Theory question- grounding and bonding SDS

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mbrooke

mbrooke

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Why do we bond an SDS to the service grounding electrode? Why is it when a building has multiple transformers they all need to be bonded together and driven to a common electrode? I can not figure out why this is done from an electrical theory perspective. :dunce:
 

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I would think in its simplest form it would go back to the definition of bonding in establishing continuity and assuring everything is at the same potential.
 
augie47 said:
I would think in its simplest form it would go back to the definition of bonding in establishing continuity and assuring everything is at the same potential.
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Perhaps, however, my thinking:

1. There is already the existence of a branch circuit EGC to the transformer.

2. With no current on the grounding system, everything is at the same potential. A fault scenario which would cause such a difference will clear an OCPD.
 
mbrooke said:
Why do we bond an SDS to the service grounding electrode? Why is it when a building has multiple transformers they all need to be bonded together and driven to a common electrode? I can not figure out why this is done from an electrical theory perspective. :dunce:
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I can't tell from your wording if you know that the NEC doesn't require an SDS to be bonded to the service grounding electrode system. More often than not, I have not seen it done so unless building steel is nearby.
 
Strathead said:
I can't tell from your wording if you know that the NEC doesn't require an SDS to be bonded to the service grounding electrode system. More often than not, I have not seen it done so unless building steel is nearby.
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My mistake in my wording- the nec itself does not require bonding to the service grounding electrode- looks like the CEC requires it however.

My despite the differences in the CEC and NEC, both require some type bonding/grounding outside of normal equipment, ie one example:


25030a4.jpg
 
Strathead said:
I can't tell from your wording if you know that the NEC doesn't require an SDS to be bonded to the service grounding electrode system. More often than not, I have not seen it done so unless building steel is nearby.
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FYI '17 NEC
"250.30(A)(4) The building or structure grounding electrode system shall be used as the grounding electrode for the SDS....................................."
 
I think what you mean to ask is why cant the EGC run with the primary supply serve as the system grounding conductor for the SDS? IF so, I agree a redundant system ground is unnecessary. I think it is just consistency with the system grounding requirements for services. Yes these requirements such as irreversible splices, physical protection, bonding at each end of a metal raceway, etc are full of ground myth influence and not commensurate with its actual importance, but these requirements remain......
 
electrofelon said:
I think what you mean to ask is why cant the EGC run with the primary supply serve as the system grounding conductor for the SDS?
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Yup- I mean it does its job well.


IF so, I agree a redundant system ground is unnecessary. I think it is just consistency with the system grounding requirements for services. Yes these requirements such as irreversible splices, physical protection, bonding at each end of a metal raceway, etc are full of ground myth influence and not commensurate with its actual importance, but these requirements remain......
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That makes a lot of sense :happyyes:
 
mbrooke said:
My mistake in my wording- the nec itself does not require bonding to the service grounding electrode- looks like the CEC requires it however.

My despite the differences in the CEC and NEC, both require some type bonding/grounding outside of normal equipment, ie one example:


25030a4.jpg
Click to expand...

Personally I think that this is a waste of time, material and someones money. I see no reason to run a common grounding electrode in a high rise building. The primary contains an EGC so it's already connected the building GES. The system bonding jumper protects against ground faults on the secondary side. We had a similar thread about this not too long ago with similar opinions.
 
infinity said:
Personally I think that this is a waste of time, material and someones money. I see no reason to run a common grounding electrode in a high rise building. The primary contains an EGC so it's already connected the building GES. The system bonding jumper protects against ground faults on the secondary side. We had a similar thread about this not too long ago with similar opinions.
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What year did they start to require this if anyone knows? Comforting to know that I am not the only one to hold such an opinion.
 
the only thing i can think of is proximal GE's , given a high AIC situation that might possibly compliment theory.....but that could be a stretch too.....~RJ~
 
I had the thought mother nature has it in for a particular SDS mbrooke

probably not a validating point

~RJ~
 
romex jockey said:
I had the thought mother nature has it in for a particular SDS mbrooke

probably not a validating point

~RJ~
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Perhaps- not entirely implausible considering that transformer were not as well built back in the day. Their failures could have been correctly or incorrectly attributed to lightning. The problem was great enough to change utility grounding practices.
 
Yeah, the last pad i grounded had the poco EE show up , who's chief focus was just how the whole ground ring should be set up. I got the impression they've a tighter doctrine , more than likely from experience

~RJ~
 
romex jockey said:
Yeah, the last pad i grounded had the poco EE show up , who's chief focus was just how the whole ground ring should be set up. I got the impression they've a tighter doctrine , more than likely from experience

~RJ~
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Often they do, they are strict about. Then again you do not want to break continuity on that MGN.
 
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