Detached Subpanel GEC

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davidg812

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Sacramento, CA US
Simple, maybe even silly question. I have the ability to run the grounding electrode conductor from a new subpanel in a detached garage back in the same pipe that the 4 wire subpanel feeders are in and then before entering the main panel being attached to the ufer ground in the main house foundation. Can this be done instead of driving two new ground rods at the subpanel? The point of connection to the existing house ufer ground is only 20 feet away from the detached garage or does the GEC have to be run separate from anything else? Something tells me it's the latter of the two.
 
I don't think it matters that the grounding electrode conductor is run in the conduit with the feeders however you will have a parallel ground-- which I believe is compliant. I think the idea is to get the protection as close to the other structure as possible but I am not sure that what you ask isn't okay.
 
davidg812 said:
I have the ability to run the grounding electrode conductor from a new subpanel in a detached garage back in the same pipe that the 4 wire subpanel feeders are in
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GECs need to be continuous and bonded to the raceways, when run with the feeder this would be a pain in the rear.

I also seem to recall a recent (2011) NEC change that says you can't do this. But I may be mistaken.
 
This is the closest I found and it does not really say what we want.

250.64 Grounding Electrode Conductor Installation.
Grounding electrode conductors at the service, at each building
or structure where supplied by a feeder(s) or branch circuit(
s), or at a separately derived system shall be installed as
specified in 250.64(A) through (F).
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iwire said:
If I recall Don put in a proposal about it, or it may have been for using the EGC as the GEC ... I can't remember. Maybe he will see this thread.
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You cannot use the equipment grounding conductor as a gec per art. 250 but that is existing. The exception is new in 2014

250.121 Use of Equipment Grounding Conductors. An
equipment grounding conductor shall not be used as a
grounding electrode conductor.
Exception: A wire-type equipment grounding conductor installed
in compliance with 250.6(A) and the applicable requirements
for both the equipment grounding conductor
and the grounding electrode conductor in Parts II, III, and
VI of this article shall be permitted to serve as both an
equipment grounding conductor and a grounding electrode
conductor.
Click to expand...
 
iwire said:
GECs need to be continuous and bonded to the raceways, when run with the feeder this would be a pain in the rear.

I also seem to recall a recent (2011) NEC change that says you can't do this. But I may be mistaken.
Click to expand...

The GEC would be running about 15 feet in SCH 40 with the feeders, which would include the insulated equipment ground to a plastic box where it would run straight through, no splice into a 5 foot piece of PVC to the ufer connection. The feeders would be running along side the GEC to the plastic junction box and then straight through to the main panel in a separate pipe from that point on. I have '05 and '08 code books and can't find anything definitive.
 
The intent of the GEC and GES is to protect from lightning. By have a remote GES, you are forcing the lightning to go out of its way to ground and thru your house panel. All that lenght and loops are not good for lightning.
 
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