Ground Rods... again

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Rock86

Senior Member
Location
new york
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Electrical Engineer / Electrician
Engineer calls for (3) 3/4" x 10' copperclad ground rods for a 1600A service. I've been going through the codes, and some google searches... but I would like to know why the need for a 3/4" x 10' rod is suggested (or is it required?)? I did find a 10 year old article... https://forums.mikeholt.com/threads/size-of-ground-rod.67325/ Does anyone have any new information?

Looking at code... 250.52(A)(5) - Rods and pipes shall not be less than 8', pipes or conduit shall not be smaller than 3/4", and rods shall be at least 5/8".
 
You need to ask designer his reasoning.

8 foot by 5/8 is all code requires or even a listed rod can be 1/2 inch. will need two unless you can prove the first it 25 ohms or less.
 
ptonsparky said:
Well, he is the designer and the Engineer on top of it, that's all the reason he needs.
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Yikes, if you follow that logic, you must think communism is a good idea too! hahaha. (Kidding)

His design was not harmful, but because of his shrugged shoulder response to my question, I thought I would research a reason which would make his over-engineered design justifiable.
 
gadfly56 said:
He likely had this from some boilerplate spec he ran across somewhere, or was doing a lot of work in some jurisdiction with local requirements.

See my post regarding "The Spec".
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Exactly. It is a common spec on commercial projects along with triads even though there is no reason for either.

Roger
 
We see these dumb 10' rods required on big projects even when there is GEC connected to 50,000' of rebar. :rolleyes:
 
Code only requires 2 rods 6' apart and rods are generally 5/8' x 8'. Engineers will often require more than that. I have seen them require 3/0 copper to the rods when all the code requires is a max #6.

It doesn't hurt anything so....
 
Dennis Alwon said:
Code only requires 2 rods 6' apart and rods are generally 5/8' x 8'. Engineers will often require more than that. I have seen them require 3/0 copper to the rods when all the code requires is a max #6.

It doesn't hurt anything so....
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This always makes me feel weird when sizing the GEC... if #6 is the max to a ground rod, but code requires a 3/0 GEC, and for some hypothetical reason you're only using ground rods (no building steel)... where does the 3/0 go?
 
Rock86 said:
This always makes me feel weird when sizing the GEC... if #6 is the max to a ground rod, but code requires a 3/0 GEC, and for some hypothetical reason you're only using ground rods (no building steel)... where does the 3/0 go?
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Keep in mind grounding electrodes are not intended to carry current for clearing ground faults.

at some point it has been determined a typical ground rod can not dissipate any more energy into earth than a 6 AWG copper can deliver to it. You can run 3/0 if you want, it won't change the resistance of the rod to earth connection.

That 3/0 would be required for metallic structural components or water piping that is a qualifying electrode per 250.52

If you have a situation like OP with more rod than NEC minimums, maybe 6 AWG isn't necessarily enough for the conductor attached to it.
 
kwired said:
Keep in mind grounding electrodes are not intended to carry current for clearing ground faults.

at some point it has been determined a typical ground rod can not dissipate any more energy into earth than a 6 AWG copper can deliver to it. You can run 3/0 if you want, it won't change the resistance of the rod to earth connection.

That 3/0 would be required for metallic structural components or water piping that is a qualifying electrode per 250.52

If you have a situation like OP with more rod than NEC minimums, maybe 6 AWG isn't necessarily enough for the conductor attached to it.
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Thanks for that.
 
Rock86 said:
This always makes me feel weird when sizing the GEC... if #6 is the max to a ground rod, but code requires a 3/0 GEC, and for some hypothetical reason you're only using ground rods (no building steel)... where does the 3/0 go?
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Not required.
 
LarryFine said:
Not required.
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Correct, seen services with 400, 600, 1200 amp service conductors, and only a CEE with 4 AWG GEC or only ground rod(s) with 6 AWG. No need for any larger conductor if you only have an electrode with a max size like these two types have.
 
Rock86 said:
Engineer calls for (3) 3/4" x 10' copperclad ground rods for a 1600A service. I've been going through the codes, and some google searches... but I would like to know why the need for a 3/4" x 10' rod is suggested (or is it required?)? I did find a 10 year old article... https://forums.mikeholt.com/threads/size-of-ground-rod.67325/ Does anyone have any new information?

Looking at code... 250.52(A)(5) - Rods and pipes shall not be less than 8', pipes or conduit shall not be smaller than 3/4", and rods shall be at least 5/8".
Click to expand...
If the engineer drew it out and stamped it it’s required.
Doesn’t matter what the NEC states as long as it meet the minimums, or is backed up with his stamp, depending on the article.
 
oldsparky52 said:
I know a pump and tank contractor in Raleigh that does it his way and argues if someone shows him the plan. Explains to them that they don't know what they are doing. :)
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If he signed the contract and does that it’s breach
 
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