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#92797 - 04/07/05 10:37 PM GEC to Grounding Electrode System  
George Little  Offline
Member
Joined: Jan 2004
Posts: 1,489
Michigan USA
I have a #6 AWG copper conductor running from a rod to building steel, this is my Grounding Electrode System. My largest service entrance conductor is copper 500 kcmil. 250.64(F) says I can run my GEC to any of the electrodes available. Can I run a 1/0 to the rod? I don't think you can but can't find it in the book.


George Little

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#92798 - 04/08/05 01:49 PM Re: GEC to Grounding Electrode System  
shortcircuit  Offline
Member
Joined: Jun 2004
Posts: 608
massachusetts
You can run the 1/0 GEC to the ground rod first, but the bonding jumper to the metal structure would have to be sized according to table 250.66

But, if you were to run the 1/0 GEC to an effectively grounded metal frame first, then the bonding jumper to the rod can be #6

Basicly there is no sequence for installing the required bonding jumpers, but the minumum GEC size for various electrodes according to table 250.66 must be followed...

Therefore the installation you describe would be a violation because the #6 bonding jumper would be undersized, whereas section 250.66 requires a 1/0...

shortcircuit


#92799 - 04/08/05 02:08 PM Re: GEC to Grounding Electrode System  
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
I think these sections may be what your looking for.

Quote
250.53(C) Bonding Jumper. The bonding jumper(s) used to connect the grounding electrodes together to form the grounding electrode system shall be installed in accordance with 250.64(A), (B), and (E), shall be sized in accordance with 250.66, and shall be connected in the manner specified in 250.70.


Quote
250.64(F) To Electrode(s). A grounding electrode conductor shall be permitted to be run to any convenient grounding electrode available in the grounding electrode system or to one or more grounding electrode(s) individually. The grounding electrode conductor shall be sized for the largest grounding electrode conductor required among all the electrodes connected to it.


Taken together IMO it is clear you may run GEC to the ground rod first but the GEC along with the bonding jumper to the building steel would need to be sized for the larger conductor required by either electrode.

JMO, Bob

[This message has been edited by iwire (edited 04-08-2005).]


Bob Badger
Construction & Maintenance Electrician
Massachusetts

#92800 - 04/08/05 02:11 PM Re: GEC to Grounding Electrode System  
George Little  Offline
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Joined: Jan 2004
Posts: 1,489
Michigan USA
Oops- maybe Iwire has the answer- to be continued.

[This message has been edited by George Little (edited 04-08-2005).]


George Little


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