Reply from: ben jacks Laszla, Your engineering discipline is correct about galvanic effects between dissimilar metals. The electrcial industry does use UL listed components to reduce such incident decay by using bronze alloy clamps between the copper conductor and #4 pickled steel rebar. Maybe you can elaborate and educate me further. Thankyou, Ben Jacks rbjpubs@earthlink.net Reply from: Mike Holt Laszlo, you make a lot interesting comments. Do you have the research that supports your comments as it relates to concrete-encased steel rebar? Reply from: T.M.Haja sahib lazla,Your assertion that lightning would blow away concrete is correct only when reinforcement bars are used as air terminations without any protrusions above concrete and as down conductors or when there is discontinuity.Otherwise things wlll work fine. Reply from: Ken Lillemo T.M. so to summarize your comments, when everything is done well there will be no problem. I guess I could share your view, only as of now, I doubt this will often be the case.
My concern is that the process of assembling rebar with wire ties is engineered to serve structural requirements, not electrical continuity or current capacity. Wire ties are only a temporary structure in the concrete. That wire ties last beyond the initial curing of the concrete or are electrically conductive is only by happenstance, not design.
If we are going to make use of rebar for lightning protection, which requires a high current carrying capacity, then the rebar assembly should be engineered and the rebar assembly controlled for this new purpose. I think current rebar assembly standards are inadequate to safely carry tens of thousand Amperes of current.
Once adequate rebar assembly standards are set we can address the next issue; are we going to make the concrete guys electrical subcontractors, or are we going to have the electricians fiddling around in the dirt before the concrete is poured?
Cheers, Reply from: Mike Holt Mr. T.M.Haja sahib is 100% correct. That's why the 2005 NEC requires steel rebars in the footer to be used as part of the grounding electrode system. Reply from: Mike Holt Structural steel rebar in concrete footers is requied to be used as part of the grounding electrode system [250.50]. Studies by Mr Ufer in the 1960's and Mr. Ralph Lee in 1971 have show that steel rebar in concrete footers this is an excellent electrode. In addition, the Ground Resistance Study currently run by the NFPA also shows the positive value of steel rebar as an electrode.
If you have a study to show otherwise, please let me know. |