 |
Search Sci.Electronics.Basics |
|
|
|
|
|
|
 |
|
|
Sci.Electronics.Basics -> Easy Question - I Hope
There are 5 messages in this thread.
You are currently looking at messages 1 to 5.
|
Author: PinkFloyd43Date: 10:28 11-05-08
|
|
First finally dropped the $$ on the big screen and as I live
in TX, which typically has huge thunderstorms this time of
year, when at home I unplug everything I value. I want to
protect the TV with one of the power strips that advertise
protection against this type of thing? Any opinions on
what works and what is pure marketing BS, I do realize
a direct strike means pretty much everything is done with,
as what happened to a neighbor last year!
Thanks!
|
|
|
|
Author: JeffMDate: 15:33 11-05-08
|
|
PinkFloyd43 wrote:
>[...]I live in TX, which typically has huge thunderstorms this time of year,
>[...]
>I do realize a direct strike means pretty much everything is done with,
>
Yup.
(In the future, have your Subject line describe your problem.)
>[...]I want to protect the TV with one of the power strips
>that advertise protection against this type of thing?[...]
>
The varistor-based devices can improve your odds
but the arithmetic is just overwhelming--even for a near-miss.
http://www.google.com/search?q=cache:3kdkwT-WISgJ:en.wikipedia.org/wiki/Lightning+inc+or
g+three.million.volts.per.meter+*-gigavolt+gigajoules+1000.ft&strip=1#Properties_of_li
ghtning
>as what happened to a neighbor last year!
>
The closer the strike, the greater the damage.
The best protection is to NOT have the highest objects in the skyline
on YOUR property.
You reminded me of the old joke
http://www.google.com/search?q=I.only.have.to.out-run.you
|
|
|
|
Author: bud--Date: 12:11 12-05-08
|
|
PinkFloyd43 wrote:
> First finally dropped the $$ on the big screen and as I live
> in TX, which typically has huge thunderstorms this time of
> year, when at home I unplug everything I value. I want to
> protect the TV with one of the power strips that advertise
> protection against this type of thing? Any opinions on
> what works and what is pure marketing BS, I do realize
> a direct strike means pretty much everything is done with,
> as what happened to a neighbor last year!
>
The best information on 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.
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.
If you use a plug-in suppressor, get a major brand with high values.
And note that all interconnected equipment must to be connected to the
same plug-in suppressor, or interconnecting wires need to go through the
suppressor. External connections, like cable, also must go through the
suppressor. Connecting all wiring through the suppressor prevents
damaging voltages between power and signal wires. These multiport
suppressors are described in both guides.
A plug-in suppressor works primarily by clamping the voltage between all
wires (power and signal) to the common ground at the suppressor. The
voltage between the wires going to the TV is safe for the TV.
A service panel suppressor is a good idea. If there is none, a very
strong surge will cause arc-over in the panel at about 6000V which dumps
most of the surge energy to earth. If you have a plug-in suppressor, the
impedance of the branch circuit to surges (which are basically high
frequency) greatly limits the current, and thus energy, that can reach
the suppressor.
Direct strikes to a house require lightning rods for protection. But
direct strikes are really uncommon unless you really exposed.
--
bud--
|
|
|
|
Author: w_tomDate: 15:06 12-05-08
|
|
On May 11, 10:28 am, PinkFloyd43 <pinkFloy...@hotmail.com> wrote:
> First finally dropped the $$ on the big screen and as I live
> in TX, which typically has huge thunderstorms this time of
> year, when at home I unplug everything I value. I want to
> protect the TV with one of the power strips that advertiseprotectionagains=
t this type of thing? Any opinions on
> what works and what is pure marketing BS, I do realize
> a direct strike means pretty much everything is done with,
> as what happened to a neighbor last year!
Get the long list of numeric specs for that "it provides complete
protection" power strip. It will list each type of surge AND
protection from each type of surge.
Take a $3 power strip. Add some $0.10 parts. Sell that protector
for $25 or $150. Claim to protect from some ambiguous thing called a
surge. Provide no numbers that make protection claims. The naive
will use word association instead of science; 'surge protector' sounds
like 'surge protection'. The power strip protector never does make
those protection claims. Show me the numbers.
What must a power strip protector do to provide surge protection?
It will stop what three miles of sky could not stop? That silly
little part will absorb the entire surge energy? Of course not.
Obviously your telco must disconnect during thunderstorms to protect
their $multi-million computer. That computer connected to overhead
wires all over town never disconnects? Correct. They may suffer 100
surges during every thunderstorm - and no damage. They do this by not
using plug-in protectors.
Protection is by doing what Ben Franklin did in 1752. Lightning
seeks earth ground. Lightning used conductive wooden church steeples
to obtain earth. Effective protection diverted lightning to earth
using something more conductive. Same protection applies to your
telco and to your big screen TV.
Lightning strikes wires out on the street. What is a good path to
earth? Incoming on your AC mains, through your TV, and out to earth.
Effective protection earths before lightning can enter your building.
Effective protection means everything in your building is protected.
Effective protector is what your telco does - put the protector where
lightning enters the building AND make that earthing connection short
(ie less than 10 feet).
Again, what does lightning seek? What provides protection? Where
lightning energy dissipated harmlessly? Inside a power strip
protector? Of course not. Therefore more responsible companies make
a 'whole house' protector - ie Cutler-Hammer, Leviton, Intermatic,
Square D, Kieson, Siemens, GE ... Not on that list is APC,
Tripplite, Belkin, or Monster Cable.
Critical to surge protection is a single point earth ground AND a
short ('less than 10 foot) connection to earth. Your telco does that
(and does not use power strip protectors). Any facility does earthed
protectors when lightning damage is not acceptable. In your case, the
effective (properly earthed) 'whole house' protector costs about $1
per protected appliance. That power strip protector costs tens (maybe
100) times more money per effective appliance.
Review citations from Bud that also show these power strip protector
problems. On Page 42 Figure 8 of his first citation: a power strip
too close to appliances and too far from earth ground earths a surge,
8000 volts destructively, through the adjacent TV. That is what
protectors do. They don't stop or absorb surges. Protectors divert
surges to earth. It earth ground is too far away (ie more than 10
feet as in that figure 8), then surges may be earthed destructively
through adjacent appliances.
Bud's second citation is blunt about what an effective protector
must do on Adobe page 8 of 24:
> You cannot really suppress a surge altogether, nor
> "arrest" it. What these protective devices do is
> neither suppress nor arrest a surge, but simply
> divert it to ground, where it can do no harm.
On Adobe page 19 of 24:
> A very important point to keep in mind is that your
> surge protector will work by diverting the surges to
> ground. The best surge protection in the world can
> be useless if grounding is not done properly.
All appliances (including that big screen TV) internally contain any
protection that would work on its power cord. Protection so robust
that 120 VAC electronics must withstand 600 or 1000 volt transients
without damage. So that the rare and destructive surge (occurs maybe
once every seven years) does not overwhelm appliance internal
protection, earth where destructive surges would enter the building.
Cable is earthed directly (if properly installed). Telephone wires
are earthed by the telco (for free). But your AC electric - the most
common source of destructive surges - has no earthing for all AC
wires. You must install one 'whole house' protector so that internal
protection inside that TV (and all other appliances) is not
overwhelmed.
Properly earth one =91whole house=92 protector to have same protection
that the telco uses for their switching computers.
Every professional citation notes what provides protection. Earth
ground. Those who promote for plug-in protectors manufacturers (and
will not admit that conflict of interest) will recommend power strip
protectors. Notice the profit margins. A $3 power strip with some
$0.10 parts selling for $150. No wonder your big screen TV salesman
was promoting that protector so avidly. That ineffective protector is
where his greatest profits lie.
A protector is only as effective as its earth ground. No earth
ground (ie too far away) means no effective protection. Provided were
examples of companies that provides effective surge protectors.
|
|
|
|
Author: bud--Date: 11:49 14-05-08
|
|
w_tom wrote:
> On May 11, 10:28 am, PinkFloyd43 <pinkFloy...@hotmail.com> wrote:
>> First finally dropped the $$ on the big screen and as I live
>> in TX, which typically has huge thunderstorms this time of
>> year, when at home I unplug everything I value. I want to
>> protect the TV with one of the power strips that advertiseprotectionagainst
this type of thing? Any opinions on
>> what works and what is pure marketing BS, I do realize
>> a direct strike means pretty much everything is done with,
>> as what happened to a neighbor last year!
>
> What must a power strip protector do to provide surge protection?
> It will stop what three miles of sky could not stop? That silly
> little part will absorb the entire surge energy? Of course not.
Poor w_ can't figure out how plug-in suppressors work. Explained in the
IEEE guide for anyone that can read and think. Hint: they don't work by
stopping or absorbing.
> Therefore more responsible companies make
> a 'whole house' protector - ie Cutler-Hammer, Leviton, Intermatic,
> Square D, Kieson, Siemens, GE ...
All the companies but SquareD make plug-in suppressors; apparently they
aren't "responsible".
For the "best" service panel suppressor, SquareD says "electronic
equipment may need additional protection by installing plug-in [surge
suppressors] at the point of use."
>
> Review citations from Bud that also show these power strip protector
> problems. On Page 42 Figure 8 of his first citation: a power strip
> too close to appliances and too far from earth ground earths a surge,
> 8000 volts destructively, through the adjacent TV.
The illustration in the IEEE guide has a surge coming in on a cable
service. There are 2 TVs, one is on a plug-in suppressor. The plug-in
suppressor protects TV1, connected to it.
Without the plug-in suppressor the surge voltage at TV2 is 10,000V. With
the suppressor at TV1 the voltage at TV2 is 8,000V. It is simply a *lie*
that the plug-in suppressor at TV1 in any way contributes to the damage
at TV2.
The point of the illustration for the IEEE, and anyone who can think, is
"to protect TV2, a second multiport protector located at TV2 is required."
w_ says suppressors must only be at the service panel. In this example a
service panel protector would provide absolutely *NO* protection. The
problem is the wire connecting the cable entry block to the power
service 'ground' is too long (a common problem). The IEEE guide says in
that case "the only effective way of protecting the equipment is to use
a multiport [plug-in] protector."
>
> Bud's second citation is blunt about what an effective protector
> must do on Adobe page 8 of 24:
What does the NIST guide really say about plug-in suppressors?
They are "the easiest solution".
>
> All appliances (including that big screen TV) internally contain any
> protection that would work on its power cord.
Nonsense.
> Protection so robust
> that 120 VAC electronics must withstand 600 or 1000 volt transients
> without damage.
Provide a source for "must".
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.
That is the source of damage in the IEEE example above.
>
> A protector is only as effective as its earth ground.
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 (or stopping or absorbing). The guide explains
earthing occurs elsewhere. (Read the guide starting pdf page 40).
Because w_ is evangelical in his belief in earthing, he uses
google-groups to search for "surge" to spread his dogma.
Never seen - a source that agrees with w_ that plug-in suppressors do
NOT work.
For reliable information read the IEEE and NIST guides. Both say plug-in
suppressors are effective.
--
bud--
|
|
|
|
1 |
|
|
|
|
Contact | Electronic Portal
|
|
|
