Equipotenetial Bonding Grid

  • 19 Jan 2011 3:50 PM
    Message # 501945
    Is it ok to use Steel Wire Mesh in direct contact with the earth for a Equipotential Bonding Grid that is required by the code? For instance under brick pavers used around an outdoor or Indoor Hot Tub.
  • 22 Jan 2011 7:57 AM
    Reply # 505172 on 501945
    Steve Losacco wrote:
    Is it ok to use Steel Wire Mesh in direct contact with the earth for a Equipotential Bonding Grid that is required by the code? For instance under brick pavers used around an outdoor or Indoor Hot Tub.
    Steve, my answer would be No because the steal mesh such as the masonry contractors will soon rust away and there will be no grid left. I have seen this question posted on other forums and the answer always come back the same- No. Makes sense to me so if there is no masonry work and you have brick pavers or if you have no perimeter decking at all you should use a grid or a single #8 solid bare copper wire properly spaced in relation to the surface and the waters edge for your "perimeter surface" grid called for in 680.26 NEC or E4204.2 MRC (2009 Edition).
  • 22 Jan 2011 2:31 PM
    Reply # 505373 on 501945
    Tony Tomasin

    Steve,

    Looks like George beat me to it but I had the post already written so, here’s my take on it and I’m afraid I might get a bit wordy here. Under Article 680 Part IV Spas & Hot Tubs of the NEC, we look in section 680.42 Outdoor Installations, which says: “outdoor installations shall comply with parts I & II of this article”.  Part II of Article 680 deals with permanently installed pools which includes equipotential bonding per 680.26(b)(2) for bonding perimeter surfaces extending 3’ from the pool or in this case, hot tub.  Now that we know we have do it the question is can we use a steel reinforcing mat, like the type used in sidewalks, in direct contact with the earth and can this be used as the equipotential grid under the perimeter in the pool.  My answer is no.  In the last code cycle most electrical inspectors were allowing the a steel reinforcing mat to be used as an equipotential grid if it was not in direct contact with the soil but embedded in the concrete.  This was being allowed even though it was never really approved in Article 680.  The proper way to do it was either with re-rod or the welded copper mat that is now required and described in section 680.26(B)(1)(b).  The problem with using just a steel mat is that if it is in direct contact with the soil and not in the concrete is that it will be destroyed by rust.  Once the inspector left the job he had no way of knowing if the mesh was installed properly in the pour.  In the 2008 NEC another option was given to accomplish the bonding of the perimeter surfaces and it’s reletivly inexpensive and accomplishes what it is intended to do.  Section 680.26(B)(2)(b) reads: (b)   Alternate Means. Where structural reinforcing steel is not available or is encapsulated in a nonconductive compound, a copper conductor(s) shall be utilized where the following requirements are met:  

    (1)        At least one minimum 8 AWG bare solid copper conductor shall be provided. 

    (2)        The conductors shall follow the contour of the perimeter surface. 

    (3)        Only listed splices shall be permitted. 

    (4)        The required conductor shall be 450 to 600 mm (18 to 24 in.) from the inside walls of the pool. 

    (5)        The required conductor shall be secured within or under the perimeter surface 100 mm to 150 mm (4 in. to 6 in.) below the subgrade.

     

    This new option should be the method used both for both paved and unpaved surfaces such as the pavers you have described.

    Hope that helps……..Tony

     

  • 26 Jan 2011 8:39 AM
    Reply # 507632 on 505373
    Tony Tomasin wrote:

    Steve,

    Looks like George beat me to it but I had the post already written so, here’s my take on it and I’m afraid I might get a bit wordy here. Under Article 680 Part IV Spas & Hot Tubs of the NEC, we look in section 680.42 Outdoor Installations, which says: “outdoor installations shall comply with parts I & II of this article”.  Part II of Article 680 deals with permanently installed pools which includes equipotential bonding per 680.26(b)(2) for bonding perimeter surfaces extending 3’ from the pool or in this case, hot tub.  Now that we know we have do it the question is can we use a steel reinforcing mat, like the type used in sidewalks, in direct contact with the earth and can this be used as the equipotential grid under the perimeter in the pool.  My answer is no.  In the last code cycle most electrical inspectors were allowing the a steel reinforcing mat to be used as an equipotential grid if it was not in direct contact with the soil but embedded in the concrete.  This was being allowed even though it was never really approved in Article 680.  The proper way to do it was either with re-rod or the welded copper mat that is now required and described in section 680.26(B)(1)(b).  The problem with using just a steel mat is that if it is in direct contact with the soil and not in the concrete is that it will be destroyed by rust.  Once the inspector left the job he had no way of knowing if the mesh was installed properly in the pour.  In the 2008 NEC another option was given to accomplish the bonding of the perimeter surfaces and it’s reletivly inexpensive and accomplishes what it is intended to do.  Section 680.26(B)(2)(b) reads: (b)   Alternate Means. Where structural reinforcing steel is not available or is encapsulated in a nonconductive compound, a copper conductor(s) shall be utilized where the following requirements are met:  

    (1)        At least one minimum 8 AWG bare solid copper conductor shall be provided. 

    (2)        The conductors shall follow the contour of the perimeter surface. 

    (3)        Only listed splices shall be permitted. 

    (4)        The required conductor shall be 450 to 600 mm (18 to 24 in.) from the inside walls of the pool. 

    (5)        The required conductor shall be secured within or under the perimeter surface 100 mm to 150 mm (4 in. to 6 in.) below the subgrade.

     

    This new option should be the method used both for both paved and unpaved surfaces such as the pavers you have described.

    Hope that helps……..Tony

     


    I want to agree with Goerge and Tony thats why I made the post. I have had this conversation with other inspectors that have allowed the mesh under pavers.  Steve
  • 27 Jan 2011 9:03 AM
    Reply # 508412 on 501945
    Tony Tomasin

    No problem Steve.  That's why these boards are here.  It's nice to have some place to go to share our knowledge of the code.  It's nice to see how others interpret something..

    Regards,

    Tony

© Reciprocal Electrical Council Inc. 2014
Powered by Wild Apricot Membership Software