Grounding and Bonding in Afghanistan

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The reasoning behind driving rods 8' deep is to reach permanent moisture, driving through rock doesn't help a whole lot unless it's conductive, iron, silver, gold ect. To comply with code, you would need to keep driving rods until you reach the 25 ohms. This is made harder due to not being able to go 8'. After a rain you will probably find that it is a lot easier to hit this goal, but when the earth dries out the resistance goes up again.
 
hillbilly1 said:
To comply with code, you would need to keep driving rods until you reach the 25 ohms.
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I agree with John here, once you drive the second rod you can call it a day.

The NEC requires the rods to be at least 6' apart, in some areas you would never reach 25 ohms before you ran out of property. :smile:
 
iwire said:
I agree with John here, once you drive the second rod you can call it a day.

The NEC requires the rods to be at least 6' apart, in some areas you would never reach 25 ohms before you ran out of property. :smile:
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My helper would run out of energy first... :grin:
 
hillbilly1 said:
Another one of those urban myths then, huh?:D Does this also apply if ground rods are the sole grounding electrodes?
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Yes. Even if the ground rods are the only grounding electrode. Drive one rod - if it is over 25 ohms, drive a second and walk away.

I wouldn't even bother to test, (and then have to verify it with the inspector), I would drive 2 and go. :cool:
 
hillbilly1 said:
Another one of those urban myths then, huh?:D Does this also apply if ground rods are the sole grounding electrodes?
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Picture placing a 3000 amp 480 volt service in the middle of nowhere. You could drive one rod or two if you had to, connect them to this service with a single 6 AWG copper and you would meet the NECs grounding requirements.
 
quogueelectric said:
I dont get the chance to tweak Peter up that often so when he throws up a softball for me I feel I gotta hit it.
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It wasn't a softball. I am challenging an assertion that you made:

The ground is not intended to carry load current only fault current.
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If you mean "The earth is not intended to carry load current, only fault current" then that is patently untrue for systems under 600 volts.

Now on the other hand if you mean "The equipment bonding system consisting of metallic conductors and raceways is not intended to carry load current, only fault current" then that's correct.

Your use of the term "ground" is very vague. Now that we starting to use clearer terms like "equipment bonding conductors" and "earth" in our language to describe these systems, simply saying "ground" is very confusing and possibly misleading at best.
 
Thanks for all of your input. The conversations sound very similiar to ours in the shop. Keep in mind we are fixing many things that have been messed up for many years since this war began. Product is hard to come by and when the military wants power, unfortunately many things were missed. Now we are fixing it. Thanks again for all your input. It has helped in fixing everything. Next time I will try and be more clear on my questions.
 
I'd recommend that the OP consider this link


Which is about this-
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iwire said:
Picture placing a 3000 amp 480 volt service in the middle of nowhere. You could drive one rod or two if you had to, connect them to this service with a single 6 AWG copper and you would meet the NECs grounding requirements.
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I knew about the #6 max. required to a ground rod, I had an inspector that tried to turn me down on a 2000 amp 480 volt service because I had a #4 (larger than I needed) running to the ground rod. He wanted a full size GEC to it. I told him about the max. size I needed was a #6, and I was oversized anyway. He wanted to know where in the code it was, and I showed him. He said that he agreed and learned something that day. I've had engineers spec 500 kcmil to ground rods before. A little overkill to a 5/8 ground rod.
 
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