Service/Building transformer bonding and grounding

[Electromatic]

I don't know if I'm still fuzzy from the holidays or if the EE is confusing me on this one...

On the attached one-line (hopefully it shows up), Notes 1 & 2, do I really need to run two separate GECs of different sizes from pipe, steel, rebar each to the primary and secondary disconnects? It seems like 250.30(A)(4)Exc.2 and 250.30(A)(5)Exc.2 allow me to use the GEC of the service as the GEC of the SDS secondary as long as I size it based on the secondary conductors [250.66]. Is this how it's typically done?

On a more minor note, if I run a grounding conductor in the slab over to the water pipe, wouldn't it be more effective bare rather than in conduit as is called for?

Thanks as always.

 

[Electromatic]

Here's an image in case the PDF doesn't work

 

[augie47]

I agree with the drawing. IMO, 250.30(A)(4)Ex2 does not apply as this is not an SDS that is part of listed service equipment

 

[Electromatic]

I don't understand why you couldn't run the #1/0 from the pipe, steel, rebar to the 208V switch then tap a #4 to the 480V switch. Wouldn't that be an overall lower impedance path than a separate #4?

 

[lkdiaZ]

Try 250.24 as a requirement to ground the 200A Main Service Disconnect and 250.32 to ground the 400A building disconnect. The assumption is that the 200A main service disconnect is mounted to a structure separate from the building structure. I would think that if the main is located on the building wall then that's the only ground you need.