What is a surge
A surge protector is an electronic device
that limits transient overvoltages to a safe level, thus protecting
equipment from damage or disruption. A surge protector may also be
expressed using the following terms: SPD (Surge Protective Device), TVSS
(Transient Voltage Surge Suppressor). An arrestor (used by utility
companies and communication companies) is also a surge protector, but is
typically employed in a different part of the electrical system than a
How does a surge protector
A surge protector works by momentarily
“switching” from an open circuit mode into a low impedance mode. This
low impedance mode diverts the surge current through the protector and
in doing so, limits the overvoltage to a safe level. When the surge
event is over, the protector returns to its open circuit mode, ready for
the next event.
What is a metal oxide varistor?
A metal oxide varistor is a
voltage-dependent, semiconductor-based, variable resistor.
Electrically, it appears as an open circuit across a power line until
its voltage threshold is reached. When this occurs, the varistor will
instantaneously change from a high resistance mode (open circuit) to a
low resistance mode (short circuit), thus conducting currents through
it. Once the overvoltage event has passed and the voltage returns to
below the threshold level of the varistor, it will return to an open
circuit again until the next overvoltage event that exceeds its
What size protector do I need?
Protector size is determined by a number of
factors like geography, size of distribution transformer, surge
environment, importance of equipment operation, cost of downtime, etc.
Consult manufacturer for application assistance.
Can I install a AC surge
Although surge protectors are simple to
install, a qualified electrician should be used for all hardwired
protectors. This will ensure that a safe and effective installation is
achieved and all local codes are met. Installation is either “parallel”
or “series”. These are the two types of protectors available.
protectors are typically used at the equipment level, either right in
front of, or within the equipment they are protecting. These protectors
have an “input” and an “output” whereas parallel protectors do not. A
common example of a series connected protector is a surge protected
strip. Since they are connected in series with the equipment, they
conduct load current. It is also common for a series AC protector to
contain a EMI/RFI noise filter. This filtering is useful when it is
right in front of the equipment to filter out noise generated by other
do not conduct load current and simply “tap” into the power system via a
circuit breaker. Parallel protectors are commonly used where large surge
energies exist. They’re used on service entrance panels and switchgear,
plus branch and local panels. There are a number of reasons why parallel
protectors are very popular. They have proven reliability/effectiveness,
and are easy to install. And since parallel connected protectors do not
have to support system load currents, they are relatively small and not
costly. Parallel connected protectors are the staple for all AC
applications, except the aforementioned small equipment level
What is a modular surge
A modular surge protector performs the same
as one that is not modular. The only difference is that a modular
protector contains modules that are field replaceable, thus making
maintenance easy and minimizing time with reduced protection, or no
protection at all in some cases. The modules usually contain the metal
oxide varistors and fuses (although sometimes the fuses are external to
the modules). They are the heart of the surge protector. If one should
fail, the entire unit does not have to be sent back to the manufacturer
for service – just replace the module(s) and you’ll be up and running
again. The manufacturer sends replacement modules and fuses only.
Replacement usually takes anywhere from 5 to 30 minutes. A modular
protector also allows for decreased labor and cost required for
servicing the protector.
do the lights on the front of my protector indicate?
High quality surge protectors include
status lights on the front panel. These indicators let the observer know
right away if the protector is operating at 100% capacity, or not.
Is a UPS a surge protector?
A UPS is not a surge protector. A UPS
(uninterruptible power supply) maintains AC power to the building should
the utility have an outage or a brownout scenario. Typically a surge
protector is installed ahead of the UPS to protect the sensitive line
monitoring circuits at the front end of the UPS.
Is a surge protector a UPS?
No. A surge protector is not a UPS. A surge
protector will not maintain AC voltage to the loads should a voltage
outage or reduction occur.
What is redundancy?
Redundancy with respect to surge protectors
is a design feature that uses multiple fused parallel surge paths. The
benefit of this design is that the protector maintains protection to the
equipment, even if a portion of the protection circuits is not
functioning, or off line.
What does the Ipk rating mean?
The Ipk rating of a surge protector is the
protector’s maximum surge current rating. It is typically published as
per phase rating (i.e. 160,000A/Phase), but it can also be expressed as
a per mode rating (i.e. 80,000A Line-Neutral, 80,000A Line-Ground). This
rating is a critical parameter with regard to the application on surge
protective devices. This parameter is usually expressed as an 8 x 20
microsecond current pulse, which is the accepted industry standard
waveform used to test and compare surge protective devices.
What is an 8 x 20
An 8 x 20 microsecond waveform is a current
pulse whose parameters mimic the surge currents that can appear on a
power system. Surge protector manufacturers use it to test and rate
their products. It has a rise time of 8 microseconds and duration of 20
What is UL1449?
UL1449 is the standard for safety for AC
surge protective devices used on systems with voltages of 600VAC and
less. This standard addresses protectors that are installed on the load
side of the main disconnect. A UL1449 listed surge protector has been
rigorously safety tested. A UL SVR (suppressed voltage rating) or UL
rating is also assigned to a UL1449 listed protector as a result of
these tests to help users compare protectors.
What is NEMA LS 1?
NEMA LS 1 is a surge protector performance
standard. A surge protector which meets this standard is typically used
in the most hostile surge environments, at the service entrance
location. Other protector locations such as branch panel and local panel
protection usually do not require such a formidable protector.
surge counter is indicating counts. Do I have to replace the protector?
No. A surge protector counter will count
the number of surge events experienced by the protector. It is not an
indicator of how much longer the protector will function, but lets the
user know that a surge event has occurred.
Do I have to
perform any routine maintenance to my facility’s protection system?
A surge protector is one of the most
maintenance-free parts of a power quality system. The only time
maintenance is required is if the protector’s indicator lights show
reduced protection. Otherwise, full protection is present and no
maintenance is required.
How do I know my
I/O port protector is still functioning?
I/O port protectors, if undersized,
typically will fail as a short, thus preventing any data from passing.
They can also fail as an open circuit, which also will prevent any data
from passing. In some cases, an ohmmeter can be used to determine if a
port protector is damaged. The best way to tell whether the protector is
working is to test it for continuity and to test its protection
components to be sure they are functioning within tolerance. This can be
done by the manufacturer who has the appropriate test equipment.
I connected an I/O
port protector to my equipment and my system does not function properly.
What should I do?
Contact the manufacturer immediately to
make sure that the protector you are using is the right one for your
application. Misapplications can be avoided by speaking with the
manufacturer prior to purchasing the protector.
How long can I
make the ground wire coming off of my data line protector?
Given the surge environment, we find that a
ground wire no longer than six inches (15cm) will ensure that the
equipment is protected. If the ground wire is too long, excessive
voltage will reach your equipment and equipment damage may occur. A long
ground wire is, in our experience, one of the most common mistakes made
when installing I/O port protectors.
What is a lifetime
A lifetime module warranty is a policy
whereby the heart of the surge protector (the surge protection modules
(and fuses)) is warranted for the life of the surge protector. This type
of warranty means that the customer will not have to pay for new modules
and fuses, should damage occur to the protector’s modules/fuses. This is
usually a separate warranty than the one that covers the entire
My facility has a
lightning system on the roof, do I still need surge protection?
Air terminals (and Early Streamer Emission
systems) on or near a building’s roof are installed to prevent damage to
the building structure. They do not protect the electronics within the
facility from damages due to lightning surges or utility-generated
surges. Both systems work together to completely protect a building.
What is a
thermally protected varistor?
A thermally protected varistor is surge
protection component that has an integral (or nearby) thermal fuse. This
thermal fuse disconnects a varistor that is dissipating power (heating
up) beyond its maximum allowable power rating, usually long before the
component becomes a short circuit across the power line. Varistors with
integral thermal fuses ensure that should a varistor failure occur, it
will be a benign one.
What is a joule
A joule rating is an energy rating. With
regard to surge protectors it is usually expressed as the maximum single
event energy that the protector can withstand. Energy (joules) =
Voltage x Current x Time x Waveform Constant.
If my distribution
transformer secondary is a WYE, but I am not running a Neutral to my
loads, do I use a WYE configured protector or a DELTA configured
A Delta protector should be used because
the loads are not using the Neutral. The Neutral wire
stabilizes/balances the voltages. It is possible that a WYE protector
can be damaged if used on a system that does not have a Neutral wire
connect to the loads, despite the fact that it will still protect the
Why do the IEC
standards differ from the ANSI/IEEE standards, isn’t lightning the same
all over the world?
Yes, lightning, for all intents and
purposes, is the same all over the world. The standards differed in some
respects and overlap in others. In the United States, the adopted
standards for TVSS manufacturers are the ANSI/IEEE C62.41 and ANSI/IEEE
C62.45. These standards have been the basis for TVSS design and
implementation for over twenty years, and have been successful in
protecting electronics all over the world. A portion of the IEC
standards use a waveform that many feel does not represent the surge
environment in which surge protectors are utilized in.
What is a hybrid
A hybrid protector is a protector that uses
more than one protection technology.
What is a silicon
A SAD (silicon avalanche diode) is a
semiconductor device used predominantly in data line surge protectors.
It can be employed alone or in conjunction with other technologies. Its
high-speed characteristics make it a viable protection component.
However, its low energy ratings, as compared to metal oxide varistors
make it undesirable for use on AC power lines.
What is a crowbar
and what is it used to protect?
A crowbar protector is a voltage dependent
device which will “crowbar” the DC bus. Crowbar means to short out like
a switch turning on and staying there. A crowbar device differs from
other types of surge protection devices, like a varistor, in that it
will not return to an open circuit unless power is removed. Crowbar
devices are often used to protect a load from damage due to a runaway
power supply. When power supply regulation fails, a critical load can
be damaged if its maximum supply voltage rating is exceeded. A crowbar
device prevents the damaging voltage from damaging the load by shorting
out the supply at a predetermined voltage level.
29) I have AC surge
protection, but a recent lightning strike damaged some NICs (Network
Interface Cards) in my office. Why did this damage occur and how do I
The most popular cause of I/O port damage
is differences in ground potential within a facility or between two
buildings. To prevent this damage a data line protector must be
installed at the port(s). The protector will simply bypass the surge
current as opposed to it damaging the port(s). Usually a protector is
installed at both ends of the cable, thus protecting both pieces of
There are so many
surge protector manufacturers to choose from, is there an easy way to
Choosing a protector manufacturer can be a
daunting task, especially when the reputable ones often get mixed in
upon the not so reputable ones. Look for open technology,
straightforward specifications, reliable track record, and how long the
manufacturer has been in operation. A mfr’s technical team should be
glad to spend time on the phone regarding your application – w/o any
pressure to buy.
Why is a circuit
breaker required in series with a parallel surge protector?
A circuit breaker used in series with a
surge protector for the same reason a circuit breaker is used to protect
a branch circuit, to prevent a fire. A circuit breaker is “invisible”
to a transient or surge so it will not open during most transient
events. But should the surge protector start to draw large amounts of
AC current (which is not normal operation of parallel AC surge
protector), the breaker will open and disconnect the protector from the
AC line. Fuses may also be used in series with the surge protector to
achieve the same level of safety, but we find that circuit breakers have
better transient withstand capacity.
If I don’t have
any spare circuit breaker spaces in my panel to connect a surge
protector, what should I do?
You can use an external molded case circuit
breaker, a fuse block, or a fused disconnect switch in series with the
protector. An external circuit breaker is preferred.
What is the
difference between a series surge protector and a parallel one?
Series or two port surge protectors carry
load current. So if you have a 500A service, the series surge protector
would have to be designed to carry 500A. Series surge protectors are
typically employed at the equipment level so the load current they would
have to carry is not high, and they are usually small enough to fit
within a cabinet or chassis. A series protector may also employ a series
choke or inductor as part of its filter for EMI/RFI purposes. A
parallel (or shunt) type surge protector does not carry load current.
Also, failure of a series protector may mean that power is removed from
the load is some cases. Failure of a shunt protector results in the
protector being removed from the AC power line. AC power to the load is
not interrupted but the load is now unprotected.
For the most part, no. Failure of a
properly designed and appropriately applied surge protector is rare and
usually caused by the protector being operated outside of its limits.
For example, if the power system Neutral wire connection becomes undone,
excessive AC voltage may appear across the protector. This sustained AC
voltage will cause the protection components to overheat, and eventually
the protector will disconnect itself from the power line. But a common
cause of protector failure, whether it be an AC line protector, or a
data line protector, is misapplication.
35) What does the term
“headroom” mean with regard to surge protection devices?
“Headroom” is Line Voltage Variation
Allowance (LVVA) of the protector. This is the difference between the
nominal line voltage amplitude and the voltage level that the surge
protector will conduct or “turn on” with. Usually headroom is expressed
as a percentage of the nominal line voltage, like 15% or 20%.
Electrical equipment, like a surge protector, has limits with regard to
the AC voltage applied that it can handle. Electrical equipment can
handle these common utility swells without damage or disruption. But a
surge protector with inadequate headroom may be damaged as it is not
designed to conduct such currents and may short out as a result of the
AC current flowing through the protection components. The most reliable
surge protectors are able to “ride through” common utility voltage
variances (i.e. +/-20%) without conducting, while still providing
exceptional protection. A protector with inadequate headroom may be
damaged and taken off line by an otherwise harmless AC power frequency
voltage swell. Now the equipment is left unprotected and the protector
either needs to be serviced or replaced.
36) I am comparing
let-through levels between surge protector manufacturers, should I just
choose the protector with the lowest let-through levels?
Published let-through levels do not always
represent actual installed performance. Keep in mind that if the
published let-through levels do not include the protector’s connection
cable, then they do not represent the performance of the surge protector
system when installed. If you are comparing data, be sure to compare
apples to apples, and keep in mind that the protector you choose should
have adequate headroom (See question # 35).
37) How do I protect a
multi-story office building?
To protect a multi-story office building
may seem like a difficult task, but once you break it down into separate
systems, it is not. If you have any questions, the best and easiest
approach is to contact the manufacturer and speak to their applications
personnel. An electrical one-line diagram of the facility is also
helpful to the manufacturer to assist in making the right
The following is a typical approach to
protecting a multi-story facility:
For AC protection, install a surge
protector (Category C class) on the main panel service coming into the
building. Sometimes multiple services exist. If this is the case, each
service should have a surge protector connected to it. The service
entrance protector is the most critical protector and should be sized
accordingly. Protect branch panels or PDUs (power distribution units)
with Category B class protectors on each floor where critical equipment
is needed. Then protect local panels with Category A class surge
protectors feeding critical loads (i.e. network closets). Keep in mind
that a reduction in the quantity of Category B protectors and Category A
protectors is possible. If the building has a generator/UPS/ATS system,
then protectors should be located at the utility side of the ATS (in
front of the UPS), the generator side of the ATS, and the load side of
Panels feeding HVAC
equipment on the roof or other outdoor equipment require surge
protection too to prevent back feeding into the building.
For data and communication lines, protect
the telephone switch, the LAN/WAN routers and hubs on each floor,
especially equipment found in the Network Closets. Also protect the I/O
ports at each point of use device, like the NIC (Network Interface
Cards), work stations, cashiers, modems, and fax machines. If something
is deemed nonessential, then you can omit protection for that piece of
For alarm systems and close circuit TV, all
lines which terminate at a central control console should be protected
with coaxial, DC, data, and communications protectors at the central
station as a minimum. Protectors located at the equipment may also be
necessary depending on the application.
38) I have a PV
(photovoltaic) system with net metering; does it need a surge protection
Yes. For PV systems, DC surge protection
should be installed where the DC voltage from the PV arrays terminates
at the charge controller/inverter. AC protection should be installed at
the inverter’s AC output to protect it from transients on the utility
power lines caused by lightning or utility switching transients. In
certain cases, protection should be located at the PV array locations,
and at the array’s local DC control circuits-where applicable.
39) I need AC surge
protection, should I look for a protector that uses mov (metal oxide
Yes, metal oxide varistors are used by the
top surge protection manufacturers due to their high energy handling
capacity and their unmatched and proven reliability (over 30 yrs in
40) I don’t want to
protect my entire facility but I have to protect a few areas with
critical equipment, can I spot protect?
Yes, surge protection equipment may be
installed only where the critical loads are located. This will leave
other non-essential equipment unprotected, but will also reduce the
overall cost of the surge protection system.
41) What is a UL
Suppressed Voltage Rating (SVR)?
A UL SVR is a voltage rating that is
assigned to every surge protector that is UL1449 tested. The
manufacturer must include this rating on the front label of the
protector. This rating is achieved by pulse testing the protector with a
500A (8 x 20 microsecond) pulse in various modes using six inches of
wiring lead length exiting the enclosure. For example, a 120VAC surge
protector might have a UL rating of 500V. This means that the protector
limited the overvoltage to somewhere in the range from 401 volts to 500
volts. If the protector had a 600V rating, then the results would have
fallen in the 501-600 volt range.
42) How do I know my
protector is working?
Most AC surge protectors have indicator
lights on the front panel to show protector status. Some also have
audible alarms and relay contacts to indicate protector status. Data
line protectors do not usually have indicator lights, as these lights
may influence the operation of the system. If the protector is passing
the signal or the data (i.e. a 4-20mA loop or 10/100 BASE-T), then most
likely, it is operational. Data line protectors, when damaged, usually
have a short to ground which will no longer let the signal pass. This is
a telltale sign that the protector should be replaced. In certain cases
though, the protector can fail as an open circuit too.
43) I have an old AC
surge protector that’s roughly 20 years old, should I replace it?
MOV (metal oxide varistor) based surge
protectors do not lose their capacity to divert surges with age. They
can, however, go out of tolerance under extreme cases. Keep in mind that
newer surge protectors, like any other product, contain the latest
technology and safety features, and would easily outperform an older
protector. Also, the UL1449 standards are also constantly being revised
to ensure that the utmost safety is built into the surge protector.
44) Can I connect my
protector before the main disconnect?
A UL1449 listed surge protector should not
be connected before the main disconnect switch. It should always be
connected after the main disconnect switch. There are certain arrestors
that are designed, and have been UL safety tested, for use ahead of the
main disconnect, but these are usually installed by the electrical
utility and lack many of the features of a UL1449 protector. For
example, they usually have no indicator lights so you never know if they
are still functioning or not.
45) Why is the lead
(wire) length of an AC surge protector so critical?
The shorter the lead length between the
protector and your panel, the lower the let-through voltages will be to
your equipment. This is crucial to the effectiveness of all
parallel-connected surge protectors.
Surge protectors are typically connected in
parallel with the load. This means that the protector does not carry
load current. But more importantly, it means that the protector must
efficiently divert transient currents through it during an overvoltage
event. The surge protector must “look” like an electrical short circuit
momentarily in order to efficiently divert large amounts of current. If
it does not do this, then the residual voltage (or let-through voltage)
that “reaches” your equipment will be too high, and damage or disruption
The let-through voltage of a surge
protector is based on the following formula: Vlet-through =
(I x R) + (L x di/dt). The (I x R) term is pretty straightforward. This
is the current through the protection system multiplied by the
resistance of the protection system. Modern day surge protectors have
low (I x R). A surge protector’s resistance will decrease substantially
and instantaneously when it is in the conduction mode. It will
transition from an open circuit to a short circuit during a surge event.
The second term (L x di/dt) can be the more dominant one. This term is
the inductance (L) of the system multiplied by the rate of rise of the
current (di/dt). di/dt is very high for surge currents (lightning) so
we’ll have to live with that for a while. However, the factor (L) is
controllable. L is the inductance of the protection system. Wiring, by
nature, is inductive. The longer the wire, the more inductance it has,
and the greater the (L x di/dt) factor will be. So when installing
parallel surge protectors, keep the leads as short as possible for best
46) What is a “ground
Ground potential difference (or ground
voltage difference) occurs when the voltage on the grounding system at
one location is different from the voltage on the grounding system at
another location. This causes a current to flow. When lightning currents
flow through a grounding system, voltages are formed. The voltages
formed are based on the following equation: Vground = (I x R)
+ (L x di/dt). Vground location A does not always equal Vground
location B, especially when the distance between the two points is
great. With regard to surge protection, it is this phenomenon that is
the most common cause of I/O port damage in unprotected equipment. For
example, if a communication cable is connected between two pieces of
equipment that are at a different ground potentials, the I/O ports
(NICs, etc) may be damaged because the resulting current that will flow
during this event will damage the I/O port. To protect equipment, a
surge protector located at each port will bypass this current safely
away from the port.
47) What is a gas
A gas tube is a voltage-dependent device
used to protect equipment from overvoltages. During an overvoltage the
gas tube will conduct (or fire), thus diverting the surge currents
through itself. Gas tubes are sealed devices which contain an inert gas
which helps the device conduct at a predetermined voltage. Gas tubes are
typically used in data line protection devices. Most often, they are
used in conjunction with other high speed protection technologies due to
their slow response time, which is on the order of microseconds.
48) How can such a
small surge protector handle so many thousands of Amps?
Surge protectors are rated using a very
fast pulse of current. The industry standard current pulse is 20
microseconds wide (although some transients can last much longer) and is
representative of lightning current. The components (and the conductors)
used in a surge protector are designed to handle very high currents, but
only for a short duration. In use, they are only passing the current for
the duration of the surge event. After a surge has passed, they return
to their non-conducting state ready for the next event. A surge
protector differs from an AC line voltage regulator because a surge
protector can be damaged if it is conducting AC current for a long
period of time. Surge protectors are used to protect UPS
(uninterruptible power supply) systems which can be damaged by surges.
Both technologies work well together as part of your overall power
quality system. In a surge protector, the protection components can
overheat and permanently short out if their average power ratings are
exceeded. However, for short bursts of current like that of surges,
modern protectors can divert such currents day in and day out,
protecting your equipment reliably.
49) What is the
difference between “surge current” and “fault current” with regard to a
A protector’s surge current rating depicts the protector’s capacity to
divert currents that are the result of momentary overvoltages caused by
lightning or utility switching. A protector’s peak current (Ipk) rating
is usually based on the industry standard 8 x 20 microsecond waveform,
which is a pulse that mimics lightning currents on a power line. This
parameter is often used to describe the “size” of a protector. It is
also used to recommend a protector for a particular location in a power
system. For example, a branch panel may require an 80kA/Phase
protector. This means that an 80kA/Phase protector is the right size
protector for that particular location in the electrical system.
Although you would be hard pressed to witness an 80kA surge in a branch
panel location – the higher surge current rating translates into longer
protector life. You would not want to use a 10kA rated protector in an
area that has repeated 10kA surges as the protector will only survive
one event. The surge current rating is also used often to compare
protectors from different manufacturers as it is one of the least
Fault current is often confused with surge current. Fault current is the
AC current that is generated from the AC power system during a fault
condition. It is NOT the lightning current or the surge current rating
of the protector. Fault current ratings are commonly found on
electrical panels, fuses, circuit breakers, transfer switches, etc. A
fault condition could occur for a number of reasons, such as a phase
conductor that becomes disconnected and shorts to ground. Fault current
also flows when a piece of equipment fails or shorts out. When a piece
of equipment fails, it will draw as much current as the power system can
deliver until the circuit is “cleared” or “opened” by a fuse operating
or a circuit breaker tripping. Fault current is limited by the
transformer size, the system impedance, and the impedance of the short
circuit. Any piece of electrical equipment connected to a power line can
fail. If the device fails, it may fail as a short circuit. A short
circuit will cause large amounts of AC current to flow through the
failed piece of equipment, until the circuit is broken or cleared. This
potentially large and dangerous amount of current that flows into a
failed electrical device is known as fault current. With regard to a
surge protector, the surge protection system, which usually contains an
upstream circuit breaker, must be able to safely disconnect itself from
the power line should it short out. An example of a surge protector’s
fault current rating is 85kAIC which stands for 85,000 Amps Interrupt
Capacity whereas an example of a protector’s surge current rating is
200kA/Phase. A surge protector should be sized correctly for the surge
environment and the fault current rating of the system it is connected
to for safety reasons.
50) I have a surge
strip connected to my pc, is this all I need to protect my computer?
Well, if you have a quality strip, it is a
good start. A quality strip is one designed and built by a reputable
surge protector manufacturer under stringent quality control standards
(i.e. ISO-9001). Your pc may also contain a modem which is connected to
an outside cable line or telephone/DSL/T1) line. These communication
lines are susceptible to surges that will eventually couple into and
damage your computer if it is not protected. The surge strip will only
protect from surges on the AC power system, not on the communications
lines (unless the strip also has protection for communication ports).
The communications port on your computer should be protected whether it
is part of a Local Area Network or if it is connected directly to the
outside communications line.
51) Why are some surge
protected strips so inexpensive and others are not and which one should
A surge strip is a temporary power tap with
some kind of overvoltage protection device inside. They usually have
multiple AC outlets which enable the user to plug in many devices. If
you don’t need a surge protected strip, then you can purchase a basic AC
outlet strip. Surge strips come in all different sizes,
colors, and shapes. Some are massed-produced by the millions. Although
high-quality surge-protected strips exist, there are many that are
either unsafe (will “work” only once, then burn out) or simply will not
protect your equipment due to poor design and poor quality. Many do not
contain status indicators which let you know if the protection is
functional. For starters, make sure that you choose a strip that is UL
Listed for safety reasons. Next, choose one that is manufactured by a
reputable manufacturer. A reputable manufacturer would be less likely
to produce a marginal product. Also, choose a manufacturer that is able
to answer any questions you may have about the product. If they cannot
answer your questions, or you cannot contact them, then they probably
are just reselling some other manufacturer’s product. Choose a strip
that has all modes protected. (Line-Neutral, Line-Ground, and
Neutral-Ground). Also choose one with at least 3,000 Amps surge rating
per mode. The higher the rating per mode, the more capable the
protector. Avoid protectors that do not contain these surge current
ratings on the specifications. Make sure it contains indicators which
let you know the protector’s status. A published UL SVR (Suppressed
Voltage Rating) of 330V, 400V, or 500V is typical of surge strips and
any of these ratings is acceptable to protect equipment, as long as all
of the modes are protected.
The differences in cost boil down to
construction quality and the protector’s capacity to repeatedly divert
transients, and the quality of its noise filter (if it contains one).
There are some very good, economical, models available that should
handle all but the largest surge events, but most likely, these would
not be in the $2.00 - $15.00 range. A strip with thermally protected
surge components gives the user an extra measure of safety. These strips
will safely disconnect a failed varistor from the power line, thus
possibly preventing a fire.
Surge strips are no substitute for the more
capable hardwired protectors (the kind that connect to your electrical
panel) but they can be a helpful addition to such a system. And, it just
might save your computer or A/V system from damage.
52) Can installing a
surge protector save you money on your utility bills?
No. A surge protector will not save you
money on your utility bills. Many disreputable TVSS manufacturers have
tried to claim this to increase their sales. Some have been sued to
stop advertising this. This is not to say that installing TVSS may not
save you money though. If your building or residence is unprotected and
a transient is coupled into the lines as a result of a nearby lightning
strike, or a utility-generated transient enters your building, it is
then highly likely that some equipment will be damaged and/or that
downtime will occur. These two scenarios could be costly and a surge
protector would have been enough to prevent these from occurring.
Installing surge protection saves you money, but not on your utility
53) How much AC
protection do I need for my facility?
Surge environments have been defined by the
ANSI/IEEE C62.41 standard. This standard divides the surge environment
of a facility into three categories – Category C, Category B, and
Category A, where the Category C environment is the harshest, the
Category A environment is the most benign, and Category B is middle
ground. The surge environment at the service entrance is represented by
Category C. As you move away from the service entrance, deeper within
the building, branch panel surge environment is represented by Category
B. Further downstream, local panel surge environment or equipment level
is represented by Category A. Although there are some exceptions, the
following guidelines will help with selecting surge protectors with the
correct amount of surge handling capacity. The electrical service
entrance (the location where the utility power enters you facility or
home) is the first line of defense against surges. Because of the surge
energy levels at this Category C location, a surge protector with a
minimum surge current rating of 120kA/Phase is recommended. For branch
panels, or Category B locations, an 80kA/Phase – 120kA/Phase protector
is recommended. For local panels and equipment level locations,
80kA/Phase and less is recommended. Using these guidelines will ensure
that your facility has a reliable AC surge protection system, at a
reasonable cost, that will last for the life of the building.
54) What is
Let-through voltage is the maximum voltage
measured across a surge protector when suppression takes place. For
example, a surge protector will limit a 20,000V surge to 650V. So
instead of 20,000V reaching and damaging your equipment, it would only
be exposed a safe 650V for the duration of the surge. The 650V is the
“let-through voltage”. Also known as the “remnant voltage”.
55) What is an 8 x 20 microsecond
The 8 x 20 microsecond waveform is the
industry standard current waveform by which surge protection
manufacturers design by and test by. It represents the surge energy
that is imposed on a power system during a lightning event. Since it is
the surge current that a surge protector must pass through it each day
(24 hours a day/7 days a week), this is a very important parameter to
help you understand the capability of a given protector. Keep in mind
that all surges are not exactly 8 x 20 microseconds. Surges on the power
line, or in your building wiring, have many different durations and
amplitudes. This waveform also gives users an easy “apples to apples”
way of comparing surge protection devices.