** Reply to message from "Jeffrey Race" <os2-wireless_users@2rosenthals.com> on
Thu, 11 Jun 2009 21:34:54 +0700
> Further to previous msg I'd appreciate recommendations about
> coax and ethernet protective devices (clamping devices) to
> protect my equipment so not destroyed a second time
> jeffrey race
This could get to be a long discussion - lightning problems pre-date
electronics by centuries and the first practical lightning arrestors were the
ones Benjamin Franklin devised in the late 1700s. First, don't even sweat the
internal wiring like coax until you REALLY solve the external threat: your
power lines. Those expose you for a radius of miles in some cases. Next, look
at the building itself. Such things as aerials, chimneys, and metal gutters -
ground those really well. You might even want to install a specific lightning
rod and grounding mesh if your area is prone to a lot of lightning. As part of
this, verify and test your internal power ground - I see too darned many of
those 3rd wire power grounds that are worse than useless. Once you have done
that, you can proceed to reduce the risks elsewhere but until you provide a
reasonable shell around the internal equipment you are really just wasting time
and money.
When you have snubbed the environmental exposures the next step is the power
system. Virtually all the damage I've dealt with in nearly 40 years of site
installations entered the system through either the power line or external
communications lines (telephone, TV cable or antennae, etc.). While structural
strikes cause some electronic damage, you usually have bigger problems to deal
with than electronics when they hit. The most common point of entry is the ac
power line. Several companies make gas tube protectors which will shunt up to
several kilojoules. These are sturdy glass and metal tubes with a gap in an
inert gas (typically argon) which will arc to ground with a breakover voltage
of 150 volts or so. One or more of those each lead of the power line followed
by an isolation transformer is pretty much the best you can do. Those wall
socket mounted to power strip jobs are useful for small glitches but they are
really too puny to give major protection.
As a compromise, I use a relatively small gas tube/inductor coil setup ( the
manufacturer that made mine is out of business now) followed by a hefty UPS for
the main station with smaller UPS units for the other clusters of gear. That
has served through several nearby lightning strikes (Colorado gets more than
its' share!) and a single UPS is a lot cheaper to replace than the whole
system. Note: GROUNDING IS CRITICAL!!!
For the phone and TV lines, I put my own gas tube shunt (minus the inductors)
across the input lines and to ground from each side. I follow that with
smaller MOV type shunts at the place my equipment plugs in but I don't even try
to isolate the internal wiring. The only time I've seen problems with that was
in a metal building where the internal leads were installed near the roof or
walls and a strike would arc between the metal building and the wires. I can't
recall ever losing equipment to a direct strike on internal wiring in a wood
frame structure - it always got zapped either by proximity to some externally
connected metal part or by over powering the protection on the input leads from
outside.
All the years of experience point to one primary target: GROUND. I can't say
it enough for that is the single most important component of any protection
scheme. If you have doubts, simply run a heavy copper lead - 8 ga. or so -
between the third wire "ground " lead and a nearby cold water pipe (assuming
metal pipes - plastic pipes are useless) every place you can. That will do as
much to protect you as most of the cheap surge suppressors on the market and
without a good ground even those are worse than useless.
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