I can tell you from experience that it is very important to safe guard your valuable electronics from surges (also know as transient voltage; transient meaning change or phenomenon and voltage being the measure of variance in electric energy). In the past two years, I've lost 2 televisions and the household has lost a total of 4 not including mine. Luckily, each computer has had surge protection. Wanting to learn more about my wise investment is the reason I researched information for this article on Surge Protectors.
Before we get to the different types of protection systems, let's get acquainted with some technology and terminology.
Everyone should know what fuses are. They are devices used to prevent surges from damaging other parts in an electrical circuit. By placing an element that can resist damage until a certain voltage level in a circuit, the rest of the circuit is less likely to be damaged. When a powerful surge invades a device with a fuse, it burns or breaks the fuse therefore breaking the circuit. This technology has been around for many years and has many different incarnations including car fuses and standard appliance fuses. Even though fuses are effective, they can't guarantee that extremely high level voltages will not bypass the fuse system and damage other parts.
MOV is short for "metal oxide varistor". These things exist is many devices at many levels of protection. What they actually do is move extra energy. The metal oxide inside the MOV has a unique physical property: It changes resistance levels when certain amounts of voltage flow though it. A low voltage will cause the metal oxide to create high resistance and a high voltage will cause it to create low resistance. Now, you be asking, "How can this be a good thing for protection?" Well, the MOVs are connected to not only the main line of power but the grounding wire as well with semiconductors, which allows them to release extra energy to the ground. When voltage is low, it lets more energy to flow through the system. A very nice technology and the more MOVs in a circuit, the more protection you have. Different MOVs have different absorbency levels as well. There are MOVs that can take more instant voltage than others and different MOVs suited for different power levels. The amount of energy it can absorb is measured in joules. Each MOVs joule rating is added up for the unit's total joule rating. When the max level is reached, the MOV will split open breaking that section of the circuit. There are other similar technologies that do the same thing such as gas discharge arrestors. Some technologies claim to be much better than MOVs, but every technology has its own flaws.
Here's a picture of a split MOV. It will no longer conduct any current. However, some cheap units will keep working after all the MOVs are destroyed.
"Protect the family jewels."
A joule is an amount of energy. It equals one watt-second which is one watt for a second. Duh. A watt is a unit of power. If you don't understand this, perhaps you should take some physics.
Joule ratings vary from the cheap power bar to the commercial strength UPS (Uninterruptible Power Supply). Now that we have the basics out of the way, let's continue to the first class of protection, the power bar.
The Power Bar
Now, we all know what these are. This has got to be the most widely used form of protection. In nearly every home, you can see one of those long, white, simple and cheap power bars. Most people buy them so they can plug up more electronic devices, but who buys them for their protection abilities? Hopefully, not many! The majority of these bars consist of simple fuses, ground wiring and/or very few MOVs. You can get these pieces of junk for $5-20 USD. Lighting will take these things out and anything connected to them easily. BELIEVE ME!
In reality, they are all surge protectors and surge protection is in all types of devices. But I call them this because this class is the first level of reliable protection. Most of these units can be had for $20-100 USD with varying features and quality. You can find these anywhere, including places like Wal-Mart and Radio Shack. These will save your electronics in almost any circumstance.
With most things, you get what you pay for and these are no exception. Some cheaper surge protectors function even after the MOVs are shot, making the protector useless. Look for models with a shut off feature when it has reached full capacity. There should be a light that will notify you if you have protection or not on most models. There are even ones that emit a sound when they have reached their limit. Also look for ones that have a ground light to show you there is a secure ground. Without good grounding, the extra energy will have nowhere to go but through the AC system.
It is best to find one with Coaxial (TV/Antenna), Satellite/Cable and phone jack protection as well. With models like this, you can protect your entertainment system or PC on all fronts. If you have a PC with a TV card and the antenna or cable line in is not protected, the surge protection will be nullified.
Most of these surge protector units also have line conditioning. Line conditioning cleans up the 'line noise' by using an electromagnet device called a toroidal choke coil. This conditioning can be used for not only the power line but the phone jack, TV and Satellite lines as well.
When buying one of these, staying above the $75 USD level is best. Try for at least models with protection at 400 joules. Some companies use deceptive joule ratings to make you think you're getting over 1,000 joules of protection. Since there is no standard way to classify a joule rating, some try to add up the joule rating for each plug to make a huge total rating. This is misleading and so the joule rating should not be considered as seriously as other specifications. Don't forget you get what you pay for. Try to keep it above $75 USD. Let's discuss what makes a surge protector good enough before we get to the UPS.
Seperating the Bars from the Protectors
The most important things to look for in a surge protector's specifications are:
- Three-way protection, like 'L-G, N-G, L-N' stand for all three types of line protection. Don't settle for one or two.
- UL or Underwriters Laboratories rating, if a unit doesn't have this, do not buy it! If it's not complete junk, it will have a UL sticker or logo on it. Make sure the label says Transient Voltage Surge Suppressor and not something like Re-locatable Power Tab. The Transient Voltage Surge Suppressor rating will guarantee that you get a product that meets the minimum requirements of a surge suppressor. UL 1449 on the label only means it passed surge protector safety standards. The Power Tab spec is OK, but is not the better qualification.
- The voltage level is the voltage at which the protector will start to move energy away. There are a few levels of voltage as classified by the UL. A few that I have found are 140, 330, 400 and 500. You want one with at least 330 because it will clamp at a low level and offer more protection.
- Response time is how fast the clamping system will work. This needs to be low to ensure that the extra energy is moved out as fast as possible. You really need around a nanosecond response time, anything more is dangerous. There are ones with around a picosecond response time that are even better.
The Mighty UPS! This is a cheap power strip. The MOV was much to close to the other components and in some cases this could start a fire. If loosing your stuff isn't a good enough reason to buy a good surge protector, maybe your house burning up is.
The UPS is the top of the line power conditioning class. Not only will it protect from to much power, but it will also ensure that your electronics get a constant supply of power if there is not enough voltage. When there is to much power it is stored in a battery. Then, when the power is needed later in case of voltage sags or total blackouts the system will supply power from the battery. There are many units that come with specialized software to help you out in case of emergencies and there is also generic support in Windows. There are models that just work when needed and ones that continuously charge their battery and condition power. Always go for a continuous UPS and not a standby one. Some people even use surge protectors in tandem with their UPS so the UPS won't suffer damage. Due to the UPS's complexity, it can easily cost $100 USD and more. Again, more expensive is usually better.
I hope that I answered your questions about personal surge protection and the many options you have as a consumer. Nearly any surge protector will do, but always remember that it's better to be safe than sorry. You can spend a lot of money on surge protection and power conditioning or you can spend even more replacing your expensive electronics down the road. I have a $25 UDS surge protector and it has protected my entire computer system several times when other electronics in the house have gotten zapped. Will you choose something that will almost guarantee your stuff is protected or would you rather be thrifty like me and wait to see if you need to make a trip to the insurance office? The choice is yours, choose wisely.
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Revision: 1/15/2003 - Added titles for sections and organized them better. Added/Subtracted some content to gel the reorganized sections better.