Must Have UL Markings
When you choose a surge protectotor, the most basic requirement is an Underwriter Laboratories (UL) sticker or other marking referencing a Standard 1449, Transient Voltage Surge Suppressor, its acronym TVSS, or a combination of them. Note that in September 2009, there was a change in terminology as the standard moves forward with ANSI/UL 1449 approved plug-in type surge protectors, referred to as Type 3 Surge Protection Devices (SPD). Furthermore, some manufacturers may adopt the new standard early, so a UL mark referencing a Type 3 SPD is also acceptable. A UL sticker not mentioning those standards might only be approved as an extension cord or outlet splitter, so read carefully.
The UL marking will also refer to a Clamping or Transfer Voltage, the point at which the surge protection kicks in and begins to send voltage away from your equipment and back through your building’s ground wire. Lower is better, 330 is best and 400 is acceptable. Another part of the UL listing is what kind of surges are dealt with; since surges can occur between any pair of Line, Neutral, and Ground wires, look for a listing that states all three pairs: L-N, L-G and N-G.
Not part of the UL information, but still important is the joule rating, used to measure how quickly the unit can dissipate unwanted power. You should look for a unit that has about as many joules as the equipment you’re plugging into it has watts… 400 is suitable for a simple PC and peripherals. Another important statistic is response time, or how long the surge protector takes to begin protecting your equipment when the power is too high. Obviously, lower is better, you’ll want something under one nanosecond. Keep in mind that since these aren’t numbers from UL, manufacturers have lots of leeway in how they measure and present these last two numbers, so don’t get too excited about outstanding numbers on a $6 unit from a brand you’ve never heard of.