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Computer Power Protection

I decided that the purchase of a new computer was a good time to assess my level of electrical protection. I have my headphone rig covered with a PS Audio Duet. My primary video system is plugged into a Panamax MT8Pro. I am really happy with both of those units, and both are less than one year old. However, my computers are overdue for a power protection upgrade.

I have the computer, monitor, and speakers plugged into a 4-year old APC RS800 UPS, which is still using the original battery. This UPS model uses line interactive topology, which means that it switches to battery power via a transformer when the AC voltage is interrupted or falls outside of the defined operating range. This type of UPS outputs a stepped square wave signal when powering via battery.

I have a nagging problem with the UPS that caused me to do some research. Occasionally, my power supply would emit a 3-4 second buzz, then a click. Nothing else bad happens. My old Dell did this once in a while and I could never figure it out. I was concerned that the power supply was being overworked, or perhaps preparing to fail. However, when my new Antec Signature SG850 did it, I became very interested in diagnosing it. I was further intrigued by the fact that my Dell had stopped exhibiting this symptom when I moved it to a new location and plugged it into a normal surge protector.

It turns out that the sound was caused by the square wave signal from the UPS. It occurred when power voltage variations triggered the UPS to switch to battery for short intervals. Apparently, newer power supplies with Active Power Factor Correction do not respond well to square wave signals. In fact, according to Antec, this type of signal can damage the power supply over extended use. Antec, and other manufacturers, recommend that only UPS units that output a true sine wave be used with newer model power supplies.

I became concerned about this. What if I left the house for a while with the computer on, and the power went out? My computer could be subjected to this square wave input for several minutes on battery power until the automatic shutdown sequence was triggered... assuming it worked... or until the UPS battery died if the shutdown software didn't work.

Online UPS units are the only type that output a true sine wave. An online UPS continually converts the AC input to DC for the battery and then back to AC from the battery, providing a steady supply of clean regulated power. When the AC input is interrupted, the UPS continues to supply AC from the battery without interruption, but the battery begins to drain because it is no longer being charged. These units start at $250 and a unit with enough wattage and VA to handle my system would be $300-400! Hmmm... let's review... why do I need a UPS?

Controlled shutdown? I am not in a commercial environment. If my system goes down during a session, at worst I have lost some work or been kicked off my WoW server. Nothing that I couldn't get over easily with a glass of wine.

Protection from voltage variations? Aside from the fact that this was causing my problem in the first place, it turns out that my new power supply has AVR (Automatic Voltage Regulation) circuitry that works exceptionally well. I read a comprehensive review that tested this feature and found that the SG850 will output a constant DC voltage even when the AC input drops to 90V! My power supply, if left alone, does a better job of covering this issue than the UPS.

Surge protection? Most UPS units do a fair but not superb job of surge protection. They are all MOV (Metal Oxide Varistor) units, and usually offer mediocre voltage ratings. In addition, once the MOV takes a hit that exceeds its rating, it will sacrifice itself and no longer function. They can also wear out over time from many small spikes that are not noticeable except to the surge protector. There are many stories of surge protectors that have totally failed but still have a "protected" circuit light shining joyfully. It is a good idea to replace surge protectors in critical service every couple of years as a precaution. I don't want to be doing that with a $300 UPS.

Would I rather have protection from spikes or uninterrupted power? I began to research surge protectors. I quickly discovered that MOV units are not the best kind. What you want is a "Series Mode" surge protector. These units never fail, last a lifetime, and totally stop all current from passing through when they encounter a surge. They offer excellent, fail-safe protection... but they cost $200-300, and I have three computers and two bedroom video systems to protect! I can't justify the expense to protect all of those units with this alternative either.

My conclusion and new power protection strategy... I will buy a new high-quality MOV surge protector ($25-35) for my gaming computer every year, and rotate the older units down the chain to less critical components. Eventually, some will become power strips only, and the oldest units can be thrown away. I will always have 1-2 year old surge protectors on my computers, and decent protection on the other units. I am going to start by buying two new surge protectors for the main computers, and retiring the UPS unit that is long overdue for replacement.


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