Bonded Lightning Protection Systems
Lightning Protection Terminology
A
Adhesive Work - Refers to installing material that will have to be adhered in
place rather than mechanically fastened in place. This work will usually
require significant dry time prior to the installation of conductor.
Air Terminal - A device intentionally installed to intercept a lightning strike.
Air Terminal, Sharp or Needle Point - An air terminal that is tapered to a
sharp pointed tip.
Air Terminal, Blunt Tipped – An air terminal that has a rounded tip.
Aluminum - A highly conductive metal used for lightning protection conductor
and components.
B
Base - A device designed to be mounted on a surface to hold an air terminal
and usually has a conductor clamp.
Base, Adhesive - A base designed for application with some type of
adhesive or sealant.
Base, Concealed - A base designed to conceal the clamp and conductor
below the roof with a solid rod penetration up through the roof.
Base, Cone or Dome - A base designed for use on a pointed or round
surface.
Base, Extended Side Mount - A side mount base with an extended arm to
allow the air terminal clear an obstruction.
Base, Ridge or Saddle - A base designed for use on a roof ridge.
1
Base, Side Mount - A base designed for mechanical attachment to the side
of a parapet or vertical surface. The cable runs horizontally through the base
clamp.
Base, Top Mount - A base designed for mechanical attachment to the top of
a parapet or horizontal flat surface.
Base, Vent - A base, without a cable holder, designed for mounting an air
terminal to a roof top unit.
Base, Vertical - A base designed for mechanical attachment to the side of a
parapet or vertical surface. The cable runs vertically from the base
downward.
Bimetals, Bimetallic Fittings - Bimetallic fittings are used to connect, yet
isolate, dissimilar metals, thereby preventing the effect of dissimilar metal
corrosion.
Bonding - The process of making a connection between a conductive object
and lightning conductor to reduce or equalize potential difference.
Bonding Clamp - A bonding device that accepts conductor and is attached to
an object by means of a bolt or screw. The clamp will usually have a
relatively small O.D. range and is used primarily to bond pipes and hand rails.
Bonding Conductor - Conductor that is being used for the purpose of
bonding an object. This may be a section of primary or secondary conductor.
Bonding Lug - A bonding device that accepts conductor and usually has one
screw hole for mounting to a flat conductive object.
Bonding Plate - A bonding device that is flat on one side and accepts
conductor on the other side. It is primarily used for bonding objects subject to
a direct strike.
Bonding Strap - A bonding device made of perforated strapping material and
a conductor clamp. A bonding strap will usually have a relatively wide O.D.
range.
Brace - A device used to support an air terminal against displacement.
Braces are typically in the form of a tripod.
Bridge - A section of rod or other substantial stock used to support conductor
and prevent it from spanning freely across an open space.
2
Building, Ordinary - A building of conventional construction used for
commercial, farm, industrial, institutional or residential purposes.
C
Cable - A conductor formed of a number of wires stranded together.
Cable Clamp - 1) A clamp for splicing conductor. 2) The portion of a base, or
fitting that accepts the conductor.
Cable Guard - A cover or guard installed over a section of conductor to
prevent damage or displacement.
Cable Holder - A small adhesive pan-type plate that is adhered down and
has clips to hold the conductor in place. Also regionally referred to as
“adhesive clips” or “clips”.
Cadweld - 1) A brand name for exothermic welding equipment and
processes. 2) Slang often misused to categorize all exothermic weld
processes. “See Exothermic Weld”.
Cadweld Mold - Slang for the graphite mold used to clamp material together
and hold powder while making an exothermic weld.
Cadweld Shot - Slang for the powder used to make an exothermic weld.
Slang for the making an exothermic weld connection.
Chair Drops - The act of dropping down the side of a structure using a
window-washer-type seat and ropes. This is usually done to install exposed
down leads on an existing structure.
Chimney - A construction containing one or more flues that does not meet
the criteria defined for a heavy-duty stack.
Class I Building - A building 75 feet or less in height.
Class I Material - Materials designed for use on buildings or roof levels that
are 75 feet or less in height. Class I materials may not be used on roof
levels exceeding 75 feet in height.
Class II Building - A building over 75 feet in height.
3
Class II Materials - Materials designed for use on buildings or roof levels that
exceed 75 feet in height. Class II materials may also be used on class I
buildings and roof levels.
Clips - Slang used for adhesive cable holders or loops.
Common -Term indicating objects are electrically continuous and therefore
possess equal static potential.
Common Bonding, Common Grounding - The process of connecting
grounding mediums, piping systems and specified metallic objects together
for the purpose of creating equal potential.
Concealed System - Refers generally to a system that has the down leads
concealed within the structure or hidden from view.
Concrete Encased Electrode - These are also referred to as ‘”Uffer
Grounds”. They may be considered for use as lightning protection grounding,
in new construction only, and under rigid installation guidelines and
requirements.
Conductor Clamp - A device made for connecting two pieces of conductor
together. (See Splicer)
Conductivity - The measure of an object's ability to conduct an electric
current between two points.
Conductor - The cable used to conduct the lightning charge or to accomplish
bonding tasks.
Copper - A highly conductive metal used for making lightning protection
conductors and components
Copper-Clad Steel - A coating of copper alloy that has been bonded to a
steel object. Example: copper clad ground rods, copper clad wire. Also
referred to as “copper-bond”.
Counterpoise - A loop of conductor, basically horizontal in nature, used to
bond objects together.
Cross Run - Conductor run in the mid-roof area to provide air terminals and
bonded roof top equipment paths back to the perimeter roof circuit.
D
4
Dead End - To provide an air terminal only one path back to the main
conductor run to ground.
Deviation - A term used by UL, in their inspection process, to indicate that in
their opinion some part of an installation or process is not in compliance with
a standard.
Dissimilar Metals - Metals that when in contact with each other, especially in
moist conditions, chemically react causing a residue that inhibits or reduces
conductivity. The residue will appear as a white chalky substance. This
reaction can eventually cause the weaker metal to completely deteriorate.
This reaction is also referred to as “Galvanic Corrosion”.
Down Lead - The source over which lightning current travels from the roof
circuit to the ground terminals. Also referred to as “Downs”.
E
Earth - Finished grade level around a building.
Exothermic Weld - A portable welding process that uses molds, chemical
mixtures and heat to fuse conductors and/or other metals together.
Explosive Materials - Materials, including explosives, blasting agents, and
detonators, that are authorized for transportation by the Department of
Transportation or the Department or Defense as explosive materials.
Exposed System – Refers to a system where the down leads are surface
mounted on the outside of the structure. Also sometimes referred to as a
“Retrofit System”
F
Faraday Cage - The Faraday Cage is named after physicist Michael Faraday.
A Faraday cage or shield is based on the theory that enclosing a room or
building with highly conductive material tends to block out external static fields
while simultaneously electrical charges within the conducting material
redistribute themselves so as to cancel the field’s effects within the cage’s
interior. This theory is the basis for the design of a conventional lightning
protection system.
5
Fastener - 1) An attachment such as a loop or clip used to secure conductor
to a structure. 2) A screw, nail or anchor.
Fender Washer - A washer with an oversized width.
Fittings - Clamps and connectors used for splicing conductor and for bonding
applications.
Flat or Gently Sloping Roof - A roof having a span of 40 feet or less and a
pitch of less than 1/8, or a roof having a span exceeding 40 feet and a pitch
less that 1/4.
Franklin Theory - The theory, commonly attributed to Benjamin Franklyn’s
experiments, that a tall strike termination device (air terminal) provides a cone
or “zone of protection” for the immediate surrounding area adjacent to it. This
theory was more accurately developed in experiments published by W. H.
Preece in 1880. These findings are still used in modern conventional
lightning protection standards and systems.
G
Galvanic Corrosion - See “Dissimilar Metals”
Ground Grid, Ground Loop, Grounding Counterpoise - A “catch all”
phrase used to describe a system of grounding conductors, rods, piping
system bonds, service grounds and other specified metal objects with the
intent of creating equal potential on all grounded objects and of enhancing the
performance of the overall grounding system. This method is used to lower
the resistance of the grounding system to earth by creating more contact with
the earth.
Ground, Ground Electrode - The portion of the system that is installed for
the purpose of providing electrical contact with the earth.
Ground Radial – A section of conductor that is installed in a trench running
away from the building.
Ground Resistance Test - A test of the resistance a ground or grounding
system has to earth. The test is performed using an earth ground tester
(megger) and the results read in ohms of resistance. The test involves the
ground under test and two test probes. This is also referred to as a “Three
Point or Fall-of-Potential Test”.
6
Ground Rod - A rod driven into the earth to serve as the earth contact of a
grounding system. The ground termination, or discharge, point of a lightning
protection system.
Ground Plate - A solid copper plate used as a ground termination point,
usually where shallow soils prohibit the use of ground rods.
Grounded - Connected to ground or to a conductive body that extends the
grounding system.
H
Heavy-duty Smoke Stack - A smoke or vent stack with a flue that has a
cross-section of the flue area of more than 500 sq in. and a height greater
than 75 feet.
I
Inherently Bonded, Inherently Grounded - The property that an object
possesses because it is electrically common because of the building
construction process. It is a metal object that is attached to the structural
steel frame work of a building that has been grounded.
Intermediate Roof Ridges - The inner roof ridge(s) of a building that has a
series of parallel roof ridges.
Intermediate Air Terminals, Intermediate Runs – Air terminals and
conductors installed in mid-roof areas as opposed to the perimeter. Also
known as “Cross Run(s)”.
Irregular Roof Line - An edge of a roof that does not follow a straight line,
but has a series of jut outs or curves, or has an elevation that does not
continue basically in a straight, rather it consists of a series of up and down
or zigzag shapes.
J
Jumper - Slang term for a bonding connection.
7
L
Labeled - Equipment or material to which a label has been attached
signifying that an inspecting authority, identified by the label, is involved with
the manufacturing of the product.
Listed - A published list by an organization stating that the materials or
services included on the list meet appropriate standards and/or have been
tested and found suitable to provide a service.
Lightning - A flash of light in the sky caused by an electrical discharge
between clouds or between a cloud and the earth's surface. The flash heats
the air and usually causes thunder. Lightning may appear as a jagged streak,
as a bright sheet, or in rare cases, as a glowing red ball.
Lightning Arrester - A term referring to arresters that were developed to
prevent a lightning strike from following the electrical wiring into a structure
and causing a fire. They do little, if anything, to protect sensitive electronics.
Note: This term if often misused by laymen when referring to lightning rods.
Lightning Preventer - A static dissipation device attached to the top of a
grounded pole professed by the manufacturer to “bleed off” static build up
thus preventing a lightning strike in most instances. The manufacturer
proclaims that one preventer will afford protection for an entire building or a
large roof area of a very large building. Preventer systems do not qualify for
the UL Master Label Certification Program.
Lightning Protection Institute (LPI) – The LPI was chartered as a non-profit
corporation dedicated to promote public awareness of lightning safety
practices and to promote the quality and credibility of properly installed
lightning protections systems. Through the LPI, education programs are
conducted for the general public, architects, engineers, building owners and
contractors involved in the construction industry. The LPI provides a set of
standards with training for the design, installation, inspection and certification
of lightning protection systems.
Lightning Protection System, Conventional System - A complete system
of strike termination devices, conductors, grounding electrodes,
interconnecting conductors, surge protective devices, connectors or fittings. A
properly installed conventional system using UL labeled and listed
components will qualify for the UL Master Label Certification Program.
Lightning Rod - See Air Terminal.
8
Loops - Term referring to metal strips that are mechanically fastened in place
to secure conductor. Also referred to as “loop clips.”
M
Mast Protection - A method of creating a zone of protection by installing a
single grounded or protected pole near an object.
Master Label Certificate- Certification by UL that a lightning protection
system complies with their standards for lightning protection systems.
Metal Body, Grounded (Non-Isolated) - A metal body having a ground path
independent of the lightning protection system. Example: A motorized roof
vent.
Metal body, Isolated (Ungrounded) - A metal body having no ground path.
Example: Roof counter flashings, pitch pans, etc.
Metal-Clad Building – A building with either sides or roof made of, or
covered with sheet metal.
Metal-Framed Building – A building with electrically continuous framing of
sufficient size and conductivity to be used as a part of the lightning protection
system.
Monel Metal -Monel is the brand name for a metal primarily composed of
nickel, copper and iron. It is similar to stainless steel and highly resistance to
corrosion and rust. Monel is usually much more expensive than stainless
steel.
N
NEC - Abbreviation for National Electrical Code. A set of rules governing
safe wiring methods. Local codes—which are backed by law—may differ from
the NEC in some ways.
NFPA 780 – National Fire Protection Association’s Standard for the
Installation of Lightning Protection Systems.
9
Nail-in - Term used for a masonry expansion anchor.
Neoprene Washer - A type of rubber washer used to help seal around a
penetration.
O
One Way Drop - Conductor drop from a higher to a lower roof level that
interconnects air terminals on the lower roof.
Open Area - A court yard or mechanical well that is located within a flat roof
area.
Overhead, or Catenary System - A method of creating a zone of protection
by stretching conductors above an object between tall poles.
P
Perimeter Roof Circuit - The circuit of air terminals and conductors located
at the outside perimeter of the roof.
Primary Bond - A bond requiring full size conductor and fittings as applicable
to the building height, e. g. Class I or Class II.
R
Radius of Conductor Bend - The diagonal distance measured from the
center of a conductor bend back to the interacting point of imagined right
angle lines from where the bend begins and ends. Imagine it as the radius of
an arc.
Retrofit System - A system that is to be installed after a structure has been
completed. Also referred to as an “Exposed System”. See “Exposed
System”.
Rolling Ball (Sphere) Theory - A method of determining the zone of
protection of a structure based on an imaginary 150’ radius (300’ diameter)
rolling ball. The area falling below the arc of the ball as it rests tangent to
ground and against an elevated air terminal or protected structure is deemed
10
to be within a zone of protection and not subject to a direct strike. This can
also be calculated mathematically in most cases.
S
Sealant - A compound, typically in tube form, used to seal penetrations and
as an adhesive.
Secondary Bond - A bond only necessary to prevent a “side flash” between
a grounded metal object within 6 feet of the main conductor, or another
grounded metal object. These bonds can be made with secondary conductor
and fittings.
Secondary Conductor - Conductor smaller than the required primary
conductor and to be used for the prevention of a “side flash”.
Secondary Fittings - Fittings smaller that those required for primary
connections and primary bonding.
Secondary Roof Area - A secondary roof is less that 10 percent of the total
roof area of the protected building, and is lower than adjacent roofs.
Side Flash - An electrical spark, caused by differences of potential, that
occurs between conductive metal bodies or between conductive metal bodies
and a component of a lightning protection system or ground. This is
prevented by secondary bonding.
Sleeve - 1) A piece of material stock or an adaptor that is used to increase
the size of something. 2) The act of using sleeve material.
Soil Resistivity Test - This is a complicated test that is designed to
determine the conductivity of the soil at a site. The results of this test would
be helpful to an engineer in determining the extent of grounding required to
achieve a desired low resistance of the ground system to earth.
Splicers - Clamps used for making parallel, straight or tee connections when
connecting wire to wire.
Strike Termination Device - A metallic component of a lightning protection
system that intercepts lightning flashes and connects them to a path to
ground.
Striking Distance – The distance over which final breakdown of the initial
lightning stroke to ground or to a grounded object occurs. The striking
11
distance for determining zone of protection for ordinary buildings is based on
150’.
Subject to a Strike - A structure, part of a structure or object that is
vulnerable to a direct lightning strike. Something that is not within a zone of
protection afforded by taller adjacent lightning protection.
Surge Protective Device (SPD) - A device of any combination of linear or
nonlinear circuit elements intended for omitting surge voltages on equipment
by diverting or limiting surge current.
Swivel - A fitting use to make plumb an air terminal that is installed on a
sloped or uneven surface.
T
Test Well - A concrete, metal or plastic inspection well with lid that is set
around a ground connection. This is used to access the ground system for
future testing.
Thermoweld - A brand name for exothermic welding equipment and
processes.
Thru-Roof - A sealable threaded rod penetration through a roof that is used
for continuation of the lightning protection system.
Thru-Wall - A sealable threaded rod penetration through a wall that is used
for continuation of the lightning protection system.
Top Off Work - Refers to the work to be done on the roof. This usually occurs
in the final phase of a project.
Transient Voltage Surge Suppression (TVSS) - A protective device for
limiting transient voltages by diverting or limiting surge current; it also
prevents continued flow of follow current while remaining capable of repeating
these functions.
Tripod or Triad - A grounding configuration where ground rods are driven in
the shape of a triangle and interconnected with conductor.
U
12
UL-(Underwriters' Laboratories) - An independent testing agency that
checks electrical devices and other components for possible safety hazards.
UL 96 - UL Standard for Safety for Lightning Protection Components.
UL 96A – UL Standard for Safety for Installation Requirements for Lightning
Protection Systems.
U-Pocket - Routing of conductor in a manner that forms a “U or V” (up and
down) pocket in lieu of maintaining a horizontal and downward coursing.
Uffer Ground - A ground comprised of cooper conductor and/or reinforcing
steel. See “Concrete Encased Electrode”.
Z
Zone Of Protection – 1) The space adjacent to a lightning protection system
that is not subject to a direct strike because of its proximity to the system as
determined by a 150’ radius sphere abutting the structure. The 150’ radius is
based on a 150’ striking distance of the initial stroke as it reaches ground.
See “Striking Distance”. 2) When providing lightning protection for structures
housing flammable and/or explosives, a 100’ striking distance is used in lieu
of 150’ that is used for ordinary buildings.
13