Re: Test for Surge Protector?

[MFHult@xxxxxxxxxxxxxxxxxxxxx]

On Thu, 15 Sep 2005 19:48:51 -0400, w_tom <w_tom1@xxxxxxxxxxx> wrote in message
<432A0863.EF6BC261@xxxxxxxxxxx>:

>  If two electrodes are used in a single ground 'system', they
>individually perform better when separated by 6+ feet.
>Furthermore, if the interconnecting wire is buried, then that
>wire also enhances the earthing system. For example, the first
>rod could be right outside the wall.  Second rod daisy chained
>to a point 6+ feet farther from the building.   I believe that
>#4 AWG wire is suppose to be 18" or deeper.  One reason why is
>because grounding remains effective when below the frost line.

There are at least two effects here.

The '6-foot' rule of thumb seems to stem from the geometry of the electrical
field around a  conventional 6-foot-long grounding rod. My understanding of the
geophysical principles is that longer 'rods' (such a  transmission tower anode
wells) would require larger spacing to be optimal.

The increased 'grounding' owing to the interconnecting wire would seem to be
the result of decreased impedance between the wire+rods combination and the
soil/porous media that the wire and rods are in.


>  Don't forget to learn where any buried utilities might be
>located.

If you goof, it's not pretty ... The FCC has mandated a national "call before
you dig" number -- 811 -- which is supposed to be in effect within 18months. In
the mean time, check your phone book.

Or look here for your state:

http://www.digsafe.com/company_onecalldirectory.htm

>  Meanwhile these figures from a utility might add further
>insight into how that earthing system is installed:
>  http://www.cinergy.com/surge/ttip08.htm

Coincidentally this is the very utility that installed the whole house ground
protector in my house and didn't check the rod, the connection to it, or the
adjacent cable and telephone entry -- all of which were deficient. When I
pointed out the problems to the utility rep who came to replace it when one of
the LED's stopped indicating OK,  he said that all he did was install or
replace the protector. Seemed to know nuthin and care less. They also provided
'insurance' for which the paperwork was so onerous that I have yet to actually
collect ...


Marc
Marc_F_Hult
www.ECOntrol.org