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1) What is a surge protector?
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 surge protector.


2) How does a surge protector work?
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.


3) 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 threshold occurs.


4) 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.


5) Can I install a AC surge protector?
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.

  Series installed 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 loads.

  Parallel protectors 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 applications.


6) What is a modular surge protector?
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.


7) What 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.


8) 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.


9) 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.


10) 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.


11) 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.


12) What is an 8 x 20 microsecond waveform?
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 microseconds.


13) 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.   


14) 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.


15) My protector’s 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.


16) 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.



17) 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.



18) 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.



19) 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.


20) What is a lifetime module warranty?
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 protector.


21) 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.


22) 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.


23) What is a joule rating?
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.   


24) 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 protector?
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 loads.


25) 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.


26) What is a hybrid protector?
A hybrid protector is a protector that uses more than one protection technology.


27) What is a silicon avalanche diode?
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.


28) 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 prevent it?
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 equipment.


30) There are so many surge protector manufacturers to choose from, is there an easy way to compare?
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.


31) 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.


32) 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.


33) 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.


34) Do surge protectors fail?
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 recommendations.  


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 the ATS.

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 equipment.

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 system?
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 varistor) technology?
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 normal use).


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 may occur.  

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 performance.


46) What is a “ground potential difference”?
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 tube?
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 surge protector?
Surge Current: 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 ambiguous parameters.

Fault Current: 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 I use?
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 bill.

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”?
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 waveform?
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.



                   ARRA 1605 Compliance                ISO9001:2008 File Number: 10002093

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