Building steel ground

[scwirenut]

Im doing my first strip mall, its a metal building and im required to use one of the steel columns as part of my grounding system. I plan on exiting the back of my meter pack with 3/0 copper. my questions are: if the connection to the steel is not accessible does it have to be cadwelded? (such as the empty space behind the sheetrock wall). If so, I have never done a cadweld , could I bring the 3/0 up the interior wall into the accessible dropped ceiling and use a mechanical lug? also, regardless of connection location do I have to run the 3/0 in conduit?

 

[iwire]

if the connection to the steel is not accessible does it have to be cadwelded? (such as the empty space behind the sheetrock wall).

The GEC to building steel connection must be accessible no mater how you make it.

could I bring the 3/0 up the interior wall into the accessible dropped ceiling and use a mechanical lug?

Yes, grind the paint away first, not just a quick wire brush, get some bare steel showing.

also, regardless of connection location do I have to run the 3/0 in conduit?

No, at least as far as the NEC.

 

[scwirenut]

The GEC to building steel connection must be accessible no mater how you make it..

what about 250.68A ? 2005 nec

Exception No. 2: An exothermic or irreversible compression
connection to fire-proofed structural metal shall not be re-
quired to be accessible.

 

[jmsbrush]

If you use conduit, use pvc. If you use a metal raceway it must be bonded on both ends of the conduit.

 

[cadpoint]

what about 250.68A ? 2005 nec

Exception No. 2: An exothermic or irreversible compression
connection to fire-proofed structural metal shall not be re-
quired to be accessible.

Close but no cigar ? I doult that they sprayed the stuff...
Owners are to cheap, and aren't that green. JMO :roll:
Besides, I thought ya'll changed over to 08' !

 

[elect4]

jmsbrush- If you use conduit, use pvc. If you use a metal raceway it must be bonded on both ends of the conduit.

what if it is bare copper in a metallic raceway then the bare copper is already touching metal all over what would be the purpose of a bond bushing on each end

 

[benaround]

jmsbrush- If you use conduit, use pvc. If you use a metal raceway it must be bonded on both ends of the conduit.

what if it is bare copper in a metallic raceway then the bare copper is already touching metal all over what would be the purpose of a bond bushing on each end

250.64(E) will explian it to you.

 

[wbalsam1]

jmsbrush- If you use conduit, use pvc. If you use a metal raceway it must be bonded on both ends of the conduit.

what if it is bare copper in a metallic raceway then the bare copper is already touching metal all over what would be the purpose of a bond bushing on each end

To alleviate the "choke effect". :smile:

 

[Pierre C Belarge]

jmsbrush- If you use conduit, use pvc. If you use a metal raceway it must be bonded on both ends of the conduit.

what if it is bare copper in a metallic raceway then the bare copper is already touching metal all over what would be the purpose of a bond bushing on each end

Don't forget that during fault conditions the magnetic forces will move the conductor about.
Incidental contact within the raceway will not provide the same contact as the bonding at both ends provides.