On Jul 13, 12:52*am, Richard Clark wrote:
On Mon, 12 Jul 2010 21:21:24 -0700 (PDT), Tom Horne

wrote:
Can anyone make a recommendation, based on actual training and
experience, as to what width and thickness of copper strap would be
needed as the down conductor from the antenna mounts at the peak of my
house roof, some twenty five feet above local terrain.

Hi Tom,

Consult the NEC code for your area. *I have never seen them specify
strap in any situation, and don't try your own interpretations of what
"continuous"or "direct" means.

73's
Richard Clark, KB7QHC

Richard
I will certainly make the installation code compliant. What I was
looking for help on was how to make it effective in avoiding damage
from lightning. I have read all of the applicable material from the
Polyphaser, NIST, and several other sites but what I was hoping to
elicit was specific guidance on what size strap to use for the down
conductors and what size to use for the ground ring so that they might
actually work rather than just comply with the code. I can certainly
add any regular wire conductor that would keep the electrical
inspectors happy since I already have 2/0 bare copper for the ground
ring; were only #2 is required and, the ridiculously undersized,
number ten that the code requires for down conductors in hand.

810.58 Grounding Conductors — Amateur Transmitting and Receiving
Stations.
Grounding conductors shall comply with 810.58(A) through (C).
(A) Other Sections. All grounding conductors for amateur transmitting
and receiving stations shall comply with 810.21(A) through (J).
(B) Size of Protective Grounding Conductor. The protective grounding
conductor for transmitting stations shall be as large as the lead-in
but not smaller than 10 AWG copper, bronze, or copper-clad steel.
(C) Size of Operating Grounding Conductor. The operating grounding
conductor for transmitting stations shall not be less than 14 AWG
copper or its equivalent.

810.21 Grounding Conductors — Receiving Stations.
Grounding conductors shall comply with 810.21(A) through (J).
(A) Material. The grounding conductor shall be of copper, aluminum,
copper-clad steel, bronze, or similar corrosion-resistant material.
Aluminum or copper-clad aluminum grounding conductors shall not be
used where in direct contact with masonry or the earth or where
subject to corrosive conditions. Where used outside, aluminum or
copper-clad aluminum shall not be installed within 450 mm (18 in.) of
the earth.
(B) Insulation. Insulation on grounding conductors shall not be
required.
(C) Supports. The grounding conductors shall be securely fastened in
place and shall be permitted to be directly attached to the surface
wired over without the use of insulating supports.
Exception: Where proper support cannot be provided, the size of the
grounding conductors shall be increased proportionately.
(D) Mechanical Protection. The grounding conductor shall be protected
where exposed to physical damage, or the size of the grounding
conductors shall be increased proportionately to compensate for the
lack of protection. Where the grounding conductor is run in a metal
raceway, both ends of the raceway shall be bonded to the grounding
conductor or to the same terminal or electrode to which the grounding
conductor is connected.
If metal enclosures such as steel conduit are used to enclose the
grounding conductor, bonding must be provided at both ends to ensure
an adequate low-impedance current path.
(E) Run in Straight Line. The grounding conductor for an antenna mast
or antenna discharge unit shall be run in as straight a line as
practicable from the mast or discharge unit to the grounding
electrode.
(F) Electrode. The grounding conductor shall be connected as
follows:
(1) To the nearest accessible location on the following:
a. The building or structure grounding electrode system as covered in
250.50
b. The grounded interior metal water piping systems, within 1.52 m (5
ft) from its point of entrance to the building, as covered in 250.52
See the commentary following 250.52(A)(1).
c. The power service accessible means external to the building, as
covered in 250.94
d. The metallic power service raceway
e. The service equipment enclosure, or
f. The grounding electrode conductor or the grounding electrode
conductor metal enclosures; or
(2) If the building or structure served has no grounding means, as
described in 810.21(F)(1), to any one of the individual electrodes
described in 250.52; or
(3) If the building or structure served has no grounding means, as
described in 810.21(F)(1) or (F)(2), to an effectively grounded metal
structure or to any of the individual electrodes described in 250.52.
(G) Inside or Outside Building. The grounding conductor shall be
permitted to be run either inside or outside the building.
(H) Size. The grounding conductor shall not be smaller than 10 AWG
copper, 8 AWG aluminum, or 17 AWG copper-clad steel or bronze.
(I) Common Ground. A single grounding conductor shall be permitted for
both protective and operating purposes.
(J) Bonding of Electrodes. A bonding jumper not smaller than 6 AWG
copper or equivalent shall be connected between the radio and
television equipment grounding electrode and the power grounding
electrode system at the building or structure served where separate
electrodes are used.

--
Tom Horne, W3TDH