original ground rod not found, new one installed. disconnect old one?

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Stevenfyeager

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United States, Indiana
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electrical contractor
I always drive a new ground rod for a house panel replacement. I can't find the old one for the 200 amp panel. Should I leave the old one connected to the panel or disconnect it? Two rods within probably a couple of feet apart, is this bad? Thank you
 
Stevenfyeager said:
I always drive a new ground rod for a house panel replacement. I can't find the old one for the 200 amp panel. Should I leave the old one connected to the panel or disconnect it? Two rods within probably a couple of feet apart, is this bad? Thank you
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What do you mean you can't find it? Way below grade? Is it encased?- may even not be a rod, could be an ufer/old water pipe- you should try to verify what is there- if it is indeed run to ufer/ water pipe, needs to stay connected.

Whatever you decide to do don't forget that you need a supplemental electrode: See 250.53(A)(2)

And per your "couple of feet" est between the old rod (if that's what ends being there) and the new one, you need to disconnect it, drive another rod that is not less than 6ft apart from your new one : See 250.53(A)(3)
 
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user 100 said:
What do you mean you can't find it? Way below grade? Is it encased?- may even not be a rod, could be an ufer/old water pipe- you should try to verify what is there- if it is indeed run to ufer/ water pipe, needs to stay connected.

Whatever you decide to do don't forget that you need a supplemental electrode: See 250.53(A)(2)

And per your "couple of feet" est between the old rod (if that's what ends being there) and the new one, you need to disconnect it, drive another rod that is not less than 6ft apart from your new one : See 250.53(A)(3)
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(A)(3) only requires a supplemental rod to be at least six feet away from the one it supplements, otherwise you can drive as many as you want right next to one another - though you get lower overall resistance if you spread them out.

To get maximum effect of the "sphere of influence" a minimum of six feet between them is usually desired.
 
IMHO there is no requirement to disconnect the old rod or to locate it and make sure that it is more than 6 feet from any other rods. If you can't find it just leave it connected and install whatever is required as if that rod were not there.

250(A)(3) is the relevant section, and it says 'If multiple...electrodes are installed to meet the requirements of this section, they shall not be less than 1.8m apart'. I read this to mean that an electrode which is too close simply doesn't count to meet the requirements, not that it needs to be removed.

Think about the physics. Ground rods that are close together are not as effective as ground rods that are spread apart, but if you had two ground rods installed side by side touching each other that would be no worse than a single ground rod.

-Jon
 
winnie said:
IMHO there is no requirement to disconnect the old rod or to locate it and make sure that it is more than 6 feet from any other rods. If you can't find it just leave it connected and install whatever is required as if that rod were not there.

250(A)(3) is the relevant section, and it says 'If multiple...electrodes are installed to meet the requirements of this section, they shall not be less than 1.8m apart'. I read this to mean that an electrode which is too close simply doesn't count to meet the requirements, not that it needs to be removed.

Think about the physics. Ground rods that are close together are not as effective as ground rods that are spread apart, but if you had two ground rods installed side by side touching each other that would be no worse than a single ground rod.

-Jon
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I agree completely.
 
Stevenfyeager said:
I always drive a new ground rod for a house panel replacement. I can't find the old one for the 200 amp panel. Should I leave the old one connected to the panel or disconnect it? Two rods within probably a couple of feet apart, is this bad? Thank you
Click to expand...

If you can't find the old ground rod that means it's probably not there. It was common a few years ago just to ground to the cold water pipe ( within 5 ft of entrance). The cold water ground is not acceptable anymore in most areas because the metal water pipes have been replaced by plastic. If there are still metal water pipes in the house they need to be bonded.

In the areas where I work you would need to drive 2 new ground rods not less than 6 ft apart unless you can prove that a good cold water ground still exist and that's almost impossible without lots of digging.
 
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