His reinforcing steel inside his driveway is probably way far
out of the realm of Ufer grounds, due to it being small gage
conductors. Aside from the great difficulty of boring into the
concrete and adequately bonding to those wires, I wouldn't try
this anyway out of concern that the current density during a
major lightning hit might be sufficient to produce widespread
cracking of the concrete.
If it was the sole ground, or the major part of a ground that might have to
handle a direct hit, I wouldn't use it.
If it were simply something to augment an already good lighting ground or
improve an RF buried ground system, I would not worry one bit about using
it.
Now I'll have to go re-read and brush up on Ufer grounds, but
as I remember, his driveway setup would be woefully inadequate
for the possible current levels involved in the event of a direct
lightning strike. Personally, I wouldn't go there. A concrete
drive would be a little pricey to replace, especially considering
the relatively small prospective gain in HF ground quality he
might see by connecting his radial field to it. I'd much rather
connect *over* that drive using strategically sawed grooves
and lightly concreting in a few wires at the surface in a few
places- this assuming he has somewhere to go on the far side of
the drive with those wires anyway.
Again, it is only a problem if that is the major part of the ground. If it
is incidental and only an additional improvement, and the rests of the
system was OK without it, I'd use it.
I've tied my heating ducts and water pipes in, in the past. It does take
some common sense in whether it is worth the work, and knowing if the rest
of the system is large enough that it creates no hazard.
I know a ham who thought his well pipe might make a dandy
addition to his ground radial system. He connected it, and
eventually had to replace a 600 dollar well pump after a strong
lightning hit on his property. This driveway question reminds me
of that. Properly designed Ufer grounds, fine- but I sure don't
want to invite lightning hits to dissipate through anything
concrete on my property. My two cents (two dollars, adjusted
for inflation...)
That is just asking for problems. Many well pipes are only metal at the
head. Below the head or cap, they are often plastic. Well casings are almost
always plastic today. The only guaranteed metal paths are the wires to the
pump, even if it starts as metal at the top. Also, the wires are outside any
metal pipes if metal pipes do exist, and lighting travels on the outermost
surfaces. That would be the wires.
The well is nothing like concrete remesh. I would not bother connecting to a
unknown rebar system, but if I knew it was bonded or remesh (screen) I sure
would use it. Not as a primary ground, but to augment an existing pretty
good ground in a direction the existing ground might not go.
I remember a few people who had houses in the way of a full system, and they
ran the radials right under the floor joists. They used heating ducts,
fences, water pipes, and everything else they could. The more they used, the
stronger they got.
73 Tom
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