[TowerTalk] #2 solid or stranded for tower leg grounds

[wa5zup]

The tower is a crank up and tilts over.  I would prefer a ground connection
that I can unbolt and not have to redress the ground connections each time I
want to tilt the tower over.  Once the antennas are up and everything works,
tilting it over may not be much of an issue. That is where I was headed with
the stranded idea.  I understand not to make any sharp bends from the tower
to the first ground rods.

 

The tower is bolted to the base with 5 ¾” bolts on each leg.  Of course you
can not buy lugs with that big of a hole.  I was thinking of using flat bar
material, say 1.5” wide, drill a ¾” hole in it, and create a “tab” to attach
the ground wires to.  You can buy this stuff on line, in small amounts, in
stainless, brass, bronze, and aluminum.  I was thinking bronze.

 

I work for an electric utility.  Although grounding in a switchyard is for a
different purpose, more than lightning protection.  The standard is 2/0
stranded to every structure, tied to a grid.  You hardly ever see solid used
for anything.  Interesting--I have never asked the question of why stranded
is used instead of solid.

 

John wa5zup

 

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From: Bill MacLane [mailto:ai4wm at yahoo.com] 
Sent: Thursday, September 13, 2007 7:50 PM
To: John Elsik
Subject: Re: [TowerTalk] #2 solid or stranded for tower leg grounds

 

John,
All the broadcast installations I worked on we used solid for everything.
If stranded or braided wire is exposed to teh elements it'll corrode between
the strands.  

I like copper strap, but it is hard to find and expensive.

As far as flexible; do you plan on bends?  Lightning does not like bends or
coils.  A bend in a lightning protection conductor is almost assured to
break if the tower takes a hit.  Slight gentle curves from the tower to the
grounding electrode is best.  

There are various methods of fastening the conductors also, brazing and
silver soldering are fairly easy to do.  I've seen installations where the
ground plane was attached mechanically to the tower base and then brazed.
Of course broadcast towers sit on a base insulator so the tower itself has
no grounding conductors on it.  A correctly adjusted arc gap takes care of
the strike (hopefully).




John Elsik <wa5zup at msn.com> wrote:

I acquired 250' of #2 bare copper and 15 ground rods left over from a job at
work. So that is a start on what I am using for my ground system for a new
LM-354HD crank up tower installation. Base is installed, waiting for the
concrete to cure. Tower is not here yet.
I have to get more wire and rods. I have most of the exothermic one-shots,
but of course, need more of them too. I am pretty much committed to using #2
for everything.
The plan is to just pigtail up the #2, for now, to each tower leg.
I have a choice of either #2 tinned solid copper or #2 stranded for these
pigtails. The one-shots should work with either one by spec. At the moment,
I am not sure how I will attach the fat #2 to the tower legs. I was thinking
of using stranded for that because it would be somewhat more flexible.
Is that a good idea, or should I just stay with the solid?
John wa5zup
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73,
Bill
AI4WM

  

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