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Re: [OM] XP networking - it was the @$%^* router after all

Subject: Re: [OM] XP networking - it was the @$%^* router after all
From: Rand E <rtomcala@xxxxxxxxxxx>
Date: Wed, 03 Aug 2011 11:15:38 -0400
You are totally correct Ken, with the following exceptions that make is 
more difficult to get a good ground in my part of the country  (central 
Maryland).
Almost all of our well casings and septic systems are done with PVC.   
And in my particular area, if you are on a well (very common), the water 
system is also
best to be CPVC due to the high acidity of the water, which eats copper 
piping.
Rand E
------------------------------------------------------------------------


Ken Norton wrote:
> Ah, granite. How lovely.
>
> Your electrician is absolutely correct. The well casing is great for most
> grounding applications and still should be tied in. But building a proper
> groundfield (which can be expensive if installed commercially for a large
> current load facility like a telephone switching office), creates a relative
> ground instead of an absolute ground. It is possible that you are literally
> miles away from an absolute ground connection. In eastern Kentucky, for
> example, there are areas which are dozen or more miles away from an absolute
> ground. The power-lines in those areas include a return ground. Our
> telephone networks in those areas are even more convoluted.
> The well casing would provide a decent grounding for standard 60Hz powergrid
> return path, but won't address lightning because a hit two miles away can
> still affect you as it travels through the water table before finding an
> area to neutralize the discharge.
>
> So, depending on local code (some areas don't allow for double-bonding of
> grounds), what I would do is build a ground-field. This would incorporate an
> array of copper spikes driven somewhere around eight feet into the ground
> and connected with large-guage braided copper.This is then brought back
> inside (usually to your basement to the large sheet of plywood which all
> your panels and interfaces are), and bonded/bolted to a large copper buss
> bar. Each utility entrance is then grounded to this buss bar with its own
> bolt. (Do not use any form of solder at the buss bar). Again, depending on
> local code, you will also run a large-guage copper wire to the well casing.
> These grounding wires MUST conform to minimum radius bends. The key to
> survival here, is that EVERY wire, conduit, pipe or even fiber (fios cables
> almost always have a metallic wire in them, btw), that comes into the house,
> entrance either near the grounding buss bar, or have a substantial grounding
> wire going to the buss.
>
> Another thing to do, if your code allows for it, is to build a halo ground
> in the attic. A halo ground can be internal or external if you don't have to
> access inside the roof. I've seen halo grounds built under eaves. This is
> also bonded to the grounding buss. If properly done, the halo ground will
> protect all internal wiring within the building.
>
> Sewer systems and septic system also need proper entrance (exit?) grounding.
> In fact, this is a real problem in some areas because they can be a
> tremendous source of back-fed lightning. "Yup, it came right up out of the
> toilet!" Septic systems can also be a source of RFI coming back into a
> building. "Honey, why is it that the local radio station plays in the
> shower?" Basically, anything that comes in from the outside gets grounded to
> the buss bar. No exceptions.
>
> So, what does all this mean in the real world?
>
> Lightning will enter a house via one utility service and exit via another.
> Cable TV is very common. The lightning comes in on that cable, blows through
> the television and exits the power grid. You always want a shortest path
> solution for the lightning. And that shortest path should always be to the
> buss bar.
>
> Yet, there is another issue with lightning. That's static buildup. The
> general rule of thumb is that if you can drain off static fast enough,
> you'll never get hit. This is true with airplanes and radio masts. In fact,
> with tall television/radio towers, there are static wicking arrays that can
> be installed at various points on the tower. These are so successful that
> when the tower does get hit, it's at the midpoint on the tower between
> arrays.
>
> The problem you are encountering is that the water-table grounding (through
> water pipes or well casings) is that it is lousy for static grounding. A
> ground-field, however, is excellent for static drainage. One provides an
> absolute ground, the other provides a relative ground. For static grounding,
> you need a relative ground.
>
> AG
>   
-- 
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