Page 1 of 3 123 LastLast
Results 1 to 10 of 25

Thread: Insulated vs. Bare Ground Wire Application

  1. #1
    Join Date
    Aug 2014
    Location
    Rockville, MD
    Posts
    17

    Insulated vs. Bare Ground Wire Application

    Hey All,
    I may be overthinking this one, but one of our interns asked about the application of bare ground wire vs insulated ground wire, and I can't stop second-guessing my answer.

    My gut response was that bare copper wire allows the user to connect to earth or other grid materials (thinking ground grids, rebar and the like), and the reason we use insulated is to prevent unintentional grounding to objects not intended for that use.

    Could someone please confirm or school me on other differentiating applications?

    All the Best,
    --Nate

  2. #2
    Join Date
    Jul 2005
    Location
    Tennessee
    Posts
    15,973
    If you are going to "school" him, the 1st step would probably be to teach him the NEC tern "Ground" refers to EARTH, so if he qants to talk conductors he needs to learn "groundED" and "grouindING".
    But I think you answer is likely a good one. Applying the above, a groundING condcutor can often be insulated or bare but the groundED conductor needs to be insulated as you say to prevent an unintentional and non-compliant connection to grounding.
    At my age, I'm accustomed to restaurants asking me to pay in advance, but now my bank has started sending me their calendar one month at a time.

  3. #3
    Join Date
    Jul 2003
    Location
    New Jersey
    Posts
    25,194
    Quote Originally Posted by BlaineXD View Post

    My gut response was that bare copper wire allows the user to connect to earth or other grid materials (thinking ground grids, rebar and the like), and the reason we use insulated is to prevent unintentional grounding to objects not intended for that use.
    What possible unintentional objects would you be grounding by using a bare EGC? For the most part bare or insulated can be used interchangeably in most applications.
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

  4. #4
    Join Date
    Dec 2007
    Location
    NE Nebraska
    Posts
    36,778
    Quote Originally Posted by BlaineXD View Post
    Hey All,
    I may be overthinking this one, but one of our interns asked about the application of bare ground wire vs insulated ground wire, and I can't stop second-guessing my answer.

    My gut response was that bare copper wire allows the user to connect to earth or other grid materials (thinking ground grids, rebar and the like), and the reason we use insulated is to prevent unintentional grounding to objects not intended for that use.

    Could someone please confirm or school me on other differentiating applications?

    All the Best,
    --Nate
    Bare conductor laying in the earth or in concrete can't increase overall resistance when dealing with grounding electrode conductors, but nothing in code states you must use a bare conductor either. I typically only keep #6 and #4 bare on hand and if a GEC needs to be larger typically just use an insulated conductor for it. It can have insulation stripped where you make connections

    There are some places where NEC does require an insulated EGC. I believe EGC for swimming pool equipment and the feeder to a mobile home both need to be insulated, not really certain why. Might be some other places, otherwise general rule ordinarily allows bare, insulated or covered. Aluminum conductor has more requirement to be insulated or covered - especially if installed in wet/damp or other more corrosive locations.
    I live for today, I'm just a day behind.

  5. #5
    Join Date
    Apr 2003
    Location
    Planet macmikeman
    Posts
    3,449
    My thoughts. Depending on where your gec is terminating to it sometimes might be better to use one over the other. For instance: when bonding to the rebar in the footing for an offer ground electrode, should we be looking at the listing of an insulated wire as to it's ability to be encased in concrete? This is something an electrical inspector has asked me in the past when I used a stranded #4 thwn copper insulated wire to my bonding clamp. I think he was concerned with the stranding of the wire due to it's size rather than the covering on the outside. Now bare solid #4 cu wire has no outer covering and it in itself as a twenty foot of footing concrete encasement is an acceptable electrode even without rebar bonding. Will it corrode given time due to the nature of the concrete itself? How about when either is exposed to direct burial in dirt/soil? Which one is more subject to possible corrosion? I think probably the insulated one would outlast the bare one in that situation, but again is the thwn wire listed for direct burial? (NOTE: bent up rebar exposed above slab is typically rejected here, we must bond to the rebar at the bottom of the footing)
    85deg. an Sunny today.

  6. #6
    Join Date
    May 2011
    Posts
    4,194
    Other than for isolated ground, I think the only reason anybody uses insulated EGCs or GECs is to reduce physical damage to the wire. And because it's available, or they had it on the truck, or they've seen others do it and haven't thought about the reasoning. It's not the greatest idea to pull bare stranded wire with other conductors in a wire pull, and solid conductors larger than 8awg, IIRC, are not allowed to be pulled in raceways. Smooth outer insulation of THHN probably makes for an easier pull in many cases. For GECs run outside raceways the insulation provides a bit of extra protection from damage.
    Last edited by jaggedben; 06-08-18 at 12:41 PM.

  7. #7
    Join Date
    Dec 2007
    Location
    NE Nebraska
    Posts
    36,778
    Quote Originally Posted by jaggedben View Post
    Other than for isolated ground, I think the only reason anybody uses insulated EGCs or GECs is to reduce physical damage to the wire. And because it's available, or they had it on the truck, or they've seen others do it and haven't thought about the reasoning. It's not the greatest idea to pull bare stranded wire with other conductors in a wire pull, and solid conductors larger than 8awg, IIRC, are not allowed to be pulled in raceways. Smooth outer insulation of THHN probably makes for an easier pull in many cases. For GECs run outside raceways the insulation provides a bit of extra protection from damage.
    Damage from what? The insulation is physically weaker then the conductor it envelops. Corrosion - has to be pretty severe for copper to really matter much - aluminum is a different story. So what if the copper turns green - that is what copper does but just on the surface.
    I live for today, I'm just a day behind.

  8. #8
    Join Date
    May 2011
    Posts
    4,194
    Quote Originally Posted by kwired View Post
    Damage from what? The insulation is physically weaker then the conductor it envelops. Corrosion - has to be pretty severe for copper to really matter much - aluminum is a different story. So what if the copper turns green - that is what copper does but just on the surface.
    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.

  9. #9
    Join Date
    Dec 2007
    Location
    NE Nebraska
    Posts
    36,778
    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.
    Ok maybe some point there with finer stranded conductors. I was thinking mostly of grounding electrode conductors that are 6 AWG and larger in most instances. I don't know that many suppliers even stock bare conductor smaller then 8 AWG. All I can usually get is solid and in 8, 6 and 4 AWG, but that must just mean nobody is demanding much of anything else so they don't stock it.
    I live for today, I'm just a day behind.

  10. #10
    Join Date
    Aug 2014
    Location
    Rockville, MD
    Posts
    17
    Thanks for the replies, gentlemen. I really enjoy thinking about how our 'standard practices' formed, and challenging the BoD. You guys rock!

    --Nate

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •