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Posted by bud-- on July 12, 2007, 10:22 am
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For reliable information on surges and surge protection try:
http://omegaps.com/Lightning%20Guide_FINALpublishedversion_May051.pdf
- the title is "How to protect your house and its contents from
lightning: IEEE guide for surge protection of equipment connected to
AC power and communication circuits" published by the IEEE in 2005
(the IEEE is the dominant organization of electrical and electronic
engineers in the US).
And:
http://www.nist.gov/public_affairs/practiceguides/surgesfnl.pdf
- this is the "NIST recommended practice guide: Surges Happen!: how to
protect the appliances in your home" published by the US National
Institute of Standards and Technology in 2001
The IEEE guide is aimed at those with some technical background. The
NIST guide is aimed at the unwashed masses.
>
> For example, Leythos suggests a surge entered on a phone line?
> Why? Telco earths an effective 'whole house' type protector on every
> phone line - for free. How would a surge enter on phone line? First
> lightning must bypass AC electric lines to get to phone line. Then it
> must ignore earthing from a telco provided protector. Finally, to
> damage a computer, first, it forms a conducting circuit to earth.
> Incoming on telephone line, through modem, through motherboard, then
> out to earth ground via table top, AC electric wire, etc. Right out
> of primary school science - first a complete circuit must exist before
> electricity (a surge) can flow.
According to NIST guide, US insurance information indicates equipment
most frequently damaged by lightning is
computers with a modem connection
TVs, VCRs and similar equipment (presumably with cable TV
connections).
All can be damaged by high voltages between power and signal wires.
An example of how a surge can enter on a signal wire is illustrated in
the IEEE guide starting pdf page 40. A surge comes in on a CATV service.
The CATV entry block is not connected with a short ground wire to the
power service earthing wire at the power service. Surge current on the
long ground wire creates a high voltage between power and CATV wires
causing damage. The same can happen with the phone entry. Entry
protection blocks should be adjacent to the power service with short
interconnect wires. (If not the IEEE guide says "the only effective way
of protecting the equipment is to use a multiport protector.")
>
> An effective protector is simply a connecting device to earth
> ground. It does not stop or absorb what three miles of sky could not
> - as Leythos claims. An effective 'whole house' protector earths
> direct strikes to computers as Ben Franklin's lightning rod earthed
> direct strikes to church steeples. Computers are damaged by direct
> lightning strikes. If that surge current is not earthed before
> entering the building, then it will find destructive paths through
> household appliances.
>
> Whether a lightning rod or protector - it is only a connecting
> device to earth ground. Protection is earth ground. No earth ground
> (ie. that UPS) means no effective protection. Those who never learned
> how electricity works will deny all this.
The 6 EEs that wrote the IEEE and NIST guides deny all this, as applied
to plug-in suppressors. And no one says suppressors "stop" or "absorb".
w_ has a religious belief (immune from challenge) that surge protection
must use earthing. Thus in his view plug-in suppressors (which are not
well earthed) can not possibly work. The IEEE guide explains plug-in
suppressors work by CLAMPING the voltage on all wires (signal and power)
to the common ground at the suppressor. Plug-in suppressors do not work
primarily by earthing. The guide explains earthing occurs elsewhere.
Note that all interconnected equipment needs to be connected to the same
plug-in suppressor, or interconnecting wires need to go through the
suppressor. External connections, like phone, also need to go through
the suppressor. Connecting all wiring through the suppressor prevents
damaging voltages between power and signal wires. These multiport
suppressors are described in the IEEE guide. [Leythos was correct that
the printer needed to connect to the UPS. I read his post as connecting
the printer to the UPS surge protected outlet, not the UPS outlet.]
Plug-in suppressor ratings range from junk to very high. UPSs can have
the same protection as plug-in suppressors, but suppression ratings are
probably not as high as a good plug-in suppressor. Any suppressor in the
US should be listed under UL1449.
--
bud--
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