On Jul 20, 9:06 am, westom<[email protected]> wrote:
On Jul 19, 2:45 pm, Doug Brown<[email protected]> wrote:
. We've lost 3 computers in the last 4 years tolightningand around
5 dsl filters have been fried outside of that. One of them actually blew
up and plastic shrapnel hit me in the head.
The best information on surges and surge protection I have seen is at:
<http://www.mikeholt.com/files/PDF/
LightningGuide_FINALpublishedversion_May051.pdf>
- "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 major organization of electrical and electronic engineers in the
US).
And also:
<http://www.nist.gov/public_affairs/practiceguides/surgesfnl.pdf>
- "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.
The phone line should be protected by the phone company at the point
of entry to the building. The voltage on each phone wire is clamped
(limited) to a ground terminal. There shouldn't be damaging voltage
between the phone wires past the entrance protector. If you are losing
filters, I would question whether this protection, furnished by the
phone company, is effective. I would ask them to replace it.
There is a ground wire from this entrance protector to the earthing
system. For good protection, the entrance protector should be near the
power service and there should be a *short* ground wire to the
earthing at the power service. The NIST guide, using US insurance
information, suggests that most equipment damage is from high voltage
between power and phone/cable wires. A short ground wire minimizes the
voltage between power and phone wires. The IEEE surge guide has an
illustration of a wire that is too long starting pdf page 40.
If you unplug power wires you also need to unplug phone wires to the
same equipment.
For over 100 years, buildings that can never suffer
damage have been using the 'whole house' protector. So that direct
lightning strikes do not 'explode' anything inside the house.
Service panel suppressors are a good idea.
But from the NIST guide:
"Q - Will a surge protector installed at the service entrance be
sufficient for the whole house?
A - There are two answers to than question: Yes for one-link
appliances [electronic equipment], No for two-link appliances
[equipment connected to power AND phone or cable or....]. Since most
homes today have some kind of two-link appliances, the prudent answer
to the question would be NO - but that does not mean that a surge
protector installed at the service entrance is useless."
That is because service panel suppressors do not prevent high voltages
from developing between power and phone (cable, ...) wires.
If surges are coming in on the phone wires, a service panel suppressor
won't help (but it is definitely good for surges coming in on power
wires).
Cable TV is earthed directly - only by a wire.
A wire that connects short (ie 'less than10 feet') to earth.
A ground block should be installed at the entrance of the cable to the
building and, like phone, there should be a short ground wire from the
ground block to the earthing at the power service. The ground block
earths the cable shield.
But the IEEE guide notes that the voltage between cable center
conductor and shield is limited by the breakdown of F-connectors which
is typically 2-4,000V. The guide notes that connected equipment can be
damaged at those voltages. (Plug-in suppressors are likely to clamp
the voltage to a reasonable level.)
Either you earth every incoming AC wire - either directly or via a
'whole house' protector. Or you have no surge protection. No
protection even if you have 1000 plug-in protectors inside.
More responsible manufacturers sell effective solutions. Companies
such as General Electric, Leviton, Square D, Keison, Intermatic,
Siemens, Polyphaser, ABB, etc.
All of these "responsible" manufacturers except Square D and
Polyphaser also sell plug-in suppressors (which westom claims don't
work).
Square D for its ‘best’ service panel suppressor says "electronic
equipment may need additional protection by installing plug-in [surge
suppressor] devices at the point of use."
All grounds remains separate until all meet
at the single point earthing electrode.
If you have strong surge current to earth, the "ground" at the house
can rise thousands of volts above "absolute" earth potential. Much of
the protection is that power and phone and cable wires rise together.
To do that you need short ground wires from the phone and cable
entrance protectors to the earthing system *at* the power service.
If you are using plug-in suppressors, 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. The IEEE surge guide has 2
examples of this at the end. If correctly connected, a plug-in
suppressor with high ratings should protect what is connected
downstream.
Service panel and plug-in suppressors should have a UL1449 listing. So
should UPSs that you depend on for surge protection.
--
bud--
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06:36:00
