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Bonding the UFER
- Thread starter mbrooke
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mbrooke
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It strikes me that you may not understand what an NEC concrete encased electrode is and where it is installed.
From 2011 NEC 250.52(A)(3).
It is installed in the footing not the slab and the slab is most times isolated from the foundation and footing
Check this out
In this application the CEE would be in the footing 2' to 4' underground and away from human contact. Notice the slab is isolated from the foundation.
Ill go back to this latter...
Lets start with this to keep it simple: I believe structural rebar should be bonded to the building's service.
mbrooke
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I was.
The explain to me why it would not provide equal potential. Forget concrete electrodes, Im talking rebar.
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Yes lets put aside facts and go with opinion.
This strongly suggest you don't know how structural rebar is installed in a building. It is not all connected together and to bond it all would require a great many connections.
The NEC recognizes this and added text to the section to make that clear.
Again from 2011 NEC 250.52(A)(3)
mbrooke
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Yes lets put aside facts and go with opinion.
Because if I presented my whole theory now it would not go over well for reasons you know well.
Ok lets jump to this then: why do we bond to building steal?
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We do not unless it qualifies as an electrode or is likely to be energized.
mbrooke
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And this is where the problem lays imo. While it may not qualify as an earthing electrode per NEC, it still can extend remote earth to a person.
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Many things can happen, but adding requirements without a documented problem is not cool.
I am much, much much more concerned with the outdoor located service gears potential to 'dirt' during an open neutral condition than building steel.
Typically exposed building steel is bonded by the metal raceways, boxes etc attached to it. Of course that is not an NEC bond but it does get the job done.
mbrooke
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Theory would say otherwise. This comes across as a curve ball to many, but when protecting people you actually want to energize everything around them during a contingency, or more accurately: bring everything to an equal potential.
A perfect example is a pool. Everything is bonded together in an intentional effort to create an equal potential mesh around the person. While a hand rail might kill at 120 volts, in theory it would not when everything else is energized at 120 volts (water, deck, ect) relative to remote earth. So in essence we are trying to remove anything from remote earth potential.
A second real world example is a dairy farm with stray voltage. Everything is bonded together to mask the situation.
Explain. This can have validity to it. But I might be thinking differently...
True, but why would the NEC require bonding if it classifies as an electrode and not when it doesn't? We can either ditch all steal bonding (because conduit would bond it regardless) or the NEC has a concern that conduit may not be a sufficient bond.
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Exactly. theory would point to that but reality is not pointing that way.
Yes, only astute folks like yourself understand these outlandish concepts.
For sure, and before those rules for pools came into being I am willing to bet that people had been injured or killed and this was the reason for code rules being added.
Again, the problem was not just a theroy, cows were not producing enough milk etc.
See the pattern? Problem first, than a code section to address it.
We don't install traffic lights at every intersection because of what might happen, we do it when it is demonstrated that the intersection is dangerous without one.
In truth we do not bond it if qualifies as an electrode, we use it as an electrode which ends up bonding it as well.
The only time we are required to bond building steel is when it is likely to be energized.
I do not think the NEC is concerned with bonding the steel in the least (and neither am I) unless it is likely to be energized.
Are you going to put in a code change proposal AKA a 'public input' voicing your concerns?
romex jockey
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That i do have a history of Mr MBrooke.....
Isolation can be a rather lofty aspiration, short of dressing cattle in faraday suits in fiberglass barns....
One naturally considers internal vs. external influence(s)
~RJ~
mbrooke
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Exactly. theory would point to that but reality is not pointing that way.
Open neutrals do happen in reality do they not? Same goes for incidental contact with higher voltages?
Why Thank you!
(Im joking) My point is that there are still much myths and misunderstanding around grounding and bonding. I still have old books from the 70s which say ground rods open a breaker. In fact I would even say that article 250 is built on a foundation of myth. Article 250 is almost exclusively concerned with earthing, but I see gaping holes in bonding. I have a theory that in the past CMP members actually believed that it was earthing that made systems safe rather then bonding. Yes earthing has its place but so does bonding. I will post a vid to back up my theory regarding the CMP.
Correct, and it has shown the concept works. Further it has shown that bonding is doing it rather then grounding.
Of course, due to voltage drop across the neutral. People become like cows when a service neutral opens or some other contingency take place.
Why not be proactive?
There are thousands of fires from open neutrals, some even with meters pulled, why has the CMP not addressed this yet despite actual evidence saying so?
I see new intersections that automatically get traffic lights without someone waiting for an accident to take place at that intersection.
Which I would argue: almost all building steal has the ability to become energized, or at least have a difference of potential.
My theory is that the NEC's qualifier for bonding only when it is a grounding electrode stems from old myths and misunderstandings once held by the CMP members. At one point it was believed that soil itself was essential to human safety. Just look at the misnomer term for EGC: "equipment grounding conductors" Its not earth that trips a breaker, its bonding back to the source. This I think is key to understanding...
I may do so. I first need to run some theoretical models to help come up with some better wording (and conceptual evidence), but I doubt I can change anything due to a wide laundry list on the CMP's part.
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Mbrooke, as a side note if I recall Florida requires metal studs in a building to be bonded. If I recall this was in response to a death.
mbrooke
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It takes two to tango :thumbsup:
In my eyes both internal and external need to be considered. It is impossible to isolate all building material, and it is impossible to dress all people in metal suits, but the system itself can do that and already does to some degree (bonding of water pipes).
mbrooke
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Exactly my point, stray statistics exist.
By chance do you, or does anyone else know what exactly happened?
BTW, Iwire, you are not far off when you speak of low impedance earthing in regards to soil... I will get to that...
mbrooke
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What is your experience in that? I think you would contribute a lot to the discussion.
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For sure.
What does not seem to be happening is a trail of death, injury or property damage from human contact with building steel during these open neutral conditions.
Why Thank you!
For sure, but I doubt (and hope) the CMP members do not have those misunderstandings.
I am highly confident the CMP members understand equal potential.
So throw the book out.
Somewhat, I think a better way to put it is that the CMPs are hesitant to lessen up the connection to dirt requirements without some strong substantiation.
See you are astute, you see gaping holes where 100s of engineers, electricians and other trade related folks do not.
In the past we burned witches too, stick with the present CMPs.
Go for it but I doubt I will watch it.
No one has said it does not work, no one has said it was grounding.
Peoples milk production drops? Man glad that did not happen to the wife while nursing our kids.
But as far as building steel can you show any documentation of people being electrically injured by contact with building steel because of an open neutral event?
Because that is not how life of earth works. 40,000 folks a year die on US roads, a great many of them from impacting objects on the side of the road. Why don't we place gaurd rails on all roads?
By this point (2015) we have built many steel framed structures, many of them have likely had open neutral conditions.
Where is the injury data?
Link to this evidence of "thousands" of fires caused by open neutrals. And more to the point how bonding the building steel would have prevented these fires.
Typically those would intersections that are on a road that has already demonstrated the need. But I will agree that happens sometimes.
I am not going to go down that road, 'likely to be energized' is an area where the NEC is lacking and no amount of discussion here is going to fix it.
As much as you feel otherwise I do not look at the NEC with reverence and I do not get butt hurt when folks want to change it. I do however find it amusing when one person sees so much wrong with it and thinks they can fix it all.
That is all fine and dandy, it may be accurate or not, I do not know.
But I do know that you have not provided any links or evidence at all that unbonded building steel is causing injuries.
Forget the figure it out on paper mission, find the data showing the injuries, that is what would get the code changed.
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Exactly that, stray, random etc. I am sure someone has died from being impaled with a pencil, we don't outlaw pencils.
No it was a while ago, send a PM to BPHGravity, he knows all the details and likely has the actual wording of the rule.
mbrooke
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Exactly that, stray, random etc. I am sure someone has died from being impaled with a pencil, we don't outlaw pencils.
No it was a while ago, send a PM to BPHGravity, he knows all the details and likely has the actual wording of the rule.
Errr, could you by chance? Im sure he isnt to happy about the stuff Ive been saying. (As though a person ought to be punished for speaking truth) :happyno:
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