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Total Solution to Earthing & Lightning Protection |
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Within certain markets installation of an LPS, including
component selection, is governed by American NFPA and
UL standards rather than their IEC/BS EN equivalent.
The appropriate standards for lightning protection in
these markets are:
–– UL 96 Lightning Protection Components
–– UL 467 Grounding and Bonding Equipment
–– NFPA 780 Standard for the Installation of Lightning
Protection Systems
–– UL 96A Installation Requirements for Lightning
Protection Systems
UL 96 and UL 467 are product standards for lightning
protection components; NFPA 780 and UL 96A are application
standards governing satisfactory installation of an LPS.
UL 96 & UL 467
These standards define the requirements for lightning
protection components, including their design, material
composition, performance and testing to ensure they are
suitable for application in an LPS. UL 96 covers above ground
lightning protection components, including:
–– Air termination components (air terminals and bases)
–– Conductors
–– Connector fittings (conductor clips, clamps, bimetallic
connectors and bonding plates etc)
Components are divided into 3 Classes, to reflect their
intended application (Class l, Class ll, Class ll modified).
UL 467 covers grounding (UK - earthing) and bonding
equipment used to create a grounding system in line with the
requirements of NFPA 780. Products include:
–– Ground clamps, bushings and fittings
–– Grounding electrodes (rods/plates) and ground mesh
Products are determined suitable for use in an LPS following
testing and evaluation by UL. Where a product successfully
passes UL evaluation it may carry a UL Mark appropriate
to the testing carried out.
Installation of lightning protection systems
to NFPA 780/UL 96A
Application standards NFPA 780 and UL 96A cover
assessment of risk from lightning and installation of an
appropriate LPS. Structures to be protected are defined as
one of two classes, as follows, which correlates back to the
product grade which should be installed:
–
–
Class l:
buildings less than 75 feet in height
–
–
Class ll:
structures greater than 75 feet in height, and
special structures such as heavy duty stacks and steeples
Three options are proposed for the design of air
termination systems:
–
–
Air termination placement:
Air terminals are placed in a
grid pattern at intervals of up to 20 or 25 feet
–– (dependent on air terminal height), with a relaxation in the
spacing if air terminals are not on the perimeter of the
structure (for roof lengths or widths exceeding 50 feet).
These spacings
–– apply to flat or gently sloping roofs only with more complex
roof structures requiring specific design to protect all parts
–
–
Rolling sphere method:
Similar in principle to
IEC/BS EN 62305, though with a single sphere radius of
150 feet. At all times the rolling sphere should only be
in contact with the tips of the air terminals and not the
fabric of the structure
–
–
Protective angle method:
Based on the ratio of height/
size of a higher building with regard to a lower one. It does
not apply for structures over 50 feet in height, where air
termination placement or the rolling sphere should be used
Installed air terminals (air rods) should not be less than 10” in
length or
3
⁄
8
” in diameter, and where above 24” in height
require bracing at minimum half their height.
There should be at least two down conductors from air
termination system to the grounding system, which should be
secured to the structure with suitable connectors at intervals
no more than 3 feet apart.
Air termination and down conductor components can be
manufactured from copper, copper alloy or electrical grade
aluminium, unless otherwise specified, on the proviso that:
–– Copper components should not be in contact with
aluminium or external galvanized steel surfaces
–– Aluminium products should not be in contact with the earth,
be set in concrete or masonry, be installed in wet locations,
or be in contact with coated surfaces using alkaline paint
The grounding system for lightning protection should be
bonded to all other grounding systems at the structure,
including those for power and communication, as well as
underground metallic services (utilities etc). The bonding
conductor should be the same size as the main down
conductor and main system conductor.
Grounding electrodes can be rods or plates. Rods should not
be less than
1
⁄
2
” in diameter and 8 feet in length, and
should be manufactured from copperbonded steel, solid
copper or stainless steel. Grounding arrangements
using ringed conductors or steel rebars are also acceptable.
Note:
products shown in this catalogue with the UL Mark
have been successfully evaluated by UL.
Technical reference
Lightning protection to NFPA & UL standards