installing a new ground rod too close the old one

[1clock]

Good morning, I need to replace a ground rod that during time is degraded,
of course I can't slide it off the ground because it is very deep, so I have to install another
one that due to lack of space it will be very close some inches to the old one. The old ground
round will be disconnected and it will die on the ground, it will be not connected anymore
to any wire.

I know that ground rods need to be spaced at least the lenght of the ground rod because
when you install them too close together their effective fields of influence overlap,
but since the old ground rod is disconnected I wanted to know if it affects the new one anyway.

Thanks

 

[LarryFine]

No, you can ignore the abandoned rod. The concern with two rods too close is that the advantage of having a second rod is reduced, not that the effectiveness of each rod is reduced.

In other words, the closer two rods are, the more they behave like one rod, and the less like two. Two rods are used to reduce resistance between the electrical system and the earth.

 

[infinity]

The spacing minimum is 6' not the length of the rod which is a minimum of 8'

 

[winnie]

IMHO leave the old rod _connected_ unless doing so creates more work.

I concur with LarryFine, two rods very close together will act much like a single rod, not more poorly than a single rod.

If these are standard copper clad steel rods, then the old corroded rod will act a little bit like a sacrificial anode protecting the new rod for a time, so I see no reason to disconnect it. I would try to drive the new rod as far a practical from the old one simply so that the new one doesn't bang into the old one and get its copper scraped off.

-Jon

 

[charlie b]

Perhaps I am misreading the situation. But I tend to disagree with Larry and Winnie (as risky as that may be). My opinion is that a chunk of metal that is buried into the dirt, that has no wires attached, and that is located close to a ground rod that does have wires attached will have no influence whatsoever on the function of the ground rod.

 

[LarryFine]

Perhaps I am misreading the situation. But I tend to disagree with Larry and Winnie (as risky as that may be). My opinion is that a chunk of metal that is buried into the dirt, that has no wires attached, and that is located close to a ground rod that does have wires attached will have no influence whatsoever on the function of the ground rod.

What did I say that disagrees with you???

 

[charlie b]

What did I say that disagrees with you???

You spoke of the potential issues with two rods that are too close together. I said that if one of the rods has no wires attached, then those issues disappear. Do you agree with that?

 

[winnie]

My opinion is that a chunk of metal that is buried into the dirt, that has no wires attached, and that is located close to a ground rod that does have wires attached will have no influence whatsoever on the function of the ground rod.

I agree in essence with the above. The chunk of metal will of course change the shape of the potential field in the soil, but the introduction of high conductivity materials in the soil near to the ground rod could in no way reduce the performance of the ground rod or impair its function.

My opinion is that the decayed rod could be disconnected or remain connected, whichever is easier. I believe that leaving the decayed rod connected may result in a slight performance improvement, but not one that any sort of code requires.

I believe that what LarryFine was saying is that when two rods are close together, they are rendered less effective than two rods which are properly spaced. As the two connected rods get closer and closer together the performance approaches that of a single rod. I believe we are all in agreement that if you have two rods in the soil, and one is simply not connected, then the net result is an electrode that performs essentially as single rod in the soil.

 

[Knuckle Dragger]

Good morning, I need to replace a ground rod that during time is degraded,
of course I can't slide it off the ground because it is very deep, so I have to install another
one that due to lack of space it will be very close some inches to the old one. The old ground
round will be disconnected and it will die on the ground, it will be not connected anymore
to any wire.

That is how it is typically done when you cannot remove the ground rod.

 

[sameguy]

Drive the new rods at an angle if space is tight.

 

[ATSman]

You spoke of the potential issues with two rods that are too close together. I said that if one of the rods has no wires attached, then those issues disappear. Do you agree with that?

Charlie, I don't thing you understood Larry. He meant that if you are connecting a 2nd rod to reduce the resistance in a 2 rod system then you must place it beyond the "sphere of influence" of the 1st rod for it to be effective as stated in the Biddle ground rod testing manual "Getting Down To Earth." In this case it makes no difference where the new rod is placed since it is a single rod system. When I was doing ground rod testing years ago using the "3 point method" we had to make sure we drove the 2 test rods beyond a certain distance (sphere of influence) for the meter to read the correct value. I suggest you google Biddle, getting down to earth for a better explanation of the subject.

 

[LarryFine]

You spoke of the potential issues with two rods that are too close together. I said that if one of the rods has no wires attached, then those issues disappear. Do you agree with that?

Absolutely. My first sentence was "No, you can ignore the abandoned rod. "

The "potential issue" with rods too close is that you diminish the advantage of adding the second rod.

 

[LarryFine]

I believe that what LarryFine was saying is that when two rods are close together, they are rendered less effective than two rods which are properly spaced. As the two connected rods get closer and closer together the performance approaches that of a single rod. I believe we are all in agreement that if you have two rods in the soil, and one is simply not connected, then the net result is an electrode that performs essentially as single rod in the soil.

Definitely.

 

[LarryFine]

Charlie, I don't thing you understood Larry. He meant that if you are connecting a 2nd rod to reduce the resistance in a 2 rod system then you must place it beyond the "sphere of influence" of the 1st rod for it to be effective as stated in the Biddle ground rod testing manual "Getting Down To Earth."

Possibly.

 

[charlie b]

I understand the influence of two ground rods on each other when they are too close. I was focusing on the OP's statement that the old rod would not have wires attached.

 

[1clock]

thanks for everyone's suggestions