ECN Forum Forums Code Related Discussion NEC & other Code issues Dual Ground Rod Bending Direction

my electrical inspector allows us, if there is a trench already dug to just lay the rods down in the trench, not even driving them in the dirt..makes it nice and easy that way.. trench gets filled and taa daa your done

and are you driving these straight in?? I try to drive them in on a steep angle makes it alot easier. using a hammer drill

Have you tried a 50lbs demo hammer? Just because you hit rock doesn't mean you cant drive through it.

If you are going to bury the grounding electrode, you have to make sure that the dirt being back filled is compacted. Otherwise it is not making a good contact with the earth.
When a rod is driven it is going in with some resistance, which means the earth is hugging the rod snugley, in turn good contact with the earth.

Hi,
Thanks for all the replies.

So then there is a boundry between the two ground clamps? I never realized that you could NOT bend a ground rod less than 10 feet long.

The entire rod has to be between 0-45 degrees vertical or at a right angle to the trench ONLY?

I think I have case 2 but the rod is aiming towards the first.

One ground rod is down 8 feet, the second is six feet away and down 4 feet and then bent on a 45 (or so) in a 24 inch trench.

It sounds like I need to drive another in a different location to see if I can get it down 8 feet.

I was hoping to be able to just keep what I have but if it's not right it's not right.

The distance can be greater than 6 feet can't it?

How would I make a ground ring work?

-regards

Greg

[This message has been edited by mustangelectric (edited 12-12-2004).]

Mustang,

I just re-read the code section on grounding electrodes. I strongly recommend that you do so rather than depend upon 'second hand' information.

While I am sure that I remember seeing that you cannot bend the electrode, I see nothing that says you can't bend the electrode. 250.53(G) describes 1) 2) and 3) of the pictures above, and requires 8ft of length in contact with the soil, but nothing about bending. I found a _Canadian_ code reference where they required driving the rod vertically and then bending, rather than driving at an angle. Go figure , different laws, different code bodies.

The _electrodes_ (not just the clamps) need to be at least 6 feet apart. They can be farther apart.

A ground ring is a loop of bare copper wire, at least 2ga, and at least 20 feet long, which circles the entire structure, buried at a depth of 30 inches or greater.

-Jon

I misunderstood what you originally said Greg. I thought you meant you had the ground rod laying horizontally in the trench at 24" and were bending it up to make connection above ground. Which would mean you only had 5 1/2'ish feet horizontal.

What you actually have is a cross between 1 and 2 in my diagram right? I don't see anywhere that specifically prohibits that.

The optimal distance between electrodes is the length of the buried electrode. That is, if you are using 8' ground rods, they should be buried 8' apart. You can think of a ground rod as being surrounded by shells of earth, the more earth around the ground rod - the less resistance seen. When you have two ground rods, you want to keep these shells from overlapping and research has shown that the effective area of the shell is proportional to the length of the ground rod. As to why the code book allows us to go as close as 6', I don't know. BTW, I have never seen anything that would allow us to bend a ground rod. It seems that that would create a high resistance spot on the electode.

Laura J

To add some more info to Laura's post, check out this link.
http://www.leminstruments.com/grounding_tutorial/html/

Scroll down through the tutorial.

Roger

Hi,
Thanks for the replies. Where is it in the code that says a ground rod can not be bent?

I have seen a lot that were bent.

Whats the difference in bending one and laying it horizontal in a trench?

I do not see the difference electrically what position the rod is in when in contact with the earth at a prescribed depth.

They make ground rods up to 20 feet I think.

What is the largest size ground rod?

-regards

Greg