On Jul 19, 1:03*pm, Jim Higgins wrote:
On Mon, 19 Jul 2010 09:23:53 -0700, Jim Lux
wrote:

Tom Horne wrote:

Owen
The NEC only requires 5.261 (mm)2 for the protective down conductor
and 13.30 (mm)2 for the bonding conductor between electrodes. *Since
those sizes are at best a bad joke

Perhaps you could explain why you think it's a bad joke? *Do you think a
13 square mm conductor couldn't carry the strike current? (it can)

Or, perhaps, you're thinking that there are some other design criteria
that might push one towards a larger conductor (mechanical strength in
the face of icing and storms might be one).

Maybe E=IR has something to do with wanting a larger conductor. *The
voltage between the strike point and true ground is going to be the 20
- 100 kA of the strike times the resistance of the down conductor from
the strike point to true ground. *With a smaller conductor,
fewer/shorter ground rods, or other conditions that raise the
resistance of the path to ground that voltage will be higher and if
high enough the strike will seek additional paths to ground by arcing
to nearby objects closer to ground potential.

That's why I tie everything together. In my case, the ground rods
are minimal.. Just a few copper tubes pounded into the ground
around the base of the mast. None are too deep. But I consider
the ground adequate for the purpose, and it seems to be, being
as I've taken strikes on that mast with no damage to anything.
But I tie that ground into the electrical ground, and also the
plumbing, which I clamp to just a few feet away from the base
of the mast. If all grounds are at the same appx potential, and
the connection to ground is up to par as far as resistance, you
shouldn't see flashing over to other objects. I've never had that
problem here so far. In fact, the connection to ground seems
good enough that strikes to that mast are fairly silent and
only make an electrical arc sound which sounds like throwing
a light bulb onto the ground.
On the other hand, a strike to a poorly grounded object with
high resistance is hugely loud.. Say when it strikes the tree
in the front yard.. It's like a 12 gauge going off. And this
sound is separate from the sonic boom of the strike as
it travels through the air. The sonic boom will come from
overhead and is not local like the actual strike noise at the
object being struck.