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Thread: Insulated vs. Bare Ground Wire Application

  1. #11
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    One recommendation for an insulated EGC was in either the IEEE green book or Soares, namely use an insulated EGC so in the event of a ground fault the insulation would help from damaging the adjacent conductors from the heat generated in the EGC.
    Small sized bare EGC, IE 14-12-10 are fine stranded, easy to damage, kink when pulling and harder to pull.
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  2. #12
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    Quote Originally Posted by jaggedben View Post
    Physical damage (e.g. severing of strands). Not corrosion. The insulation doesn't have to be stronger than the copper to take the brunt of abrasion.

    With that said, now I'm wondering why I shouldn't look into just using bare stranded. Anybody tried it? Almost all of our long pulls are 3-5 #10s in 3/4" conduit.
    I tried it once. I'll never do it again. The #12 we tried pulling kinked and bird-caged with little more than a strong glance. It's just not worth it. We also had several instances of the bare #12 stranded pushing up against the back of receptacles. It caused several GFCI trips and breaker trips when we began to power things up. I'm not a huge fan of the solid bare EGC in Romex either, but at least it stays where you put it.


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  3. #13
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    For EGCs and GECs, the NEC allows ground wire to be either insulated or bare in most applications. I'm not aware of any case where insulation is explicitly required by the NEC for grounding conductors. It is an engineer's/installer's discretion to specify insulated grounding wire.

    One reason to specify it, is mechanical, as insulation reduces the abrasion to other wires in the conduit during a pull. Insulated wires are also available in finer stranding patterns (which improve pull mechanics) than their bare counterparts, such as 19-strand instead of 7-strand in size 6. Another reason is chemical, as insulation avoids corrosion conflicts if the wire is routed among dissimilar metals (such as copper in contact with aluminum, zinc galvanizing, or concrete).

  4. #14
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    Quote Originally Posted by Carultch View Post
    For EGCs and GECs, the NEC allows ground wire to be either insulated or bare in most applications. I'm not aware of any case where insulation is explicitly required by the NEC for grounding conductors. It is an engineer's/installer's discretion to specify insulated grounding wire.

    One reason to specify it, is mechanical, as insulation reduces the abrasion to other wires in the conduit during a pull. Insulated wires are also available in finer stranding patterns (which improve pull mechanics) than their bare counterparts, such as 19-strand instead of 7-strand in size 6. Another reason is chemical, as insulation avoids corrosion conflicts if the wire is routed among dissimilar metals (such as copper in contact with aluminum, zinc galvanizing, or concrete).
    There are some places where it is required. A few I am aware of are in 517.13, 550.33, 680.25.
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  5. #15
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    I have a question regarding bare wire in a conduit as an EGC, maybe someone could answer this for me. Would a bare conductor pulled through conduit not give potential for the “choke” effect? Same as the age old debate for the GEC going into your meter/disconnect without a bushing of some kind.


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  6. #16
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    Quote Originally Posted by ElectricMatt View Post
    I have a question regarding bare wire in a conduit as an EGC, maybe someone could answer this for me. Would a bare conductor pulled through conduit not give potential for the “choke” effect? Same as the age old debate for the GEC going into your meter/disconnect without a bushing of some kind.


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    Insulated or bare isn't the issue here, it is magnetic fields around the conductor when it carries current. If the other conductor(s) of the circuit are inside the same ferrous tubing, those fields cancel on another. A single conductor (grounded or not) carrying current and inside a ferrous tube is basically a one turn core and coil.
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  7. #17
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    Quote Originally Posted by kwired View Post
    Insulated or bare isn't the issue here, it is magnetic fields around the conductor when it carries current. If the other conductor(s) of the circuit are inside the same ferrous tubing, those fields cancel on another. A single conductor (grounded or not) carrying current and inside a ferrous tube is basically a one turn core and coil.
    Maybe I misread the OPs statement. I thought he was talking about using bare vs insulated to prevent unintentional grounding(I.e. the choke effect). I was just thinking a bare copper wire inside a ferrous metal tube could cause unintentional grounding.

    But if you could elaborate a little more on the fields canceling one another. I would like to understand that a little more.

    Thanks


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  8. #18
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    Are there any situations where grounding/bonding conductor must be non insulated?

  9. #19
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    Quote Originally Posted by ElectricMatt View Post
    Maybe I misread the OPs statement. I thought he was talking about using bare vs insulated to prevent unintentional grounding(I.e. the choke effect). I was just thinking a bare copper wire inside a ferrous metal tube could cause unintentional grounding.

    But if you could elaborate a little more on the fields canceling one another. I would like to understand that a little more.

    Thanks


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    If the ferrous metal tube is bonded at some point anyway does it matter if it touches the grounding conductor inside? They should be at same potential.

    Clamp on ammeter measures magnetic field caused by current flowing in conductor. Clamp on to just one conductor and you read whatever current it has flowing in it. Clamp on to two conductors with same load on them but one goes out to a load and the other returns from that load - then current is flowing opposite direction at any instant in time on each of those conductors. Clamp your meter on both and it should read zero, because of opposing magnetic fields canceling one another. Same effect would be apply to how it effects a ferrous tube surrounding the conductor(s), in fact the clamp on meter does have ferrous component in the clamp to pick up the magnetic fields in the conductors you are measuring.
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  10. #20
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    Quote Originally Posted by kwired View Post
    If the ferrous metal tube is bonded at some point anyway does it matter if it touches the grounding conductor inside? They should be at same potential.

    Clamp on ammeter measures magnetic field caused by current flowing in conductor. Clamp on to just one conductor and you read whatever current it has flowing in it. Clamp on to two conductors with same load on them but one goes out to a load and the other returns from that load - then current is flowing opposite direction at any instant in time on each of those conductors. Clamp your meter on both and it should read zero, because of opposing magnetic fields canceling one another. Same effect would be apply to how it effects a ferrous tube surrounding the conductor(s), in fact the clamp on meter does have ferrous component in the clamp to pick up the magnetic fields in the conductors you are measuring.
    Thanks for going into a little more detail. I completely understand what you are saying now. I appreciate you taking the time to explain it further.


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