UL 1449 -- What does it mean?

The Underwriters Laboratories standard UL® 1449 establishes suppression ranges for comparing surge suppressors.  These tests are conducted with 6000-volt surges applied to the AC line while measuring the clamping voltage.  As an example, an established UL range is 400 volts.  If one surge suppressor is tested and clamps at 335 volts and another 395 volts, UL would classify both as 400-volt units.  UL rates suppressors in ranges rather than at exact clamping voltages.  These actual clamping voltage levels should be noted when comparing surge suppressors.  In a critical application, the 60-volt difference in the above example could be significant.


Initial Clamping Voltage

Clamping Voltage is the initial voltage at which a surge suppressor begins to conduct.  The voltage is measured when 1mA DC (milli-amp) is input into the device through the AC power line.  By itself, this information is incomplete as performance criteria because most manufacturers use the same components which all begin clamping at 200 volts.  Don't be fooled by this number!  Look for the "let-through voltage", it will tell you the actual performance of the product.


Let-through Voltage

The let-through voltage of a surge suppressor is how much of a power surge it will allow through to connected equipment before it starts clamping.  This is measured by applying a power surge (defined by ANSI/IEEE) to the suppressor and measuring the number of volts above the power line sine wave that it allows to pass through.  The let-through voltage is an excellent way to compare surge suppression performance.  Obviously, a lower let-through voltage means a better performing product., and more protection for your connected equipment.


EMI/RFI Noise Filtration

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 such things as vacuum cleaners or household appliances.  This noise shows up as glitches or errors on computer systems, or "snow" on a TV screen.


Thermal Fuse

Many surge suppression products have what their manufacturers are calling a "catastrophic event" fuse.  In many cases this is nothing more than an ordinary fuse that will trip if there is too much current being drawn through the surge suppressor.  All Power-Tracker products are designed with "thermal" fuses.  This is a heat sensitive fuse that will take the surge suppressor and all connected equipment off line if the internal components reach dangerous heat levels caused by surges and/or sustained over-voltages.  Thermal fuses insure better protection for connected equipment and eliminates potential fire hazards.

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