Lightning Protection assessment NFPA 780 - Complex Structure

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Hello,

I am performing a lightning protection assessment using NFPA 780. I have a very complex structure both in variations of roof heights, lengths, widths, and shapes. Any idea on how this calculation is performed? The only thing that NFPA 780 talks about when it refers to complex structures is the overlap, but it does not necessarily dive into how the lenght, width, height is calculated.

Thoughts?
 
Use your 3D cad program to create a model of the building roof, then make a 150' diameter sphere. Move the sphere around so it's tangent to the high roof and the low roof. Everything in the area between the two tangent points is protected by the high roof and doesn't need lightning rods. The area of the low roof beyond the tangent point does need them.

I hope this helps.
 
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