Common GEC & Taps

[Pierre C Belarge]

This is all hypothetical:

Lets say there is a 10 story building, all concrete.

There will be a transformer installed in an electrical closet located on each floor.

The GEC for the SDS (transformers) is required to go to steel or the water pipe within 5 feet of entrance to the building.
Since the building is all concrete, one would have to bring the GEC from the water pipe up to the SDS.

The NEC also permits a common grounding electrode conductor with taps permitted off of the common GEC to the transformers.



MY question:
Can one install the GEC up to the 8th floor and tap off of it 3 times on that floor to supply the transformers on the 8th, 9th, and 10th floors?
OR
Does the common GEC have to be run up to the 10th floor?

 

[infinity]

MY question:
Can one install the GEC up to the 8th floor and tap off of it 3 times on that floor to supply the transformers on the 8th, 9th, and 10th floors?
OR
Does the common GEC have to be run up to the 10th floor?

My guess is that as long as the GEC's from 9 and 10 run unbroken to the 8 th floor it's compliant.

 

[augie47]

I must admit I get a bit lost at this particular rule, but does 250.104(D) not allow you to "hit" the metallic water system at the SDS rather than with 5 ft of entry ?

 

[guschash]

I say you can tap off three times. Looking in the 2008 Workbook Exhibit 250.15 shows exactly what you are talking about, according to 250.30(A)(4)(a) and A4b.
Gus

 

[Pierre C Belarge]

I must admit I get a bit lost at this particular rule, but does 250.104(D) not allow you to "hit" the metallic water system at the SDS rather than with 5 ft of entry ?

Augie
That is bonding, I am speaking of the grounding electrode system.

 

[don_resqcapt19]

I don't see any limitations on where you make the tap to the common GEC.

 

[mpd]

had a similar situation very large 2 story all concrete, they installed a common GEC, because the water service was not practical, it has worked out good for present & future, don't see a problem with it pierre

 

[ibew501ed]

I must admit I get a bit lost at this particular rule, but does 250.104(D) not allow you to "hit" the metallic water system at the SDS rather than with 5 ft of entry ?

250.104D1 is the section that requires the water "in the area of the SDS" to be bonded however exception#2 seems to usually eliminate the requirement since bldg steel and incoming metal water are BOTH always used as the GES

 

[Pierre C Belarge]

250.104D1 is the section that requires the water "in the area of the SDS" to be bonded however exception#2 seems to usually eliminate the requirement since bldg steel and incoming metal water are BOTH always used as the GES

Take a look at 250.30, specifically 250.30(A)(7).
250.104 is bonding, not grounding.

 

[ibew501ed]

Take a look at 250.30, specifically 250.30(A)(7).
250.104 is bonding, not grounding.

I believe that is what i also was saying

what is your response to 250.104d1 except 2

 

[M. D.]

This is a good article on the subject... As for your question short,... as possible.

http://ecmweb.com/mag/electric_beyond_nec_changes/

 

[radiopet]

No, as long as the GEC's for each SDS are run to the CGEC then I see no limitations on this application. The NEC simply says that a common grounding electrode can be used and what sizes it must be, and the location of where the GEC's for each SDS are to run from ( Based on where the SBJ is located) to the CGEC then it does not mean it would need to run all the way up. But again thats my opinion of it....