250.66(A) question

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Energize

Senior Member
Location
Milky Way Galaxy
I know the sole connection to the ground rod only has to be # 6 copper. I believe the reason is because of the amount of resistance that the ground rod can absorb will not exceed the capacity of a #6.

Any help/links where I can find more clairification or more information for the reasoning for the #6?

Thanks in advance for your help -
 

raider1

Senior Member
Staff member
Location
Logan, Utah
Energize said:
I know the sole connection to the ground rod only has to be # 6 copper. I believe the reason is because of the amount of resistance that the ground rod can absorb will not exceed the capacity of a #6.

Any help/links where I can find more clairification or more information for the reasoning for the #6?

Thanks in advance for your help -

It is not the resistance of the earth that is restrictive, it is the fact that the ground rod itself can not carry any more current than a #6 copper conductor.

Chris
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
raider1 said:
It is not the resistance of the earth that is restrictive, it is the fact that the ground rod itself can not carry any more current than a #6 copper conductor.
I can't see that, sorry. A 1/2" rod, even if solid steel, must be a better conductor than a #6 copper wire. I haven't investigated it, but if a larger rod made a difference, they'd make us upsize the #6.

Anyone?

I say it's the interface between the rod and the earth. The earth on a grand scale has little resistance. It's the little pinpricks of driven electrodes that don't have all that much contact area with it.
 

raider1

Senior Member
Staff member
Location
Logan, Utah
LarryFine said:
I can't see that, sorry. A 1/2" rod, even if solid steel, must be a better conductor than a #6 copper wire. I haven't investigated it, but if a larger rod made a difference, they'd make us upsize the #6.

Anyone?

I say it's the interface between the rod and the earth. The earth on a grand scale has little resistance. It's the little pinpricks of driven electrodes that don't have all that much contact area with it.

You may be correct that it is the contact resistance between the earth and the rod that has given rise to the #6 maximum conductor size.

I know that once you get into the earth the resistance is low due to the unlimited parallel paths throught the earth.

Chris
 
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