Re: [TowerTalk] Different lightning ground question.

[Gary Schafer <garyschafer@comcast.net>]

Jim Lux wrote:
> ----- Original Message -----
> From: "Dudley Chapman" <chief@thechief.com>
> To: <towertalk@contesting.com>
> Sent: Monday, January 17, 2005 11:17 AM
> Subject: [TowerTalk] Different lightning ground question.
>
>
>
> > Keith's comment below reminded me of a question I had about horizontal
> > ground rods on lightning protection systems.  Current wisdom seems to
> > suggest that if it is impossible to drive ground rods vertically, that
> > laying them out horizontally underground is the next best thing.  This
> > sounds reasonable, but I am wondering what the difference is between a
> > horizontal ground rod and the thick bare conductor leading up to it.  Both
> > are thick copper conductors running horizontally.  Another way to ask the
> > question is, if I substituted a 10 foot piece of #8 wire for a 10 foot
> > horizontal ground rod, what would be the difference?
>
>
> Absolutely no difference...well... you'd need a bit more length of wire to
> equal the surface area of a 5/8" rod.  Say 20 ft of bare AWG8.
>
> You can also bury a metal plate.  All covered in the various codes and
> specs.
>
>  If there is no
>
> > difference, then just bury thick wire radials and be done with it.  It
>
> would
>
> > save on all the worry about joints except where the wire is bonded to
> > whatever is being protected.
>
>
> Sure would, and that sort of thing is why UFER grounds (concrete encased
> grounding electrodes) exist.


There is not much difference in effectiveness for different amounts of 
surface area for ground rods. It is the length that counts.

As far as differences in buried horizontal wires verses driven ground 
rods, there are two reasons to drive rods:

First, there is better contact with a rod driven into undisturbed soil 
than what you get by digging a hole and back filling it with a rod 
planted in it. Same of course is true for burying horizontally. The soil 
has been disturbed.

Second, when a rod is driven it gets down to where there is more 
moisture than if it is buried in a rather shallow trench.

Burying radials is ok if you can not drive a rod in.
It is also good to bury interconnecting leads between ground rods. It 
gives more connection to the soil.

73
Gary  k4FMX



_______________________________________________

See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA.

_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk