Re: DSL speed

w_tom wrote:


For most homes, that means at least a 10 foot earth ground rod.
Soil should be conductive (not granular like sand). Rod should be in
earth that is below the frost line and best when always moist. Since
these conditions don't always exist, then we use other solutions such
as a network of ground rods with buried internconnecting wires,

It must be a challenge to drive a ten-foot rod. A rod needs to be long enough to reach moisture. At the farm, I added two eight-foot rods. The three gives me more area than a ten-footer, and I could check resistance to ground.

a halo
ground, Ufer ground (installed so that lightning would not even cause
munitions explosions), a ground plate, etc. Notice that the water
pipe is not listed as a best ground. Best earth ground is a connection
to earth that is most conductive. This sometimes made challenging
when building also uses a well pump.

It's possible to detect the ground surge from a strike fifty miles away. The farmhouse routinely suffered damage from strikes more than a thousand feet away. Water pipes could bring in those surges, so I bonded them to the other grounds.

One of the symptoms of trouble had been snapping under a cast-iron lavatory when lightning struck even in the distance. Electricity was jumping from the cold water pipe to the drain. The pipes to the spring and the septic tank were plastic, so I wouldn't have thought these metal pipes would pick up enough to cause trouble. What's more, my meter showed zero ohms. I guess ground surges must have seen a lot of inductance. I bonded them and the snapping stopped.



Second, effective protection provides equipotential. Since we
cannot provide sufficient conductivity, then we also must provide
equipotential. That means earth beneath all parts of the building is
predominately at a common voltage. Some achieve this by a deep
grounding rod.

In a car or a ship equipotential protects you with no grounding rod, and a deep grounding rod won't provide equipotential. Suppose your washer is grounded through a three-prong plug to the ten-foot rod at your service entrance. If a ground surge comes as you lean over the washer to turn the water valve, you could get a shock if the outlet ground and the pipe ground are not at the same potential.

Other better solutions include a halo or Ufer ground
that loops the building. Latter solutions are more often installed in
sandy locations as demonstrated by pictures from Gfretwell:
http://members.aol.com/gfretwell/ufer.jpg
Others also discuss Ufer solutions:
http://www.psihq.com/iread/ufergrnd.htm
http://scott-inc.com/html/ufer.htm

In each case, both equipotential and conductivity are increased.
Again, a protector being only as effective as its earthing.

For example, lightning strikes a nearby tree. The circuit is a
connection from cloud, down the tree, many miles through earth, to
earthborne charges. But a shorter path is up a cow's hind legs and
down his fore legs. Cow is electrocuted because he did not have a
single point ground.

The phone man who replaced my phone fuse told me the power company's neutral is like that cow, and that's how most lightning surges arrive at a house. It hits a tree and goes up the ground of a nearby utility pole like the leg of a cow. That way all the power ground rods in the area help dissipate the current, and every house gets a surge. By letting that surge flow to the power conductors as well, the whole-house protector protects your single-link appliances.

My modem was okay because the surge on the power ground flowed through my bonding wire to my phone ground. The phone man said the surge flowed from the telco ground through the telco protector to the telco line, where it blew a fuse on the pole. He said that's why the telco doesn't like bonding although the code calls for it. (He told me it was a fuse, but it might have another name in the phone business.)

Number of ways to achieve that single point ground. Have cow stand
only on its hind legs while keeping them together. Another would be a
halo ground wire buried around the cow. Electricity that does not
have both an 'incoming and outgoing' path or tht finds a better path
therefore not pass through the cow. BTW, same reason why humans are
advised to keep feet together if caught out during thunderstorms -
create a single point ground.

Humans are also safer inside buildings because wood is a conductor.

The 1964 Britannica said most fatal lightning shocks in American households came through plumbing, phones, and chimneys. Household lightning deaths declined sharply in the 1950s. It attributed this to the coming of TV antennas on roofs. I guess the antenna grounds conducted a lot better than wood. Slab construction may have helped, I think (equipotential).



Those two points are the principles. What defines effectiveness of
a protector? That single point earth ground. Therefore all utilities
must enter a building at a same point. The most conductive path to
earth being earth connected to each wire in each cable by 'less than
10 feet'.

Another important concept - impedance. For example, wall receptacle
may be 50 feet from breaker box - even longer to earth ground. But
wall receptacle is only a safety ground; not earth ground. Wire
resistance may be less than 0.2 ohms. But wire impedance to a surge
may be 120 ohms. A trivial 100 amp surge would leave wall receptacle
at 100 x 120 or something less than 12,000 volts during a surge.

If you could really establish equipotential, why would there be a hundred-amp surge in the ground wire at a receptacle?


Demonstrated is why surge currents permitted inside a house find
numerous and destructive paths inside that house. Demonstrates also
why a connection from each utility wire to single point earth ground
must be 'less than 10 feet' ; or shorter. Electrically shorter also
means no sharp bends, no splices, not inside metallic conduit, etc.
Protection means earthing wire also must be separated (at least one
foot) from other non-grounding wires. AC recpetacle ground violates
every requirement - why a plug-in protector has no earthing.


You said there could be 12,000 volts on the grounding conductor at a receptacle. If the phone and power conductors didn't see a corresponding surge, wouldn't that 12,000 volts on the ground wreck a computer and modem? For twenty years, point-of-use protectors have kept my equipment from seeing surges such as you describe.


However since even electricians don't understand these concepts,
then some homes are constructed with utilities entering in multiple
directions. That created the above 'dead cow' situation. One utility
offers a solution:
http://www.cinergy.com/surge/ttip08.htm
With an interconnecting wire buried, then every utility is making some
kind of connection to a common ground. Clearly, better is for all
grounds connect at a same point. Also better would be a wire
encircling the building - halo ground. Bottom line conclusion remains
same. Earthing defines the quality of that protection system.

I don't entirely trust bonding wires because of inductance. I depend on point-of-use protectors to get what's left.



Note, for example, a picture in an app note from an industry
professional:
http://www.erico.com/public/library/fep/technotes/tncr002.pdf
Two structures. Each has its own single point earthing. All wires
(even underground) that enter a building must first make that single
point ground connection. Wire from tower to building must connect to
both structure's single point ground before entering structure. To
make both earthings even better, a buried ground wire interconnects
both single point grounds.

It recommends six measures. The first three are about lightning rods. The fourth is about bonding. The fifth and sixth are about surge protectors.


Cable company needs no protector. For better protection with lower
capacitance, the earthing connection is made with a $2 ground block
and 12 AWG wire. Again, that connection must be short which is why a
cable TV ground to a water faucet or AC electrical receptacle is not
earthed. Check your cable. Did the installed ground 'less than 10
feet' direct to the electrode? If not, then even DSL is at risk.

You say the ground at my TV could have 12,000 volts. If the cable is at zero and there's no point-of-use protector, won't my TV have to eat that 12,000 volts?
.

Relevant Pages

  • Re: Just had a thought about surge suppressors...
    ... Those "couplesurgestrips" did what no protector must do - failed. ... A surge found earth ground destructively via dishwasher, ... That means a connection from each incoming wire to earth ...
    (alt.home.repair)
  • Re: Whole house surge suppressors
    ... Ground tester is for measuring the conductivity of earth. ... created by wire too long, splices, sharp bends, wire inside metallic ... Conductivity of earth ground is only one factor in surge protection. ...
    (sci.electronics.basics)
  • Re: Surge protectors to use with home electronics when grounding is not available?
    ... A plug-in protector interposed between the load and the mains, ... romex may be less than 0.2 ohms, that same wire is maybe 120 ohms ... A trivial 100 amp surge 'clamped' by ... all wires are at something less than 12,000 volts to earth. ...
    (sci.electronics.basics)
  • Re: "chain" surge suppressers?
    ... because the protection device is further from ground. ... The typically destructive surge is ... will rise as high as necessary to obtain earth ground. ... positive voltage on the black wire and a negative voltage on white. ...
    (alt.home.repair)
  • Re: Surge protectors to use with home electronics when grounding is not available?
    ... romex may be less than 0.2 ohms, that same wire is maybe 120 ohms ... A trivial 100 amp surge 'clamped' by ... all wires are at something less than 12,000 volts to earth. ... protection requires low *impedance* earthing which a plug-in protector ...
    (sci.electronics.basics)
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