[mythtv-users] Protecting against power surges

Stephen P. Villano stephen.p.villano at gmail.com
Sat Jan 3 03:08:22 UTC 2015


On 1/2/15 3:31 PM, Rob wrote:
> Does anyone here have good recommendations for how to properly (if
> there is such a way) protect their gear from electrical surges? 
> Depending on the environment, surges can enter the network via the AC
> lines or networking lines.  I've traditionally relied on metal oxide
> varistors (MOV), but began reading up on them lately and am feeling
> less comfortable with the idea of a device degrading and silently
> failing.  Is there any reliable protection which doesn't involve
> air-gapping the networking lines and running the protected electronics
> behind series-mode surge protectors?
>
I my own experience, MOV devices rarely silently fail. Indeed, the
failure, if not contained properly by the case is a spectacularly
incendiary event.

Like every other protection strategy, one performs a risk appraisal. Are
you in an area prone to rapid geological current changes? Do you get a
lot of thunderstorms? Do you have "dirty" power (loads of spikes, surges
and sags)? What is the value of the equipment you are protecting? Is
your home wired to code? Do you have a true earth ground driven into the
ground near your electrical service entry?

The list of questions can go on at some length and level of protection
would then be inquired upon.
For, every technology has its limits. I've observed industrial plant
electrical surge protectors blown off of the wall and breaker boxes
requiring bus replacements due to carbon tracks caused by a direct power
line lightning strike at the pole that held the wire leading to a home
(the owner was an industrial electrician, hence the expensive surge
protector).
My own personal risk exposure is a bit lower, as I had terminated cable
service in favor of fiber optic delivered cable/telephone service. That
leaves geological currents, which are not that large in my particular
area, surges and the occasional thunderstorm.
For my servers and primary network switch (a Cisco Catalyst 4006
switch), I insured proper wiring practices were utilized for the power
lines going to that point, then ran power to a Tripp Lite Isobar surge
protector (it's MOV based, has a pi filter circuit inline as well), then
to an online UPS.
In other areas I've lived, more protection was required.
In industrial settings, such as data centers, well, that's an entire
profession in that context. Large plants create special requirements due
to induced voltages in various conductors, geomagnetic storm protection
for some areas, ground current differential mitigation, load switching
transients and more.




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