Code does not state distance to water pipe because code
addresses human safety issues. Wire length in a residence is
irrelevant for human safety. But wire longer than 10 feet has
adverse effects to earthing for surge protection. Again, code
is only concerned with wire resistance. Surge protection
worries about wire impedance which is why that wire must be
short and other requirements (no splices, no sharp bends,
etc).

Transistor safety (also known as surge protection) is beyond
scope and purpose of the NEC. After all, who creates NEC
requirements? National Fire Protection Association - because
code is written to protect human life.

But for transistor safety, that ground wire length and how
the earthing system is connected (single point earth ground)
exceeds what code requires. We must enhance an 'NEC
required' earthing system to also provide an effective 'surge
protection' earthing system.

For example, a ground wire can be grouped with other wires
to meet NEC. But for effective surge protection, that
earthing wire must be separate from other wires - so as to not
create induced surges on those other wires. Ground wire must
not be in close electromagnetic proximity with other non
earthing wires. Code does not require this because code does
not fully address surge protection issues.

Ground wire from incoming utility can connect to breaker box
ground to meet code. But for surge protection, the earthing
system must be enhanced. All earthing wires must run
independently and meet at the central earth ground - be it the
MGB, bulkhead, earthed structural member, or earth ground
rod(s). All utilities must meet at this single point ground
to upgrade an 'NEC required' earth ground into an effective
surge protection earth ground.

Other limitations. Buried ground wire may be 2 foot deep to
meet code. But for surge protection, that wire must also
remain below the frost line. Earth ground is non conductive
when frozen. Therefore many ring grounds also include 8'
earth ground rods to address problems such as deep frozen
earth and geology variations.

Sand is also a serious problem for earthing.

Halo or ring ground addresses problems beyond what code
requires; especially if in sandy soil. Since we cannot make
earth ground conductive enough, then we attempt to make earth
under the building "equipotential". But wire is not a
conductor to surges. Wire becomes an electronic component.
So we also want that ring ground to become the best conductive
earth ground in the facility - the 'single point earth
ground'. IOW ring ground enhances an NEC required earth
ground for two complementary reasons as demonstrated in that
previously cited Lem Instrument URL and in a figures from
another industry professionals:

http://www.erico.com/erico_public/pd...es/Tncr002.pdf
http://www.xantrex.com/support/docserve.asp?id=337
http://www.cinergy.com/surge/ttip08.htm


Mark or Sue wrote:
"'nuther Bob" wrote in message
...
On Sat, 12 Jul 2003 03:22:50 GMT, "Mark or Sue"
wrote:
To summarize, if you have a metal water pipe that is in contact
with the earth for 10 feet or more, you MUST use it as your
primary grounding electrode.

WOuld "MUST" still apply if the proper attachment location to the
water pipe is 35 feet from the panel ? Or would the code then
prefer two grounding rods ?

Bob

Code says "must", but is silent on the distance from the panel.
You have to run a wire to the pipes anyway (whether outside pipes
are metal or plastic), the wire is just larger when it is your
GEC. So you can't skip this part.