Power Protection in the Home Theater - Use of Surge Suppressors to Guard Expensive Electronic Gear

Surge Suppressors - A First Line of Defense

All home theater equipment should be equipped with at least some form of surge protection. Surge suppressors represent the most basic form of power protection - a first line of defense for all sensitive electronic gear.

Keep in mind that a surge in the ac voltage or a lightning strike, could lead to disaster - turning expensive gear into a smoking heap of plastic and metal. Investing in a suitably rated surge protector is surely a lot cheaper than having to replace expensive home entertainment electronics.

The large selection of suppressors available on the market at an even wider range of price levels can make the process of selecting an appropriate protection device far from simple. Many of these surge suppressors would look the same to a non-technical person - with almost nothing that distinguish the cheapest from the best.

In their simplest form, surge suppressors often come as an inexpensive surge protected multiple-outlet power-strip. More expensive units would normally incorporate additional surge protected connections for the phone line and the coax TV input; some units include surge protected LAN connections as well. In this manner, anything that interconnects with your equipment would have to go first through the surge protection circuitry within the power-strip.

How Surge Suppressors Work

The basic operational principle behind surge suppressors is to clamp high transient voltages while absorbing this potentially destructive energy. This energy is then dissipated in the form of heat - thus protecting vulnerable circuit components and preventing system damage.

In the event that the surge lasts for several milliseconds, the process may also cause enough current to trip the house circuit breaker, or blow the equipment fuse, thus protecting your gear.

Surge suppressors usually make use of a mix of components to suppress voltage spikes on the line. However, the mostly used component in surge protection circuitry is the Metal Oxide Varistor (or MOV).

The MOV is not the only surge protection component - gas-tube surge arrestors, avalanche diodes (similar to power zener diodes), and reactive type passive circuitry using inductors and capacitors, all possess the desired electrical properties required to dampen a transient behavior.

None of these devices does represent the perfect surge suppressor. Some lack speed, while others - like avalanche diodes - though extremely fast acting, do have a limited energy absorption capacity. For this reason, commercial surge protection devices combine several of these technologies arranged in multiple stages, to prolong surge suppressor life and improve response times.

Surge Suppressor Ratings

This discussion will not be complete without highlighting a few of the most basic parameters that define the capabilities of a surge suppressor; these are the UL listing, voltage rating, peak surge current, and power handling.

IEEE 1449 Underwriters Laboratories Listing: Referred to as 'UL 1449' or simply 'UL listing', represent a set of specifications that determine if a surge suppressor is safe during use.

Ensure that the selected surge suppressor is labeled as 'UL-listed transient voltage surge suppressor (TVSS) 2nd edition'. A UL-listing as 'power tap' is not sufficient.

A UL-listed TVSS does not imply that it will protect your equipment from surges, but rather that the surge protector is not likely to pose any personal hazard to you during use e.g. through electrocution, fire, etc.

Operating Voltage: The lower the voltage rating of a surge suppressor, the more effective protection the surge suppressor will provide, however the voltage rating has to be in line with the respective application. In particular, the chosen suppressor voltage rating should allow the normal peak AC voltage to exist across the line - this is 1.414 times higher than the specified RMS value.

Peak Surge Current: This represents the maximum transient current that the suppressor can handle during a surge.

Joule Rating: Also referred to as 'Energy rating', this is a measurement of the energy absorption capability of the surge protection device. Typical values may vary from 500 to 3000 and over. The higher the joule rating, the better is the surge suppressor capability to absorb energy spikes on the line.

A Word of Caution

Designed properly, surge suppression devices can work over-and-over again, but...

Do not take surge suppression devices for granted. Beware of cheaply made power line conditioners and other protection gear. Some surge suppressor components used in these devices are typically a one-time use only. This means that your system may end up completely unprotected after a surge.

Quality: The quality of a surge suppressor is reflected in the price of the protection device, but not only. Check the joule rating of the surge protector to get an indication of how much damaging energy the suppressor can handle. The bigger the joule rating is, the better. Keep in mind however that unlike the UL-1449 Listing, there is no standardized testing methodology to determine the energy rating of a surge suppressor. Hence, do not rely on the joule rating alone - look also at the built-up quality and in particular, at the product warranty on offer.

Warranty: In addition to the standard product warranty, some manufactures also offer a 'Connected Equipment Product Warrant'. This is normally in the region of several tens of thousands of dollars.

A longer product warranty period and a higher connected equipment warranty value reflect a higher level of confidence on part of the manufacturer that the surge suppressor can protect your expensive home theater gear. Try to go for surge suppressor devices that come with at least a 5-year product warranty period, and a minimum of $10,000 (preferably $25,000), connected equipment warranty.

Performance: The performance of surge suppressors degrades with each surge absorbed. The problem here is that the rate of degradation is totally unforeseen due to the unpredictable nature of the surge. Surge rise time, peak voltage, energy level, and duration, all have a varying effect on surge protection circuitry.

A surge may have a higher energy level than the suppressor can handle, leading to the destruction of the suppressor and zero protection against possible future surges. To minimize this risk, top-quality power protection gear would normally make use of over-rated components in protection circuitry - thus allowing multiple surges to take place without any damage to the equipment.

Surge Suppressors are not lightning protection devices: Surge suppressors can provide adequate protection from 'normal' surges on AC power lines. Protection against lightning strikes it is a completely different story. No surge suppressor device can offer you the required level of protection in this respect.

Personal safety: Ensure that your surge suppressor is clearly specified as UL listed Transient Voltage Suppressor (2nd edition). This will reduce the risk of personal harm from fire or electrocution especially during a surge. At the same time, keep in mind that a UL-listed device does not guarantee that it will protect your equipment.

Conclusion:

In reality, surge suppressors are just a first line of defense - they do not provide protection from damaging voltage fluctuations and noise on the line that can seriously degrade the performance of your AV gear.

Surge suppressors should form part of an overall power protection solution - the use of line conditioners and ac-regenerators coupled with an appropriately rated surge suppressor would surely provide a more comprehensive approach to protecting expensive electronic gear.

Obviously, there is a price to pay for power protection, but it is literally - an ounce of prevention that can save you a big headache down the road!

Andrew Ghigo - A Telecoms/Electronics engineer by profession, with specialization in digital switching and telecoms fraud management systems.

Editor and publisher of http://www.practical-home-theater-guide.com - a site dedicated to all home theater enthusiasts with the scope of serving as a comprehensive home theater guide to home theater systems, product reviews and home theater design.

This article is an excerpt from a series of articles appearing under thePower Protection section of the site.

Topics covered include benefits of power protection in the home theater, power line conditioners, ac regenerators, and surge protection. There is also a 'before-you-buy' power protection checklist, and a short discussion on the possible use of inexpensive computer-grade uninterruptible power supplies, as part of a home theater power-protection solution.