer there would be no need for a 4/0.

Thanks ..trying to figure way to maybe not have to run a separate conduit from ground bar to each tenant space. So each floor would require 6 separate runes from the ground bar and there are 6 tenants spaces. To be clearer there are 2 rooms on each floor with ground bar in each so it would be 3 separate conduits from each room/ground bar. Is there a way it could maybe run one conduit from each ground bar daisy cabining 3 tenant spaces? Thank you

 

[Alwayslearningelec]

Thanks ..trying to figure way to maybe not have to run a separate conduit from ground bar to each tenant space. So each floor would require 6 separate runes from the ground bar and there are 6 tenants spaces. To be clearer there are 2 rooms on each floor with ground bar in each so it would be 3 separate conduits from each room/ground bar. Is there a way it could maybe run one conduit from each ground bar daisy cabining 3 tenant spaces? Thank you

Or maybe I'm assuming wrong saying there needs to be separate conduit to reach tenant space ...there is only ONE line from the ground bar that says to each tenant space so hoping it can be a common conduit.

 

[Alwayslearningelec]

Because there is a grounding riser doesn't mean there is building steel.

Do you think running one conduit from ground bar to each tenant room is acceptable or you would need individual?

 

[kwired]

Is it common in those type buildings to have 480-480/277 transformer at each tenant space?

I guess there are some advantages to that. Impedance of that transformer would help keep a fault within a tenants space from potentially taking out upstream overcurrent protection and affecting other tenants.

 

[Alwayslearningelec]

Is it common in those type buildings to have 480-480/277 transformer at each tenant space?

I guess there are some advantages to that. Impedance of that transformer would help keep a fault within a tenants space from potentially taking out upstream overcurrent protection and affecting other tenants.

Not really....

 

[Alwayslearningelec]

Again, per code would it be allowable to run one conduit from ground bar to each tenant space.

Where do you think the ground wire would land in the tenant space? e.g ground bar ot xfrmr?

 

[don_resqcapt19]

Again, per code would it be allowable to run one conduit from ground bar to each tenant space.

Where do you think the ground wire would land in the tenant space? e.g ground bar ot xfrmr?

You can run a separate grounding electrode conductor to each separately derived system (transformer). It the GEC is for a single transformer, it is sized based on the secondary conductors and Table 250.66. If you are using a common GEC that goes to multiple locations, it must be 3/0.

The only reason to run a GEC to a tenant space is for the grounding of a transformer secondary.