Whole House Surge Protector Definitions

surge protector - an device engineered to protect electrical devices from spikes. A surge suppressor tries to control and regulate  voltage supplied to an electric appliance by either blocking or by shorting to ground voltages above a safe levels.

• Clamping voltage — this is better described as the "let through" voltage. This specifies what voltage will cause the metal oxide varistors inside a protector to conduct electricity to the ground line. Suppressors with a lower clamping voltage are better but do not last as long.
• Joules — Joules indicates how much energy a device can take on before failing. The higher the number, usually means better quality and more life expectancy. An indicator of a good surge protector is one where the joules number is greater than 1000 and 40,000 amperes. Generally speaking, approximately 5-30 joules are dissapated into the ground for every joule absorbed by the suppressor. 
• Response time — Basically how fast a device responds. There is a slight delay from the time the device is exposed to the surge to the time it is able to divert the excess voltage. The longer the response time the longer the connected equipment will be exposed to the surge. This is not all bad because surges don't peak instantaneously either. Typically speaking, a surge protector with a response time in nanoseconds is generally fast enough. 
• Standards — The surge protector may meet IEC

Components of Various Surge Protectors

Metal oxide varistor — Surge arrestor used to suppress voltage transients and reduces the likelihood of damage to the fixture or the control caused by voltage surges or line noise.

Transient suppression diode

Gas discharge tube (GDT) — These rely on a gas trapped between two electrodes that is ionized by the high voltage to conduct electrical current. GDTs can conduct more current for their size than other components. Like MOVs, GDTs have a finite life expectancy, and can take a few very large transients or a greater number of smaller transients. GDTs also take time to trigger permitting a higher voltage spike to exist before the GDT conducts significant current. It is not uncommon for a GDT to let through pulses of 500V or more of 100ns in duration. In some cases additional protection is necessary to prevent damage due to this effect. GDT create a short circuit when triggered, so that if any electric power (spike, signal, or power) is present, the GDT will short this, and will continue conducting until all electric current sufficiently diminishes. Unlike other protector devices, a GDT will conduct at a voltage less than the high voltage that ionized the gas. Gas arrestors are often used in telecommunication equipment. Due to an exceptionally low capacitance, GDTs are commonly used on high frequency lines.

A selenium voltage suppressor is a "clamping" semiconductor similar to a MOV, but it does not clamp as well. However, it usually it has a longer life than a MOV. It is used mostly in high-energy DC circuits, like the exciter field of an alternator. It can dissipate power continuously, and it retains its clamping characteristics throughout the surge event, if properly sized.

A quarter-wave coaxial surge arrestor is used in RF signal transmission routes. It features a tuned quarter-wavelength short-circuit stub that makes it pass a bandwidth of frequencies, but presents a short to any other signals, especially down towards DC. The bandwidths can be narrow (about ±5% to ±10% bandwidth) or wideband (above ±25% to ±50% bandwidth). Quarter-wave coax surge arrestors have coaxial terminals, compatible with common coax cable connectors (especially N or 7-16 types). They provide the most rugged available protection for RF signals above 400MHz; much better than gas discharge cells typically used in the universal/broadband coax surge arrestors. Quarter-wave are useful for Telecom, Wi-Fi at 2.4 or 5 GHz but less useful for TV/CaTV. Since a quarter-wave shorts out the line, it is not compatible with systems sending power for a LNB up the coax downlink.

Carbon block spark gap overvoltage suppressor — an older technology still found in telephone circuits. A carbon rod is held with an insulator a specific distance from a second carbon rod. The gap dimension determines the voltage at which a spark will jump between the two parts and short to ground. The typical spacing for telephone applications in North America is 0.003 inch (0.076 mm).^[10] Carbon block suppressors are similar to a gas arrestor but with the two electrodes exposed to the air.

Series Mode (SM) surge suppressors are not rated by joules because they operate completely differently than the above suppressors, and are vastly superior, offering no materials that wear out over time, even after thousands of surges and spikes. Their starting prices are thus higher, starting at around 130US and up. The main differences in this type of suppressor and the others is that this type absorbs the surge, whereas the others discharge it, and the fact that MOV types wear out over time, or even with one large surge or spike.^[11]

Return to Whole House Surge Protector Home