Ground Wire Buried Above Ductbank

[jbt260]

Time and time again I have seen ductbank details that show a bare ground wire (usually 4/0) buried 12" above a concrete encased ductbank. It is not required by the NEC. Is anyone aware of the reason for this? Is there a history to this practice?

Thanks,

 

[charlie b]

I have had clients that wanted a bare copper ground wire imbedded in the concrete between the conduits. But I have never come across a ground wire outside the concrete envelope. I cannot think of any purpose it would serve.

 

[Razzap]

It could be a counterpoise. I once installed a bare copper wire above underground lighting conductors at an airport runway. It has something to do with shielding the conductors from lightning strikes. This was a long time ago and I have forgotten all the details. Hope this helps.

 

[GoldDigger]

Time and time again I have seen ductbank details that show a bare ground wire (usually 4/0) buried 12" above a concrete encased ductbank. It is not required by the NEC. Is anyone aware of the reason for this? Is there a history to this practice?

Thanks,

What sort of sites and run distances have you seen this for?

Sent from my XT1080 using Tapatalk

 

[don_resqcapt19]

Like Charlie, I have seen in the duct bank concrete but never above it....maybe it is just a very expensive "dig-in" warning

 

[jbt260]

What sort of sites and run distances have you seen this for?

It usually shows up in a concrete encased ductbank detail intended for MV cables.

 

[captainwireman]

Could it possibly have anything to do with HEMP (high altitude electromagnetic pulse) shielding?