Aluminum parts are not to be used on copper roofing materials and must not contact other copper
surfaces such as gutters, flashings, and trim. Similarly, do not use copper lightning protection materials on
aluminum structures or on structures using aluminum roofing materials or aluminum siding. Avoid contact
between copper conductors, terminals, and fasteners and aluminum gutters, windows, and trim.
In aluminum lightning-protection systems, copper, copper-covered, or copper-alloy fixtures and
fittings must not be used for connectors. Where aluminum must connect to copper, only UL-approved
bimetallic connectors are to be used.
Welded or brazed bonds are preferred over all other types; in particular, junctions in inaccessible
locations should be welded or brazed whenever practical.
Never use soldered connections for bonding any part of the lightning protection system.
Bolted or clamp-type connections should employ only UL-approved connectors.
Where bolted connections to flat surfaces are necessary, the surface contact area should be 3 square
inches (19.5 square cm) or greater.
18.104.22.168 Physical Protection.
Protect all elements of the lightning protection system from damage and physical abuse by routing
conductors to take advantage of any protection offered by structural features. Install appropriate guards or
covers preferably made of wood or noncombustible synthetic material.
Where conductive conduit is used, bond the conduit to the enclosed lightning conductor at each end
of each isolated section of the conduit. (Standard conduit grounding lugs are acceptable.)
The use of ferrous conduit to enclose lightning conductors should be avoided because it increases the
impedance of the lightning conductor.
1.4 FAULT PROTECTION SUBSYSTEM.
1.4.1 Purpose. In Volume I, the equipment fault protection subsystem was described as a network which
ensures that personnel are protected from shock hazard and equipment is protected from damage or destruction
resulting from faults that may develop in the electrical system. To accomplish this, ground connections must
be adequate for both normal and fault currents. The fault protection subsystem includes the green wire and all
exposed noncurrent-carrying metal parts of fixed equipment such as raceways and other enclosures which are
likely to be energized under power fault conditions. Any conductor used for grounding purposes shall not
Penetrate any designated rf barrier, screen room, shielded enclosure etc., but shall rather be bonded to a welded
stud on the barrier. In general, the equipment fault protection subsystem will conform to the requirements
established in MIL-STD-188-124A.