w_tom wrote:

I'm not disagreeing with you Tom, however....in defense of the NEC.....

Pop` wrote:
Everything you said is correct, as best as I recall it. But what are you
citing? It sounds more like a local code than a national code.

National Electrical Code now calls for all utilities to share a
common earth ground. Water pipe as earth ground is no longer
sufficient.

It's only fair to say _why_ a water pipe is no longer "sufficient." In
fact, the NEC still requires that an underground metallic water pipe in
contact with earth for at least 10 feet shall be used per (2002) NEC
250.50, if available. It's not that an underground metallic water pipe
isn't a good ground, it is, it's just that some clown may come along
and replace it with plastic pipe, rendering it ineffective as a
grounding electrode. Which leads, as to why, to the next requirement
by NEC, 250.53, that a metal underground water pipe shall be
supplemented by an additional electrode, usually a ground rod. Also,
that connection shall not depend upon the water pipe.

Water pipe is bonded to breaker box. That connection
must be within five feet of where pipe leaves earth. But that
connection is electrically better if it does not pass through a solder
joint to earth. Also meter must have a bypass ground wire.

Yes, and _that_is_ the wire (per NEC 250.94) that is intended for
intersystem grounding, such as telephone and cable, to be connected.
This is critical for "life" safety and "transistor" safety. As you
know, bonding all the systems together, thus, making them the same
potential, allows all of the interconnected systems to come up to the
same potential during a surge or nearby lightning strike, resulting in
no destructive paths for current to flow. If different systems
grounding is not at the same potential by not being bonded, a
destructive path is established during a surge or nearby lightning
strike and _will_ find it's way through phones, modems, TVs, whatever.


Here in Florida we get a lot of serious lightning and I've been called
to repair a lot of that kind of damage. Almost always the systems are
not bonded before the fact. I've think that I may have noticed a
pattern. Many times the VCRs will get blown out and the TV is OK.
I've also noted that modems got spared while the phones get fried. I'm
beginning to wonder if it isn't a good idea to leave those old, no
longer used VCR's and telephones connected first in line, to act as
sacrificial lambs, so to speak.

These code
requirements are for human safety have changed significantly since 1970
construction.

To make the same earthing sufficient for transistor safety means both
meeting and exceeding post 1990 National Electrical Code. Therefore an
earthing wire must be even shorter than required by code - 'less than
10 feet'.

The NEC actually does require, in NEC 250.30(A)(4), that the grounding
electrode to be "as near as practicable" and "preferably in the same
area" as the grounding electrode conductor.
The NEC can't dictate where a utility will bring in it's service. In
my house, for example, the electric and phone comes in on the right
side of the house, the water comes in the front, and the cable comes in
on the left side of the house, all due to the physical layout of the
utilities.

Other requirements such as not inside metallic conduit,

I believe that NEC 250.64(E) solves that problem by requiring that the
wire be bonded to the pipe at both ends.

wires separated, no sharp bends, etc are for electric currents (ie
transients) that are beyond the scope of NEC - that will not harm
humans and that can harm transistors.

I don't think Article 250 comes right out and says it, but the
implications are there if one looks in Article 285 (Transient Voltage
Surge Suppressors), specifically, 285.12 "The conductors used to
connect the TVSS to the line or bus and to GROUND shall not be any
longer then necessary and shall avoid unnecessary bends." Similar
statements are made in Article 280 (Surge Arrestors), actually, 280.12.

Saftety ground to a gas pipe is unique to that gas company's
requirements. NEC does not require that ground.

Most certainly does, in NEC 250.104(B). "Where installed in or attached
to a building or structure, metal piping system(s), including gas
piping, that may become energized shall be bonded to the service
equipment enclosure......etc."

Gas companies also
typically put an electrical insulator adjacent to the gas meter so that
their outside gas pipes are not functioning as an earth ground.
Bonding a gas pipe to breaker box would only bond gas pipes inside the
building for human safety- and again only if required by that gas
company.

That's true, some localities, persuaded by gas companies, will amend
their _local_ codes so that gas pipes are not bonded to the electric
grounding system. However, one will usually find that the gas
appliance is grounded by the equipment grounding conductor of the
circuit that supplies the power to the appliance.

For safety reason's, it's very critcal that an interior metal water
piping be bonded to the electric grounding system, even if the incoming
underground water pipe is plastic.

I would like to see the NEC require a Ufer ground, though. IMO, a
ground rod (even two, 6 to 10 feet apart) is about the worst grounding
electrode permited by NEC. A Ufer ground (concrete encased electrode)
is easily installed during new construction, and there is no real
excuse, other than laziness, NOT to install one.