bclumen
Member
- Location
- Elkridge, MD
680.26 is a commonly misinterpreted Article. In particular 680.26(B)(2)(a) the alternate means for the equipotential bonding of perimeter surfaces. 680.26(B)(2)(a)(5) states "The required conductor shall be secured within or under the perimeter surface 100 mm to 150 mm (4 in. to 6 in.) below the sub grade". This seems to cause a lot of confusion for inspectors in the various Counties across the state of Maryland in which each county has its own permitting and inspections department. What is the sub grade? Is sub grade a specific material or a plane on which the final grade sits? Can sub grade be dirt? Can sub grade be gravel? Do any of you believe the intent of this code is to have the copper bond wire in direct contact with dirt or earth? Several Counties we work in have banded together and determined that sub grade is the dirt beneath any gravel that a perimeter patio (poured concrete without structural steel or paving stone patio) We wire several pools built partially or entirely out of the ground within an outer foundation where the perimeter area around the pool and within the outer foundation is back filled with gravel. I feel strongly that requiring the conductor to be installed in dirt beneath 2-8' of gravel would defy the intent of the equipotential perimeter bonding being too deep to prevent stray current where a swimmer may stand.
I am curious to hear how others interpret this as my interpretation is that sub grade is any material which lies beneath the final grade and the code clearly states that the required conductor is to be installed 4-6" below that. I feel strongly that sub grade is not a material of varying thickness but a plane which the final grade sits on. This is bonding...not grounding and dirt/earth or gravel should have nothing to do with this Article.
I am curious to hear how others interpret this as my interpretation is that sub grade is any material which lies beneath the final grade and the code clearly states that the required conductor is to be installed 4-6" below that. I feel strongly that sub grade is not a material of varying thickness but a plane which the final grade sits on. This is bonding...not grounding and dirt/earth or gravel should have nothing to do with this Article.
