GEC to Grounding Electrode System

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GEC to Grounding Electrode System

#92797 04/07/05 10:37 PM

Joined: Jan 2004

Posts: 1,507

Michigan USA

G

George Little Offline

OP

Member

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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Re: GEC to Grounding Electrode System

#92798 04/08/05 01:49 PM

Joined: Jun 2004

Posts: 613

massachusetts

S

shortcircuit Offline

Member

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

Re: GEC to Grounding Electrode System

#92799 04/08/05 02:08 PM

Joined: Jan 2003

Posts: 4,391

North Attleboro, MA USA

I

iwire

Moderator

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