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Thread: Ufer ground

  1. #21
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    [QUOTE=petersonra;1918120]
    Quote Originally Posted by MBLES View Post

    Not what I said. IF the footer for the skid qualifies as a GE, you have to use it. It may not. For instance it may use wire mesh instead of rebar as the steel reinforcement. If there is no qualifying CEE, you should just pound in two ground rods and use them as your GES.

    What I said is you do not have to bond the GES of the new skid to the GES of the existing structure, although the EGC of the feeder or branch circuit going from the existing structure to the new skid will effectively bond the two GES together.
    Here's a thought for you. Would you consider adjacent pipe supports (each with two footings w/ rebar-based CCEs) independent of each other when considering their EGS? They would only be connected by the pipes resting on them (which you can argue can be painted/coated). Is it a matter of physical proximity (10' apart, 20', etc.)? What defines separate EGS?

  2. #22
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    Quote Originally Posted by petersonra View Post
    only if it is in the footing.
    You quoted:

    "Metallic components shall be encased by at least 50 mm
    (2 in.) of concrete and shall be located horizontally within that
    portion of a concrete foundation or footing that is in direct
    contact with the earth or within vertical foundations or structural
    components or members that are in direct contact with
    the earth."

    I can still very easily see how an inspector can look at a 20" slab of concrete with rebar in it and say it qualifies under a "concrete foundation in direct contact with the earth". Am I missing some civil/structural jargon that precludes a slab from being a foundation?

  3. #23
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    Quote Originally Posted by MRKN View Post
    I can still very easily see how an inspector can look at a 20" slab of concrete with rebar in it and say it qualifies under a "concrete foundation in direct contact with the earth". Am I missing some civil/structural jargon that precludes a slab from being a foundation?
    The NEC does not contain a definition of footing or foundation, but they are common terms in building trades. A footing is underground below frost line and a slab is not. If an inspector wants to get pushy building codes could be referenced.
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  4. #24
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    Thank you

  5. #25
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    Quote Originally Posted by MRKN View Post
    If it's already poured and the AHJ didn't hold them up from pouring you're good to go under 250.50 "that are present". Welp, guess it's no longer present now.
    They changed wording in about 2008 or 2011 because the way it was worded before that is exactly what was happening. "are present" is what got changed from "if available" or something close to that wording. Before the change - concrete was poured before EC was ever on site and it "wasn't available" and seldom was ever used as an electrode.

    Now that it says "that are present", just because it got covered up before you got there doesn't make it "not present". They did throw in an exception for existing construction though, you don't need to tear up a footing just to gain access to the rebar when putting new service into existing construction. New construction you need to plan accordingly though.

    Quote Originally Posted by petersonra View Post
    The steel that is encased in the concrete would be the rebar mentioned in the code.

    250.50 says all the GE at a structure have to be bonded together. however you are dealing with a separate structure here. The new skid CEE is not associated with the existing structure.
    I agree sounds like this generator pad possibly is a separate structure and if so it needs it's own grounding electrode system. Question then is whether there is a qualifying CEE or not, and that sounds like it may depend if there truly is a footing or just a slab. If no qualifying CEE then pound in two rods and move on.

    A lot of "if's" go along with this for no more then what we know.

    Quote Originally Posted by MRKN View Post
    You quoted:

    "Metallic components shall be encased by at least 50 mm
    (2 in.) of concrete and shall be located horizontally within that
    portion of a concrete foundation or footing that is in direct
    contact with the earth or within vertical foundations or structural
    components or members that are in direct contact with
    the earth."

    I can still very easily see how an inspector can look at a 20" slab of concrete with rebar in it and say it qualifies under a "concrete foundation in direct contact with the earth". Am I missing some civil/structural jargon that precludes a slab from being a foundation?
    There is a fairly recent thread where this is under debate. (is a slab a footing, can a slab with thicker perimeter be considered a footing) There is mixed opinions on it, and NEC isn't really all that clear either for some situations.
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  6. #26
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    "Now that it says "that are present", just because it got covered up before you got there doesn't make it "not present". They did throw in an exception for existing construction though, you don't need to tear up a footing just to gain access to the rebar when putting new service into existing construction. New construction you need to plan accordingly though."

    I still tend to interpret this to mean they have a right to not let you pour the concrete, but if you have already poured, as you say they can't make you tear it up.

    I don't really understand the risk of not bonding a rebar CEE to the GES, can anyone give me one example of why this would be of benefit?

  7. #27
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    Quote Originally Posted by MRKN View Post
    "Now that it says "that are present", just because it got covered up before you got there doesn't make it "not present". They did throw in an exception for existing construction though, you don't need to tear up a footing just to gain access to the rebar when putting new service into existing construction. New construction you need to plan accordingly though."

    I still tend to interpret this to mean they have a right to not let you pour the concrete, but if you have already poured, as you say they can't make you tear it up.

    I don't really understand the risk of not bonding a rebar CEE to the GES, can anyone give me one example of why this would be of benefit?
    They changed wording because they found out that CEE's weren't being used all that much.

    CEE's have much more contact surface with soil and therefore usually much lower resistance to earth then a typical ground rod driven into same soil. In fact if you have a CEE you don't even need to drive any rods per NEC. Rods are just the simplest thing to use if there is no other electrode present or with water pipe electrodes they do require a supplemental electrode. If you have a CEE, or qualifying building steel electrode, then that is the supplemental electrode to the water pipe - no rods required.

    They can and have made people tear up concrete to gain access to reinforcing steel on new construction. The exception is for existing construction. Brand new building with a qualifying CEE - NEC says you must make it a part of your GES.

    First sentence of 250.50:

    All grounding electrodes as described in 250.52(A)(1) through (A)(7) that are present at each building or structure served shall be bonded together to form the grounding electrode system.
    (A)(3) is concrete encased electrodes. It no longer says where accessible (or something close to that), this new wording (new about 10 years ago) means if it is there it will be used.

    the exception says:

    Concrete-encased electrodes of existing buildings or structures shall not be required to be part of the grounding electrode system where the steel reinforcing bars or rods are not accessible for use without disturbing the concrete
    Only applies to existing buildings.
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  8. #28
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    Fair enough, is there a set of notes from the committee that validates what you're saying? It would be nice to have on hand in case someone does ask concrete to be torn up. It seems to me without an understanding of the history it is unreasonable to expect every electrical engineer to interpret the gray area of the code this way and plan accordingly for hold points during the foundation work. And it doesn't do the relationship between the owner and inspector any good if the inspector chooses to force costly foundation rework in this type of example..

  9. #29
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    Quote Originally Posted by MRKN View Post
    Fair enough, is there a set of notes from the committee that validates what you're saying? It would be nice to have on hand in case someone does ask concrete to be torn up. It seems to me without an understanding of the history it is unreasonable to expect every electrical engineer to interpret the gray area of the code this way and plan accordingly for hold points during the foundation work. And it doesn't do the relationship between the owner and inspector any good if the inspector chooses to force costly foundation rework in this type of example..
    Find the ROPS from when the change was made - I'd bet at least some of what I said is in there. My comments are from recollection of what went on for discussions back when that change went into effect.

    Concrete was being ordered to be torn up back then. Now the majority of the concrete contractors are on board with this rule and if the EC doesn't approach them about it, they often are trying to contact the EC to coordinate with them. Might not be same in other places, but our inspectors were notified by their department heads of the change back then and no matter where you went within the jurisdiction (which is statewide) it was being enforced pretty consistently. Our State AHJ has been pretty good at addressing new code changes in the past as a group and all the inspectors are usually on the same page when it comes to knowledge of changes in code.

    Add: and especially true for changes to items in chapters 1-4, which apply to things they see all the time. A change in chapters 5-7 could be something they don't see all that often and might have a better chance of being missed.
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  10. #30
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    250.50 seems at odds with 250.52(A)(3) wherein it states "If multiple CCEs are present a building or structure, it shall be permissible to bond only one into the GES". I presume this statement overrides the require of 250.50 that all grounding electrodes in a GES are bonded together?

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