User Tag List

Page 2 of 2 FirstFirst 1 2
Results 11 to 18 of 18

Thread: Sizing equipment grounding conductor for sub panel

  1. #11
    Join Date
    Aug 2004
    Location
    Northern illinois
    Posts
    17,054
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    the whole problem is solved by using metallic raceways as the EGC.
    Bob

  2. #12
    Join Date
    Jun 2012
    Location
    NW Ohio
    Posts
    1,098
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by petersonra View Post
    the whole problem is solved by using metallic raceways as the EGC.

    Unfortunatly convincing the AHJ’s this may be problematic as most I’ve dealt with want to see the wire EGC and by first hand experience I agree with them, as metallic raceway fittings become loose and/or corroded.
    A ground fault condition happened in a barn where the couplings were loose subsequently showering sparks down onto some straw.......Good thing people were around when it happened.

  3. #13
    Join Date
    May 2018
    Location
    Jamaica and london
    Posts
    1,250
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    but in the case of NM and SER cables arent the grounds based upon the size of the Live conductors? So if you switch from 8 NMb to 14 NMb isnt the ground smaller in the 14 than the 8? Thus, the size of the ground is based upon the size of the live wire?

    I have heard of proposals that the ground and neutral should always be the same size as the live wire, but in UK am allowed to size the egc or ground smaller, though there is a specific table for such use.
    Student of electrical codes. Please Take others advice first.

  4. #14
    Join Date
    Aug 2004
    Location
    Northern illinois
    Posts
    17,054
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by mopowr steve View Post
    Unfortunatly convincing the AHJ’s this may be problematic as most I’ve dealt with want to see the wire EGC and by first hand experience I agree with them, as metallic raceway fittings become loose and/or corroded.
    A ground fault condition happened in a barn where the couplings were loose subsequently showering sparks down onto some straw.......Good thing people were around when it happened.
    the code specifically allows for this. it is not up to the ahj.

    in any case if the metallic raceway fittings are not done correctly so they become loose, what makes you think the wire was done right?

    I have seen some cases where metallic raceways have come loose due to damage or poor installation techniques. But failing to repair them when it is noticed is the issue.
    Bob

  5. #15
    Join Date
    Jun 2012
    Location
    NW Ohio
    Posts
    1,098
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by petersonra View Post
    the code specifically allows for this. it is not up to the ahj.

    in any case if the metallic raceway fittings are not done correctly so they become loose, what makes you think the wire was done right?

    I have seen some cases where metallic raceways have come loose due to damage or poor installation techniques. But failing to repair them when it is noticed is the issue.

    Unfortunatly you you do not have control over how a building moves and causes conduit fittings to become loose. Go back and check your fittings after 10 years and tell me they’re still all tight.

  6. #16
    Join Date
    Feb 2003
    Location
    Bremerton, Washington
    Posts
    8,031
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by petersonra View Post
    the code specifically allows for this. it is not up to the ahj.

    in any case if the metallic raceway fittings are not done correctly so they become loose, what makes you think the wire was done right?

    I have seen some cases where metallic raceways have come loose due to damage or poor installation techniques. But failing to repair them when it is noticed is the issue.
    Loose fittings is an installation issue, not a product issue, and that what the code panel would answer if you submitted a change.
    but I agree run an EGC.
    Moderator-Washington State
    Ancora Imparo

  7. #17
    Join Date
    Feb 2003
    Location
    Bremerton, Washington
    Posts
    8,031
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by infinity View Post
    Our mod Don has been proposing for years that the EGC be sized according to the circuit conductor size not the OCPD that would help to end this nonsense.
    The theory is the larger the circuit conductors the more energy they can contribute to a fault, so the EGC needs to be larger. There was a study done some years ago sponsored by the Steel Tube Institute, saw it explained in Soares Book On Grounding. Later there was an interesting software program called GEMI, that have various parameters, ex length of circuit and voltage, solved for size of EGC
    Moderator-Washington State
    Ancora Imparo

  8. #18
    Join Date
    May 2013
    Location
    Massachusetts
    Posts
    2,438
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Dennis Alwon View Post
    I agree as I stated in my pm before the thread was started but I do understand where the op is coming from. If I only need a #6 equipment grounding conductor when I have a 250 amp breaker why do I need a larger conductor when the breaker size is smaller. It is hard to wrap your head around as this section doesn't always make sense.
    You'd need a #4 Cu with the 250A breaker. But you are correct, this can lead to clever work-arounds, meeting the wording of the NEC.

    Such as a 125A circuit, that upsized from #1 Cu to #3/0 Cu, and the EGC is required to be upsizes from #6 to #3. You could swap your 125A breaker for a 200A breaker, and then the 3/0 wire is compliant with the default #6 EGC. One would think that a larger OCPD in general means a larger EGC, yet here, a larger-than-necessary OCPD in the same range means the EGC doesn't need to be upsized as much.

Posting Permissions

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