"w_tom" wrote in message ...
Posted in the paragraph that discusses earthing:
IOW if water pipe is used for earthing, then another
dedicated electrode must also be installed. But if that
other dedicated electrode is installed, then water pipe
earthing is not required. In short, the water pipe is
not sufficient for earthing.

Earthing - not bonding. Two separate functions. Bonding
was defined previously in same post. Stated quite clearly
that a water pipe must connect to breaker box safety ground:
NEC requires connection to water pipes - to remove electricity.


Perhaps its just semantics, but if a water pipe is in contact with the earth for 10 feet or more, it
MUST be used as a grounding electrode. Because it could be replaced by plastic in the future, NEC
mandates an additional ground in case this one gets disabled by a plumber. It should make an
excellent ground, as its usually much longer than rods. Ideally, the water pipe would be near the
main panel so you can have a short grounding electrode conductor to that pipe.

If the pipe is not in contact with the earth, then it must be bonded. Whether you're bonding or
grounding, NEC requires the same size of wire (sized per the 250.66 grounding electrode conductor
sizes) for water pipes. Normally, bonding only connections can use smaller wires per 250.122.
Whether you're grounding or bonding the water pipe, you end up doing the same thing with the same
size wire. Only difference in the ground -vs- bond case is where that wire must be attached --
within 5' of where the pipe enters the house if it is a grounding electrode.

Only thing I'd like to know from Tom Horn's impedance measurements is at what frequency they were
measured. I would expect lightning surges to be high frequency and skin effect and wire bend radius
could me much more important than they are at 60 Hz.

--
Mark
Kent, WA