Tom Horne wrote:
On Jul 13, 1:52 pm, Owen Duffy wrote:
Owen Duffy wrote :

...

But, firstly, you should determine if there are regulatory
requirements, such as NEC etc.
Is "NFPA 780: Standard for the Installation of Lightning Protection
Systems" a relevant standard in your jurisdiction?

Owen

Owen
It is relevant as a consensus standard but it is not adopted as local
or State law. Do you have a link to a copy that can be read online?


NFPA 780, like NFPA 70, is a copyrighted document *sold* by NFPA.
However, there *are* online copies of various provenance and age around.
http://www.atmo.arizona.edu/students...A_780_2004.pdf

Unfortunately, the bare code doesn't tell you much about the "why" for
various code provisions, so if you're thinking of going "off code" for
one reason or another, you don't have a lot of information to tell you
whether it's a good idea.

There's also some interesting seeming inconsistencies.. NFPA 780
requires a minimum length of a ground rod of 8 feet (4.13.2.1) but also
requires that they extend vertically not less than 10 feet into the
earth (4.13.2.3(A))) The figure makes it clear.. the top of an 8 foot
rod is 2 feet below the surface of the soil.

NFPA 780 says 29 square millimeters for main conductors (6 mm in
diameter or a strip that is 1.3mm thick x 22.3 mm wide).. That's AWG 6
roughly.


There's also a great site by Carl Malamud: publicresource.org that has
all the California Building Codes (including an older rev of the NEC)
although it doesn't have NFPA 780 on it, as far as I know.