supplemental ground rod with concrete encased electrode?????

[klineelectric]

An inspector here is saying I have to add a ground rod to my service which is a 200 amp residential with a concrete encased electrode system (ufer ground) in a monolithic slab. I asked where in the code it says this and he says ( while arrogantly laughing at me) that if it is more than 25 ohms an additional electrode is needed. To which I said did you take an ohm reading....lol. Oh no they wont give us a ground tester, he says. Am I wrong or is the 25 ohms or less only for single rod, pipe or plate electrodes. Thats where im reading it anyway 250.56(2008 nec) or 250.53(2011nec)

 

[iwire]

The inspector is mistaken.

If you have a uffer you do not have to add any additional electrodes.

 

[klineelectric]

All replies welcome. I am going to meet with this inspector and his boss Monday for clarification and all ammo is appreciated. I have 25+ yrs exp ( i am a licensed ec) I do not concede to "know it all", but in 25yrs I have never heard this before.

 

[skeshesh]

There's not much more add to the previous response. Your code reference is correct. Good luck and I hope that you succeed in doing this fellow the favor of imparting some humility. A piece of advice I've gotten from many experienced engineers, inspectors, contractors, technicians, etc. is that there's always plenty to learn in this trade and having a know-it-all attitude is just setting yourself up for an embaressing encounter with reality...

 

[Dennis Alwon]

I think a better reference is 250.53(D)(2).

250.53(D)(2) Supplemental Electrode Required. A metal underground water pipe shall be supplemented by an additional electrode of a type specified in 250.52(A)(2) through (A)(8). Where the supplemental electrode is a rod, pipe, or plate type, it shall comply with 250.56. The supplemental electrode shall be permitted to be bonded to the grounding electrode conductor, the grounded service-entrance conductor, the nonflexible grounded service raceway, or any grounded service enclosure.
Exception: The supplemental electrode shall be permitted to be bonded to the interior metal water piping at any convenient point as covered in 250.52(A)(1), Exception.

Now ask him where it states that a CEE needs to be supplemented. As stated CEE, IMO, is a much better electrode esp. in most areas of the country where 25 ohms with 2 rods is not likely.

 

[augie47]

Locally a few of the POCOs require a rod in addition to any other electrode.
You might verify their requirements just to CYA.

 

[hurk27]

To add with Dennis which is the code that allows a concrete encased electrode to supplement a water pipe electrode:

250.53(D)(2) Supplemental Electrode Required. A metal underground
water pipe shall be supplemented by an additional
electrode of a type specified in 250.52(A)(2) through
(A)(8). Where the supplemental electrode is a rod, pipe, or
plate type, it shall comply with 250.56. The supplemental
electrode shall be permitted to be bonded to the grounding
electrode conductor, the grounded service-entrance conductor,
the nonflexible grounded service raceway, or any
grounded service enclosure.

No where is this requirement stated for a concrete encased electrode, see above in red.

250.56 Resistance of Rod, Pipe, and Plate Electrodes. A
single electrode consisting of a rod, pipe, or plate that does
not have a resistance to ground of 25 ohms or less shall be
augmented by one additional electrode of any of the types
specified by 250.52(A)(4) through (A)(8). Where multiple
rod, pipe, or plate electrodes are installed to meet the requirements
of this section, they shall not be less than 1.8 m
(6 ft) apart.

Ask him where he see's concrete encased electrode in the above requirements for meeting 25 ohm's?

 

[tom baker]

Even if you are not on the 11 NEC, it rearranges the text in Art 250 to make it very clear that a Ufer ground does not require a ground rod, if you have a copy take it with you.