Finding electrode on wooden pier

[SpaceTentacle]

I am installing a new 30kva 480-120/240 transformer on a wooden pier. I cant drive a rod, there is no building steel. Im installing next to a 480v panel which will feed the primary. The 480v panel seems to have a good ground and is fed from switchgear several hundred feet away. Is there any reason i shouldnt use the EGC in the 480v panel feeder conduit as my electrode for my new transformer, making sure the wire is bonded correctly to the electrode at the switchgear? Then, let the conduit serve as the EGC.

 

[Dennis Alwon]

The panel should have a ground rod however this may satisy the code if the equipment grounding conductor is as large as what is needed for the grounding electrode conductor.

250.121 Use of Equipment Grounding Conductors. An
equipment grounding 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.

 

[infinity]

Wouldn't the separate structure require it's own GES?

 

[GoldDigger]

Wouldn't the separate structure require it's own GES?

My take is that it requires its own GEC, but not necessarily its own GES.
That way the main building GES can serve as long as you run a compliant GEC all the way back to it.
And then the joint EGC/GEC exception applies.

I do not see any limit in the NEC about how far away from the panel the GES can be. Not a prohibition of sharing a GES.

 

[Dennis Alwon]

My take is that it requires its own GEC, but not necessarily its own GES.
That way the main building GES can serve as long as you run a compliant GEC all the way back to it.
And then the joint EGC/GEC exception applies.

I do not see any limit in the NEC about how far away from the panel the GES can be. Not a prohibition of sharing a GES.

I ag

ree, I believe it is compliant if the equipment grounding conductor is sized accordingly.

 

[infinity]

I agree, I believe it is compliant if the equipment grounding conductor is sized accordingly.

I have never seen a separate structure where they just pulled an over sized EGC instead of using a CEE or driving ground rods.

 

[Dennis Alwon]

I have never seen a separate structure where they just pulled an over sized EGC instead of using a CEE or driving ground rods.

Neither have I but I believe it is compliant. Personally, I would want my electrode closer to the panel.

 

[SpaceTentacle]

The EGC in the feeder to the 480 panel is a 1/0. Im installing a 30kva transformer with a 100 amp panel, so the conductor should be adequate as a GEC for my transformer install, right? As for 350.6A, if i bonded the conduit the GEC runs through on each end, would the fact that the conduit itself is mechanically bonded to the switchgear and 480v panel cause objectionable current? Im a bit confused with the 250.6A section.

 

[SpaceTentacle]

Im trying to avoid running a conduit 300 feet simply for the GEC if i could use the EGC that is already available and plenty large enough.