Common Grounding Electrode

[infinity]

Recently I did a walk through in a large office building that had a 500 kcmil common grounding electrode riser that ran from floor to floor through the electric closets. This conductor terminated at a grounding bus in each closet for the connection of any GEC's from each separately derived system within that closet.

The contractor installed a 2" EMT sleeve about 24" long to protect the conductor as it passed through the floor. My question is at what point or at what length does this sleeve need to be bonded to the GEC? GEC's in ferrous metallic conduits require that the conduit be bonded to it at both ends. Would a 24" sleeve require this? Opinions please.

 

[George Stolz]

250.64(E) ...Ferrous metal enclosures that are not physically continuous from cabinets or equipment to the grounding electrode shall be made electrically continuous by bonding each end of the raceway or enclosure to the grounding electrode conductor. Bonding shall apply at each end and to all intervening ferrous raceways, boxes, and enclosures between the service equipment and the grounding electrode. ...

This seems to be written with sleeves in mind. I'd say technically what you saw is a violation.

 

[don_resqcapt19]

While there should never be a high current flow on this conductor, even a single ferrous locknut can cause a problem if it encircles a single conductor that carries a high amount of AC current. I think that the rules in the Canadian electrical code for things like this apply to circuits rated 200 amps or greater.
Don

 

[infinity]

This seems to be written with sleeves in mind. I'd say technically what you saw is a violation.

I agree. Someone mentioned that they were simply sleeves and did not require bonding. Seems that the thought of trying to get a 500 kcmil around the bonding bushing was impractical. There are better installation methods that could have solved this problem.

Onto what Roger was saying, what if the sleeves were PVC but passed through the steel metal decking on the underside of each concrete floor. Still a problem?

 

[jwelectric]

Onto what Roger was saying, what if the sleeves were PVC but passed through the steel metal decking on the underside of each concrete floor. Still a problem?

Yes, use PVC.
is the decking welded to the red iron or supported by masonary and condrete?

 

[infinity]

Yes, use PVC.
is the decking welded to the red iron or supported by masonary and condrete?

It's a typical high rise steel and concrete building. Steel I beams with metal corrugated decking and concrete over the decking.