[TowerTalk] Tower grounding

[Cqtestk4xs at aol.com]

Correct.  In FL almost all homes are built on concrete  slabs.  Wherever 
the copper pipe goes through the concrete, the pipe is  sleeved with rubber or 
plastic.  Part of the reason is mechanical since  when using the power 
trowel it is easy to damage the pipe.  Part two  is the corrosion factor.
 
Bill K4XS/KH7XS
 
In a message dated 7/18/2013 7:32:23 P.M. Coordinated Universal Time,  
xdavid at cis-broadband.com writes:


Actually, the problems with copper tubes in concrete aren't at  all as 
well documented as you might imagine.  Google "copper tube  concrete" if 
you don't believe me.   The research a few decades  ago that concluded 
corrosion in concrete *due to the cement itself* was  the primary issue 
was poorly done, and more recent studies indicate that  
expansion/contraction differences ... or mechanical stress due to bends  
in the tubing ... may alo have a significant influence. Other studies of  
actual failures point to chlorine or sulphur attack from soil chemicals  
that penetrated the porous concrete.  Most codes require sheathing of  
embedded copper tubes for protection, but it isn't exactly clear what  
the protection mechanism is ... mechanical or chemical.  In at least  one 
set of cases the failure analysis conculsion was that the plastic  
sheathing CAUSED the failure by trapping contaminated water around the  
tubing.

Here's an interesting link which, while no doubt self  serving, points 
out that concrete heavy in sulphur from cinders or fly ash  can indeed be 
corrosive to copper.  Fly ash is often used to improve  the workability 
of concrete, and also it's resistance to freeze/thaw  damage.

http://www.copper.org/applications/plumbing/techcorner/problem_embedding_cop
per_concrete.html

This  thread really hasn't been about copper wires inside concrete tower  
foundations, though.  If it were, all of us should be worried about  how 
we connected our towers to the Ufer ground in the first place ... all  of 
which I bet used copper wire.  Instead we have been talking about  
whether there is a problem with copper wire exiting the concrete  
directly into the soil.  That's a different issue entirely.

So  no, unless you can describe a mechanism where such an exit 
exaggerates any  other deleterious effect on the copper or the 
foundation, I don't think  the logic holds at all.

Dave   AB7E




On  7/18/2013 8:16 AM, Grant Saviers wrote:
> Agree that the Ufer wiki entry  re "chip and flake" is soft. However, 
> the potential problems with  buried copper or copper in concrete are 
> well documented/known issues,  so I think the logic holds.  I think the 
> codes tend to "get it  right" over time and experience, and they 
> support the  conclusion.
>
>
> Grant   KZ1W

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