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Old 08-07-2012, 11:45 PM   #1
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Earth Grounding Rod Requirements


Hello,

I am redoing my electrical system from the weatherhead to the breaker box so I'm sure I'll be asking quite a few questions in the relatively near future.

My city uses the 2008 NEC with virtually no amendments (none pertaining to what I'm doing).

I've got a copy of the NEC... wow, what a document, HA!

I've got the permit already and have been in contact with the inspector already.

He says my best bet is to use 2 grounding rods (so he doesn't have to measure resistance in the soil etc if I only have one).

What size (diameter) solid copper rods are used?

What length?

When they are placed 6' apart, is that: no more than 6, no less than 6, or exactly 6'?

Thank you all for your help!

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Old 08-07-2012, 11:55 PM   #2
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Earth Grounding Rod Requirements


Copper ground rods have to be a minimum " in diameter, 8 feet long.

You can get 3/4" rods that are 10 feet long, if you prefer.

The 6 foot spacing is a minimum, and if you can space them further apart, they will be more effective.

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Old 08-08-2012, 12:41 AM   #3
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Earth Grounding Rod Requirements


just be sure to run the ground wire from the panel to each rod and back to the panel again.
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Old 08-08-2012, 05:30 AM   #4
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just be sure to run the ground wire from the panel to each rod and back to the panel again.
There is no basis for such a requirement in the NEC.

Only one lead is required to be connected to the panel, and that single lead can loop from rod to rod and end at the farthest one.

IF the grounding electrode conductor is cut at the first rod, a second clamp would be required for the jumper to the next rod in most cases.
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Old 08-08-2012, 05:48 AM   #5
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IF the grounding electrode conductor is cut at the first rod, a second clamp would be required for the jumper to the next rod in most cases.
I'm not sure if this may have changed in '08 or '11 but, I always thought it had to be continuous unless of course it was by irreversible connection?
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Old 08-08-2012, 06:23 AM   #6
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I'm not sure if this may have changed in '08 or '11 but, I always thought it had to be continuous unless of course it was by irreversible connection?
Continuous until you terminate at the first rod.

Note the multiple clamps on the rods in this graphic:

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Last edited by kbsparky; 08-08-2012 at 06:25 AM.
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Old 08-08-2012, 06:36 AM   #7
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Guess I've been saving money using less clamps..
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Old 08-08-2012, 07:25 AM   #8
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Earth Grounding Rod Requirements


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Copper ground rods have to be a minimum " in diameter, 8 feet long.

You can get 3/4" rods that are 10 feet long, if you prefer.
There are also 5/8"x8' clad or galv rods.
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Answers based on the 2008 & 2011 NEC.
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Old 08-08-2012, 07:26 AM   #9
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I'm not sure if this may have changed in '08 or '11 but, I always thought it had to be continuous unless of course it was by irreversible connection?
This is a very common misconception. The wire from the panel to the first rod is the GEC. The wire between the two rods is a bonding jumper.
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Old 08-08-2012, 08:52 AM   #10
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Earth Grounding Rod Requirements


Wow, thanks for all the replies!

How deep should the ground wire connecting the rods be?

What gauge wire?
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Old 08-08-2012, 09:52 AM   #11
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Earth Grounding Rod Requirements


I use #6 Cu grounding wire.

Kb and Petey, thank you for clearing that up. I have never seen any such code either, but the inspector i use asks for this ground loop.
Never questioned it. Just figured he was the one passing my work
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Old 08-08-2012, 10:27 AM   #12
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Earth Grounding Rod Requirements


I just went through this grounding and NEC2011 for my electrical permit in CO. I could not have succeded without the book and my electrician friend.

My building site is on a granite mountain. We tried, but could not pound the grounding rod far enough into the ground. I had the excavator dig a trench near my sub panel. Since it is a sub panel, I only need one grounding rod.

Before I bought the property, it had a house that burned down. The garage is still standing (150ft from the former house and transformer), but no electricity. My permits are to connect the garage and begin the process for a new house.

When the inspector came to inspect the trench and grounding we discussed a bit about the future house. He mentioned a Ufer grounding system. NEC has nothing about this, but I did find some details on line. Does anyone here know about Ufer?
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Old 08-08-2012, 10:40 AM   #13
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Earth Grounding Rod Requirements


A Ufer is called a concrete encased electrode in the code.
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Old 08-08-2012, 11:19 AM   #14
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Thanks Jim
I found it. p239
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Old 08-08-2012, 12:06 PM   #15
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Earth Grounding Rod Requirements


Quote:
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just be sure to run the ground wire from the panel to each rod and back to the panel again.
Please explain.

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