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comp.dcom.xdsl NewsGroup Archives: Re: ADSL Surge Protection

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From: w_tom@my-deja.com
Date: Fri Sep 15 2000 - 22:57:08 PDT


  It is called basic circuit theory.  Ohms law.  Capacitors.
Inductance.  Electricity requires a complete circuit.  If not
knowledgeable of the basics, then one cannot recommend any surge
protection.

 Where does the PTEL2 connect to earth ground?  A connection to
electric socket ground is not earth ground.  That electric socket
typically connected to a fuse box by 50' of 14 AWG wire has 180 ohms
reactive impedance between the surge protector and earth ground.  IOW
using basic circuit theory, the PTEL would we all but totally
ungrounded.

  A 100 Amp surge would charge the PTEL2 to 18,000 volts because earth
ground is all but not existant.

  That same 14 AWG wire might have less than 1 ohm resistance - good
for human safety.  But lightning has different electrical
characteristics.  A surge protection device must be less than 10 feet
from a good, common earth ground.

  Properly installed phone lines had effective surge protection for
many decades.  Surges typically don't come from phone lines.  Modem and
answering machines are destroyed by surges from the electric service.
Those surges find earth ground on the telephone line - via answering
machine and modem.

  A surge must come in and go out to damage the appliance - from basic
circuit theory.  An effective surge protector shunts (shorts or
diverts) that surge at the service entrance and far from transistors -
again for reasons in basic circuit theory.

  Telco installed surge protector uses concepts of 'whole house' surge
protection.  Every incoming service (even CATV) must connect to a surge
protector at the service entrance.  Each surge protector connects to a
good, earth ground using a short (less than 10 feet), direct,
independent connection.  A surge protector is only as good as its earth
ground - a basic fundamental from the 1930s.


In article <p4Dw5.117$3H3.59665@news.pacbell.net>,
  "Marc Kupper" <Marc.Kupper~NO~@~SPAM~Allin.com> wrote:
> <w_tom@my-deja.com> wrote in message
news:8put2n$ljf$1@nnrp1.deja.com...
>>   If lightning were that dangerous, then all operators would
>>remove their headsets and stop working until the storm has passed.
>>(snip)
>> The weak link in a surge protection system is the human who
>>does not know basic fundamentals demonstrated since the 1930s.
>>We still wire homes as if the transistor did not exist - because
>>so many humans worship the words on a plug-in surge protector or
>>UPS box rather than learn some basic circuit theory.  A surge
>>protector is only as good as its earth ground - something all
>>but missing on plug-in surge protectors and in this thread.
>
> Ok, I'd like to hear some specific recomendations on what
>people should be doing.  "learn some basic circuit theory" is
>a bit vague in my book. :-)
>
> Also FYI, many of the phone line protectors, such as the
>PTEL2, do have earth grounding cables.


Sent via Deja.com http://www.deja.com/
Before you buy.


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