Ground Rod at Detached Structure

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ritelec

Senior Member
Location
Jersey
When installing a subpanel at a detached structure.....it's required to drive another ground rod and bring a ground conductor from it to the panels ground bar (along with the egc from the feed).

#1 , would it be required to be any larger than a #6?
#2 , would that ground bar have to be driven at that location? Is there a max how far it could be from that subpanel?
would it be permissible to bring 2 grounds to that panel? One from the ground bar of the main panel, and one from any of your made electrodes from your grounding electrode system?

Just wondering.

Thanks,
Rich
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
The feeder from the first building to the second has to have the ungrounded conductors, grounded conductor (if the system has one) and the equipment grounding conductor.
The grounding electrode conductor to a ground rod never has to be larger than a #6. The second structure is required to have a grounding electrode at that structure.
 

ritelec

Senior Member
Location
Jersey
thanks jumper........

I wait to see about "separate from structure".

About not larger than #6.
Correct me if I'm wrong, I was told for the wire going to the ground rod at the service as the supplemental ground it did not have to be larger than
#6 as that is only what the ground rod is rated for.......is that correct? IF so...now if that ground rod was your primary ground electrode (or has to be larger than #6) how would it be that you would bring a larger ground conductor
to that ground rod?

I'm guess here that because you would now need 2 made electrodes (2 rods) you would have to bring the larger ground conductor to both...?
 
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infinity

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Staff member
Location
New Jersey
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Journeyman Electrician
GEC to a rod electrode never has to be larger than #6 unless subject to physical damage. The NEC does not classify an electrode as a primary electrode but you're correct if you're hitting the rod first and then connecting to an electrode that requires a larger GEC.
 

ritelec

Senior Member
Location
Jersey
Thanks infinity...........

If there are no electrodes that require a larger than #6 GEC.

Could you install a 1200 amp service, and hit 2 ground rods with #6 as your grounding electrode system?

Rich
 

kwired

Electron manager
Location
NE Nebraska
250.66 (A) (B) and (C) tell us we never need to be larger than a specific size for certain electrodes - if it is a conductor that is the sole connection to that particular electrode.

The reason AKAIK for not needing anything larger than 6 for a ground rod or 4 to a CEE is that the electrode is not likley to be able to dissipate any more energy than the conductor can deliver to it. Why run a 1/0 to a ground rod that will never conduct more than a #6 can?, is the concept.
 

ritelec

Senior Member
Location
Jersey
Thanks.....what a concept........so 2 ground rods with a number 6 is permissible for a 1200 amp service if there are no other electrodes requiring larger on the premises.

What a concept..............
 

kwired

Electron manager
Location
NE Nebraska
Thanks.....what a concept........so 2 ground rods with a number 6 is permissible for a 1200 amp service if there are no other electrodes requiring larger on the premises.

What a concept..............

If you run a separate #6 to each rod yes. If you run from service to rod and then to second rod - probably not. I'm not finding anything so far that allows that, unless we consider both rods a single electrode - which I don't see it that way.

Same with 4AWG to a CEE. 200 amp service or 2000 amp service the CEE does not need a GEC any larger than 4AWG.
 

Cow

Senior Member
Location
Eastern Oregon
Occupation
Electrician
Thanks.....what a concept........so 2 ground rods with a number 6 is permissible for a 1200 amp service if there are no other electrodes requiring larger on the premises.

What a concept..............

Yes, we've built large standalone services with nothing more than #4 to the rods....

Secondly, I've also installed a service feeding two seperate structures fairly close together, say 50' feet apart and drove rods between them. Ground wire from house---across two rods---and on to the detached building. One continuous wire and one grounding electrode system for two buildings.

I wouldn't try to push my luck and go much farther than that though....but it didn't make sense to drive two sets of rods that close together.
 

roger

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Staff member
Location
Fl
Occupation
Electrician
Thanks.....what a concept........so 2 ground rods with a number 6 is permissible for a 1200 amp service if there are no other electrodes requiring larger on the premises.

What a concept..............
Yes.

Roger
 

ritelec

Senior Member
Location
Jersey
Same with 4AWG to a CEE. 200 amp service or 2000 amp service the CEE does not need a GEC any larger than 4AWG.

Thanks guys.............................
I'm a numb nuts..............what's CEE please?


common?conductor?electrode?earth?entrance?Lucille Ball.................??? ahhh Ricky




EDIT:>>>>>> construction something.............the book right?? Electrical Engineering????
 
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ritelec

Senior Member
Location
Jersey
If the grounding electrode is a water pipe, the gec must be sized to 250.66 and a supplemental electrode must be installed (rod,pipe,plate) sized at #6.

If the ground electrode was a CEE it does not have to be larger then #4cu.

Would a CEE require a supplemental electrode?

If the electrode was building steel, the gec would be sized to 250.66.

Does building steel require a supplemental electrode?

Ground ring??? Not smaller than a #2. Again, would it need a supplemental?

SO? Water pipe is sized to entrance conductor size but would still need a supplemental?
Made supplementals not smaller than #6 and would need supplementals not smaller than #6?
The only "real" "non supplemental electrode would be metal frame of building structure and ground ring. Building structure would be sized to 250.66 and ring doesn't have to be larger than #2....and both would not
need a supplemental?

(reading on the ground ring..... not smaller than #2.......would that #2 be sized to go back to bond/ground, or would you have to hit the #2 with a gec sized to 250.66?)

Is any of what I wrote correct???:D
 
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