jar546
Forum Coordinator
Can you tell me if this is a violation of the NEC IF the contractor chooses to bond to the rebar only and does not use ground rods? If so, what section?
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Problem with Concrete Encased Electrode
- Thread starter jar546
- Start date
steveray
SAWHORSE
The rod is only required to be there to supplement the water pipe as a GE.....CEE does not require supplemental...250.53(2)
jar546
Forum Coordinator
Oh, I think you are missing the point. Look a little closer.......
Builder Bob
Sawhorse
Aren't the concrete encased electrodes supposed to be 20 feet continuous and located where concrete is in "direct" contact with the earth?
jar546
Forum Coordinator
The key component here is in direct contact with the earth which this is not
Mr. Inspector
SAWHORSE
If there was gravel in the forms is that direct contact with the earth?
linnrg
Sawhorse
why in the world are they using the fabric under the footings? Is the use of tyvek type materials being considered a crawl space vapor barrier and are they sealing to this material? A proper UFER is important because in today's world the incoming water service lines are usually plastic materials then transitioning to other plastic materials approved for interior piping. We have been using the frost protected shallow foundation method (insulated slab on grade) for some time. And there is a requirement for the vapor retarder under the slab so that you do not have moist floors. Most prefer this because they want in-floor heat. So anywhere there is a UFER I make them take out any vapor retarder that occurs in the footing area.
jar546
Forum Coordinator
No and why would it be? The concrete is separated by a barrier from earth and this is in the code as an informational note under NEC 250.52(A)(3)
linnrg
Sawhorse
interesting point the informational note does not state "the bottom of the footing" and just above the info note the description includes "...vertical foundations..." . I have always felt that the best footings are bound by soil to their tops. But our excavation methods now days leave all of the interior footing at the surface.
I would like to hear why anyone would be putting the fabric in the footing to begin with
I would like to hear why anyone would be putting the fabric in the footing to begin with
A membrane might be used because they are concerned about moisture from the ground passing through the slab and foundation thus causing failure of linoleum or promoting mold under the carpet. These were big concerns several years ago. I have seen a membrane used when building was built on a site where there might be residual contaminants in the soil.
The water lines have been converted to plastic pipe because when connected to the house ground there were currents passing through the water lines which resulted in corrosion of the water pipes.
The NEC provides for several types of ground electrode. The choice of which one will be used is that of the permit applicant. A building official that tries to dictate that a certain type of ground be used is overstepping.
The water lines have been converted to plastic pipe because when connected to the house ground there were currents passing through the water lines which resulted in corrosion of the water pipes.
The NEC provides for several types of ground electrode. The choice of which one will be used is that of the permit applicant. A building official that tries to dictate that a certain type of ground be used is overstepping.
jar546
Forum Coordinator
Under normal circumstances where the footer was in direct contact with the earth and not separated by a barrier as stated in NEC 250.52, they would not have to use another method as a grounding electrode but since the steel in the footer no longer qualifies as a grounding electrode, they must install another one of their choice.
steveray
SAWHORSE
Jeff, I was seeing what looked like a conductor in the "middle" section going to the rebar where there is no "footingwrap".....If that piece was 20' I would have to approve the installation I believe....
JCraver
Sawhorse
I have a question in regards to the ufer ground. Here the locals are pouring a footing with #4 steel re-bar and a little bit after they scraped the excess concrete off the top of the footing they go around and stab the re-bar vertical wall re-bar up-rites. The install the wall panels and some guy spray paints a piece of re-bar and claims it's the ufer ground!!
I can't verify the up-rites is in contact with the 20-ft required horizontal ufer in the footing? So I have been requesting a secondary grounding rod near and below the electric meter and attaching to the panel grounding bar.
The other day I had a builder say I can't request that second grounding source like Mark K just eluded too.
Overstepping?
I think I am a bit!
I can't verify the up-rites is in contact with the 20-ft required horizontal ufer in the footing? So I have been requesting a secondary grounding rod near and below the electric meter and attaching to the panel grounding bar.
The other day I had a builder say I can't request that second grounding source like Mark K just eluded too.
Overstepping?
I think I am a bit!
You are not overstepping if you have a legitimate concern that the ufer ground was not properly installed. Stabbing verticals is poor practice. You should be able to confirm the electrical connection between the vertical bar and the 20 foot length when you inspect the rebar. If no positive connection is observed prior to concrete pour it does not exist.
Providing multiple grounding electrodes can cause problems. The problem is that this can result in ground loop currents. "Ground loops are a major cause of noise, hum, and interference in audio, video, and computer systems."
Providing multiple grounding electrodes can cause problems. The problem is that this can result in ground loop currents. "Ground loops are a major cause of noise, hum, and interference in audio, video, and computer systems."
Builder Bob
Sawhorse
IF you want to , use ACI and state that vertical rebar cannot be wet sticked, it must be tied and secured in place prior to placement of concrete........Also, wet sticking of anchor bolts, straps, etc. are not permissible either.
steveray
SAWHORSE
Right or wrong, it is required...NEC reads the same....
E3608.1 Grounding electrode system. All electrodes specified
in Sections E3608.1.1, E3608.1.2, E3608.1.3, E3608.1.4
E3608.1.5 and E3608.1.6 that are present at each building or
structure served shall be bonded together to form the grounding
electrode system.
Obviously you have changed versions of the NEC Since previously the focus has been on article 250. I have available the 2011 NEC. But I doubt the basic intent will have c hanged.
250.50 states that when none of these grounding electrodes exist that one or more shall be installed. Note that it recognizes that only one electrode is possible.
The key is which of the electrodes exist.
-- Water pipes can be eliminated as a grounding electrode by placing a plastic pipe element when it goes underground. In many cases the water company automatically does this. This also protects your water pipes from corrosion from grounding currents.
-- The building steel frame does not exist as an electrode if holdown bolts are not connected to an electrode. By the way as a structural engineer I would not want the electrician welding to the holdown bolts.
-- A ufer ground does not exist if one is not installed.
-- A ground ring need not be installed.
-- If you do not install a rod electrode it doesn’t exist.
Obviously you will need to install one electrode but it should be clear that you can chose not to install the others. It is agreed that if you decide to install multiple electrodes they should be bonded.
The choice of which electrode or electrodes to install is at the option of the permit applicant.
The key is how you interpret the language in the NEC. I suggest that this interpretation, which is informed by an understanding of electronics, would be consistent with the way an electrical engineer would interpret it.. It may be possible to apply an interpretation that ignores electronics but that does nobody any good.
As a structural engineer I would not want the steel frame to be part of the grounding system for several reasons:
-- Ground currents could promote corrosion in the steel.
-- I am dubious that bolted connections will provide quality electrical connections. This is aggravated when the steel is painted before installation. Some times the steel will have a thin layer of rust which is not significant structurally if in an enclosed space but which could impact the resistance. You want a low impedance electrical ground which I doubt the steel frame would provide.
-- The steel frame could cause other elements of the building to be exposed to high grounding currents . On the other hand if you use dedicated grounding wires the currents would follow a well defined path where they could be isolated from other building elements.
250.50 states that when none of these grounding electrodes exist that one or more shall be installed. Note that it recognizes that only one electrode is possible.
The key is which of the electrodes exist.
-- Water pipes can be eliminated as a grounding electrode by placing a plastic pipe element when it goes underground. In many cases the water company automatically does this. This also protects your water pipes from corrosion from grounding currents.
-- The building steel frame does not exist as an electrode if holdown bolts are not connected to an electrode. By the way as a structural engineer I would not want the electrician welding to the holdown bolts.
-- A ufer ground does not exist if one is not installed.
-- A ground ring need not be installed.
-- If you do not install a rod electrode it doesn’t exist.
Obviously you will need to install one electrode but it should be clear that you can chose not to install the others. It is agreed that if you decide to install multiple electrodes they should be bonded.
The choice of which electrode or electrodes to install is at the option of the permit applicant.
The key is how you interpret the language in the NEC. I suggest that this interpretation, which is informed by an understanding of electronics, would be consistent with the way an electrical engineer would interpret it.. It may be possible to apply an interpretation that ignores electronics but that does nobody any good.
As a structural engineer I would not want the steel frame to be part of the grounding system for several reasons:
-- Ground currents could promote corrosion in the steel.
-- I am dubious that bolted connections will provide quality electrical connections. This is aggravated when the steel is painted before installation. Some times the steel will have a thin layer of rust which is not significant structurally if in an enclosed space but which could impact the resistance. You want a low impedance electrical ground which I doubt the steel frame would provide.
-- The steel frame could cause other elements of the building to be exposed to high grounding currents . On the other hand if you use dedicated grounding wires the currents would follow a well defined path where they could be isolated from other building elements.
steveray
SAWHORSE
Bonding and grounding are two different things (albeit slightly)
Jar,
My Soars book on grounding under an Informational note states:
"Concrete installed with insulation, vapor barriers, films or similar items separating the concrete from earth is NOT considered to be in 'direct contact' with the earth.
Using a vapor barrier between the concrete and the earth would render the electrode ineffective.
My Soars book on grounding under an Informational note states:
"Concrete installed with insulation, vapor barriers, films or similar items separating the concrete from earth is NOT considered to be in 'direct contact' with the earth.
Using a vapor barrier between the concrete and the earth would render the electrode ineffective.
jar546
Forum Coordinator
A few questions and comments:
1) What are ground currents?
2) The purpose of grounding and bonding is essentially for short circuit protection (and more) and not for carrying current under normal circumstances so I am not sure how "ground currents" would affect.
3) The code recognizes rebar in concrete as structural steel
4) Every single commercial structure with structural steel has the frame bonded to the grounding electrode system and to transformers that serve the building.
Ground currents are any current that flows to the ground. While normally these currents are small they do occur under normal operation. Electrical equipment, such as computers and audio systems, that operates at high frequencies often produce some high frequency grounding currents that can cause electrical noise and other problems. This is related to the concept of impedance which is frequency dependent resistance to high frequencies. Understanding this typically requires a formal course in electronics where you learn about imaginary numbers.
While these grounding currents are not a problem in many buildings, they can be a real problem in some.
The IBC and the steel code referenced from the IBC are clear that rebar is not structural steel. I repeat reinforcing steel is not structural steel. I could not find any provision defining rebar as structural steel in the NEC. In any case the NEC has no business trying to redefine the term structural steel.
Your claim that the structural frame is bonded to the grounding electrode system will be news to structural engineers designing these frames. Structural engineers do not want anybody welding or punching holes in the structural steel except as they have provided for. An electrician that welds grounding wires to structural steel could in some cases result create a situation that could lead to a premature failure of the structural system.
There is a difference between bonding and grounding. Bonding allows the current resulting from voltages to flow to the grounding elements while the grounding elements are concerned with allowing the current to flow to the earth ground. We do not want the structural frame to be the primary path of the current directly to the ground.
While it is common to think of a ground having zero resistance there can be significant resistances in the ground circuit. If you try to make the steel frame the path to the ground you will likely find that the resistances are larger than the resistances associated with a copper grounding wire that goes directly to the earth ground. If you bond the steel frame to the grounding system you do not need to create a second low resistance path directly to the earth ground.
While these grounding currents are not a problem in many buildings, they can be a real problem in some.
The IBC and the steel code referenced from the IBC are clear that rebar is not structural steel. I repeat reinforcing steel is not structural steel. I could not find any provision defining rebar as structural steel in the NEC. In any case the NEC has no business trying to redefine the term structural steel.
Your claim that the structural frame is bonded to the grounding electrode system will be news to structural engineers designing these frames. Structural engineers do not want anybody welding or punching holes in the structural steel except as they have provided for. An electrician that welds grounding wires to structural steel could in some cases result create a situation that could lead to a premature failure of the structural system.
There is a difference between bonding and grounding. Bonding allows the current resulting from voltages to flow to the grounding elements while the grounding elements are concerned with allowing the current to flow to the earth ground. We do not want the structural frame to be the primary path of the current directly to the ground.
While it is common to think of a ground having zero resistance there can be significant resistances in the ground circuit. If you try to make the steel frame the path to the ground you will likely find that the resistances are larger than the resistances associated with a copper grounding wire that goes directly to the earth ground. If you bond the steel frame to the grounding system you do not need to create a second low resistance path directly to the earth ground.
jar546
Forum Coordinator
I am still not 100% sure of what your argument is, nor do I think you completely grasp the concept of the original post. As far as a "formal course in electronics where you learn about imaginary numbers." I find that to be a bit of an arrogant statement. I for one am formally trained in electronics, electrical and electronic theory, but others may not be. Regardless of my training and comprehension of the subject matter it is not necessary for the understanding of the concept of grounding and bonding.
When you discuss your "ground currents," are you talking about voltage gradients due to objectionable current? If so, that is why we have a low-impedance ground fault current path that we need back to the soil in order to eventually reach back to the transformer from the utility company.
Concerning bonding of structural framing members, this has been required for decades for obvious safety reasons when it comes to ground fault and short circuit protection. Might I suggest that you spend some time reading all of article 250 of the NEC and get some formal training yourself on this matter. Every set of MEP plans that I received from a licensed engineer or engineering firm seem to grasp and understand this concept as they always specify the grounding and bonding of the service equipment and metal structure. It might be a good idea if you submit a proposal to the NFPA to eliminate bonding of building steel.