Experts recommend the Series Mode type for modern computing systems, or any sensitive electronic system that may be interconnected with other electronic systems. A heavy duty surge reactor acts to deflect surges rather than perting surges where they can do further harm.

The following list of specifications should be carefully examined and compared:

  1. Let-through voltage at maximum rated surge (not simply clamping level, which is the onset of clamping) using standard test pulses. (Let-through voltage is the amount of the surge voltage that is let-through to your protected equipment and should be as low as possible. 180 volts is the theoretical lower limit for 120 volt powerlines).
  2. Service life for various surge levels (including maximum rated surge). A service life of 200 minimum worst-case surges is recommended for a five year life in high exposure locations.
  3. Filter response. (i.e. greater than 30 dB at 100 kHz.) The important frequency range for surges is 5 kHz to 500 kHz. Greater than 20 dB at 100 kHz is desirable.
  4. Safety Ground Wire contamination should be avoided if equipment is to be interconnected. Suppressors that claim “all three modes of protection” pert surges to the Safety Ground Wire and should not be used with interconnected equipment.
  5. Self-test or failure indication (not “protection working” indicators which are often little more than power applied indicators).

There are basically two types of powerline surge technology, patented Series Mode and the older Shunt Mode (so-called hybrids are usually Shunt Mode). The Shunt Mode technology was developed over thirty years ago to protect standalone equipment, but this older technology is no longer suitable for modern sensitive interconnected equipment.

Shunt Mode suppressors are still very common because this older technology is inexpensive to manufacture with high profit margins, and as long as people can be seduced by the low prices, these products will continue to be sold. They generally pert powerline surges to the safety ground wire, using circuits described as “All Three Modes of Protection”. The resulting surges perted to the ground wire can exceed 1000 volts, exposing sensitive motherboards and data boards to surge disruption, degradation and damage.

This surge voltage on the ground wire varies along the length of the wire. When equipment such as modems, printers and other computers are interconnected, the interconnecting cable creates a “ground loop”. If the surge induced on the safety ground wire of one computer is 1000 volts and the surge induced on the safety ground wire at another location is 600 volts, then the difference of 400 volts is fed into the interconnecting cables causing the disruption, degradation, or damage.

While large surges will cause damage, small surges can result in data problems such as lock-ups, data errors, and “mysterious problems.”

It is better to avoid Shunt Mode surge suppressors that claim “All Three Modes of Suppression” than to try and live with the problems they cause when they pert surges to the ground wire.


Both ways, depending on the circumstances… A violent electrical storm can induce enough surge energy into powerlines to destroy your computer in an instant, if left improperly protected. Smaller, internally generated surges can, over time, “wear out” delicate circuits, causing intermittent problems, and slowing down the operation of a system. Series Mode surge suppression technology, as designed by ZERO SURGE Inc., employs a surge reactor that serves as a powerline filter, much like the oil filter in your car.  The surge reactor filters out damaging energy, just as your oil filter removes impurities that can destroy your engine over time. The result with a good oil filter or a good powerline filter is longer, trouble-free operation.

Problems can range from “soft” errors where information is scrambled in computing systems to gradual circuit deterioration resulting in premature failure and intermittent operation to outright destruction of circuits.

Surge problems appear to be worsening because of the increased use of electronics. As the tiny integrated circuits used in electronics proliferate, more of them are exposed to the dangers of powerline surges.

According to industry standards, powerline surges inside a building can reach up to 6,000 Volts, and 3,000 amperes, and deliver up to 90 joules of energy.

Very large storm induced surges occur from a few times a year in medium exposure areas to 40 times a year in high exposure areas, but surges over 1,000 Volts may occur many times a day since they are caused by normal equipment operation.

Surges can be classified as external and internal. External surges are generally more severe than internal surges while internal surges generally occur more frequently (about 80% of all surges are internal). External surges are frequently caused by storms and normal power company switching operations. Internal surges occur when equipment within the building is cycling on and off.

Surge Protection

Other powerline surge suppressors rely mainly on the 40 year old “All Mode” surge suppression technology developed by General Electric in 1972.

The newer, patented Series Mode technology used by Zero Surge limits surge current as well as surge voltage. This technology was developed by J. Rudy Harford, Zero Surge’s founder.  It was modeled to provide exceptional performance with interconnected equipment and overcomes the serious shortcomings of shunt suppressors, namely excessive let-through voltage, limited service life, poor filtering, and safety ground wire contamination. Series Mode technology is recommended by experts for modern interconnected computing systems, where reliability and performance are essential.

NO. Properly designed Series Mode suppressors limit not only surge voltage, but surge current, thus avoiding the problems of neutral wire (common mode) and ground contamination.

IEEE-587 specifies test conditions, not performance. Any inexpensive extension cord can claim to meet IEEE-587. It is the detailed results of the testing to the IEEE-587 standard that is important, not the fact it has been tested.

The joule rating is a limitation of the product. Shunt suppressors should not be subjected to surges larger than their joule rating or they will likely fail. Unfortunately, you have no way of knowing in advance how many joules will be in a surge!

ZERO SURGE products do not have a joule rating limitation since they do not work on the diversion principle of shunt suppressors. The series elements internally limit surge current. Even a surge with enough current to blow out the largest shunt suppressor will not harm ZERO SURGE suppressors.

Some surge suppressors fail after a single large surge. The largest surge you can expect on a 120 Volt powerline within a building is 6,000 Volts / 3,000 Amps according to industry guidelines). Some surge suppressors fail in thermal runaway, can overheat and cause fires.

Before buying a suppressor, compare rated service life for various surge levels. Do not purchase a surge suppressor unless it has a stated service life that is reasonable for your application.

The response time is the time it takes for Shunt Mode suppressors to go from an “off” condition to an “on” condition. Unfortunately some manufacturers state the time for their suppressor to start coming on as opposed to being completely on, giving a misleading view of actual performance. ZERO SURGE uses a Series Mode reactor which is always active, so the response time is zero, or instantaneous.

Yes. A dedicated line can minimize internal surge damage, but provides a direct pipeline for the more dangerous external surges.

No. Zero Surge does not recommend incorporating cable and telephone line protection at the point of use.

Cable and telephone line protection are frequent add-ons to power line surge suppressors. Users should know that providing an interface between the power line and various cables, as is done in these protectors, is very complex and may be dangerous to your electronics and in some cases, your health!

A “whole building” protector generally means protection at the powerline service entrance.  A review of the clamping levels for most main panel protectors show their clamp levels to be so high as to be ineffective for sensitive electronics. Whole building protector manufacturers, therefore, recommend supplemental point-of-use protection.  Plug-in, point of use protectors with low let-through levels are necessary since they should be the first line of defense for sensitive electronics.

Customer Service

Stock items like our plug-in models, usually ship within one business day.  Non-stock items usually ship in 2-3 business days, depending upon the item and the quantity.

Zero Surge products are shipped via UPS ground service.

Yes. Zero Surge Inc. warrants its products to be free from defects in materials and workmanship under normal 120VAC and 240VAC service conditions, including energization by means of the relevant standard 120V or 240V, 60 Hz electrical power, for a period of 10 years.