[TowerTalk] RF Ground is a Myth

[Jim Lux]

On 1/19/15 5:55 PM, Jim Brown wrote:
> On Mon,1/19/2015 5:29 PM, Brian Carling wrote:
>> The advice varies about this considerably. This week is the first time
>> I've even heard of UF ER or conductive concrete!
>>
>> The professional experts that I know recommend putting a 20 to 30 foot
>> ground rod into the ground at each corner of your house and connecting
>> heavy gauge copper conductors up to lightning rodsup on the roof.
>
> You and your "experts" are only 70 years behind. :)
>
> http://en.wikipedia.org/wiki/Ufer_ground
>
> The Ufer ground is VERY well known among the Electrical Engineers who
> design power systems for all sorts of buildings.
>


But a Ufer/CEGR is really only practical in new construction. I think 
that pouring a concrete beam just to make a earth connection would be 
impractical.  If nothing else, it would probably require more time, more 
inspections, and involvement of more trades (e.g. you'd need to get 
concrete people in).

For instance, driving a bunch of rods is something the electrical 
contractor can do (and is clearly within scope of their license), but 
trenching, forming, and pouring concrete might not be legal.  In 
California, if you don't have a general license, a C10 Electrical 
license probably doesn't let you do concrete work (needing a C8 
Concrete). I don't know if a C10 can do lightning protection.. It might 
be a C61 specialty license, but still, I suspect that it wouldn't cover 
concrete work.


Likewise, if you have the right tools, driving a bunch of rods can go 
pretty quick, and you use the workers already on your crew.  A couple 
hours driving rods is probably faster than waiting for concrete to cure.


Interestingly, the Air Force is looking for vendors to install new 
lightning protection at Vandenberg AFB. The original system was done in 
the 60s and doesn't meet current standards.  It used 8 foot rods and 2/0 
ring; they're looking to replace it with either an enhanced concrete 
encasement of the ring or enhanced ground rods (the hollow ones which 
are loaded with electrolytic salts that leach into the soil)

XUMU 09-1229B Lightning Protection at Vandenberg AFB, CA

https://www.fbo.gov/index?s=opportunity&mode=form&id=d3fe3198414a108719de69c8ece6efb5&tab=core&tabmode=list&=

The specifications for the bid describe what the existing system is, and 
what they are looking to do.