On 11/23/2009 7:43 PM D Yuniskis spake thus:

Phil Allison wrote:

** In the US and Canada - it is NOT permitted to link neutral and earth
or plumbing within a premises.

"*within* a premises". The neutral *is* "earthed" right outside
the home, typically. The Code goes to great lengths telling
you exactly *how* to earth the mains at the service entrance.

However, this ignores the fact that most residential wiring
is grandfathered into "acceptance". Previously, homes *were*
grounded through their "water main" (e.g., my parents home
has ground at the water meter).

Grounding a home's electrical system through the plumbing is perfectly
safe, and probably the best way to do it, assuming the plumbing is steel
or copper.

This is no longer permitted according to the NEC (American electrical
code). Why? Because not all pipe nowadays is steel or copper. In fact,
one can get into great trouble replumbing part of a house with plastic
and severing an old ground connection.

So, you can encounter all sorts of different situations
here in the US (I've even worked on homes with knob & tube
wiring!)

I've worked on lots of knob and tube wiring around here (San Francisco
Bay area). It's actually a very good wiring system, and in most cases is
still perfectly safe and functional 60 to 80 years later. It's permitted
to be "grandfathered" in under the NEC, but of course is no longer
installed anymore.


--
I am a Canadian who was born and raised in The Netherlands. I live on
Planet Earth on a spot of land called Canada. We have noisy neighbours.

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