Geopelia wrote:
> The two lights that are always on are still there. (A yellow and an orange).
> It was a very expensive surge box, as recommended by the computer shop.
> Hubby says he could have got one a lot cheaper from Bunnings, but I don't
> think that is the same kind.
Those lights only indicate failure when the failure is a type that
must never happen. Meanwhile, other failure modes remain unreported.
A protector must earth direct transients and remain effective.
However, to sell protectors on myths, then many are intentionally
undersized so that a homeowner will assume, "The protector sacrificed
itself to save my computer". Such protectors failed prematurely AND
left protection inside the appliance to protect electronics. Some
surges too small to harm a computer will still destroy an undersized
plug-in protector. It promotes more sales.
Protectors are essentially a maybe $3 power strip with some $0.10
parts inside. Active component is called an MOV. MOVs must never fail
by vaporizing or shorting. An MOV manufacturer demonstrates how MOVs
work:
> The change of Vb shall be measured after the impulse ...
> is applies 10,000 times continuously with the interval of
> tens seconds at room temperature.
Does this sound like a device intended to fail on the first surge?
Does this sound like a device intended to absorb the entire energy of a
surge? Of course not. That is not what shunt mode protectors do. As
Vb changes, then the MOV degrades. It must not vaporize as so often
happens to promote grossly undersized plug-in protectors. It must
degrade.
Effective shunt mode protectors do same a Ben Franklin demonstrated
in 1752. Lightning will seek earth ground destructively via a church
steeple. Franklin simply gave lightning a non-destructive path to
earth. We don't stop or absorb surges. We shunt them to earth on
paths that are not destrutive. No shunt to earth and typically
destructive surges will find earth ground via household appliances.
Shunt mode protectors are effective with a less than 3 meter connection
to earth.
Down at the telephone Central Office is how effective protection
works - as was standard even long before WWII. Every incoming wire on
every cable connects to earth ground. A connection made by hard wire
or made via a 'whole house' type protector. Shunt mode protectors
earth. A shunt mode protector without earthing is not effective.
So instead we take that $3 power strip, add some $0.10 components,
and hype it as a miracle solution to the naive. Review for yourself.
Where in its numerical specs does that plug-in protector even claim
protection from each type of transient? It does not. Why do its own
specs forget to claim protection from the typically destructive
transient?
Two important numbers are joules and let-through voltage. Joules
defines a protector's life expectancy. A number used in charts to
determine number of transients and size of those transients before a
protector degrades. Not fail. Properly sized protectors always remain
functional and only degrade. A grossly undersized protector (too few
joules) is destroyed by only one surge - ineffective.
Look for the let-through or threshold voltage on that protector. For
240 VAC, thern may be maybe 500+ volts. Any 'noise' created by
household appliances (refrigerator, vacumm cleaner, etc) is completely
ignored by a protector. Protection inside all appliances makes that
'noise' irrelevant. The protector is for a transient that might
otherwise overwhelm internal appliance protection. Therefore every
incoming utility wire (cable TV, telephone, AC electric) must be
earthed, less than 3 meters, to a common earth ground. Telephone and
AC electric require protectors to make that earthing connection. Cable
TV makes that earthing connection using ground block and hardwire. If
all incoming utilities are properly earthed, then a transient that may
overwhelm internal appliance protection is made irrelevant.
This applies to all incoming utilities - overhead or underground.
What makes a shunt mode protector effective is earthing. No earth
ground means no effective protection. So plug-in protector don't even
discuss earthing - a hope you don't learn about the most critical
component in a protection system: single point earth ground.
Meanwhile look what happens to those lights on a protector where all
MOVs are removed. The lights remain on because those lights actually
do not report a protector as effective. Those lights will only report
one type of failure. If that one type failure occurs, then the
protector was grossly undersized - just another reason why the plug-in
protector was ineffective:
http://www.zerosurge.com/HTML/movs.html
Protector was completely destroyed - "All 6 MOVs removed" - and still
those lights say protector is OK. Effective protectors, instead, earth
transients so that protection inside an appliance is not overwhelmed.
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