Hello to all and thanks for any help you can provide me.

Some time back I looked into installing a wifi antenna on the outside of
my brick office building here in town. I would offer free wifi to the
immediate area, shops, coffee houses, etc. and perhaps get some free
advertising out of it.

When I investigated the installation of such an antenna I was stopped in
my tracks because of the bonding (grounding) requirements. The need to
install #6 copper wire from the antenna to the building ground on a
direct external-to-the building path was something I was not prepared for.

Yesterday, the lottery agency had a defent size (bigger than home size)
satellite dish installed on the roof of our building. There is a small
store upstairs from me and this will replace the phone connection they
had been using all these years.

As I look at the installation from the ground I can see what looks to be
the coax wire and a greenish wire leading from the dish mast to the base
of a vent pipe that has been on the roof. They lead in together at that
point. The store is below. The roof is an A-frame and made of wood as is
the entire building more or less.

Question: Is this to code? I do not believe it is since the ground wire,
if that's what it is, leads inside the building somewhere and not
externally to the main ground. If hit by lightning it would direct the
energy into the building which is wrong.

Second, it leads away from the building bonding point, which is down on
my ground level in the electrical room at one end of the building.

My hunch is it has been connected to a water pipe or electical conduit
in the ceiling or wall.

I'd like to call the town electrical inspector but I want to make sure
I am correct in this. The theory of bonding at least and the need for
an external lead to building bonding point.

Recently, a building was hit by lightning in town and the damage went
from the roof down three floors and was very extensive.

Can anyone advise me on this?

" Some time back I looked into installing a wifi antenna on the outside of
my brick office building here in town. I would offer free wifi to the
immediate area, shops, coffee houses, etc. and perhaps get some free
advertising out of it.

When I investigated the installation of such an antenna I was stopped in
my tracks because of the bonding (grounding) requirements. The need to
install #6 copper wire from the antenna to the building ground on a direct
external-to-the building path was something I was not prepared for.

Yesterday, the lottery agency had a defent size (bigger than home size)
satellite dish installed on the roof of our building. There is a small
store upstairs from me and this will replace the phone connection they had
been using all these years.

As I look at the installation from the ground I can see what looks to be
the coax wire and a greenish wire leading from the dish mast to the base
of a vent pipe that has been on the roof. They lead in together at that
point. The store is below. The roof is an A-frame and made of wood as is
the entire building more or less.

Question: Is this to code? I do not believe it is since the ground wire,
if that's what it is, leads inside the building somewhere and not
externally to the main ground. If hit by lightning it would direct the
energy into the building which is wrong.

Second, it leads away from the building bonding point, which is down on my
ground level in the electrical room at one end of the building.

My hunch is it has been connected to a water pipe or electical conduit
in the ceiling or wall.

I'd like to call the town electrical inspector but I want to make sure
I am correct in this. The theory of bonding at least and the need for
an external lead to building bonding point.

Recently, a building was hit by lightning in town and the damage went from
the roof down three floors and was very extensive.

Can anyone advise me on this?

That gauge of wire will not provide and sort of lightening protection so it
can only be there for electrical safety. Are you sure that is requirement
really applies to the type of installation that you are undertaking?

Jeff

Jeff wrote:

That gauge of wire will not provide and sort of lightening protection so it
can only be there for electrical safety. Are you sure that is requirement
really applies to the type of installation that you are undertaking?

At the time I looked into my needs I was directed to read the NEC
codebook... articles 800, 810, 820 and 830 that deal with communications
wiring.

scooterspal wrote:
Jeff wrote:

That gauge of wire will not provide and sort of lightening protection
so it can only be there for electrical safety. Are you sure that is
requirement really applies to the type of installation that you are
undertaking?


At the time I looked into my needs I was directed to read the NEC
codebook... articles 800, 810, 820 and 830 that deal with communications
wiring.

Google for the Mike Holt Low Voltage Handbook. It covers all the NEC
stuff for grounding antennas.

FWIW, the NEC bonding requirement is NOT for lightning protection (at
least against a direct hit). It's more to insure that if something
energized touches the antenna, that the fault current goes somewhere
other than to someone touching a piece of equipment connected to the
antenna. Think of it as similar to the "green wire" third prong ground.

And, for many installations, the coax shield can serve as the grounding
conductor. For many cable TV/satellite dish installations, the coax
will be routed (externally) to a grounding block, where a short
continuous segment of aluminum or copper wire connects the coax shield
to the building's grounding point.

Note that there are probably millions of improperly grounded dishes out
there.

On Nov 8, 5:49 pm, scooterspal wrote:
At the time I looked into my needs I was directed to read the NEC
codebook... articles 800, 810, 820 and 830 that deal with communications
wiring.

NEC is about wiring for human safety. However that ground wire is
also installed for lightning protection - from a direct strike. Those
who fail to first learn numbers will post only their feelings. That 6
AWG is sufficient to earth a direct lightning strike and still remain
intact.
... consider that a bare 18 AWG (1 mm diameter) copper wire, in
air, normally will conduct at least 10 amperes safely, with very low
self-heating temperature rise. If the current slowly rises, the
temperature will increase until the melting temperature of 1065 C
(1950 F) is achieved at about 83 A. This same temperature could
be reached "instantly" by an 8x20 s pulse at a current of 61 kA.

Above numbers are from the front page of a professional engineering
publication (Electrical Engineering Times) of 1 Oct 2007. That 6
AWG can be expected to conduct 200,000 amps which is ten times more
than current from the typically lightning bolt.

Meanwhile, every wire entering the building must connect to earth
ground before entering the building - also for lightning protection.
Even underground wires. Principles are summarized in a figure
entitled "The Need for Coordinated Protection":
http://www.erico.com/public/library/...es/tncr002.pdf

Unfortunately your WiFi antenna will act like a Ben Franklin
lightning rod. When (not if) lightning strikes it, then energy must
be dissipated somewhere. Either energy is dissipated harmlessly in
earth, or that energy is dissipated inside the house. How much energy
is dissipated in earth? Answer is determined by the quality of
earthing as the other end of that 6 AWG wire.

Often better is to mount the antenna so that lightning will strike a
higher mounting pole; to make a connection to earth that need not pass
through the antenna.

Better is to also route that WiFi wire to the building earth ground
before entering the building. Any transient that might try to enter
the transceiver via that antenna wire would first dump that energy
into earth via a ground block and short connection to the earthing
electrode. Dump energy into earth before wire enters the building.
Should you not do that, then better is to have that WiFi mounting pole
higher so that lightning will strike the pole; less likely to conduct
through antenna.

w_tom wrote:
On Nov 8, 5:49 pm, scooterspal wrote:

At the time I looked into my needs I was directed to read the NEC
codebook... articles 800, 810, 820 and 830 that deal with communications
wiring.


NEC is about wiring for human safety. However that ground wire is
also installed for lightning protection - from a direct strike. Those
who fail to first learn numbers will post only their feelings. That 6
AWG is sufficient to earth a direct lightning strike and still remain
intact.

... consider that a bare 18 AWG (1 mm diameter) copper wire, in
air, normally will conduct at least 10 amperes safely, with very low
self-heating temperature rise. If the current slowly rises, the
temperature will increase until the melting temperature of 1065 C
(1950 F) is achieved at about 83 A. This same temperature could
be reached "instantly" by an 8x20 s pulse at a current of 61 kA.


Above numbers are from the front page of a professional engineering
publication (Electrical Engineering Times) of 1 Oct 2007. That 6
AWG can be expected to conduct 200,000 amps which is ten times more
than current from the typically lightning bolt.

Sort of true..
One can find the equations at http://home.earthlink.net/~jimlux/hv/fuses.htm

Onderdonk's equation takes into account the time course of the pulse,
and is probably more relevant here. AWG16 for a 10 microsecond pulse
melts at 12.6 kA. AWG6 is 100 times the size, so one might expect 1.26
MA fusing current.

HOWEVER.. in a fast pulse, the current is carried only in the surface of
the conductor, which Onderdonk's and Preece's equations don't deal with,
nor does the simple approximation in EETimes.

Also, for fast high current pulses, the magnetic fields are important:
a) because of the forces on the conductor which tend to deform it and b)
because of the effects of inductance.


Note also that the code also allows oddball stuff like AWG17 copperclad
steel for the grounding conductor. I surmise that the sizes are chosen
more for mechanical ruggedness than for current carrying capacity.


It is true, however, that a short length of AWG6 can carry a typical
stroke current without fusing or failing.

... consider that a bare 18 AWG (1 mm diameter) copper wire, in
air, normally will conduct at least 10 amperes safely, with very low
self-heating temperature rise. If the current slowly rises, the
temperature will increase until the melting temperature of 1065 C
(1950 F) is achieved at about 83 A. This same temperature could
be reached "instantly" by an 8x20 s pulse at a current of 61 kA.



Above numbers are from the front page of a professional engineering
publication (Electrical Engineering Times) of 1 Oct 2007. That 6
AWG can be expected to conduct 200,000 amps which is ten times more
than current from the typically lightning bolt.

I searched for this issue of EETimes and couldn't find the reference.
Have you an author's name?

Jim Lux wrote:
w_tom wrote:

On Nov 8, 5:49 pm, scooterspal wrote:

At the time I looked into my needs I was directed to read the NEC
codebook... articles 800, 810, 820 and 830 that deal with communications
wiring.



NEC is about wiring for human safety. However that ground wire is
also installed for lightning protection - from a direct strike. Those
who fail to first learn numbers will post only their feelings. That 6
AWG is sufficient to earth a direct lightning strike and still remain
intact.

... consider that a bare 18 AWG (1 mm diameter) copper wire, in
air, normally will conduct at least 10 amperes safely, with very low
self-heating temperature rise. If the current slowly rises, the
temperature will increase until the melting temperature of 1065 C
(1950 F) is achieved at about 83 A. This same temperature could
be reached "instantly" by an 8x20 s pulse at a current of 61 kA.



Above numbers are from the front page of a professional engineering
publication (Electrical Engineering Times) of 1 Oct 2007. That 6
AWG can be expected to conduct 200,000 amps which is ten times more
than current from the typically lightning bolt.


http://www.planetanalog.com/features...leID=201807127

note that the author also speaks about the mechanical force issues with
the transient current. (And cites my website for lightning data, which
is kind of cool)..

Jim

On Nov 12, 11:58 am, Jim Lux wrote:
I searched for this issue of EETimes and couldn't find the reference.
Have you an author's name?

EE Times of 1 Oct and 8 Oct 2007. Kaufmann
http://www.planetanalog.com/showArti...leID=201807127