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Wednesday, January 11, 2017
Question:
There seems to different opinions on whether to bond residential metal roofs to the grounding electrode system of houses.
NEC doesn't seem to address it so what is your stand on this.
Thanks, Bill Cecchini
A
Answer:
Hey Bill thanks for your question. Metal roofs are not required to be connected to the grounding electrode systems by the NEC. Exposed metal building frames that are likely to become energized must be bonded as stated in 250.104(C). A metal roof is not a metal building frame and is also not likely to become energized. Informational Note 1 to 250.104(B) indicates that bonding all metal piping and air ducts provides additional safety, but as we know Informational Notes are not enforceable as stated in 90.5(C). Also additional Informational Notes have been added to 250.4 (A) & (B) for the 2017 NEC that reference NFPA 780, Standard for the Installation of Lightning Protection Systems, to point out that the NEC does not address lightning protection systems.