Jim Lux wrote:
Thomas Horne wrote:


I am an electrician by craft. The US National Electric Code
Requires that underground metal water piping on the premise be used
as a grounding electrode for the electrical system. There is no way
around


Ahhh...The water pipe must be bonded to the electrical system, but the
main ground must be at the entrance. Here, we have plastic water pipe
all the way to the main from the meter, yet we have to bond the meters
which are metal with plastic running in and plastic running out.

it. No matter how fast people talk you cannot avoid using an
underground metal piping system as a grounding electrode unless the
electrical inspector is incompetent.


It's really easy to avoid here. We do not have metal piping available
for grounding.
Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com


That has nothing to do with not using an underground metal water pipe
that is present on the premises.
--
Tom Horne

that would really depend on the local AHJ (Authority Having
Jurisdiction).. For instance, in the City of Thousand Oaks, CA, only
Concrete Encased Grounding Electrodes (aka Ufer grounds) are allowed in
new construction. (other grounding electrodes are permitted, but you
better have the Ufer ground, and, of course, they would need to be
bonded together, per NEC). With respect to my house, built in 1998, I
don't think there is a bonding jumper from water pipe to the system
ground at the service entrance (which is a Ufer ground). Obviously,
there IS a jumper from the telco drop, the cable TV drop, etc. to the
ground at the service entrance (and all the "drops" are actually
underground services in plastic conduit). Partly this is because the
water service comes in on the opposite of the house from all the "wired"
utilities. I'll have to go take a look, though.

I believe the new code (which I don't have here to hand) does require
that metallic water piping, if any, be bonded to the electrical system
ground (presumably to eliminate "touch voltage").

I believe also, that the code prohibits use of a water pipe as the sole
grounding electrode (NEC 250-(a)(2) in 1999 code, 250.53(D)(2) 2002,2005
codes). As always in code matters, what the AHJ says takes precedence.

As a practical matter, a properly constructed Ufer ground is probably
lower impedance and more reliable than rods, wires, and pipes.

Jim Lux, P.E.
W6RMK

Jim
I would hope you are aware that most concrete encased electrodes are
not, in fact, a true UFER. In spite of that it is undoubtedly the most
reliable electrode; which is not to say lowest impedance; commonly
installed in homes. You are correct that an underground metal water
piping electrode must always be supplemented with another electrode but
the code still requires it to be used as an electrode were it is present
on the premise. In my location the public water utility is entirely
metallic, including the service laterals to buildings. It covers about
fifty miles from north to south and more than thirty five miles east to
west at it's widest point. That large an underground metal piping system
has the lowest obtainable impedance to ground of any electrode on a
premise served by the water system.
--
Tom Horne