Grounding Electrode System

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donruggs

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Fredericktown, OH United States
I recently installed a 800 AMP single phase 120/240 volt main service to an office complex. It consisted of 4 meters. 3 were 200 AMP, 1 was 250 AMP with breaker under meter. I paralleled 500 MCM CU into the meter set overhead. I installed a 3/4 x 10' CU ground rod and installed 2Q AWG CU wire to it from the meter set. The rebar in the footer was 1/2" and the cement contractor had run #4 AWG CU and we installed it to the meter set. The plumber installed 1 1/2 CU type K water line to the building which I ran #6 AWG CU wire from the meter set to it. The first electrical inspector passed it and Power Co. supplied power to the meter set. I had a different electrical inspector for rough-in wiring of one office and in our conversation said that I should have installed 2Q AWG not only to the ground rod but also to the water line. The ground rod is 4' away from the meter set and water line is 60'. My argument is that I consider the ground rod as the main grounding electrode and the other 2 as supplemental. I base my argument on the ground rod is less likely to be compromised over the life of the electrical system. Rebar can and will rust, ferrous water lines could be replaced or repaired with plastic thus diminishing grounding integrity. The 2nd inspector said his argument is that the water line and rod are both main grounding electrodes. I know all grounding electrode systems are important and work in concert with each other to insure proper operation of the electrical system. How does the code address this?
 
You are batting 50/50:)
250.66(A) provides that the grounding electrode conductor soley to the ground rod need not be larger than #6 Cu (If that GEC is a link to any additional electrodes it would need to be sized accordingly)
250.53(D) requires the grounding electrode conductor to a metallic underground water pipe be sized per 250.66 based on the phase conductors. In your case that would require a 2/0

The Code does not recognize a "main grounding electrode". When the metal water pipe is an electrode it must be supplemented but all electrodes on the premises are to be addressed accordingly.
 
Code requires all grounding electrodes if present to be used. If you had used the reinforcing steel there would of been no need for the ground rods.
Mr Ufer wanted to find a permanent, low cost grounding electrode in place of water lines, and his system does that.
Was your ground rod UL listed? Do you understand why copper clad ground rods are used?
 
Do you understand why copper clad ground rods are used?

I do not !
 
tom baker said:
... If you had used the reinforcing steel there would of been no need for the ground rods.
Mr Ufer wanted to find a permanent, low cost grounding electrode in place of water lines, and his system does that. ...
Click to expand...
Code requires a ground rod electrode to supplement the water pipe electrode. A second ground rod is required if you don't prove the first is not more than 25 ohms to ground.
 
Copper clad rods are used to reduce corrosion. A galv rod and copper wire will become a battery, due to the dissimilar metals and will corrode. A UL listed copper clad rod has thicker copper coating.
 
Smart $ said:
A little high on the latter number according to...

http://www.erico.com/catalog/literature/E1011B-WWEN.pdf
Click to expand...

The study they quoted only lasted 45 years, so that may be why they quote that as the expected lifetime. I had read a paper a few years back (it may have been based on that same study) that 60-70 years wasn't unlikely either. Copper takes an awful long time to break down, even with current going through it.

Either way, I'm happy with 45 years, too!
 
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