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Just to expound a bit:<br>
<br>
The bundling of cables Bob is talking about is because of inductance.
If one wire is energized (even during normal use), the energy can
induce the electrons in a nearby parallel wire to become active,
causing the power surge to "hop" wires, even if they aren't physically
connected to each other. This is the reason for keeping higher risk
lines at least 12 inches from lower risk lines and for crossing each
other perpendicularly. In normal use, this feature can cause electrical
"noise" on nearby wires, reducing signal quality. Normally, this isn't
much of a problem in, for instance, bundled low voltage ethernet cables
at the rack. However, in a power surge situation, bundled wires can be
a way for non-connected wires to further the damage.<br>
<br>
<br>
<pre class="moz-signature" cols="72">-----------------------
Chad Neeper
Senior Systems Engineer
Level 9 Networks
740-548-8070 (voice)
866-214-6607 (fax)
-- Full LAN/WAN consulting services --
-- Specialized in libraries and schools --</pre>
<br>
<br>
Bob Neeper wrote:
<blockquote cite="mid:4A65C915.6010408@oplin.org" type="cite">
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Since Chad mentioned my name...Here 's a few thoughts. Some duplicates
of Chad's.<br>
<br>
We did have a few hits and lost a couple of PC's, telephone module, etc<br>
Also some electronics in the main power distribution panel when a bird
fried on the pole.<br>
<br>
Point of interest.<br>
A static spark from your finger to a doorknob can be over 6,000volts.<br>
It can easily destroy or damage an electronic chip, depending on
contact.<br>
Lightning can be over 300 kilovolts for a few milliseconds.<br>
<br>
With a direct hit it probably won't matter too much what you have.<br>
Mettler-Toledo sold many truck scale protection kits in lightning prone
areas and still lost load cells.<br>
(Load cells generate low voltage signals representing weight changes.)<br>
<br>
Always keep your insurance paid up !<br>
Make certain the coverage is correct !<br>
Keep your inventory list up to date and handy!<br>
<br>
M-T headquarters has a nice setup for their workstations.<br>
Each one has it's own special surge protected.power distribution box.<br>
Some outlets were for printers etc. Ethernet and phone lines too if I
remember correctly.<br>
Special outlets for the PC and monitor went straight to a battery
backup system.<br>
It had a BIG battery bank and an outside emergency generator.<br>
<br>
Fiber optic cables are very nice, they won't conduct surges.<br>
Just having an Ethernet cable close to power cables could knock out a
NIC.<br>
As Ethernet cables are usually bundled from the rack you could easily
take out every attached NIC.<br>
Racks can come with built in surge protection, for a few dollars more.<br>
APC ProtectNet can be used at the PC<br>
<br>
M-T always specified low voltage cables to be at least a foot away from
AC cables.<br>
Never directly next to a power cable and only cross at right angles.<br>
<br>
So don't tie wrap Ethernet cables with the AC power cords because it
makes a neat bundle.<br>
Keep the mouse, k/b, and monitor signal cable separate too.<br>
Definitely don't tie anything to the surge protector power cable!<br>
<br>
Have the power company insure there is lightning protection at the pole
transformer.<br>
Add something similar to the main power distribution panel in the
building.<br>
<br>
Don't forget to protect the T1 (or whatever) cable and the alarm
system phone line.<br>
Maybe even consider 2 inline protectors.<br>
An alarm installer saved his unit this way. The first one blew off the
wall.<br>
The second died to save his system.<br>
<br>
Especially protect power and Ethernet outlets on outside walls.<br>
We lost a NIC and the a single port on the switch at the other end.<br>
And the hit was waaaayy over there somewhere.<br>
<br>
Bob<br>
<br>
<br>
<pre class="moz-signature" cols="72">R. W. (Bob) Neeper Cell: (740)-407-3572
Community Library
44 Burrer Dr.
Sunbury, Oh 43074
Tel: (740)-965-3901</pre>
<br>
<br>
Chad Neeper wrote:
<blockquote cite="mid:4A6525D7.9060407@level9networks.com" type="cite">Excellent
questions! With the exception of the server room and/or wiring closets:
<br>
<br>
Speaking from my own experience and observations, I'd suggest not
paying particular attention to having isolated grounds or even
necessarily isolated circuits for your general use patron and staff
computers. Naturally, however, DO pay attention to the estimated load
on each circuit. If it's intended to have a large number of workstation
at a particular location (a lab, for instance), then of course you'll
need to figure out how many computers you can have on one circuit and
then have enough circuits run to keep your load WELL below the maximum
loads. Same goes for anywhere that you know you are going to have
devices (computer or otherwise) that draw power. This is an interesting
read I stumbled upon with a quick Google search about IG systems and
how they might NOT work as you might think. I suppose this could affect
its use in a server room as well and worth investigating further,
probably best with a full-blooded electrical/electronics engineer: <br>
<br>
<a moz-do-not-send="true" class="moz-txt-link-freetext"
href="http://ecmweb.com/mag/electric_demystifying_isolated_grounded/index.html">http://ecmweb.com/mag/electric_demystifying_isolated_grounded/index.html</a>
<br>
<br>
Definitely food for thought, especially when you factor in the added
costs of an IG system. <br>
<br>
As for whole-building surge suppression, it would seem that a
whole-building surge suppressor is a good way to go, but it would be
wise not to rely on it completely. You should still use point-of-use
surge suppressors to protect your more valuable items...computers,
electronics, all the normal stuff, etc. You'll have to work with your
general/electrical contractor to work out if you want circuit-based
suppression or whole-building and to find out what options are
available to you. While I don't know what commercial-grade
whole-building surge suppressors are available, I suspect that you just
might find the cost to be perfectly acceptable as a one-time cost
insurance policy. (If lightning were to strike within 1/2 mile from the
library, how many devices are plugged in 24/7 that might get fried or
degraded. When the power goes out, or more specifically, when it comes
back on again and "yo-yos" as it often will...how many devices are
having their lifespans degraded and what is the cost to replace/repair
those items? Think refrigerator, furnace control system, dishwasher,
alarm system...anything electronic...) As for how common it is...Well,
amongst my own library clients, not a single one currently has a
whole-building or whole-circuit surge suppression. I can quickly name
several clients that might have benefited from it, however! <br>
<br>
Also consider the fact that your phone system is expensive/important
and that power surges can travel just as readily into your library via
a telephone line. If you protect the lines at the point they enter your
building you just might save yourself a major expense and headache down
the road. Again...I have several libraries that pop to mind here
too...and, at the time, those each had only 3-4 analog phone lines that
could easily have been protected with off-the-shelf protection just
before they entered the multi-thousand dollar phone systems...for under
$150 total. Those were hard-earned lessons! Actually, I think Bob
Neeper might have been around for one of these incidents. He can attest
to this one! <br>
<br>
Same with network data cables...You can get surge suppressed rack-mount
data ports to replace your "normal" rack-mount ports. But last time I
looked, they weren't particularly cheap. Unless you have a smallish
number of computers, you might be limited to protecting select
computers. Seven or eight years ago Hurt/Battelle Memorial Library was
hit with a direct lightning strike. At the time they had about 26
six(ish)-month old computers. All but four or five had immediate damage
to the network cards, with the mainboards failing completely shortly
after. Having dutifully protected every computer with good surge
suppressors, none of the power supplies failed during the period the
computers remained in sporadic use. Thank goodness for good
insurance!!! <br>
<br>
Good luck! <br>
Chad <br>
<br>
<br>
----------------------- <br>
Chad Neeper <br>
Senior Systems Engineer <br>
<br>
Level 9 Networks <br>
740-548-8070 (voice) <br>
866-214-6607 (fax) <br>
<br>
-- Full LAN/WAN consulting services -- <br>
-- Specialized in libraries and schools -- <br>
<br>
<br>
<br>
Phil Shirley wrote: <br>
<blockquote type="cite">Could you help me with these two questions
about electrical systems for <br>
computer equipment? We're planning a renovation of the main part of
our <br>
library. <br>
<br>
1. Should we have electrical circuits with an isolated ground, or at <br>
least separate electrical circuits, for our computer equipment? (I'm
talking about workstations around the library, as well as everything in
our server room.) I assume the answer is yes, but early drafts of the
electrical plans do not have anything like this. One of the EEs told
me that often, instead of having a true isolated ground setup, many
places will simply have separate circuits designated for computer
equipment (with orange outlets); supposedly, the ground noise that's
caused by a sweeper or something doesn't travel far enough to be of
concern to a computer on a separate circuit. A little bit of searching
suggests that maybe a true isolated ground system is not necessary for
most modern computer equipment. <br>
<br>
2. Is it common to have surge protection built into the electrical
system, as opposed to plugging surge protectors into the wall and
plugging computers into those? I'm told that it's possible to have
surge protection built into the electrical system in any of several
places, but I don't know if it's cost-efficient for most organizations.
<br>
<br>
Phil <br>
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