On Fri, 22 Aug 2008, in the Usenet newsgroup alt.os.linux.mandriva, in article
4ax.com>, David Powell wrote:
>email@example.com (Moe Trin) wrote:
>>That depends where the fault or lightning strike may occur, and what
>>you have to measure against. If the whole house is momentarily at a
>>zillion volts, things are fine as long as there isn't something that
>>is actually a "true ground" voltage.
>Usually rare these days in residential areas; no so rare in industry.
>Difficulty is that the regulations are "one size fits all" and it's
>impossible to rule out the existence of premises where elderly and
>possibly abandoned copper or lead water pipes, and/or gas pipes or
>whatever provide a "true earth" over many premises.
I'm not sure how good the bonding of the gas system pipe are. The
pipes are "black steel", and the ground consists of a 0.10 inch copper
wire secured by a band clamp at both ends. Corrosion? Wazzat?"
Actually, the house painters probably slapped some latex based paint
over everything when the house got painted last.
Water lines as grounds are quite chancy here - the pipes in the
street are concrete. At best, you have the line from your house entry
point out to the meter, and from there out to the line in the street -
and even that may not be true. When we bought the house I'm in now, I
noted a one inch soft copper supply line coming up out of the ground
(with a 1/3 inch diameter wire bonded to it) and thought "Wow -
quality!". A year after we moved in, a neighbor mentioned that the
actual supply pipe underground was polybutylene (a product noted from
cracking/splitting in time). Later still, I get up one morning, and
note that the water pressure is low. As I'm backing the car out of the
garage, I discover the front yard is flooding - badly. Yup. the
polybutylene line had split. Got some plumbers out and replaced it with
copper, and as they did so, I noted that the copper stub I had admired
when I bought the place transitioned to polybutylene about a foot below
grade. In reality, I was only grounded by the (reportedly 10 foot long)
utilities ground at the demarc.
>I don't think that we are very far apart in the principles.
>I'll bow out now, have the last word if you wish.
No need for that - sit around and contribute (or at least point fingers