The fundamental principle in protection against lightning is to provide a means by which a discharge may enter or leave the earth without passing through a non-metallic or non-conducting part of a structure or other object.
An adequate protection system for buildings must include:
Properly sized, placed and installed air terminals to receive the lightning stroke
Down conductors designed to carry the discharge from the air terminal to the ground
Ground rods of adequate size, properly located into moist earth to serve as a ground terminal
Interconnecting conductors of proper size and type to securely fasten together all system components.
Materials used in protection systems must be resistant to corrosion, Copper, copper alloys, copper-clad steel and aluminum are approved materials, with copper and aluminum the most common.(SEE our page on FARAGAUSS Ground Rods)
Combinations of materials subject to electrolytic action should be avoided. There is one exception. Because aluminum conductors corrode when in contact with earth.
Such conductors should terminate at least one foot above ground level and connect with corrosion-resistant, copper conductors that carry the discharge under the earth surface to the grounding electrode.
Always use a special bi-metal connector to bond the aluminum and copper conductors.