ground rod

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rowdyrather

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this is dum is question an i'm sure someone will have something smart to say but how many grounds rod can you use on one service?
 
I know a cell tower job I was on once upon a time has 30 for the service. The tower erectors drove God knows how many for the tower. They were sectionals, going down to the core of the earth, I believe. (well, maybe not quite that far).
 
A better question might be how many rods would you need??

If you are looking for compliance with the NEC probably not more than two.

As you mentioned, if you are doing a cell tower or munitions storage area, or other critical installation you might use as many as you need!!
 
ground rod

thank you for the warm welcome i'm glad i found this site I am at this working in Djibouti Africa an am waiting on my code book to got here thanks for the help looking forward to talking again soon take care an happy hoilydays to all
 
Well if you are in Austin Texas the answer is 0 If it is home. The city of Austin doesnt accept ground rods per there ordinance you have a CEE or dig in a ground plate. The 1 exception is for a entrance sign.
 
See if you can understand this answer.
You are not required to install any ground rods
However you are required to install a grounding electrode, more than one shall be bonded together to form the grounding electrode system.
Your grounding electrode can be ground rod, or some other type.
Our industry is in this rut of only using ground rods.
Why?
Because we don't know the NEC.

IMO the only time (unless its a cell tower or similar) to use a ground rod is on a time and materials installation.

Does the city of austin know studies have shown the ground plate to have the highest grounding resistance of any grounding electrode?
 
NEC 250-84 requires 25 ohms or less of resistance to ground for made electrodes; or that made electrode shall be augmented by one additional electrode etc.. We've done this before and the resistance is still above 25 ohms but meets code. However when we're doing testing to meet more stringent specs, more ground rods are driven or we use various means of earth soil conductivity enhancements.
 
tom baker said:
Our industry is in this rut of only using ground rods.
Why?
Because we don't know the NEC.

IMO the only time (unless its a cell tower or similar) to use a ground rod is on a time and materials installation.
Click to expand...
What is your preferred "added" electrode?
 
A CEE or Ufer, for 99% of the applications.
Plates are worthless.
The 1% are locations where grounding is done to protect specific equipment or for a specific purpose.
 
tom baker said:
Our industry is in this rut of only using ground rods.
Why?
Because we don't know the NEC.
Click to expand...

I would take that one step further and say that it's because, in general, people don't understand the engineering behind the Code, and forget that the NEC is only the minimum requirements.
 
tom baker said:
A CEE or Ufer, for 99% of the applications.
Plates are worthless.
The 1% are locations where grounding is done to protect specific equipment or for a specific purpose.
Click to expand...
Okay, we do a residential service upgrade, where there were no rods originally. We will bond the metal water pipe, but we can't ascertain that there is at least 10' continuous in the earth, so we have no electrodes yet.

What would you recommend?
 
tom baker said:
Does the city of austin know studies have shown the ground plate to have the highest grounding resistance of any grounding electrode?
Click to expand...

Ok I should have read all the posts after the quote. I did not know that a plate has the highest resistance? I know that the inspecton department did a study supposedly and they decided that was the best route if the ufer was missing?



Yes the city does If the ufer is missing at time of inspection on a residence then we have to dig a 3' 3' 3' hole for a plate electrode.

I am not sure why the wrote a exception for the service at a subdivsion entrance.

Mark
 
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LarryFine said:
Okay, we do a residential service upgrade, where there were no rods originally. We will bond the metal water pipe, but we can't ascertain that there is at least 10' continuous in the earth, so we have no electrodes yet.

What would you recommend?
Click to expand...


Larry
I do not know if you just want an answer from Tom, here is my 2 cents.

If there are no other NEC recognized electrodes present, then you would/could use a ground rod and walk away.
 
Pierre C Belarge said:
Larry
I do not know if you just want an answer from Tom, here is my 2 cents.

If there are no other NEC recognized electrodes present, then you would/could use a ground rod and walk away.
Click to expand...
All responses always welcome. I'm an equal-opportunity poster. :)

One rod, not two, under all conditions? :-?
 
kingpb said:
I would take that one step further and say that it's because, in general, people don't understand the engineering behind the Code, and forget that the NEC is only the minimum requirements.
Click to expand...

I think many of us would still like to hear why it would matter if we had 5 ohms or 300 ohms of resistance between dirt and the electrical systems of typical structures and buildings.
 
When working on the US Capital visiters center, we had to drive a ground rod with an Inspector standing by and then take a resistance reading looking for the magic #
of 25 ohms , well , it was very dry that summer and we kept on driving grnd. rods , the darn dirt was so hard a te 76 would'nt drive squat so it was sledge hammer time - if you can imagine a guy up on a 10' ladder swinging a sledge to hit a grnd rod !!!!! lucky for us one of our farm boys who was strong and had deadly accuracy - I think we had in 21 before we got it
 
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