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Thread: Service Entrance Grounding

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    Service Entrance Grounding

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ID:	19779I am reviewing some specs and came across this section. I was wondering what you all thought of creating a loop with the grounds and connecting the ends back together, like the state is suggesting. It is not a configuration that I am familiar with. I am new to the field, but I know that a grounding system can and-- in an industrial setting-- generally does have some amount of current on it. By creating this loop, would you be degrading and making a less efficient system? I mean, because the path of least resistance is a loop? Also, what implications would this have for cathodic protection and the degradation of components (lugs, cables, and such) over time?
    Thanks for any insights and opinions.
    --Nate

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    Grounding or earthing, as in a connection to the earth gets far more attention than it deserves. It gets spoken about in hushed, reverential terms, and people come up with all kinds of schemes to appease the spirits of the electron. In reality it's about the least important part of a buildings electrical system. More important is good equipment grounding practices, that's what keeps things safe.
    If you don't think too good, don't think too much.

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    Although I can see it I cannot read the text in your graphic. Not sure why a loop would matter but maybe I'm not understanding the setup. Also in industrial or any other setting an EGC should not carry any current under normal conditions.
    Rob

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    All responses based on the 2014 NEC unless otherwise noted

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    I believe the OP is asking after Service Entrance Grounding, rather than Equipment Grounding Conductors.

    BlaineXD, I believe you are starting to think about the actual circuit diagram of a real world Premises Wiring (System) (see Art. 100 Definition). The actual circuit diagram, from source (the Power Company transformer secondary), through the Service to the Utilization Equipment with the various connections to Earth, gets to be a set of parallel current paths, especially for the Grounded Service Conductor with its connections to Earth through the Grounding Electrode System.

    Try sketching it out. Remember that current takes ALL available paths. The current return paths to the transformer secondary windings are many-fold.
    Another Al in Minnesota

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    Hi all, thanks for the comments. Sorry for the terrible image (I guess that's what you get for not previewing the post before sending it out :P The text reads as follows in reference to the service entrance grounding (where the drop meets the state's equipment, like Al said):

    (A) Install 3 ground rods in the vicinity of the service entrance. The ground rods must be at leas 6 feet apart.
    (B) Install grounding cable as sized on the plans. Grounding cable shall be one continuous cable. It shall start on the neutral bar in the service panel, go completely through the ground bar, then through the neutral bond, and then equipment ground bond, then out through the conduit to the first ground rod, then the 2nd ground rod, and then the 3rd rod before returning back through the conduit to the service panel neutral bar.

    I took your advice and sketched it out myself (see attached). Sketching it out hasn't really helped my thought process, though. It still seems, at the very least, and unusual requirement, and at worst, something that has created an unnecessary loop that undermines the purpose of the ground; creating a path of least resistance back to the terminal lugs.

    I might just be overthink the whole thing... Any more opinions would be great!
    Thanks,
    --NateModel.pdf

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    Quote Originally Posted by BlaineXD View Post

    I took your advice and sketched it out myself (see attached). Sketching it out hasn't really helped my thought process, though. It still seems, at the very least, and unusual requirement,
    It looks like a silly requirement to me. For instance, how does it make one bit of difference if the wire to the ground rods is one continuous piece instead of one jumper from the first ground rod to the second. It doesn't, it's a stupid piece of copper tying one ground rod to the next, the ground rods have no idea if the wire is spliced or not either, they are stupid too. There is also no reason to bring the grounding electrode conductor back to the neutral buss, there is no reason not to either other than it's a wast of material and effort.

    and at worst, something that has created an unnecessary loop that undermines the purpose of the ground; creating a path of least resistance back to the terminal lugs.
    Any connection to the earth has no purpose in creating any path of least resistance or clearing a fault, that is what good equipment grounding practices are for.

    I might just be overthink the whole thing... Any more opinions would be great!
    Thanks,
    --NateModel.pdf
    Unless you are working on a telecom or similar site, or maybe a fancy server room or similar then earthing connections are not a big deal.
    If you don't think too good, don't think too much.

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    Quote Originally Posted by ActionDave View Post


    Unless you are working on a telecom or similar site, or maybe a fancy server room or similar then earthing connections are not a big deal.
    And even in those applications it may be useless to go above and beyond code minimum requirements, but to designers of these sites it is like having Sports Illustrated swimsuit edition pictures posted all around the facility would be to many others

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    Quote Originally Posted by BlaineXD View Post
    I took your advice and sketched it out myself (see attached). Sketching it out hasn't really helped my thought process, though.
    Ah. Interesting text associated with the photo.

    I was able to see, in the photo, that the panel was single phase, and I assumed 240 / 120 V.

    Three ground rods ! ! Are there no other Grounding Electrodes present at this Structure? I had assumed that there was, at the very least, something like water pipe and / or a concrete encased electrode. I apologize for the assumption, if such is not the case.

    Given three ground rods as your only grounding electrode, a missing part of the circuit diagram is the Grounded Service Conductor between the neutral in the circuit breaker panel (shown in the photo) and the Power Company transformer neutral terminal. The Power Company transformer neutral will also have a wire type conductor leading to an local ground rod (or ground "ball"), and this same wire-type conductor will be solidly connected to any Power Company primary neutral (from the high side of the transformer). The primary neutral may only be the lightning protection conductor run with a purely delta circuit.

    If there is a potable water service provided in metallic piping by a municipal water utility, and there are neighbors, who share electrical supply from the same transformer, there will be multiple "loops" formed by the low impedance water piping from Grounding Electrode Conductor (GEC) connection to GEC connection in all the premises that have a Grounded Service Conductor connection to the single Power Company transformer neutral terminal.

    The current path through Earth, from premises grounding electrodes to the Power Company transformer Earth connection also are additional "loops".

    The circuit diagram, including the source (transformer secondary, and, maybe even the primary transmission circuit) becomes any number of loops.
    Another Al in Minnesota

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    Quote Originally Posted by BlaineXD View Post
    Hi all, thanks for the comments. Sorry for the terrible image (I guess that's what you get for not previewing the post before sending it out :P The text reads as follows in reference to the service entrance grounding (where the drop meets the state's equipment, like Al said):

    (A) Install 3 ground rods in the vicinity of the service entrance. The ground rods must be at leas 6 feet apart.
    (B) Install grounding cable as sized on the plans. Grounding cable shall be one continuous cable. It shall start on the neutral bar in the service panel, go completely through the ground bar, then through the neutral bond, and then equipment ground bond, then out through the conduit to the first ground rod, then the 2nd ground rod, and then the 3rd rod before returning back through the conduit to the service panel neutral bar.

    I took your advice and sketched it out myself (see attached). Sketching it out hasn't really helped my thought process, though. It still seems, at the very least, and unusual requirement, and at worst, something that has created an unnecessary loop that undermines the purpose of the ground; creating a path of least resistance back to the terminal lugs.

    I might just be overthink the whole thing... Any more opinions would be great!
    Thanks,
    --NateModel.pdf
    In looking at the attachment there is basically a waste of material. The GEC goes from the rods to the neutral, the MBJ bonds the neutral to the EGC bar. Nothing else is required. The loop and extra jumpers are just a waste of money.
    Rob

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    All responses based on the 2014 NEC unless otherwise noted

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    Quote Originally Posted by infinity View Post
    The loop and extra jumpers are just a waste of money.
    Yup.

    I my opinion, residential services in towns and cities, by far the most common of services, are replete with "loops."

    It is the cognitive disonnance at the core of America's distribution system.
    Another Al in Minnesota

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