The following is a quote from a Screwfix catalogue:

"6G 2m high spec surge protection lead, incorporates surge protection for BT
/ Modem supplied with 1 x BT Male to RJ11 connector and 1 x RJ11 to BT
Female connector. LED confirms protection with audible alert warns when unit
is not protected. Filters RFI which can interfere with TV / Audio
Equipment."

What does it mean by alerting when it's not protected? Why would it not be
protected?




a

"al" wrote in message
...
The following is a quote from a Screwfix catalogue:

"6G 2m high spec surge protection lead, incorporates surge protection for
BT
/ Modem supplied with 1 x BT Male to RJ11 connector and 1 x RJ11 to BT
Female connector. LED confirms protection with audible alert warns when
unit
is not protected. Filters RFI which can interfere with TV / Audio
Equipment."

What does it mean by alerting when it's not protected? Why would it not
be
protected?

when it has exploded - which is what they do

On Sun, 23 Nov 2003 19:59:51 -0000, al wrote:

What does it mean by alerting when it's not protected?

When the "protection" isn't working it makes a noise to tell you.

Why would it not be protected?

Because a surge has destroyed the "protection" devices.

--
Cheers
Dave. pam is missing e-mail

"Dave Liquorice" wrote in message
. 1...
On Sun, 23 Nov 2003 19:59:51 -0000, al wrote:

What does it mean by alerting when it's not protected?

When the "protection" isn't working it makes a noise to tell you.

Why would it not be protected?

Because a surge has destroyed the "protection" devices.


So it's pretty much like a fuse - how does it not blow if there's a large
load being driven by it (6 sockets could be powering quite a bit) if it's
delicate enough to stop (and very quickly) a surge in power?



a

"al" wrote in message
news
"Dave Liquorice" wrote in message
. 1...
On Sun, 23 Nov 2003 19:59:51 -0000, al wrote:

What does it mean by alerting when it's not protected?

When the "protection" isn't working it makes a noise to tell you.

Why would it not be protected?

Because a surge has destroyed the "protection" devices.


So it's pretty much like a fuse - how does it not blow if there's a large
load being driven by it (6 sockets could be powering quite a bit) if it's
delicate enough to stop (and very quickly) a surge in power?

Think of them as voltage, rather than current, sensitive fuses

Big ones would be mounted in an armoured case

In article ,
"Chris Oates" none writes:

Think of them as voltage, rather than current, sensitive fuses

Yes - they short-circuit during spikes, absorbing some of the
energy (rest lost in cable impedance). They have a fixed amount
of energy they can absorb before they are destroyed, and each
spike absorbed (except very small ones) uses up some of the
device.

Big ones would be mounted in an armoured case

A large spike which would require more energy to be dissipated
than the device is capable of can result in it exploding, and
they can also fail to a permanent short circuit which might
have the same effect. They can be destroyed by the back-emf
from inductive loads too.

--
Andrew Gabriel

"Andrew Gabriel" wrote in message
news:bpsu56$re6$1@new-
Yes - they short-circuit during spikes, absorbing some of the
energy (rest lost in cable impedance). They have a fixed amount
of energy they can absorb before they are destroyed, and each
spike absorbed (except very small ones) uses up some of the
device.

Big ones would be mounted in an armoured case

A large spike which would require more energy to be dissipated
than the device is capable of can result in it exploding, and
they can also fail to a permanent short circuit which might
have the same effect. They can be destroyed by the back-emf
from inductive loads too.


Thanks all for the advice. It's only £11 from Screwfix, but I'm wondering
if it's really worthwhile or not. Just about to get a new PC in a few
months so the more protection the better. Ideally I'd like to have a UPS to
condition the power and prevent loss from power cuts (battery life not
really important), but I can't find anything that falls into the small,
cheap and quiet category!! I'm used to dealing with 5U monsters in racks to
power my servers - noisey and very expensive!



a

Surge protector that has failed catastrophically is
indicated by the light. But a surge protector that fails
catastrophically was grossly undersized - failure directly
traceable to a human. Other modes of protector failure
exist. For example, a properly sized protector will
eventually degrade - the preferred mode of failure. Indicator
light would never report this failure. No earth ground means
no effective protection. That dedicated earthing wire to
central earth ground must be less than 3 meters. These
failure conditions also are not reported by that indicator
lamp.

IOW it says that light reports failure. It forgets to
mention which type of failure - or why. It forgets to mention
that the light can not report a good protector. All an
indicator can report is that the protector was grossly
undersized for the task - a failure directly traceable to
human installation failure.

Surge protectors do not operate like fuses. Fuses take so
long to open that 300 consecutive transients could pass
through a protector before that fuse even considered blowing.
The fuse is only to protect humans because a surge protector
was grossly undersized - too few joules.

The fuse keeps surge protector from burning down the house -
which is why surge protectors under a pile of papers or behind
a desk can add new dangers. Fuse would not disconnect
appliances from AC power. Just another reason why effective
protectors are located when utilities enter the building, at
the service entrance, and less than 3 meters to central earth
ground.

al wrote:
So it's pretty much like a fuse - how does it not blow if there's
a large load being driven by it (6 sockets could be powering quite
a bit) if it's delicate enough to stop (and very quickly) a surge
in power?

On Sun, 23 Nov 2003 19:27:23 -0500, w_tom wrote:

No earth ground means no effective protection. That dedicated
earthing wire to central earth ground must be less than 3 meters.

Do I detect an American? Not quite UK terminology being used.

The fuse is only to protect humans because a surge protector
was grossly undersized - too few joules.

Fuses don't protect humans, they protect the wiring. RCDs protect
humans.

Just another reason why effective protectors are located when
utilities enter the building, at the service entrance, and less than
3 meters to central earth ground.

Very few places in the UK have such protection installed there doesn't
appear to be the need.

Another reason to suspect a US based poster (that and the Path:...).
Our 230v mains doesn't suffer so badly from sags/spikes when heavy
loads are switched on/off, apart from I^2R losses inductive effects
are from the size of the current flowing not the voltage. Lower
voltage = more current for same power, more current = bigger
spikes/sags.

--
Cheers
Dave. pam is missing e-mail

Fuses protect humans. RCDs protect humans. Neither
provides surge protection.

There is no need for plug-in surge protectors. Urban myth
says that switching on and off an appliance creates a surge.
If true, then we were replacing household appliances every day
before computers existed. At most, switching creates a single
digit voltage spike called 'noise'. Surge protectors remain
inert until the transient exceeds hundreds of volts. Surge
protector do nothing when appliances are powered on and off.

Surges are rare events that occur once every eight years -
and even less so in the UK. But so destructive that surge
protectors are installed. Surges cannot be stopped.
Typically destructive surge must be earthed. Earthed by a
protector that is up to the task (has sufficient joules),
protects everything in the house at a cost that is typically
tens of times less per protected appliance, and that has a
less than 3 meter connection to earth to do as Andrew Gabriel
has described: short circuit that transient to earth ground.

No reason for any building to suffer surge damage.
Effective surge protectors are so cheap and so easily
installed with the less than 3 meter connection to earth.
Plug-in protector don't even claim to provide such necessary
protection.

Dave Liquorice wrote:
...
Fuses don't protect humans, they protect the wiring. RCDs protect
humans.

Just another reason why effective protectors are located when
utilities enter the building, at the service entrance, and less than
3 meters to central earth ground.

Very few places in the UK have such protection installed there doesn't
appear to be the need.

Another reason to suspect a US based poster (that and the Path:...).
Our 230v mains doesn't suffer so badly from sags/spikes when heavy
loads are switched on/off, apart from I^2R losses inductive effects
are from the size of the current flowing not the voltage. Lower
voltage = more current for same power, more current = bigger
spikes/sags.

Dave Liquorice wrote:
On Sun, 23 Nov 2003 19:27:23 -0500, w_tom wrote:

No earth ground means no effective protection. That dedicated
earthing wire to central earth ground must be less than 3 meters.

Do I detect an American? Not quite UK terminology being used.

w_tom appears to be some kind of autoposter that springs up when someone
mentions surge protection. It posts answers roughly related to the question.
Most of what it posts makes sense, it just isn't presented very well.

--
James...
http://www.jameshart.co.uk/

Dave Liquorice wrote:
On Sun, 23 Nov 2003 19:27:23 -0500, w_tom wrote:
snip
Do I detect an American? Not quite UK terminology being used.
snip
w_tom's lectures on the subject are a regular feature of the
sci.electronics.* hierarchy. He does have a point (sometimes) but seems
only interested in this 1 topic.


--
Chris
-----
Spamtrap in force: to email replace 127.0.0.1 with blueyonder.co.uk

"Dave Liquorice" wrote in message
. 1...
Do I detect an American? Not quite UK terminology being used.

Most American's don't have a clue how to measure with real units though and
this guy's quoting metric in his posting. A rare catch indeed if he is form
the US of A!! ;o)



a