Volts: With a 35 foot run from my panel to the acceptable spot on
your water pipe, what size wire should I run (or would _you_ run
on your house if you had that situation ?)
I always heard that if the run was much longer than 5 feet that
you would have problems dissipating a lightning type surge. I can
get a short run like that to a grounding rod (and then another
5 to a second rod from the first). But, there's no way I'm going
to get that sort of run to the water pipe. Also, eventually I plan
to put in a whole house lightning/surge protector, I'd like to be
ready for that - and fix the current issue right now.
Code does not define how to measure resistance of earth
ground. The same application notes that demonstrate how to
install a more serious 'single point earth ground' (which is
labeled MGB in the picture):
http://www.leminstruments.com/pdf/LEGP.pdf (figure on page
(section entitled "Measuring Ground Resistance at Cellular
Sites,Microwave and Radio Towers")
That Lem Instrument application describes measuring earth
ground resistance since that is what they are selling.
'nuther Bob wrote:
Code does not state distance to water pipe because code
addresses human safety issues. Wire length in a residence is
irrelevant for human safety. But wire longer than 10 feet has
adverse effects to earthing for surge protection. Again, code
is only concerned with wire resistance. Surge protection
worries about wire impedance which is why that wire must be
short and other requirements (no splices, no sharp bends,
Transistor safety (also known as surge protection) is beyond
scope and purpose of the NEC. After all, who creates NEC
requirements? National Fire Protection Association - because
code is written to protect human life.
But for transistor safety, that ground wire length and how
the earthing system is connected (single point earth ground)
exceeds what code requires. We must enhance an 'NEC
required' earthing system to also provide an effective 'surge
protection' earthing system.
For example, a ground wire can be grouped with other wires
to meet NEC. But for effective surge protection, that
earthing wire must be separate from other wires - so as to not
create induced surges on those other wires. Ground wire must
not be in close electromagnetic proximity with other non
earthing wires. Code does not require this because code does
not fully address surge protection issues.
Ground wire from incoming utility can connect to breaker box
ground to meet code. But for surge protection, the earthing
system must be enhanced. All earthing wires must run
independently and meet at the central earth ground - be it the
MGB, bulkhead, earthed structural member, or earth ground
rod(s). All utilities must meet at this single point ground
to upgrade an 'NEC required' earth ground into an effective
surge protection earth ground.
Other limitations. Buried ground wire may be 2 foot deep to
meet code. But for surge protection, that wire must also
remain below the frost line. Earth ground is non conductive
when frozen. Therefore many ring grounds also include 8'
earth ground rods to address problems such as deep frozen
earth and geology variations.
Sand is also a serious problem for earthing.
Halo or ring ground addresses problems beyond what code
requires; especially if in sandy soil. Since we cannot make
earth ground conductive enough, then we attempt to make earth
under the building "equipotential". But wire is not a
conductor to surges. Wire becomes an electronic component.
So we also want that ring ground to become the best conductive
earth ground in the facility - the 'single point earth
ground'. IOW ring ground enhances an NEC required earth
ground for two complementary reasons as demonstrated in that
previously cited Lem Instrument URL and in a figures from
another industry professionals:
Mark or Sue wrote:
Once again I have typed too fast. The abbreviation I meant to use is GEC.
That primary telephone protector should be located outside the home.
That will keep much of the surge and spike energy outside of your home.
That part of the code CEOs not refer to the Electrical Service GEC but
rather to the Communications Grounding Conductor. This conductor bonds
the communications protector to the GEC or the other accessible
grounding means. W_Tom's suggestion to run the communications grounding
conductor to the Ground rod itself will cause a few challenges. One is
that conductors smaller than #6 must have protection from physical
damage. Lawn mowers, edge trimmers, & weed eaters expose GECs to severe
physical damage so any conductor that is run within reach of such
equipment must be number four or be run in protective raceway. If the
conductors would run adjacent to each other anyway than a split bolt or
saddle clamp would be just as effective.
Did the electrician say you need a NEW grounding rod or a SECOND grounding
rod? The reason that I am asking is that a local electrical inspector just
told me that the "new electrical code" now calls for TWO grounding rods to
be installed 6 feet apart -- instead of just one grounding rod. He said one
continuous #6 grounding wire would go from one rod to the next rod 6 feet
away (and looped around it) and then to the neutral block on the electric
I know nothing about how all of this works and will probably just have an
electrician do it. But, when I saw your subject line, I figured I'd pass on
what I was just told in case it helps.
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