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#209851 - 05/07/13 01:45 PM GEC Question
akmaster Offline
Member

Registered: 06/11/12
Posts: 70
Loc: alaska
Hi,
I am working on an ethanol plant and the ground grid is 4/0. From the ground grid to building steel and large stainless steel tanks they are using #2 XHHW for bonding..This is the GEC correct? They have also used this #2 from the grid to bond the case of some very large 4160V Motors..Should this not be sized by the largest OCPD?

Thanks
Greg
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#209855 - 05/07/13 02:12 PM Re: GEC Question [Re: akmaster]
gfretwell Offline


Member

Registered: 07/20/04
Posts: 9063
Loc: Estero,Fl,usa
You use 250.66 to size ground electrode systems based on the service conductor size.
#2 gets you up to a 350Kcmil copper or 500Kcmil aluminum service conductor.
If the service conductor is larger than that you need a bigger GEC.
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#209857 - 05/07/13 04:33 PM Re: GEC Question [Re: akmaster]
HotLine1 Offline


Member

Registered: 04/03/02
Posts: 6831
Loc: Brick, NJ USA
The 4/0 grid may be the GEC, or it may be a 'ground ring' that the various conductive items/equipment are 'bonded to'. ie: an equipotential grid. IF it is a 'eq grid', then it was designed or spec's by a PE/EE.

As to the motor case...sounds like a 'eq grid' to me.



Edited by HotLine1 (05/07/13 04:33 PM)
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#209858 - 05/07/13 05:07 PM Re: GEC Question [Re: akmaster]
akmaster Offline
Member

Registered: 06/11/12
Posts: 70
Loc: alaska
Thank you very much!

Greg
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Don't drive and TEXT! Drive now TALK LATER!

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#209859 - 05/07/13 07:31 PM Re: GEC Question [Re: akmaster]
gfretwell Offline


Member

Registered: 07/20/04
Posts: 9063
Loc: Estero,Fl,usa
The GEC is the conductor that lands on the grounding bus bar in the service disconnect enclosure where the main bonding jumper resides. Everything else is a jumper or an electrode.
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#209865 - 05/08/13 04:39 PM Re: GEC Question [Re: akmaster]
akmaster Offline
Member

Registered: 06/11/12
Posts: 70
Loc: alaska
#2 from 4/0 to building steel, tanks, or any motor..

Just does not look right to me..

I drive a ground rod run #6 to meter base this is the GEC correct? The GEC is run with circuit conductors..an equal potential grid is a grounding mat/grid connected to ground rods..for the whole plant they have 4/0 in the ground and #2 insulated ground for grounding tanks, motors or building steel..thanks for the replies..


Attachments
2to4_0_tap_cr.jpg

Description: #2 tap to building steel from 4/0 ground grid


_________________________
Don't drive and TEXT! Drive now TALK LATER!

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#209866 - 05/08/13 04:41 PM Re: GEC Question [Re: akmaster]
akmaster Offline
Member

Registered: 06/11/12
Posts: 70
Loc: alaska
#2 from 4/0 to building steel


Attachments
2gec_to_4_0_cr.jpg

Description: #2 from 4/0 to building steel




Edited by akmaster (05/08/13 04:42 PM)
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#209867 - 05/08/13 07:06 PM Re: GEC Question [Re: akmaster]
gfretwell Offline


Member

Registered: 07/20/04
Posts: 9063
Loc: Estero,Fl,usa
The only way a GEC can be a #6 is if the only electrodes are rods. 250.66(A) says " that portion of the conductor that is the sole connection to the grounding electrode shall not be required to be larger than 6 AWG".
If this is going on to another electrode, the GEC must be sized to the best electrode you have in the system, up to what you get from the 250.66 table.

From the handbook


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#209869 - 05/08/13 08:00 PM Re: GEC Question [Re: akmaster]
HotLine1 Offline


Member

Registered: 04/03/02
Posts: 6831
Loc: Brick, NJ USA
akmaster:

"I drive a ground rod run #6 to meter base this is the GEC correct? The GEC is run with circuit conductors"

The 'GEC' terminates at the neutral block in first means of disconnect of the service. Your POCO may allow it to be terminated within the meter base, but that is forbidden here by PSE&G.

The 'ground' with the circuit conductors is "EGC" for Equipment grounding conductor.
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#209871 - 05/08/13 11:20 PM Re: GEC Question [Re: akmaster]
gfretwell Offline


Member

Registered: 07/20/04
Posts: 9063
Loc: Estero,Fl,usa
We had two policies here from the same PoCo. In Collier County they wanted the GEC in the meter can. In Lee County they wanted it in the service disconnect.
I understand they have now decided the service disconnect is the right place.
The code says
Quote:
The grounding electrode conductor connection shall be made at any accessible point from the load end of the service drop or service lateral to and including the terminal or bus to which the grounded service conductor is connected at the service disconnecting means.

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