Out building

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domnic

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Electrical Contractor
I have a out building to wire 50" from house . it has a copper water line from house to out building i will run four wires 2 hots 1 neutral and EGC how do i bond water line. it is bonded in the house?
 
Water line

Water line

If i bond the water line to the EGC in the out building the EGC and the neutral in out building would be same ,
 
Your neutral at the outbuilding will not be bonded to the EGC or GEC.
Your copper water line at the outbuilding and the house will all be bonded which is what you would want.
 
domnic said:
If i bond the water line to the EGC in the out building the EGC and the neutral in out building would be same ,
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The only connection between neutral and any part of the Equipment Grounding System (EGS) should be the Main Bonding Jumper (MBJ) at the service disconnecting means. The fact that, under optimal conditions, they will be at the same potential is irrelevant. Neutral must be isolated from EGS/GES (Grounding Electrode System) at outbuilding.
 
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Sparky3141 said:
Would this be called an "auxiliary" effective ground fault current path?
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No it is establishing a grounding electrode system at the second building. A grounding electrode system is not intended to be an effective ground fault current path, though sometimes (as in this case) they incidentally become one.
 
kwired said:
No it is establishing a grounding electrode system at the second building. A grounding electrode system is not intended to be an effective ground fault current path, though sometimes (as in this case) they incidentally become one.
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Sorry, I didn't mean to be vague. I was referring to the water pipe and the feeder EGC running a parallel path back to the source, not the GES portion. If the copper water pipe is already bonded to the source I just don't see a practical reason for doing it again, though I don't see any harm in it either.
 
It may be a parallel path for the equipment grounding conductor but that won't hurt anything. If the neutral were bonded then it would be an issue and I believe that may one reason in the 2005 and earlier version no equipment grounding conductor was required if there were no metal pathways back to the house. Clearly then the neutrals and equipment grounding conductor were bonded and the grounding electrode conductor would be connected there. That would make for a parallel path on the neutral.
 
Objectionable current

Objectionable current

Dennis Alwon said:
...That would make for a parallel path on the neutral.
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Yeah, I vaguely remember something like that because there were phone lines running between buildings but as an apprentice I was mostly just boxin' houses and pullin' romex so I wasn't getting a good education. I've only recently discovered to what extent my poor training has affected me. That's why I lurk around here; to discover what else I'm clueless about.:slaphead:

I've also purchased the 2014 Master/Contractor Comprehensive Library DVDs from the Holt collection that I'm working through. So if I say something awkward, just ignore me; I'll catch up eventually.:blink:
 
How about starting with 250.50 an 250.52. Which basically require a grounding electrode system at each building or structure, and if certain electrodes are already present you must use them - metallic underground water piping over 10 feet long is one of those.
 
kwired said:
... if certain electrodes are already present you must use them - metallic underground water piping over 10 feet long is one of those.
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I wasn't questioning the need for a GES. The original question was how to bond the water pipe. The answer then according to 250.50 is you don't. Instead, the water pipe {250.52(A)(1)} acting as the permitted grounding electrode, is connected to the GEC; which precludes the necessity of adding ground rods as your required GES is complete. Essentially then, that also bonds the water pipe to the feeder EGC that was brought to the sub-panel.

Answer: the water pipe is required to be used as the grounding electrode. Run your GEC to it and you're done.

Thanks for helping me wrap my brain around that. :)
 
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Sparky3141 said:
...Instead, the water pipe {250.52(A)(1)} acting as the permitted grounding electrode, is connected to the GEC; which precludes the necessity of adding ground rods as your required GES is complete. Essentially then, that also bonds the water pipe to the feeder EGC that was brought to the sub-panel.

Answer: the water pipe is required to be used as the grounding electrode. Run your GEC to it and you're done.
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Technically that is only correct if the section of pipe which qualifies as the water pipe electrode at the originating building is completely compliant and the same section going to the outbuilding. It may be one, the other, neither, or both. Only the latter would hold true to your comment.


But if it is both, I wonder how many AHJ's would still require another supplemental ground rod, perhaps a second, at the outbuilding???
 
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