Why 6ft Between Grounds?

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tom baker

tom baker

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I just instructed a Grounding vs Bonding class, and while I know why, I wonder who determined and when:
6 ft between ground rods?
Why only 2 ground rods?
Why a 6 awg max to a ground rod?
Why an 8 ft GR?

My suspicion is this was done as a research paper by the IEEE and made its way into the NEC, late in 1910's, about the time electrical systems were being grounded....
 
tom baker said:
I just instructed a Grounding vs Bonding class, and while I know why, I wonder who determined and when:
6 ft between ground rods?
Why only 2 ground rods?
Why a 6 awg max to a ground rod?
Why an 8 ft GR?

My suspicion is this was done as a research paper by the IEEE and made its way into the NEC, late in 1910's, about the time electrical systems were being grounded....
Click to expand...


I am not sure where the 6ft rule has come from, but I think that the distance between rods should be at least the length of the rods.


Again, I am not sure why this is in the code, I am curious how someone could convince me that two rods will actually make a difference.


This actually makes some sense...the rod electrode can only conductor so much current, why install a larger conductor.


Because driving a rod longer than 8ft would be too hard. :grin:
 
I am with marc on this but can not verify it as I dont have an IEEE green book (I am open to some sending me one though :smile: ). I dont know about the six foot rule either so I am curious if someone does know..I have several scew together rods in the ground and even a system with with 2 eights and a screw together set..Just get out the big hammer and hammer away; kind of like the hit any key tool..
 
when did the ieee begin

when did the ieee begin

tom baker said:
I just instructed a Grounding vs Bonding class, and while I know why, I wonder who determined and when:
6 ft between ground rods?
Why only 2 ground rods?
Why a 6 awg max to a ground rod?
Why an 8 ft GR?

My suspicion is this was done as a research paper by the IEEE and made its way into the NEC, late in 1910's, about the time electrical systems were being grounded....
Click to expand...

Who get's a cookie?

Here's answer based on Google via the search(as stated above)
http://ieeexplore.ieee.org/Xplore/login.jsp?url=/iel5/5/27402/01219476.pdf
Ground rods optional :)
Enjoy
 
Good Reading

Good Reading

tom baker said:
I just instructed a Grounding vs Bonding class, and while I know why, I wonder who determined and when:
6 ft between ground rods?
Why only 2 ground rods?
Why a 6 awg max to a ground rod?
Why an 8 ft GR?

My suspicion is this was done as a research paper by the IEEE and made its way into the NEC, late in 1910's, about the time electrical systems were being grounded....
Click to expand...

If you have Soares Book on Grounding and Bonding, Check out appendix B. It will cook your noodle.

I've been reading it since I saw this post and my noodle is cooked.

It talks about doubling the depth of the rod and effectively reducing the resistance by 40%, so I gather that 2 rods equates to a rod twice as deep, 16ft effectively.

And the distance away from the surface of the rod again reduces resistance, something about shells of earth surrounding the rod and how if the rods are too close the shells intersect and reduces the effectiveness of each.

Nothing yet on why only a number six GEC to a rod, but I'm looking.
 
Overkill

Overkill

We can all promote overkills, and get prodded on almost any answer. I have a customer now wanting a changeover. They live right on the river bank, soil resitivity is of no issue. I will bond to the water main and run a rod when the soil thaws. Overkill? Whatever. They're getting a rod when it is all said and done.
 
From American Electricians Handbook (T. Croft), 1953 issue:

6footground.gif
 
Also see FPN for Art. 250.56. 2008 NEC

Has anyone ever measured the resistance of a rod?

If you drove a second rod as described in 250.56 and still did'nt have 25 ohms or less resistance, then what?

But since we always drive two and go, we'll never know.
 
A Copy of Said Link ...

A Copy of Said Link ...

georgestolz said:
That link didn't work for me. Do you have to be an IEEE member to get the pdf?
Click to expand...

Here I posted it, I did sign up but found this through a search of google
:
Where did electrical engineering begin?
Bowers, B.
Proceedings of the IEEE
Volume 91, Issue 8, Aug. 2003 Page(s): 1257 - 1259
Digital Object Identifier 10.1109/JPROC.2003.814917
Summary: The term "electrical engineering" was not in use in 1871 when the Institution of Electrical Engineers (IEE) was founded under its original name of "the Society of Telegraph Engineers". The electric telegraph was the major application of electricity then, and those engaged in electric lighting were called "electricians". At the opening meeting a leading telegraph engineer made the prophecy that "this Society will develop more into an electrical society than into a society of telegraphy proper." He was soon proved right. Within a few years, the Society was hearing papers on electric lighting, and in 1880 the words "and Electricians" were added to the title. The present name was adopted in 1888. According to Alexander Pelham Trotter (1857-1947), who joined the Institution in 1885, the existence of a new branch of engineering, "electrical engineering", became apparent in 1881 when the first International Electrical Exhibition was held in Paris. Trotter had been in Paris three years earlier for the 1878 Exhibition which, he said, had shown that electric lighting was developing. At that stage Trotter was an undergraduate at Cambridge, reading Natural Sciences. He graduated in 1879 and became an engineering apprentice with Easton and Anderson. It is not clear how he came to be actively involved with the 1881 exhibition, but he was there with the British delegation and took the opportunity of studying all the equipment on show.
Edit:
Same As http://ieeexplore.ieee.org/Xplore/lo...2/01219476.pdf
 
Keep up the Good Work

Keep up the Good Work

tom baker said:
I just instructed a Grounding vs Bonding class, and while I know why, I wonder who determined and when:
6 ft between ground rods?
Why only 2 ground rods?
Why a 6 awg max to a ground rod?
Why an 8 ft GR?

My suspicion is this was done as a research paper by the IEEE and made its way into the NEC, late in 1910's, about the time electrical systems were being grounded....
Click to expand...

It's no fair the instructor is asking Questions, that he only knows the answers too ...

georgestolz said:
Oh. Yeah, I read that, but didn't see what it had to do with the OP. :D
Click to expand...

It's no fair the moderators are asking Questions, that they know the answers too ...

I post dated the OP by 30+ years, and your right no ground rod|

But thanks for the thought provoking threads ... Tom & George :)
and the all the guests and ships at sea...
 
I was taught many moons ago that a ground rod saturates at 50 amps, hence the #6 max. It's been stuck in my brain seems like forever. I can't remember how that was determined or anything else.

Anyone else ever hear that?
 
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