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#89292 - 09/08/04 09:27 PM EGC  
George Little  Offline
Member
Joined: Jan 2004
Posts: 1,489
Michigan USA
What size Equipment Grounding Conductor would be installed with the tap conductors to a 200a switch. The feeder overcurrent protection is 600 a and the tap conductors run 25 feet and are 3/0 copper and terminate in a 200 ampere switch with 200 a fuses installed.


George Little

2017 / 2014 NEC & Related Books and Study Guides

#89293 - 09/08/04 09:42 PM Re: EGC  
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
The EGCs run with the tap conductors will need to be 1/0 copper. You must base the EGC on the overcurrent device it would have be able to open. In this case that would be the 600 amp feeder.

Once you leave the 200 amp switch the EGC may be 6 awg copper.


Bob Badger
Construction & Maintenance Electrician
Massachusetts

#89294 - 09/09/04 07:09 AM Re: EGC  
George Little  Offline
Member
Joined: Jan 2004
Posts: 1,489
Michigan USA
I agree with you iwire, but it's not thst clear in the NEC. It's one of those things left silent and you need to use logic to figure it out, like you put it, what overcurrent device will it be opening.


George Little

#89295 - 09/09/04 08:14 AM Re: EGC  
gfretwell  Offline


Member
Joined: Jul 2004
Posts: 9,099
Estero,Fl,usa
As usual the handbook does a better job of explaining things. This is commentary from 250.122
"Equipment grounding conductors on the load side of the service disconnecting means and overcurrent devices are sized based on the size of the feeder or branch circuit overcurrent devices ahead of them."


Greg Fretwell

#89296 - 09/09/04 09:33 AM Re: EGC  
Ryan_J  Offline
Moderator
Joined: Aug 2003
Posts: 1,374
West Jordan, Utah, USA
When in doubt, check out 250.4(A)(5).


Ryan Jackson,
Salt Lake City

#89297 - 09/09/04 12:45 PM Re: EGC  
electricman2  Offline
Member
Joined: Nov 2003
Posts: 269
Thomasville, NC USA
In table 250.122 the heading states "Rating or Setting of Automatic Overcurrent Device in Circuit Ahead of Equipment, conduit, etc. Sometimes it takes careful reading to get the intent.

[This message has been edited by electricman2 (edited 09-09-2004).]


John

#89298 - 09/09/04 05:24 PM Re: EGC  
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
electricman2 That is exactly what I would have pointed to. [Linked Image]

Bob


Bob Badger
Construction & Maintenance Electrician
Massachusetts

#89299 - 09/09/04 05:37 PM Re: EGC  
CTwireman  Offline
Member
Joined: Feb 2002
Posts: 840
Connecticut, USA
Bob, where did the 1/0 come from? Table 250.66? or 250.122?


Peter

#89300 - 09/09/04 05:44 PM Re: EGC  
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
Table 250.122 and it is worth mentioning that the EGCs never have to be larger than the associated circuit conductors. 250.122(A)

[This message has been edited by iwire (edited 09-09-2004).]


Bob Badger
Construction & Maintenance Electrician
Massachusetts

#89301 - 09/09/04 09:10 PM Re: EGC  
CTwireman  Offline
Member
Joined: Feb 2002
Posts: 840
Connecticut, USA
Bob,

In that case, wouldn't #1 CU be sufficient for a 600 amp OCPD by table 250.122?

Just trying to figure this out as I rarely work on stuff that large.

Peter


Peter

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