400 vs 330 Volt Clamping. Most of the least expensive devices will not offer specifications better than UL’s 400 volt clamp rating. This means spikes will rise to 400 volt levels before they are contained. If this is from the bottom of the sine wave, the uncontained spike may actually rise to nearly 570 volts! Your equipment will be damaged every time the photocopier fires off a copy; or transients jolt from air conditioners, elevators or large switching motors, etc. Look for a 330 volt clamp rating.
Sine Wave Tracking. Lower quality devices do not have sine wave tracking—a high-tech capability that clamps spikes tightly against the sine wave. This prevents spikes from rising too high. High rising spikes are killers. You want sine wave tracking.
Response Time. Lower quality devices have a 5 nanosecond response time, sometimes even slower: too slow to be effective. Response time less than one nanosecond (a billionth of a second) is much more acceptable.
Safety Diagnostics. Devices with two LED diagnostic lights warn you of four critical safety features: (1) the power is on; (2) the protection is present (it’s working even if the power is turned off); (3) the wiring configuration inside the receptacle is correct (with the conducting hot wire on the correct side, otherwise you could get a severe shock by touching two appliances at the same time); (4) sufficient ground path to which damaging spikes can be directed (cheap devices may never tell you until a fatal moment. No ground path: no protection). Look for devices with the two LED diagnostic lights.
Warranties. Most general store-bought devices have NO warranty or only one year warranty. A quality device provides you a lifetime warranty with coverage of any damage from $2,500 to $25,000!
Let-Through Voltage. This is rarely mentioned in the lesser devices but is very important. For example, a quality protector under conditions of 6,000 volts 200 amps only allows 10 volts through. Lesser devices don’t even come close to offering this level of protection.
Joule Rating. This is a measure of how much damage energy suppressors can handle. The higher the better. Many don’t mention this, or they range from 50 to 200 joule level. These low ratings mean that their devices are not made to handle serious power disturbances like lightning. Look for a rating of 800 joules.
Peak Amps. A similar energy absorbing rating is called “peak surge current,” measured in amps, the force behind the voltage (more accurate than joule ratings). Look for a peak surge current rating of 200 amps.
Telephone Line Protection. If you are attached by a modem to the outside world, on the internet for example, you need this feature. Telephone lines are antenna systems that direct powerful surges right into the heart of your computer, and to anyone attached to yours, even if the lightning activity is miles away.
Noise Attenuation. Electro-Magnetic Interference (EMI) and Radio Frequency Interference (RFI) are disruptions on the smooth AC power line sine wave. This noise on the power line can be caused by lightning, generators, radio transmitters or even household appliances. This noise shows up as glitches or errors on computer systems, or “snow” on a TV.
Thermal Fuses. Few of the lesser devices have “thermal fuses” in them. They omit them because it increases the cost. This is a quality feature. These fuses are safety devices that are activated in the event that there is an extended over voltage (which can happen). They will automatically take the device off the power line, eliminating the possibility of a burned protector or damaged equipment.