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.
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