Preprufe effectively eliminates ufer ground

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Aretae

Aretae

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All of the concrete on this project is sealed from moisture intrusion and the AHJ and EOR have both deemed that the rebar will not be a proper ufer ground. The EOR has stipulated driving a rod in lieu of using the rebar but he has not stiplulated bonding the rebar to the rod. The detail does require bonding to the cold water pipe in the building within 5' of point of entry.

We want to bond the rebar, the EOR has stated this is not necessary. We contend that all potential current carrying items should be effectively bonded to ground, including the rebar.

Your opinions?
 
why would you argue with the engineer on record ? (are you qualified to dispute his opinion and also that this represents an immediate hazard to human life ? - if so, then argue away, but I think you are barking up the wrong tree)
 
nakulak said:
why would you argue with the engineer on record ? (are you qualified to dispute his opinion and also that this represents an immediate hazard to human life ? - if so, then argue away, but I think you are barking up the wrong tree)
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I would agree, but I have a simular situtation where the engineer went against the manufactures recommendations, but not against code though, and they are trying to blame the issue on me for his design. He fully knew what the manufacture required. But I was supposed to re-engineer it. It was not an immediate hazard to human life either.
 
Preprufe failure

Preprufe failure

nakulak said:
why would you argue with the engineer on record ? (are you qualified to dispute his opinion and also that this represents an immediate hazard to human life ? - if so, then argue away, but I think you are barking up the wrong tree)
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Good counter point nak.

I believe we must raise aa concern whenever life-safety is an issue. If the point raised can be shown to be invalid, then I am merely somewhat embarrassed, better than someone dead.
The preprufe is like a swimming pool liner, digging around it could damage it in the future and effectively create a grounded surface with a potential difference between it and the grounding system not bonded to it. The NEC confirms concrete as a grounded surface, so all of these (IMO) should be bonded to ground so as to reduce potential

Believe me, grounding on this job is a hot issue. Electricians must raise life safety issues and not just say, "well, the EOR said to do it this way". If someone is killed or injured, you can bet that statement will not alleviate my name on a liability suit.
 
Good example on blame shift

Good example on blame shift

hillbilly1 said:
I would agree, but I have a simular situtation where the engineer went against the manufactures recommendations, but not against code though, and they are trying to blame the issue on me for his design. He fully knew what the manufacture required. But I was supposed to re-engineer it. It was not an immediate hazard to human life either.
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This is a good example that just because the EOR says something, does not alleviate you from potential future problems. Though we (me, not necessarily you) are "just" electricians, we still need to ask if we think we see what may be a problem. A good EOR will help us (me) to understand our error in thinking or they will make changes. EOR's are not infallible, even more-so, neither am I.
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I would bond the rebar even if it is dry it has to have some potential and probably is still better than the rod.
 
Bond iy anyway

Bond iy anyway

Dennis Alwon said:
I would bond the rebar even if it is dry it has to have some potential and probably is still better than the rod.
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Thank you Dennis, I agree.

I believe in in this case it is better to be "too safe", if it is being too safe at all. Plus, it may not even be a case of too safe. Table 110.26(A)(1)Condition 2 specifically states that concrete is a grounded surface and makes no reference to the necessity of it even having rebar in it. Therefore, bond the rebar and help reduce potential issues.
 
How would an engineer of record be granted the rights to waive code rules? Unless the proper AHJ permitted what the engineer specified, no way. Code compliance or documented variance...one or the other.:)
 
Code or documented approval

Code or documented approval

wbalsam1 said:
How would an engineer of record be granted the rights to waive code rules? Unless the proper AHJ permitted what the engineer specified, no way. Code compliance or documented variance...one or the other.:)
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I never gave a lot of thought to that. The AHJ has not approved of this, I wonder how interested they would be in it?
 
Aretae said:
I never gave a lot of thought to that. The AHJ has not approved of this, I wonder how interested they would be in it?
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But from your OP,
the AHJ and EOR have both deemed that the rebar will not be a proper ufer ground.
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Perhaps you can propose an alternate solution that would allay the concerns with waterproofing of the concrete. If there are anchor bolts, bond them to the rebar and bond to the steel building frame or whatever equipment is being anchored. This will effectively bond the rebar without an additional penetration of the concrete.
 
Aretae said:
. We contend that all potential current carrying items should be effectively bonded to ground, including the rebar.
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How do you envision the rebar becoming a current carrying item?
Are you planning to bond the rebar in the driveway and sidewalks also?
 
Bonding Concrete

Bonding Concrete

don_resqcapt19 said:
How does bonding the concrete make the installation safer?
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I do not even know how you would bond concrete, but one of the other threads someone posted a link to bonding water, so I suppose you could. I mentioned it only because if the code calls it a grounded surface there must be some means of bonding it to all other grounded items, thereby reducing any potential voltage difference between it and other grounded surfaces? Sorta like equipotential grounding for pools and hot tubs?
 
Aretae said:
This is a good example that just because the EOR says something, does not alleviate you from potential future problems. Though we (me, not necessarily you) are "just" electricians, we still need to ask if we think we see what may be a problem. A good EOR will help us (me) to understand our error in thinking or they will make changes. EOR's are not infallible, even more-so, neither am I.
http://forums.mikeholt.com/images/icons/icon9.gif
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It is OK to shift the blame from the engineer to the electrician? I don't think so, If we are to re-engineer everything they do, why hire an engineer? The installation was code compliant, but the engineer did not follow the manufactures suggestions. This was a industrial job with an industrial engineer that had designed many of these plants, am I the one without a degree in engineering to tell him he is wrong?

jim dungar said:
How do you envision the rebar becoming a current carrying item?
Are you planning to bond the rebar in the driveway and sidewalks also?
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The rebar can easily become current carrying, happens all the time, PVC conduit with a fault melting the conduit, if the rebar is not bonded, it becomes live to anything grounded. Driveways and sidewalks generally do not have conduit in them, so the potential is lower for them, but is still there just the same.
 
Dennis Alwon said:
I would bond the rebar even if it is dry it has to have some potential and probably is still better than the rod.
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I would bond also, BUT I have tested rebar grounds where plastic is installed under the concrete and the readings were exceptionally high when compared to the Ground grid that was installed after construction.
 
Aretae said:
I do not even know how you would bond concrete, but one of the other threads someone posted a link to bonding water, so I suppose you could. I mentioned it only because if the code calls it a grounded surface there must be some means of bonding it to all other grounded items, thereby reducing any potential voltage difference between it and other grounded surfaces? Sorta like equipotential grounding for pools and hot tubs?
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Just because the code calls the concrete a grounded surface does not require you to bond it. And yes bonding it will reduce the potential difference to other grounded surfaces, but does that really make it safer?
 
I just looked up preprufe to find out what it is. The waterproofing membrane prevents the foundation from being a concrete-encased electrode as defined in the NEC. NEC 250.52(A)(3) says the electrode has to be encased "within that portion of a concrete foundation or footing that is in direct contact with the earth..." A waterproof membrane eliminates the direct contact. The relevant concept is not an equipotential surface (except for swimming pools), but the ability of the electrode to transfer current into the earth.
 
jghrist said:
I just looked up preprufe to find out what it is. The waterproofing membrane prevents the foundation from being a concrete-encased electrode as defined in the NEC. NEC 250.52(A)(3) says the electrode has to be encased "within that portion of a concrete foundation or footing that is in direct contact with the earth..." A waterproof membrane eliminates the direct contact. The relevant concept is not an equipotential surface (except for swimming pools), but the ability of the electrode to transfer current into the earth.
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Yes, it does disqualify it as a grounding electrode, but the potential for it to become energized is real, I'm just playing devils advocate when the lawyers ask why you didn't bond it when you knew there was a possibility of it becoming live, it's sad that you have to think this way with every installation anymore.
 
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