[TowerTalk] Tower grounding

[Grant Saviers]

"extrapolation" may have been a poor word choice, but my reasoning is 
that copper pipes are not buried without special precautions for 
domestic water service because of corrosion.  Another reason is that the 
galvanic cells and/or stray currents that exist in soils can cause 
electrolytic erosion.  Copper clad ground rods are known to have finite 
life, sometimes quite short in certain soils.  Some concrete mixtures 
were a disaster with buried radiant heating copper tubes and that 
application now very rarely uses copper in concrete. There are 
discussions on this reflector that AM broadcast station copper ground 
screens disappear over time. Copper alloys in marine environments are 
protected with sacrificial anodes or impressed voltage systems.  Copper 
in air lasts a long time, in an electrolytic or hostile chemical 
environment not so.

So, why expose a Ufer ground lead to what might be an environment that 
significantly shortens its life, particularly if it isn't possible to 
inspect it?  As I have read the Ufer literature and codes, steel rebar 
is the conductor, not buried copper wire, and the connection is to a 
protected rebar exit point from the concrete.

wikipedia re Ufer: "Ufer's original grounding scheme used copper encased 
in concrete. However, the high pH of concrete often causes the copper to 
chip and flake. For this reason, steel is often used instead of copper."

see http://www.psihq.com/iread/ufergrnd.htm and 
http://en.wikipedia.org/wiki/Ufer_ground

Grant KZ1W

On 7/17/2013 6:26 PM, David Gilbert wrote:
>
> Why is that a "reasonable extrapolation"?  Copper wire won't corrode, 
> and rust/corrosion is the ONLY reason that codes require rebar to be 
> fully embedded in the concrete.  Please explain ...
>
> Dave   AB7E
>
>
>
>
> On 7/17/2013 12:52 PM, Grant Saviers wrote:
>> Building codes now REQUIRE Ufer grounds in many jurisdictions for new 
>> foundations.  Codes also REQUIRE that rebar be covered with concrete, 
>> usually a minimum of 3" to prevent corrosion ingress along the rods.  
>> So it is reasonable to extrapolate that ground wires connected to the 
>> rebar should not exit the concrete below grade ... <snip>
>>
>> Grant KZ1W
>
>
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