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Re: [TowerTalk] CDwelding a tower leg

To: "'Frank'" <>, "'Brian Alsop'" <>
Subject: Re: [TowerTalk] CDwelding a tower leg
From: "Jeff DePolo" <>
Date: Mon, 17 Sep 2012 10:23:03 -0400
List-post: <">>
> I fail to see why a ground is needed at all.  Surely the 
> lower two feet 
> of tower is firmly embedded in dirt with the concrete anchor above 
> that.  

The tower legs are embedded in dirt???

> If it was done that way those three tower legs should serve as 
> some pretty good ground rods.  

Whatever is buried in the earth will obviously a path to ground.  But how
ideal (i.e. low resistance) is it?  Without measurements and/or real
pre-construction design, who knows...

A good ufer ground can be quite effective.  If the rebar-reinforced concrete
foundation is purposefully used as a ufer ground, it may be an excellent
ground system on its own.  But it's not the kind of thing you could rely on
without real design engineering and/or testing.  In other words, assuming
that your ground system is complete just because you have a tower foundation
embedded in the earth would be foolish.

See NEC 250.52 for some basics on ufer ground requirements.  However, I
wouldn't consider meeting the bare minimums of 250.52 to necessarily be
adequate for the sake of a tower ground system.  Fanning out the ground
system via additional electrodes could make a significant improvement over
the ufer alone without costing much money.  Also keep in mind that the
effectiveness of any ground system varies greatly with soil conductivity, so
what may be an adequate ground system in one place may be wholly inadequate
somewhere else...

A good ground system is cheap insurance.  There's also a safety issue as
well.  It's not the place to cut corners.  My opinion anyway.  

                                        --- Jeff WN3A

                                --- Jeff WN3A


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