On 10/7/2012 3:01 PM, HeyBub wrote:
bud-- wrote:
On 10/6/2012 10:42 AM, HeyBub wrote:
John Grabowski wrote:


*I took for granted that the OP had a copper pipe water service
from the street. You are correct that if he didn't, two eight
foot ground rods would provide the necessary lightning protection.


I suggest that no amount of copper pipe is a proper substitute for
ground rods.

Ground rods are the worst earthing electrode.


*So in your mind 16' of copper plated iron rod is a better ground
than the copper pipe that runs from a house out to the street and is
connected to a giant web of piping.

Of course.

You may be confusing a proper electrical ground with the grounding
of the plumbing system.

You are just confused.

What's the reference to lightening protection about?

*The primary purpose of a grounding electrode (Water pipe, ground
rod, ground ring, ufer ground, copper plate, etc.) is for voltage
stabilization and lightning protection.

Sigh. A water pipe is not a grounding electrode. It may FUNCTION as
one, but using a water pipe is not best practice.

A metal municipal water system will be a far lower resistance to earth
than any other earthing electrode you will have a house.

It certainly is a good earthing electrode, which is why the NEC has
required its use since time began.


Perhaps this will explain:

"You've probably seen project requirements that call for the grounding of
piping systems and exposed structural steel. Those requirements, although
well intended, miss the mark. The stated intention of such requirements is
nearly always the removal of dangerous voltage on specific types of metal
parts in the event of a ground fault. These metal parts include exposed
structural steel members, electrically conductive metal water piping
systems, metal sprinkler piping, metal gas piping, and other metal piping
systems. But these requirements fail to make that intention a reality.
That's because you remove dangerous voltage on metal parts through bonding,
not through grounding."

No source.

I am not fond of the term "grounding" because you may be talking about
"bonding" or "earthing".
Your quote has that problem. (The NEC has started to clarify which use
is intended.)

The NEC has 3 electrodes that are *required* to be used as earthing
electrodes (where present).
One is metal water service pipe (10 ft...).
Another, in general, is structural steel (because of its connection into
the rebar systems in the concrete foundation).

Your source is incorrect - water pipe and structural steel *must* (in
general) be used as earthing electrodes.

If they are connected as earthing electrodes they are also "bonded".


and

"The NEC (section 250-81 through 250-83) requires that the electrical system
connected to all of the following, if available for grounding purposes:
* metal frame of building
* concrete encased electrode (rod, pipe, plate, braided wire)
* ground ring and
* metallic water pipe with 10 lineal feet in contact with earth

The correct list has electodes that may already be present in a building
and does not include ground rings and everything after "concrete encased
electrode".


The NEC has noted that metal piping will corrode over time and possibly lose
its continuity with the soil (i.e. ground) or be replaced by plastic pipe.
Accordingly, should this occur, the NEC has mandated the 3 other paths to
ground be utilized."

Cite for corrode.
Cite where water pipe has worse corrosion problems that ground rods.

The NEC has NOT mandated that "3 other paths" to earth be utilized.


In other words, attaching a metal water pipe to an earth ground is used to
protect the user from the plumbing, not to provide a ground for the
electrical system. Using metal water pipe as an electrical ground is
insufficient.

The requirement to use water pipes as an earthing electrode is in a
section on the earthing system and the electrodes to be used.
It is in your list of required earthing electrodes, above.

You have bullsiht information and are using a bullsiht source.

(What a surprise.)