gronding electrodes

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vincent antonellis

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dear mike,
does article 250.52 prohibit the use of ground rods as a grounding electrode system if there is a medal undergrond water piping on said premise.or does it give us the chioce of the six that are listed.
 
See 250.50 for the required (mandatory) GE's to be used.

Then see 250.53(D)(2)


Roger
 
vincent antonellis

vincent antonellis

roger thanks,

the problem i have is in a finished basement the previous electrician ran a number 6 thhn to the water main for a grounding electrode for a 200 amp service using 4/0 feeders from mtr in a finished basement. the new electrician asked if he could use the ground rods with a number 4 conductor because of the differculty of getting back to the water piping with a number 4 thhn.
would like your opinion
thanks vin
 
vincent antonellis said:
roger thanks,

the problem i have is in a finished basement the previous electrician ran a number 6 thhn to the water main for a grounding electrode for a 200 amp service using 4/0 feeders from mtr in a finished basement. the new electrician asked if he could use the ground rods with a number 4 conductor because of the differculty of getting back to the water piping with a number 4 thhn.
would like your opinion
thanks vin
Click to expand...

"4/0 feeders"
Adding my 2 cents

If the 4/0s supplying the panel in question are actually feeders, then you can't ground the electrodes to the subpanel. You have to bring the electrode conductor wire back to the main disconnect.

Whereever the main disconnect is, it must be have all of the electrodes conductors connected to it. If the waterline enters the building in metal, you have to pick it up unless you can somehow prove that it isn't in direct contact with the earth for 10 feet or more.

Waterline electrode conductor must be sized by Table250.66.
Ground rod electrode conductor can be #6, according to 250.66(A)

I guess I ended up putting in more than 2 cents.

David
 
Maybe I'm reading too fast to fully understand the situation, but I'll throw some references at you and let you come to your own conclusions.

  • 250.64(F) states we can go to any convenient grounding electrode first, and then connect electrodes together from there, if desired.
  • 250.66(A) states that the sole connection to a ground rod needs only be a #6.
  • However, 250.64(F) states "The grounding electrode conductor shall be sized for the largest grounding electrode conductor required among all the electrodes connected to it." If the ground rod is first, then it would have to be supplied by a #4.
 
If the water is there, you MUST use it. This is non-negotiable.

I've belly crawled 50' like a snake through dirt crawl spaces only 18" high under 100 year old places to hit a water line because it came through in a difficult place. You don't have to like it, you just have to do it ;->
 
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