The power the electric utilities provide to our homes has some problems. The actual voltage is legally allowed to vary over a range of +/- 5% at the generating station. Large power loads going on- or offline can create voltage surges or sags called transients. Conditions like a hot summer day with everyone running their air conditioning full blast can tax total generating capacity causing serious brownouts or drops in available current. These can play havoc with sensitive electronic equipment, and cause extensive damage. Add to this the surges caused by electrical storms, and your computer starts to look like a duck during hunting season!
At the very least every computer should be protected by a good quality surge suppressor. This does not refer to the $3.00 bargain at the local hardware store. Expect to pay at least about $20.00 for real protection. Look for a suppressor that meets the UL (Underwriters Laboratories) 1449 rating of 330 volts or lower. This means that the suppressor will block voltage spikes exceeding 330 volts from reaching your connected equipment. It should also meet the UL 1283 specification for EMI/RFI noise reduction. This refers to Electro Magnetic noise, and Radio Frequency noise that can be picked up on the power lines acting like a big antenna, and carried on the lines into your home.
If you use a modem, it is also very important to protect it from surges, especially from electrical storms, being carried by the telephone lines. This is covered by UL497A specification for Secondary Telecommunications.
Most of the surge devices available for home use utilize Metal Oxide Varistors (MOV), these are electronic components that change resistance according to the voltage applied to them. They work very well, but they will eventually be damaged by the voltage spikes they intercept. For this reason, the suppressor should have an indicator light to show if the unit is still offering protection, If that light goes out or begins to flicker, the unit should be replaced. The amount of energy the unit can suppress is rated in joules, the higher the number of joules the better. Finally, be sure the MOV protection covers all three legs of the circuit including ground,
Better Protection – The UPS
Far greater protection is available with an Uninterruptable Power Supply (UPS). A UPS starts off by having a very good quality surge protection circuit, and in addition contains one or more large rechargeable batteries. If the electric power goes off, or drops below a safe voltage, a high speed sensing circuit boosts or replaces it with battery power in a tiny fraction of a second preventing damage to the connected equipment or data loss, and give you time to save your data, and shut down. If the power is off long enough to begin exhausting the battery, and the computer is unattended, most better UPSs will safely shut down the computer. In order to accomplish this, the UPS must be connected to the computer through a serial port, and software supplied with the UPS must be installed on the computer.
A UPS is one of the best investments a computer owner can make. A typical computer will experience several power glitches a day ranging from very minor to major. In addition to preventing a disaster, a UPS will prevent many of the mysterious data losses computers are prone to, and make all your connected components last longer, and run cooler. If you run your computer constantly or unattended, a UPS is a must. All UPS and most better surge protectors carry insurance that will replace any equipment that is damaged while connected to them.
Because any battery has a finite amount of energy stored, only the most important components should be connected to the battery backed outlets. This means the computer itself and the monitor, along with any external modems. Never connect a laser printer to the battery outlets, since they have very high current requirements, and will quickly drain the battery. Most UPSs have outlets that are not battery backed but are surge protected for your other equipment.
The amount of time that a UPS can keep a system running depends on the capacity of the UPS and the current drawn by the connected equipment. In other words, the bigger your monitor and more powerful your computer, the bigger the UPS you will need to have a reasonable run time when the power fails. A UPS is rated in watts or VA (Volts X Amperes) or both. The best way to determine how big a UPS you need is to go to the UPS manufacturer’s website. You will find a calculator to fill in listing what components you own, and the calculator will determine what size UPS will provide a specific number of minutes of battery protection. Decide the length of backup time you wish and buy that size UPS.
A simple rule of thumb is to buy a UPS that has VA rating at least twice the computers power supply rating in watts. For example, a computer with a 300 watt supply would need at least a 600VA UPS.