Question: Is My Surge Suppression Still Suppressing?
How can I tell if my Surge Suppression Still Functional? How do I tell if I have exceeded the limit.
Most power strips on the market today use the Metal Oxide Varistor (MOV) as the primary component for suppressing surges and spikes in electric voltage. The MOV is an electronic component that resembles a capacitor. It is typically a round disk with two electrical leads, and comes in various sizes for differing levels of protection. See the photo below of typical MOVs.
Most MOVs are made from zinc oxide with differing amounts of manganese, cobalt, bismuth, and other metal oxides. This matrix of materials is then placed between two metal plates to which the electrical leads are attached. The boundary between grains forms a diode junction, which allows current to flow in only one direction. The mass of randomly oriented grains is electrically equivalent to a network of back-to-back diode pairs, each pair in parallel with many other pairs. The diode pairs react differently at high and low voltages. When low or normal voltages are present, there is very little current flow through the MOV. However, in the presence of high voltages, the diode junctions break down, and a large current flows through the MOV. Another way to say this is that the MOV has a very high resistance at low voltages, and a low resistance at high voltages.
When placed in series in a typical power strip circuit, the MOV clamps down on voltages to keep them at a safe level for the electrical components using the strip. Instead of the large current flowing to the protected equipment, it instead flows through the MOV where it is dissipated as heat.
However, an MOV’s ability to choke down on high voltages is not limitless. The size of the MOV determines how many Joules* of energy can be dissipated. Once this limit is reached, the MOV is no longer effective, and new instances of high voltage will not be dissipated. Thus the high dollar electrical components are no longer protected once the inexpensive MOV reaches or exceeds its capacity.
Although MOVs are relatively cheap, replacing the MOV in a surge suppressor is not economically viable. It is more economical to replace the entire power strip.
Many power strips provide an LED to show that there is still some capacity remaining in the MOV. When the light goes out, it is time to get a new power strip. Until that point, there is still some surge suppression capability remaining, but it is impossible to determine the exact amount.
The SPF064-10 and SP104-10 are typical 15Amp surge suppressed power strips with LEDs showing active MOV protection.
Call us at 800-458-6255 for more information on what ISC can do to meet your needs for surge suppression, power strips, PDUs, UPSs, and remote power.
* A Joule is one Watt-second. A power strip like the SPF064-10 has 720 Joules of protection. It could absorb 720VA over one second, or 7200VA over .1 second, etc.
