2 ground rods required?

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865resi

865resi

Senior Member
Location
Tennessee
Occupation
Electrician
Are 2 ground rods required for a detached building that has a subpanel? Where is that in the 2017? Thanks
 
Maybe, you need a GES so a single rod proven to be 25Ω or less or two rods can be used to create the grounding electrode system. {250.32(A)}
 
Technically yes, unless you have an otherwise adequate grounding electrode system, such as a ufer, (or unless you can prove the first rod is 25 ohms or less to earth, which is not worth bothering with).

250.32 requires a grounding electrode system for the building, according to the same rules (250 Part III) as for a building with a service.

The requirement for a 2nd supplemental electrode is 250.53(A)(3).
 
Could be our rocky soil. Difficult to drive rods around here. Plus my inspectors have decades of experience.
 
865resi said:
Could be our rocky soil. Difficult to drive rods around here. Plus my inspectors have decades of experience.
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Not sure what this means. Are they allowed to make up their own code requirements? Do they not require what is in the NEC?
 
Most (not all) jurisdictions around here are fine with one rod and water pipe, or sometimes even two rods if you don't use the water pipe. I think few understand that the code says you still need a 2nd rod even if you have the water pipe. Detached buildings I frequently find done wrong in various ways, I think many inspectors are just not aware of those rules. The biggest AHJs around here enforce things thoroughly.
 
Let me apologize, I should have said I don't know why I've never been failed for not driving a 2nd rod. We are on the 2017, they do enforce the code. I apologize for any assumptions I made. Thanks
 
Our state level inspectors all require 2 but the local level inspectors (who inspect all trades but understand none of them) a lot of times just require 1. I did a service change in the winter once and one local told me if the ground is froze he doesnt call for any to be drove at all.
 
jaggedben said:
Technically yes, unless you have an otherwise adequate grounding electrode system, such as a ufer, (or unless you can prove the first rod is 25 ohms or less to earth, which is not worth bothering with).

250.32 requires a grounding electrode system for the building, according to the same rules (250 Part III) as for a building with a service.

The requirement for a 2nd supplemental electrode is 250.53(A)(3).
Click to expand...
They should have to proove it's not 25 ohms or more. Why's it on us to proove it on us to proove that it's less.?
 
jaggedben said:
Technically yes, unless you have an otherwise adequate grounding electrode system, such as a ufer, (or unless you can prove the first rod is 25 ohms or less to earth, which is not worth bothering with).

250.32 requires a grounding electrode system for the building, according to the same rules (250 Part III) as for a building with a service.

The requirement for a 2nd supplemental electrode is 250.53(A)(3).
Click to expand...
250.53A says IF multiple rods…….
 
Little Bill said:
Well that would make a good fireball!
Which 14 more rods wouldn't stop!!!
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I have to tell you, even with my field of ground rods and my lightning arrestors, my ham radio tower always made me nervous during thunder storms. One time during a snow storm I saw a lightning arrestor spark across it's air gap
 
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