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Is there a reason I should use bare copper instead of THWN for a grounding electrode conductor (e.g. bonding water pipes and ground rods; not an equipment grounding conductor)?

I cannot find anywhere that says THWN must be run inside conduit/raceway when used as a grounding electrode conductor. Section 250.62 indicates the conductor can be "solid, stranded, insulated, covered, or bare" and 4 and 6 awg THWN are generally cheaper in my area than bare copper (both solid and stranded), so I'm just wondering if there is some section of code I am missing or a practical reason to prefer a bare conductor since bare wire seems to be in wide use for this purpose where I look.

  • A licensed electrician grounded our 480V service with insulated black THWN-2 taped green. #2 I believe. Seems legit. – Harper Aug 12 '17 at 17:51
  • #6 and smaller have to be continuously colored green, if insulated. Larger wire can be identified with a permanent marking method, such as green tape. – ArchonOSX Aug 12 '17 at 20:25
  • @ArchonOSX Are you sure that color requirement applies to the grounding electrode conductor? It definitely applies to the equipment grounding conductor, but to my knowledge there is no such rule for coloration of a gec. Could you provide code sections on the color requirements for the grounding electrode conductor? Regardless, it is still a good idea to adhere to that color guidance since it looks like people have gotten hassle from inspectors over the issue per some forum posts I read before asking this question. – statueuphemism Aug 12 '17 at 23:19
  • @statueuphemism correct. I misread your question. The identification of the grounding electrode conductor is optional not required by the code. It is the equipment grounding conductor that is required to be identified. – ArchonOSX Aug 12 '17 at 23:55
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No, there is no reason. It is your choice.

In larger sizes bare wire is normally cheaper. Why pay for insulation when you don't have to.

The Code does not require bare it allows you to choose.

Good luck!

  • 1
    Strangely enough, near me the wire with insulation (THHN/THWN-2) is $0.86/ft while stranded bare wire is $1.59/ft. The seeming preference for bare and the rather drastic price differential made me wonder why bare copper was still in use. Must be an economies of scale thing for the price differences. Might also be different at the diy stores vs pro shops. – statueuphemism Aug 12 '17 at 23:38
  • That is quite a difference for not adding the insulation. The manufacturers make a lot more insulated wire. That must lead to the lower price. – ArchonOSX Aug 12 '17 at 23:58

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