Some definitions. Bus bar for household neutral and
ground wires in breaker box would be breaker box safety
ground. It must connect to cold water pipe so that water
pipes are safety grounded. A bare copper ground wire of at
least 6 AWG (4 AWG is more commonly used) connects to 8' earth
ground rod that is driven almost completely into earth. That
wire must be routed so that it has no sharp bends, no splices,
not bundled with other non-grounding wires and does not
connect to other earth grounds until they all meet at central
earth ground.

That ground rod would become your central earth ground.
Incoming cable or TV wire would also connect to ground rod
using ground block and 14 AWG (or heavier) insulated wire.
Telephone premise interface box, typically called NID, also
connects to this same central earth ground using 12 AWG
(typically they use 10 AWG that is green or gray color
insulated) wire.

Earth ground rod remains with top visible to that each
ground wire can be clamped to that rod and remain visible for
inspection. If other ground rods are added to enhance that
single point earth ground, then must be separated six or more
feet from this first rod. Other rods are often connected to
this first rod using a buried 2 AWG bare copper wire. That 2
AWG wire not only interconnects ground rods but also enhances
the earth ground network.

Some of these requirements are beyond what the NEC
requires. For example, phone wire ground meets breaker box
ground at ground rod (does not attach to 4 or 6 AWG ground
wire) to make earthing for both utilities effective also for
transistor protection. Ground wires route separate from all
other wires also for transistor protection - beyond what NEC
requires.

Is a single earth rod sufficient for earthing? Typically
yes for NEC requirements. May or may not be sufficient for
transistor protection. Geology is a fact that answers this
question. Earth that is bleached of ionic material (ie. sand
or gravel) definitely requires an expanded single point earth
ground system. If underlying earth is impregnated with veins
of conductive earth or if the central earth ground is in earth
less conductive than earth on the other side of a building,
then additional considerations are required. But in many
cases, the single or a few earth ground rods so drastically
increases a building's earth ground as to make a major
improvement in transistor safety.

I would more suspect that existing ground wire is simply a
long wire laid in and buried before foundation was
backfilled. If so, then your newly installed earth ground
rods only enhance and make more reliable an already good earth
ground.

Very important question about driving a rod into earth when
pipe locations are unknown. Maybe call utility. Tell them
you are adding some ground rods and do not know where the gas
pipe is. Also ask gas company how they want that interior gas
pipe connected to breaker box ground. A locating service will
spray paint dirt above buried gas (and other) pipe. Utilities
are very concerned about informing everyone of pipe (and wire)
locations. That locating service may also be so kind as to
trace out existing breaker box ground wire for you. But yes,
get the utility to locate that gas pipe and water pipe before
driving an 8 or 10 foot copper clad ground rod into earth.

Happy earthing!


Mark Wilson wrote:
All right, I've resigned myself to putting in a ground rod. Just a few
questions on the particulars.... To my understanding an eight foot rod is
required burried two feet in the ground. The current (no pun) bare ground
wire coming from the electrical box is what appears to be about 10 gauge.
Did someone say this wire should be 2 gauge? Is that heavy of a gauge
really necessary?

There is a cold water pipe near the eletrical box which I will ground to the
house ground. Is it better to ground this to the bare grounding wire or to
go in to one of the bus bars inside the electrical box?

The gas pipes enter the corner of the house and go only a few feet before
reaching the water heater, then up to the ground floor to supply the gas
stove. (Kitchen is in the middle of the house). It doesn't seem this is
any kind of lightening risk. Is it necessary at all to ground the gas
pipes?

Oh, and am I going to have to call the gas company before putting the ground
rod in? I was expecting to just drive the rod into the ground like a rail
road spike. But I'm worried there might be a gas pipe under there
somewhere.

Thanks a lot for your patience with me guys. I'm using a couple books for
reference, but the information I get in books is never quite as good or
detailed as the advice I've read here.