Re: 20 ft. Ufer CEGE
The 20 ft. length has seemed to hang up many on its ability to do everything
needed for lightning protection. That was not the intention of the original
post. The 20 ft. is the MINIMUM required by the NEC. In the case of JC for whom
I was discussing he would have 34 ft. assuming 3 in. spacing in from the edge
of pour and not counting the leads to connect it to the surface of the slab.
He was also considering additional copper around outside of base in the
bentonite which is still in the area of dissipation of the Ufer and there for
not a lot more useful but in no way harmful unless he disturbed soil that the
base load calculations depended on. Additional grounding would better be
accomplished by ground rods at LEAST the 8 ft. NEC calls for in a pattern that
was at least the length of rod spaced from each other and the base all bonded
to the common point (now a buss with multiple connections) ground connection.At
rocky sites I have had to have a rock drilling company come in and drill holes
up to 50 ft. deep and put in screw together ground rods with a enhancing
additive surrounding them. Also everything on commercial grids are "Cadwelded"
instead of bolted.(This is not the average do-it your self home project)
Also the #2 cu is a minimum with #2/0 or #4/0 being the norm on grids.
A Ufer in no way is a substitute for a ground radial system needed by a
vertical antenna structure. The number, layout, and type of wires for that is
another whole thread.
The ability of lightning to strike in other than the top of the tower is well
documented and addressed by the various companies the make dissipation devices.
Most all recommend devices at no more than 50 ft. intervals and some even
recommend them on insulated guy wires. They cite Field gradient differences
along sections that create arcing across insulators without strikes degrading
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