w_tom wrote:
On Nov 14, 1:31 pm, N8N wrote:
Anyone have any opinions, or can point me to a review, of a whole
house TVSS/surge protector that they think is the best? I've
currently got a Siemens breaker panel with the TVSS double breaker in
it, but the LED indicates that the surge protection on one pole is
weak and/or has failed. It's less than a year old so I'd like to
replace it with something better. I see products available from Ditek
and Panamax that just mount to the side of the breaker box, are these
worthwhile? anything else I should be looking at? Is any product
significantly better than any other?
The best information on surges and surge protection I have seen is at:
http://omegaps.com/Lightning%20Guide...ion_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.
And also:
http://www.nist.gov/public_affairs/p.../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 IEEE guide has recommendations for power service suppressor ratings.
Joules is the ballpark measurement of protector's life expectancy.
Any 'whole house' protector should be at least 1000 joules 50,000
amps. Most direct lightning strikes average 20,000 amps. As joules
increase, a protector's life expectancy increases exponentially AND
more surge is diverted to earth.
Note that if the “average” 20,000A stroke hits a high voltage power line
it will flow in all directions including utility surge arrestors and not
much of it will reach your house.
There is a paper (I could find the internet reference if interested)
that analyzes a near worst case of a strike to the utility pole behind
your house resulting in 30,000A on the neutral to your house. ‘Average’
likelihood of an event worse than this is 1 in 8000 years (higher on a
mountaintop in central Florida – if you can find one; lower in a forest
in Nevada, if you can find one). Of the 30,000A, what remains on the
neutral is directly earthed by the neutral-ground bond required in US
services (also Canada?). Some is coupled to the hot wires for a likely
worst case current of 10,000A (which you are unlikely to never see).
High device current rating is related to high energy rating which, as w_
says, is directly related to the life of the device.
All protectors must be earthed 'less than 10 feet' to the same
earthing electrode. That means the 'whole house' protector, installed
free by the telco, also must be grounded to the same electrode.
More important than the same electrode is that the phone, cable, ...
entrance protector ‘ground’ connect with *short* wires to the earthing
wire at the power service. Even if you have a good impedance to ground
of 10 ohms and a modest 1,000A surge earth current, the voltage from the
power ‘ground’ to `absolute' earth is 10,000V. You want the ‘ground’
for power and phone and cable to rise together. That requires short
interconnects. Francois Martzloff, the NIST guru on surges and author of
the NIST guide, has written "the impedance of the grounding system to
`true earth' is far less important than the integrity of the bonding of
the various parts of the grounding system." The IEEE guide has an
example of too long a ‘ground’ wire starting pdf page 40.
Some service panel suppressors have ports to wire the phone and cable
*through*.
(The service panel ‘ground’ is the magic point because the neutral and
‘ground’ are tied together at that point in US services - it is the
ground reference point of the power service.)
The NIST guide cites US insurance information that indicates equipment
most likely to be damaged by lightning is computers with modem
connection and TV related equipment - presumably with cable connection.
All can be damaged by voltage between signal and power wires.
Cable
TV wire needs no protector to have 'whole house' protection.
Doesn’t need a protector? The IEEE guide says “there is no requirement
to limit the voltage developed between the core and the sheath. .... The
only voltage limit is the breakdown of the F connectors, typically ~2–4
kV.” And "there is obviously the possibility of damage to TV tuners and
cable modems from the very high voltages that can be developed,
especially from nearby lightning."
--
bud--