April Showers Bring… Thunder Storms

Get Ready, Electrical Surges are on the Way!

As we move steadily towards spring and summer’s increased threat of violent thunderstorms, it’s time to talk about protecting your computer equipment from the damage caused by power fluctuations. This primer will help you choose the correct uninterruptible power supply (UPS) device for your system.

There are a number of potential electrical problems to be aware of and protecting your computer equipment against surges, brownouts, over voltages, and blackouts should be your goal.

Power Surges
Power surges are an increase in the voltage that powers electrical equipment. Surges often go unnoticed; often they are quick (1/20th of a second) and absorbed by the power supply of a device. Stronger surges will go through a power supply, damaging any circuits as it moves along the grounding line.

Surges come from utility power systems that have become unstable or unreliable. Power grids often generate surges as they switch between sources to generate power. Local surges can occur when power is suddenly added or taken away from a local area. Good examples are if someone starts up an electrical motor or a fuse blows. In the case of a fuse blowing, for a moment there will be more power available to the rest of a house. This sudden excess power can cause a surge.

Lightning can send a spectacular power surge along any conductive line. This is more than just a standard surge — no surge suppressor in the world will survive a direct lightning strike. By choosing the right power protection, your surge suppressor will take the hit, ending up melted, but your equipment will stay protected. Don’t forget that telephone lines are also highly conductive.

Brownouts are periods of low voltage in utility lines that can cause lights to dim and equipment to fail. Also known as voltage sags, this is the most common power problem, accounting for up to 87% of all power disturbances. Brownouts can also be caused by damaged electrical lines, or equipment that draws massive amounts of power (hair dryers, air conditioners, laser printers).

When line voltages are lowered, electrical equipment pulls more current to compensate and generates more heat in the process. Over time, this can contribute to equipment failure.

Brownouts are often caused when utility companies must reduce their voltage output to deal with high power. Demand for power exceeds the supply of power. Brownouts are also referred to as undervoltages; there is power, just not enough to meet the demand of equipment using it. Brownouts place undue strain on power supplies and other internal components, forcing them to work harder in order to function. Extended brownouts can destroy electrical components and cause data glitches and hardware failure.

Overvoltages (spikes)
Undervoltages are often followed by “spikes,” which are also damaging to computer components and data. Voltage variation can be the most damaging power problem to threaten your equipment. All electronic devices expect to receive a steady voltage (120 VAC in North America and 220/240 volts in many other parts of the world) in order to operate correctly. Overvoltages burn out power supplies and other components and can cause massive damage to electronic hardware. Extended overvoltages can even cause fires as electronics “fry” in the extra electricity.

Power failures, also known as blackouts, are the easiest power problem to diagnose. Any temporary, or not so temporary, interruption in the flow of electricity will result in a power failure which can cause hardware damage and data loss.

Blackouts can be caused by many things — weather, overburdened power grids, or the severing of a power line. Power failures are more than simply inconvenient and annoying. Because most computers use a volatile storage method (writing to memory prior to saving on to a hard-drive), information is lost when power is removed. Data can become corrupted, and some devices can be damaged by the sudden loss of power. Just as overpower occurs with brownouts, when the power comes back, spikes can occur that may cause even more damage.

Line Noise
The term “line noise” refers to random fluctuations — electrical impulses that are carried along with standard AC current. Turning on the fluorescent lights overhead, a refrigerator, laser printers, working near a radio station, using a power generator, or simply working during a lightning storm can all introduce line noise into computer systems.

Line noise interference can result in many different symptoms depending on the particular situation. Noise can introduce glitches and errors into programs and files. Hard drive components can be damaged. Televisions and computer monitors can display interference as “static” or “snow,” and audio systems experience increased distortion levels. Noise suppression is stated as Decibel level (Db) at a specific frequency (KHz or MHz). The higher the Db, the greater the protection.

UPS Sizing
To correctly size the proper UPS for your needs, all you have to do is add up the total power draw of the equipment and select a unit from the UPS technical specification page that can support that load for the amount of time desired.

First, which pieces of equipment need UPS support. Typically, only the CPU and monitor are supported to cut down on power draw to the UPS, but you may wish to include peripheral systems like modems or inkjet printers. Laser printers should never be plugged into a UPS.

List the nameplate wattage ratings for all supported equipment. Manufacturers vary in how they express draw so you may have to convert numbers to determine VA load.

If the power draw is expressed in AMPS multiply by your nominal line voltage (North America = 120, Europe = 230, etc.)

If the power draw is expressed in WATTS , multiply by 1.4 for VA load


Computer #1 –

230 watt power supply (x 1.4) = 322 VA load

Monitor #1 – 0.7 amp (x 120) = 84 VA load

Computer #2 –

2 amp power supply (x 120) = 240 VA load

Total: 746 VA


Once you have calculated the total VA draw of the equipment, look for a UPS that is rated equal to or higher than the number generated. Do not overload UPS systems! UPS systems that attempt to support excessive loads will pop their circuit breakers and provide no runtime at all.

UPS Runtime
To determine runtime, calculate the total VA required by your equipment and compare against the full- and half-load run times listed for the UPS. Fully loaded, you can expect any UPS to give between 5 and 10 minutes runtime.

The VA rating of a UPS is considered full load. Half load is simply a VA load that is half of that figure. Smaller UPS loads lead to ever longer runtimes. And since most equipment doesn’t pull its full VA load all the time, your run times may be significantly longer.

One or Several UPS’s?
There are advantages and disadvantages to either approach. You should first determine the proximity of the equipment to the UPS. Running extension cords to power remote equipment will affect warranty and may be against local electrical codes.

Some people feel there is a pricing advantage in purchasing a single, large UPS, but this is becoming less and less the case. Price competition in the 400 – 675 VA range has driven prices down to the point that multiple UPS systems are now within everyone’s price range.

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