Ground Grid Depth

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D!NNy

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San Luis Obispo
Hello,

Can some one explain how and why NEC mandates ground grid conductor burial depth to 30" minimum from the finished grade??

What if i have piping or some sort of obstacles along the ground grid routing can the depth be lowered than 30"?

does the ground grid needs to be 30" even if it is under the concrete slab??

Is it helping to maintain the earth resistance to 25ohms??

Thanks
 
That's for a ground ring and yes it's required completely encircle the structure and to be 30" deep. Sounds like a good reason never to use one when two ground rods would be just as code complaint.
 
infinity said:
That's for a ground ring and yes it's required completely encircle the structure and to be 30" deep. Sounds like a good reason never to use one when two ground rods would be just as code complaint.
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He may be on a cell site. Ground rings are common and everything gets grounded.......
 
Hello,

This is per Article 250.53 (F), Can some one explain how NEC came to conclusion and why NEC mandates ground ring conductor burial depth to 30" minimum from the finished grade??

What if i have piping or some sort of obstacles along the ground ring routing can the depth be lowered than 30"?

does the ground grid needs to be 30" even if it is under the concrete slab??

Is it helping to maintain the earth resistance to 25ohms??

Thanks
 
D!NNy said:
Hello,

This is per Article 250.53 (F), Can some one explain how NEC came to conclusion and why NEC mandates ground ring conductor burial depth to 30" minimum from the finished grade??

What if i have piping or some sort of obstacles along the ground ring routing can the depth be lowered than 30"? YES, as long as you mean deeper than 30" :)

does the ground grid needs to be 30" even if it is under the concrete slab?? YES, measured from the top of a "slab on grade".

Is it helping to maintain the earth resistance to 25ohms?? Also YES. The closer you are to the local water table, the better the electrode's resistance because damp or wet earth is an electrolyte (typically).

Thanks
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See replies within quote.
 
D!NNy said:
Thanks for the comments.

How about if the obstacles wouldn't let me go deeper than 24"?
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Then the wire you are installing is not a grounding electrode and you will have to use other grounding electrode(s) to create the required grounding electrode system.
 
don_resqcapt19 said:
Then the wire you are installing is not a grounding electrode and you will have to use other grounding electrode(s) to create the required grounding electrode system.
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What do you mean by other grounding electrode?? if i cant go deeper, how could i install another electrode? i am not trying to be mean.... this is my situation??

Thanks
 
D!NNy said:
What do you mean by other grounding electrode?? if i cant go deeper, how could i install another electrode? i am not trying to be mean.... this is my situation??

Thanks
Click to expand...
See 250.52(A)(3) Concrete Encased Electrode. There is no depth requirement.
 
D!NNy said:
What do you mean by other grounding electrode?? if i cant go deeper, how could i install another electrode? i am not trying to be mean.... this is my situation??

Thanks
Click to expand...
The code doesn't really care how difficult it is, but it does require a grounding electrode, so you have to find a way to provide one.
I have worked on jobs were a drill rig was used to drill holes for ground rods. There are always ways to go deeper, but they may be very costly.
 
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