Request for Advice re: Surge Suppressors

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Robert Zavisca

Feb 4, 1997, 3:00:00 AM2/4/97

Greetings. I need a surge suppressor for my PC, but I'm wary of
the advice given by salesmen at electronics stores/departments.
Can anybody give me some advice on what to look for and what
I can expect to pay for a good, reliable surge suppressor capable
of powering a PC, monitor, printer, and ZIP drive? Thanks.


Feb 4, 1997, 3:00:00 AM2/4/97

In article <5d684p$>,

Here's a primer... by all means, please check out our library resource Search Engine at: <A HREF=""></A>

<b>Surge Suppressor Specification recommendations:</b>

<PRE>UL TVSS 1449 Suppression Rating for _all_ 3 modes:
Hot to Neutral : 330 volts
Hot to Ground : 330 volts
Neutral to Ground : 330 volts

UL 1283 EMI Filter

UL 497A [ Telco/Modem models ]

CSA listing

Energy Dissipation Minimum 600 Joules [ AC ], 240 Joules [ DC ] for MODEM.

EMI/RFI Filtering: >50 dB rejection over 100 kHz to 10 Mhz for both Normal
(NM) and Common (CM).

IEEE 587 A Let-through Voltage < 40 Volts
[ 6kV ANSI/IEEE C62.41 (587) Category A Ring Wave test ].

Peak Surge Current @ 8 x 20 us pulse: 40,000 Amps Common Mode.

In addition...

1) Heavy Duty MOV arrays used at BOTH the Line side and the Load side for
bi-directional, forward and reverse suppression

2) High Frequency Capacitors used at BOTH the Line side and the Load side

3) Series Blocking Inductor Coils used on BOTH the HOT and the NEUTRAL

4) The Series Blocking Inductor Coils must be positioned AFTER the MOV
array and the High Frequency Capacitor arrays on the Line side and
BEFORE the MOV array and the High Frequency Capacitor array on the Load
side, so that both forward and reverse suppression is provided and so
that MOV harmonics are filtered on both the Line side and the Load side

Line -> [HFC] -> [MOV] -> [SBI] <- [MOV] <- [HFC] <- Load

5) The Series Blocking Inductor Coils must be sufficiently sized and
properly located so that RFI Emissions and EMI conduction due to
saturation at higher loads do not become a problem

6) The suppressor should have a Positive Shutdown Circuit that
automatically stops all current flow to the Load in the event of a
catastrophic surge hit _or_ in the event of a failed critical suppression

7) There should be a Diagnostic Circuit that will identify

a) An Open Ground, Neutral or Hot?
b) A Hot-Ground or Hot Neutral Reverse?
c) Verified components of the surge suppressor are functioning?

8) The suppressor manufacturer's warranty should cover Power Surges
resulting from lightning, and should be transferrable

9) The surge suppressor's MODEM surge circuit should have NO MORE THAN
50 picofarads of capacitance, and the specifications should so state.

<b>Subject: Computer and Modem Surge Protection and Electrical

Problem: Modem problems and damage, ranging from disconnects to slow
transmission, to actual damage in use. Many Modem problems are caused by
the lack of proper hardware configuration/connection information and the
lack of proper Modem/System safeguards. These will be discussed here.

An Internal Modem has two electrical from the Telco (DC) and
one from the System (AC). If proper care is not tken to assure the
integrity of these two electrical paths, damage to the Modem, the COM
port, and the MOBO can result, depending upon the severity of the
electrical abberration.

Proper Electrical Considerations....

Rule #1: It is very important that your computer system be plugged into a
*Grounded* AC outlet, and that all peripherals connected to your system
*reference the same AC Ground*.

Explanation: This means that the AC Duplex outlet that your system is
plugged into must have a good electrical Ground, as verified by a 3-light
tester or by a surge suppressor with site wiring diagnostics.

It also means that any printers, plotters, scanners, external tape drives,
CD ROM or Optical Drives must be plugged into the *same* circuit leg as
the rest of the system!

In most cases, this means a surge strip must be used for each of the two
outlets available in a Duplex outlet receptacle, and that all connected
equipment must be plugged correctly into these surge strips.

Rule #2: Any Internal OR External Modem must reference the SAME AC Ground
as the rest of the system.

Explanation: When AC electricity reaches your wall outlet receptacle, it
has its own AC Ground reference (called the Ground wire) at that outlet.

One purpose of the Ground is to provide a low resistance path for
electrical surges and noise, but to remain at a zero voltage potential
most of the time. any given instantaneous moment, an AC ground
"could" have a non-Zero voltage potential, as when an electrical surge
gets diverted to it.

If you do NOT use the same circuit leg for your system, and in fact,
sometimes if you do not use the same Duplex outlet, you may be referencing
TWO different Grounds which may at a given moment be at TWO different
voltage potentials...the result is that current can travel from one
ground, to the other, *through* your equipment. This is called a "Ground

The same reasoning applies to the Modem...its ground, if unaltered at your
computer location, is the Ground of the Telco Entrance, which may be
*substantially* different from the AC ground at the Duplex outlet. In such
cases, a Ground Loop is possible, from your Modem RJ11 connection,
*through* your Modem, the COM port, and the MOBO of your system, to the
power supply of your computer, which is referenced by the AC Ground of the
Duplex outlet! There are situations where such Ground Loops can cause
serious damage.

Rule #3: All computer equipment at one node must reference the SAME AC
ground, and must be *surge* and *noise* protected from the electrical
system and from *each other*.

Explanation: The easiest way to explain this is to present a diagram...

Surge and Noise Protection....

The short and simple of it all is that in order to get any kind of real
protection for the computers you need a *quality* surge suppressor that
has meaningful levels of Surge Suppression capability and Noise Filtration

How 'good' a surge suppressor you need depends on your "surge exposure",
the type of equipment to be protected and the system configurations, and,
finally, the quality of the electrical wiring and service.

Surge Exposure: Likelyhood of damage due to electrical surges owing to
your geographic area...high in Florida, low in NYC...if there is fairly
frequent lightening activity, and your home is serviced by overhead
utility poles, you need very good protection.

Type of Equipment: If your computer is equipped with a Modem, it needs to
be surge protected...protecting the AC line without protecting a Modem is
less than halfway protection. If there will be a laser printer, you also
need "noise filtration" so that the printer will not interfere with the
rest of the system.

Quality of Electrical Wiring & Service: Is your home wiring new and up to
the current NEC standards? Are the computers on a dedicated circuit, with
verified good AC grounds? Does the electricity seem fairly stable, or is
it subject to frequent 'brownouts' or outages as in many rural areas? If
the latter, a Line Conditioner or UPS should be used for the computer
system (not the laser printer) instead of a surge suppressor.

The following schematic would cover most scenerios calling for a quality
Surge Suppression protection scheme:

Figure 1

Duplex Wall Receptacle--has outlets "A" and "B"

----------Modem RJ11/RJ45 jacks into Modem surge ports
A--------Surge suppressor with Modem Surge------computer system
(with noise filtering)

B--------Surge suppressor-----------------------Laser printer
(with noise filtering)

In the above Figure, there is one Duplex outlet consisting of two outlets,
outlet "A" and outlet "B", on the same circuit leg.

Into one of the duplex outlets ("A") a surge/filtering strip with Modem
surge protection built-in, gets plugged in, and the computer & Modem RJ11
jacks go into that surge/filtering strip. Into the OTHER outlet ("B") the
Laser printer gets plugged into its OWN separate surge/filtering strip.

The laser printer requires its *own* quality surge/filtering strip because
it *produces* and *throws back* large amounts of 'Common Mode' and
'transverse' electrical noise when operating, and would therefore
contaminate the electrical system it is plugged into, and all else not
isolated from that connection. The separate surge/noise filtering strip
for the Laser printer prevents this from happening. A Photo Copier or
other 'noisy' piece of equipment also requires its *own* surge/noise
filtering strip.

The surge suppressor in the above Figure for the computer system and
Modem would be a UL 1449 Listed surge suppression device with built-in
UL 497 modem surge protection, and UL 1283 RFI/EMI Noise filtering; the
Joule ratings would be a *minimum* of 480 Joules for the AC surge circuit
*plus* and *additional* 240 Joules for the Modem. The Modem surge circuit
must be properly designed, with *low capacitance*, or it will actually
SLOW DOWN a Modem transmission...capacitance should be LESS THAN
50 picofarads, and should be specified as such.

Note that the Surge Suppressor with Modem Surge protection capability is
plugged into the same AC Duplex outlet as the rest of the system...the
Modem's RJ11 jacks are plugged INTO the protection ports of that DUAL
surge suppressor, and when so done, the Modem NOW REFERENCES THE SAME AC
GROUND as the rest of the system!

This electrical connection scheme will prevent Ground Loops, and it will
also prevent AC Surge Damage *and* Telco/Modem (DC) Surge damage. Instead
of a Telephone surge coming in on the Telco line, going *through* your
Modem, COM port, and MOBO, as it seeks the AC ground, it will now be
'caught' and suppressed by the Modem surge circuit in the DUAL surge
suppressor, and diverted *directly* to the AC Ground.

Best Regards,

Fred Noble
Sutton Designs, Inc.

-------------------==== Posted via Deja News ====----------------------- Search, Read, Post to Usenet

Feb 5, 1997, 3:00:00 AM2/5/97

If you want a surge suppressor which virtually eliminates powerline
surges and noise (EMI/RFI) of any magnitude, with a bullet-proof, proven
track record -- visit

Rick O'Keefe, CEC, SME
CSR Consultants, Tampa FL ("Lightning Capitol of the World") --
Zero Surge, Peradata, Innovative Technology Suppressors;
Consultants in Power Quality and Management;
Effective Lightning & Surge Protection;
Commercial Computer Furniture & Enclosures

In article <5d684p$>, wrote:
> Greetings. I need a surge suppressor for my PC, but I'm wary of
> the advice given by salesmen at electronics stores/departments.
> Can anybody give me some advice on what to look for and what
> I can expect to pay for a good, reliable surge suppressor capable
> of powering a PC, monitor, printer, and ZIP drive? Thanks.

-------------------==== Posted via Deja News ====-----------------------

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