Joules of surge protection needed?

  • Thread starter Thread starter sdlomi2
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S

sdlomi2

How much surge protection, in joules, does one actually need for home
computing system, including all-in-one pscf-machine? Are certain brands
preferable to others? TIA, s.
 
JAD said:
OMG here we go again.....................
Click to expand...
I sincerely apologize to you, Tad, if I somehow offended you by asking
this question. But, not knowing, and finding, by searching FIRST, not even
ONE response/post using the word "joule" in this entire newsgroup, I felt I
might utilize the group for its intended use. Felt sure there are
knowledgeable people who might agree to share info on this site.
Again, I'm sorry you felt the need to respond--esp. since I learned very
little from it.
Sincerely, s
 
sdlomi2 said:
How much surge protection, in joules, does one actually need for home
computing system, including all-in-one pscf-machine? Are certain brands
preferable to others? TIA, s.
Click to expand...

There's an article in the latest (August) issue of PCWorld on what they
refer to as "PC Myths". One, in particular, deals with surge suppressors
and, according to PCWorld, refutes the notion that a pricey surge protector
affords more protection that the cheapo models. The article contains a
statement from a presumed expert that the number of joules is *not* a
reliable indication of quality and all that's important is that the device
is UL 1449 rated. All this, of course, seems to fly in the face of
everything we've previously read or heard on this subject. Here's the link
to the article:
http://www.pcworld.com/news/article/0,aid,116572,pg,5,00.asp

Art
 
Art said:
There's an article in the latest (August) issue of PCWorld on what they
refer to as "PC Myths". One, in particular, deals with surge suppressors
and, according to PCWorld, refutes the notion that a pricey surge protector
affords more protection that the cheapo models. The article contains a
statement from a presumed expert that the number of joules is *not* a
reliable indication of quality and all that's important is that the device
is UL 1449 rated. All this, of course, seems to fly in the face of
everything we've previously read or heard on this subject. Here's the link
to the article:
http://www.pcworld.com/news/article/0,aid,116572,pg,5,00.asp

Art
Click to expand...
Thx, Art. Going there now. Have a good day,s
 
100 Joules ZnO varistors with clamping @ 1200 V in the input circuit breaker
cabinet, with an excellent earth ground.
Then 10 Joules ZnO varistors w/ clamping @ 275 V close to the computer to
be protected.
Those varistors shall be connected between mains wires together and between
them and the earth ground.

The telephone socket shall be protected close to the modem and the computer
it is connected to, with 10 Joule ZnO varistors w/ clamping @ 200 to 275 V
as well.

! ! ! Same earth ground as the computer, star connected with it (very
important not to have separate earth wires on separate outlets). And, of
course only one earth wire, the shortest and the straightest as possible.

For the second level protection (close to the computer), it's more important
to guarantee a very low common mode between main & telephone signals vs. the
computer housing connected to the earth wire than to guarantee a very low
earth resistance itself. The input cabinet protection does the job for that.

In case of a cable connected network with distant computers it's far more
tricky.
 
Reread that PC World article with care. UL1449 2nd edition
does not claim a surge protector is effective. UL1449 only
says the protector does not harm humans. Article even says
that. A protector with ineffective components could still be
approved for UL1449 if it does not harm humans. Computer
protection is completely irrelevant to Underwriters Labs.

Surge protectors meet two important criteria. 1) Protector
must be sufficiently sized to remain functional after each
surge. 2) Protector must make a short conductive connection
to common earth ground so as to provide that protection.

Many plug-in protectors are grossly undersized - as
indicated by their joules number. Review manufacturer data
sheets and their charts such as:
http://www.europechemicon.de/ecc01/Products/varistor/va-pulselife-e-010928.pdf
For surges of constant value, then more joules means a
protector will survive more surges. The relationship is
exponential. For example, a plug-in protector rated at 345
joules may actually use as little as 115 joules in protection
and never more than 230 joules. Assume this 115 joules only
survives two or three same size surges. Then the properly
sized 1000 joule 'whole house' protector might survive for
well over 100 such surges.

Notice that numbers are provided in this post. To disagree,
another will have to provide better numbers. That is the
problem with so many posts about MOV protectors. They provide
no numbers - only parrot myths they have heard. Provide here
even were the charts from MOV manufacturers. That is damning
evidence that says joules are important.

BTW, how does a protector fail? It degrades. No protector
properly sized fails by vaporizing or burning. That failure
mode is not even listed on those charts or by manufacturer
data sheets. Vaporization must never happen to a properly
sized protector. IOW notice how many plug-in protectors are
not just undersized. They are grossly undersized - completely
ineffective.

Why did I mention an undersized 345 joules protector? Look
at the joules claimed even on plug-in UPS protectors. It too
is undersized. But then the manufacturer did not even claim
to provide protection from the destructive type of surge. He
only says enough so that those myth purveyors will make wild
assumptions and will recommend that UPS as if it was an
effective surge protector.

Effective protector must not be close to transistors and far
from earth ground. A minimally effective 'whole house'
protector for residential AC electric is about 1000 joules and
50,000 amps. It costs about $1 per protected appliance.
Compare that to how much for the grossly overhyped plug-in
protectors? To be sized equivalent, the plug-in protectors
would be rated 3000 joules.
 
The telephone socket shall be protected close to the modem and the computer
it is connected to, with 10 Joule ZnO varistors w/ clamping @ 200 to 275 V
as well.
Click to expand...
before them also 0,4A fast fuse is nice; I change them at least once
a year, because they blow ...
 
Cited is MOV protectors that are ineffective for too many
reasons. First undersized. Second, too close to transistor
and too far from earth ground. Third, MOVs typically have too
much capacitance for phone lines. Fourth, the voltage levels
are too low as even demanded by FCC and other standards.

MOVs are shunt mode devices. They are not 'protection'.
MOVs are 'protectors' that are only effective if making the
'less than 10 foot' connection to 'protection'. Yes,
'protector' and 'protection' are two difference components of
a surge protection system. A protector that does not make the
'less than 10 foot' connection from utility wire to earth
ground does not provide effective protection. Real world
surge protector manufacturers discuss this extensively.

If protectors adjacent to phone were effective, then those
protectors are already inside the phone. However telco
already installs an effective protector for free and less than
10 feet to the single point earth ground.

A protection system is a building wide system - which is why
system costs typically tens of times less money per protected
appliance.

Another also has a silly idea that fuses stop, block, or
protect from surges. Fuses take milliseconds to blow. Surges
complete their destructive work in microseconds. 300
consecutive surges could destroy a modem 300 times before a
fuse even though about blowing.

Furthermore, if the fuse blew, then the surge would continue
to conduct through plasma inside that fuse. This is why a
fuse has a voltage rating - 32 volts or 250 volts. A surge of
greater than 250 volts would simply continue conducting
through the blown fuse. Again, numbers that demonstrate that
fuse recommendation is not based upon basic electrical
knowledge and the numbers.

Fuse recommendation is bogus for just so many reasons. The
fuse recommendation demonstrates how widespread myths are
promoted about surge protection by the naive. Those with
basic electronics training know the purpose of a fuse is to
protect humans from dangers such as fire AFTER the appliance
is damaged.

Just as in that other post: numbers, manufacturer data, and
basic engineering principles are provided. To challenge what
is posted, that poster better have those numbers and cite
industry professionals. No numbers is how junk scientists
promote their myths.
 
Another also has a silly idea that fuses stop, block, or
protect from surges. Fuses take milliseconds to blow. Surges
complete their destructive work in microseconds. 300
consecutive surges could destroy a modem 300 times before a
fuse even though about blowing.

Furthermore, if the fuse blew, then the surge would continue
to conduct through plasma inside that fuse. This is why a
fuse has a voltage rating - 32 volts or 250 volts. A surge of
greater than 250 volts would simply continue conducting
through the blown fuse. Again, numbers that demonstrate that
fuse recommendation is not based upon basic electrical
knowledge and the numbers.

Fuse recommendation is bogus for just so many reasons. The
fuse recommendation demonstrates how widespread myths are
promoted about surge protection by the naive. Those with
basic electronics training know the purpose of a fuse is to
protect humans from dangers such as fire AFTER the appliance
is damaged.
Click to expand...

miss understood; my surge protector with built in RF filter & phone
line protection had on tel.line side originally 2 fast .5A 250V fuses
followed by 3 MOVs on the output for modem side.
In last years few times saved my Supra modem .... thats a fact!
(last time 3 weeks ago with a close lightning hit !!! - all my
neighbors around had much much much more damage than I did!)

( & yes I know that everything is useless with Direct lightning hit!)
 
The protector installed for free by the telephone company
(properly earthed) had nothing to do with the protection?

Surge protectors are installed for a direct strike to
incoming wires. If nothing can provide direct strike
protection, then your telephone company, connected to overhead
wires everywhere in town, must disconnect their $multi-million
switching computer during thunderstorms? 911 emergency
response operators remove their headsets and leave the room
during thunderstorms? Neither happens because surge
protection, properly installed, protects from direct lightning
strikes without damage. Damage so easily avoided as to be
blamed on human failure.

Direct strike protection is about earthing. Without that
essential earthing, then nothing is going to stop, block, or
absorb surges. Furthermore, modems are typically damaged by
transients on AC mains - not from phone line. Again, many who
said otherwise saw evidence but forgot how electricity works;
therefore speculating erroneous conclusions.

Details will not be provided since those details have been
discussed extensively elsewhere. Fuses do not protect
electronics. If those fuses blew, then surge had already
passed through the electronics. Until you have completely
understood the event (and it must be at the building level),
then you don't know why those fuses blew. We know fuses don't
protect from surges. The numbers are blunt. Surges occur in
microseconds. Fuses take milliseconds to blow. Until one can
explain that reality, then one cannot say a fuse protected
electronics.

Without learning about lightning protection concepts well
proven since the 1930s, then one cannot say "everything is
useless with Direct lightning hit". That statement flies
contrary to what is proven by example in most every town every
year.
 
'joule'

<Re: Are mains surge protectors needed in the UK? 7/14>

you must be using one of those more sophisticated news readers

I'm not OFFENDED , but you will have quite a read
now..............carry on A1's
 
That's true with DC current because the arcing will stops when the current
does.
With the AC current of the mains, the arcing doesn't last more than 10 ms.
The reason is that the sign of the current reverts twice a period.

Some fuses contain silica. Its purpose is to lenghten the arcing path making
it easier to break. Moreover those fuses withstand better the arcing
phenomena without exploding messily.
For electronic uses (mechanically non-protected) fuses and/or fuses
potentially submitted to high short circuits currents, glass fuses are
avoided to the profit of glass/silica filled ones. Big fuses (25 Amps and
more) have a ceramic body filled with silica as well. When I say silica,
it's in fact a powder made of several ingredients which formula is jealously
kept confidential by the manufacturers.


No, the purpose of a fuse is to protect the insulation of the wires of the
electrical installation connected downstream because of overheating in case
of short-circuit. A fuse is always placed upstream the line to be protected.

A fuse is intended to withstand for one hour _without any failure_ 110% of
its rated current.
At 100% it must last forever up to the rated temperature.

Then, the time a fuse needs to blow depends on its thermal constraint (I x I
x t) I square T.
There are slow and fast fuses.

With an identical thermal constraint, a semiconductor will always protect
the fuse because the semiconductor is faster.

As an example: If you want to protect a 230V / 250 W dimmer, you shall use a
fast 1.6 A rated fuse withstanding 15 Amp during 10 ms (cold inrush current
in a bulb) and the associated triac shall be at least 20 Amp peak rated
(nominally 5 A RMS). Big die inside a TO220 package !

line protection had on tel.line side originally 2 fast .5A 250V fuses
followed by 3 MOVs on the output for modem side.
Correct.


( & yes I know that everything is useless with Direct lightning hit!)
Click to expand...

Yes and no, an umbrella put on the hole in the roof may save of the rain
what is placed underneath !
 
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