grounding electrode conductor

[treyp3]

250.66(A)?
A practice test asks: what size GEC for 3/0 ungrounded service conductor to metal water pipe? answer-4awg cu.
Is this correct? If so, what does pipe mean in 250.66(A)?
Also, when we shifted from primarily using ground rods to primarily bonding to the slab some years ago we continued to use 6cu GEC for 3/0 al 200a services. No one has ever called me out on this, but I'm looking at 250.66(B) and I'm thinking it would require 4 cu GEC. Ideas?

 

[roger]

250.66(A)?
A practice test asks: what size GEC for 3/0 ungrounded service conductor to metal water pipe? answer-4awg cu.
Is this correct?

Yes, see Table 250.66

If so, what does pipe mean in 250.66(A)?

It means a driven 3/4" pipe, see 250.52(A)(5)(a)

Also, when we shifted from primarily using ground rods to primarily bonding to the slab some years ago we continued to use 6cu GEC for 3/0 al 200a services. No one has ever called me out on this, but I'm looking at 250.66(B) and I'm thinking it would require 4 cu GEC. Ideas?

Your inspectors should be calling this a violation.

Roger

 

[Dennis Alwon]

I agree with Roger. I would use #4 to the CEE even on a 100 amp service simply because if they ever upgrade to a larger size the wire is appropriately sized.

 

[kwired]

...Also, when we shifted from primarily using ground rods to primarily bonding to the slab some years ago we continued to use 6cu GEC for 3/0 al 200a services. No one has ever called me out on this, but I'm looking at 250.66(B) and I'm thinking it would require 4 cu GEC. Ideas?

#6 Cu GEC is acceptable for 3/0 AL service conductors.

3/0 AL conductors are not acceptable for 200 amps. Even in Table 310.15(B)(6).

 

[treyp3]

#6 Cu GEC is acceptable for 3/0 AL service conductors.

3/0 AL conductors are not acceptable for 200 amps. Even in Table 310.15(B)(6).

Oops... missed the 4 and hit 3. Guess thats why nobody would pay me to type.

 

[Dennis Alwon]

Oops... missed the 4 and hit 3. Guess thats why nobody would pay me to type.

You missed it twice...:lol:

 

[treyp3]

Yes, see Table 250.66 It means a driven 3/4" pipe, see 250.52(A)(5)(a)

Your inspectors should be calling this a violation.

Roger

Ahhh... metal underground water pipe vs rod and pipe, 250.52(A)(1) and 250.52(A)(5). Although it doesnt say driven I clearly see the distinction.
Soo embarassed about the 6 cu, glad I cleared that up hear where Im somewhat anonymous.
Thanks for the help guys! Will be shure to pick up some #4 bare!

 

[treyp3]

You missed it twice...:lol:

To my understanding test questions that do not specify cu or al assume cu. Hence, 3/0 cu would be 4 GEC. Therefore, Ive only embarrassed myself once.