Buying a Surge Suppressor that works

by Don Rittner

Last week we talked about how surge suppressors are suppose to work and save your vital eletrical circuits in your computer and connected perhipherals. This week we talk about how to select the right suppressor for you.

Types of Surges

Surge types can be classified as external and internal. External surges are thought to be more severe than internal surges. However, internal surges occur more frequently. It’s estimated that about 80% of all surges are internal.

External surges are caused mainly by storms and your power company. Internal surges occur when equipment within your building is cycling on and off. Powerline surges inside a building can reach 6,000 volts, and 3,000 amps. Some surge suppressors fail after a single large surge of 6,000 volts and 3,000 amps, in a building wired for 120-volt.

Even if your workspace or building is protected commercially at the service entrance, this only minimizes problems from the 20% or so surges coming from outside like a lightening strike. The other 80% of surges from the inside of the building are not affected. It’s the internal surges that are more likely going to give you trouble.

Fortunately in most areas, very large surges occur only infrequently each year. Yet, in some areas 40 times a year is common. These are caused mainly by storms, usually lightning, or temporary dumps due to storm damage (power lines down, power relays tripping, transformer blowing). However, normal equipment operation surges can occur several times a day with charges over 1000 volts.

Basically, an ineffective surge suppressor can actually cause damage to a computer’s motherboard, data cards, and scramble data sent to interconnected computers, printers, scanners and modems.

Surge problems appear to be increasing because of the abundance of new electronic devices in our home and work place. The small integrated circuits used in these devices are exposed to the dangers of surges and can cause problems ranging from "soft" errors where information is scrambled in computing systems to complete frying.

It is well known in the suppressor industry that they fail often since one of the critical measures of a surge suppressor - how long it will work - is hard to determine until it fails, often taking your computer with it.

Most suppressors today do have the UL (Underwriters Laboratories) 1449 classification on them (they should), and are looking to add the UL 1449, Second Edition. However, this is a safety classification not a performance classification.

Since there has been no third party independent testing criteria for surge suppressors, our government recently developed a set of criteria on their own, using some of the UL’s classifications, which in turn utilize the national standard based on the IEEE's (Institute of Electronic and Electrical Engineers) C62.41-1991 standard.

For interior building use, there are three grades, A, B, and C. Each grade rates the harshness of a surge environment.

The IEEE's harshest interior environment, called Category B3, is one that could experience 100 surges of 6,000 volts, 3,000 amps in one year's time. A 6,000-volt surge is the largest voltage transient that should be experienced in the interior of a building. Underwriter Labs now tests a point-of-use surge suppressor to 1000 surges of 6,000 volts, 3,000 amps which is equivalent to ten years of IEEE's harshest environment!

This test, along with UL's lowest suppressed voltage rating category of 330V (UL has established a series of voltages for identifying the voltage suppression performance of suppressors) is what the government utilizes in defining a Grade A classification. These are pretty strong standards

If a surge suppressor maker meets these specifications and can prove it, you can almost bet the house that you will never see a surge-related problem.

Before you buy a suppressor, compare the rated service life for various surge levels. Get one that will likely do the job for where you live. According to the industry guide IEEE 587, a medium exposure location could have one 6,000-volt surge per year. On the other end, a high exposure location could produce 40 6,000-volt surges per year. So, if you think you are in a high exposure location, and expect a five year life from your surge suppressor, it should be designed to withstand at least 200 6,000 volt, 3000 ampere surges.

Kinds of Surge Suppressors.

Shunt

Shunt Mode technology was developed by General Electric over twenty years ago to protect stand-alone electrical equipment, but experts believe this technology is no longer.

Many of the low priced suppressors available are Shunt Mode type because this older technology is cheap to make.

Shunt Mode suppressors usually divert surges to the safety ground wire, using circuits described as "All Three Modes of Protection".

Yet, these resulting surges diverted to the ground wire can exceed 1000 volts, which can harm your computer.

When equipment such as modems, printers, scanners and other peripherals 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 a surge on the safety ground wire at another location is 600 volts, then the difference of 400 volts is fed into the interconnecting cables causing damage.

Ordinary surge protectors simply divert harmful surge current from the hot line to the neutral and ground wires, in a process called "all three modes of protection." Any surge suppressor, which diverts surges to the ground wire, is called a Mode 2 suppressor.

It’s this hot line that provides the only source of dangerous external surges since neutral and ground are bonded together and fastened to an earth rod at every service entrance.

Unfortunately, this "three mode protection" process diverts high-energy surges directly into delicate low voltage audio, video and computer data lines, because these lines use the power line ground wire circuit for their reference voltage.

Computers with modems or data lines to other equipment, such as networks and shared printers or scanners, should never use Mode 2 surge protectors which divert surges to the power line ground, because this will increase the likelihood of problems.

A surge, which is not diverted by a surge suppressor, will hit the computer's power supply, which is actually more surge tolerant than the delicate data line circuitry that Mode 2 suppressors put at risk. In effect, it might seem to be better not to have a suppressor at all in this situation.

It is recommended to avoid Shunt Mode surge suppressors that claim "All Three Modes of Suppression".

Series Mode

A new form of surge suppressor by a company called Zero Surge uses a Series type of suppression. It limits current (voltage) with a massive choke on the surge. It captures residual energy in a series of capacitors and slowly and harmlessly releases it to the neutral line. This resulting "let-through" voltage therefore is harmless. There is no surge current diverted to the ground wire. This technology suppresses surge energy and uses no MOVs that can wear at so it continually works.

Zero Surge is the only company that I know of that presently meets the new government criteria. Their surge suppressors are rated Grade A endurance, Class 1 performance, and Mode 1 application.

These series mode suppressors have a zero response time, unlike the shunt types, which need time to react (letting through spikes). Series mode devices are always active and always on.