International Fuel Gas Code, Page 29, Section 309.1, 2002 Edition


Gas piping shall not be used as a grounding electrode.

309.2 Connections
Electrical connections between equipment and the building wire, including
grounding of the equipment, shall conform to the ICC Electrical Code.

In my area, NO GROUNDING AT ALL to a gas line, the grounds are to be made at
the equipment, and if an inspector finds that you have a ground to a gas
line....permits are jerked, and a stop work order is issued on the spot.




"volts500" wrote in message
. com...

"w_tom" wrote in message
...

The gas and electric company in this area demands gas line
be connected to safety ground.

Yes, like I said, _interior_ gas lines must be bonded to the service
equipment.......per NEC Section 250.104(B) which states:

250.104 Bonding of Piping Systems and Exposed Structural Steel.
250.104(B) Other Metal Piping. "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,
the
grounded conductor at the service, the grounding electrode conductor where
of sufficient size, or to one or more grounding electrodes used. The
bonding jumper(s) shall be sized in accordance with 250.122 using the
rating
of the circuit that may energize the piping system(s). The equipment
grounding conductor for the circuit that may energize the piping shall be
permitted to serve as the bonding means. The points of attachment of the
bonding jumper(s) shall be accessible."


In fact, the 2002 NEC was revised to make it clear that _interior_ gas
lines
be treated the same as all other interior metal piping (such as interior
water lines). In fact, in the past many plumbers have been killed because
the interior gas lines were _not_ bonded to the service equipment, the gas
line becomes energized via a ground-fault in a gas appliance (such as the
light circuit in a gas stove), then the plumber inadvertently touches the
energized gas line while also contacting a grounded water pipe. It's not
hard to deduce how explosions can also occur when the _interior_ gas line
is
not bonded to the service equipment.


OTOH, this requirement should not be interpreted as lead one to think that
the _underground_ gas line should be connected to the grounding electrode
system. _Any_ grounding electrode that is connected to the grounding
electrode system becomes part of that system........be it a metal
underground water pipe, building steel, a concrete-encased (Ufer)
electrode,
a ground ring, rod and pipe electrodes (such as ground rods), or plate
electrodes. NEC Section 250.52(B) clearly states:

250.52 Grounding Electodes.
250.52(B) Electrodes Not Permitted for Grounding. "The following SHALL NOT
be used as grounding electrodes:
(1) Metal underground gas piping system.
(2) Aluminum electrodes."

Again, if an metal_undergound_ gas pipe is connected to the grounding
electrode system, it becomes a grounding electrode, and a violation of
NEC.


But that gas line must not be
the earth ground electrode.

If it's connected to the grounding electrode system, it's a grounding
electrode and it _will_ dissipate electrons right along with other
grounding
electrodes that it is bonded too.


Call it semantics, but it is much
like what a ground to the water pipe now does. Ground
connects to water pipe to remove any electrical currents that
may be on that pipe; not intended to earth breaker box.


Yes, an _interior_ metal water line is not intended to be a grounding
electrode, but it is required to be bonded to the service equipment, just
like an _interior_ gas line.........to protect from shock should it become
energized. OTOH, an _underground_ metal water pipe 10 feet or longer
_must_
be used as a grounding electrode per NEC Section 250.50 Grounding
Electrode
System.
"If available on the premises at each building or structure served, each
item in 250.52(A)(1) through (A)(6) shall be bonded together to form the
grounding electrode system."

These are all the grounding electrodes that I listed earlier......of
which,
a metal underground water pipe is first on the list. While newer houses
obviously no longer have metal water supply lines, many older houses _do_.
Not only must the metal underground water pipe be used as a grounding
electrode, IF available, but it _must_ be supplemented by an additional
grounding electrode (this is usually, but not restricted too, a ground
rod)
in the event that the Water Co. decides to replace an old, leaking metal
water line with a new plastic one.



Yes
water pipe does act like an earth ground from perspective of
breaker box. But the intention of that connection is for
human safety and no longer is for earthing.

Depends on whether the supply line is plastic or not. A metal underground
water pipe is still _required_ to be used for earthing, IF available. See
above.


Same with that
ground wire connection to gas pipe.


ONLY for an _interior_ gas line.


If connection to gas pipe was the only earth ground
connection, then gas pipe would be serving as central earthing
ground - not acceptable.


Nor is it acceptable to connect the underground gas line to the grounding
electrode system. If the underground metal gas pipe is connected to the
grounding electrode system.......it's becomes a grounding electrode, see
above.
Please define your term "central earth ground." Multiple grounding
electrodes, bonded together are considered a _single_ grounding electrode
system per NEC. Like I stated in a previous post, for matters of
practicality, your term "central earth ground" is the point where the
grounded service conductor (neutral) is bonded by the main bonding jumper
(usually a green screw or a bond strap or bar) to the service equipment
metal enclosure (including the meter) and the branch circuit equipment
grounding conductors, _and_ where the connection to the grounding
electrode
system (mulitiple grounding electrodes bonded together.) Depending on
local jurisdiction, the connection the grounding electrode system may be
at
the meter.

An example that is common practice is for the teleco to connect the wire
from their primary protector to the bare #4 copper wire (grounding
electrode
conductor that is connected to the neutral bus bar) that is exposed on
it's
way to the first electrode in the grounding electrode system (only one of
many possible methods.) It's considered as connected to "central earth
ground" this way. The same for cable TV. IOW, your term, "central earth
ground", to me, _is_ the grounding electrode system.


But if all other utilities connect
to another central earth ground, then gas pipe is really only
one of many earth grounds from the perspective of breaker box,


And _not_ permitted. If you insist that your local power and gas co.'s
require this, I'd be interested to know who they are.


and may even be too far to be considered earth ground to
breaker box. But, and again, other utilities must be earthed
at central earth ground (ie directly on top of earth ground
rod)


Again, define "central earth ground." A ground rod is probably the worst
grounding electrode that can be used as it will only dissipate so many
electrons in a given time limit........that's why, if a ground rod is the
_sole_ connection to a service, no matter what the size, that a grounding
electrode conductor not larger than a #6 is not required. The ground rod
chokes down the current such that it will dissipate no more than what a #6
conductor will handle.......again, this is for a _sole_ connection ONLY.
Which is why the NEC encourages multiple grounding electrodes, bonded
together to form a _single_ grounding electrode _system_. IMHO, this
grounding electrode system, and its' connection to the service equipment
neutral bus bar is what you should be referring too as "central earth
ground", especially in your discussion of differential and common mode
surges as related to point-of-use surge protectors, since the neutral and
equipment grounding conductors are bonded at the service equipment neutral
bus bar (and/or the meter) and affects the discussion.

Please define your terms differential and common mode surges too.......or
provide a web page that all can agree upon. I know what my definition is,
but let's make it clear so that all are on the same page. For example, I
consider a differential mode to also be called normal mode. Or shall we
use
"Mode 1" and Mode 2" as collaborated between the US Govenment and UL 1449?
Is All-Mode also Mode 2? Again, let's use the same terms so as to make it
clear what is being said.


AND not earthed on or closer to breaker box. That means
gas pipe is too far to be considered earth ground from the
perspective of those other utilities.

This electric and gas company has specific examples
(including explosion) why it wants gas pipe connected to
safety ground (breaker box ground). It does not want voltage
differences across gas meter (again due to previous events).

There won't be if the interior metal gas pipes are bonded to the service
equipment via the circuit likely to energize the gas line via its'
equipment
grounding conductor as discussed earlier.


Central earth ground may be all earth ground rods bonded
together BUT earth ground connection is only made to one
point - maybe one rod.


No. it isn't, see earlier comments about how a single ground rod chokes
the
current flow, and is best supplimented by other grounding electrodes.


The earthing network can be large, but
best connected by everything only at one point.


Yeah, at the neutral busbar in the service equipment and/or the meter.


Earthing
network is not connected to gas pipe. Safety ground in
breaker box is connected to gas pipe. In many cases, the wire
lengths may be so short as to make little difference as to
what really is acting as earth ground. But that is how
utilities now want their gas pipes connected so that house
safety ground and gas pipe as it enters building are at same
voltage potential; so that gas pipe does not become a
significant carrier of electric currents.


While this is correct, it seems to be a contadiction of what you've stated
earlier. The key words here are "as it enters", not the undergound part
of
it.


It also could be argued that this connection from breaker
box safety ground to gas pipe is only one more reason why
central earth ground should be enhanced - to be, by far, the
best earthing ground on a property.

In original posters case, a wire buried in earth may connect
to buried gas pipe.


No, it may _not_. Please state your references. NEC? IEEE? If it's an
IEEE reference, please quote it, as most of us don't have access to them
without forking out huge sums of money.


So that gas pipe does not become central
earth ground, that wire from breaker box should first
encounter a rod (or rods) that are the central earth ground.


If the gas line is connected to the same grounding electrode conductor as
the ground rod, like it or not, it's part of the "central earth ground."