| RICHARD DANIELS CONSULTING |
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July 29, 2002
Primer: Power Surge Protection By: Richard Daniels
Computer equipment has become much more powerful in the last decade. Computer equipment has become much less costly in the last decade. Computer equipment has also become much more fragile in the last decade.
Manufacturers in a desperately competitive environment have had to cut the odd corner to get the price point down. The system power supply is much less robust than it once was. Although the need for clean stable power has increased, the ability of the power supply to deliver has been compromised in the name of economy. Power supplies do not regulate and filter power as well as they need to, and fail all to quickly in the face of a power surge or spike. This is not true for all computer power supplies. There are still good solid units being produced. The average home system (bought by most small businesses) does not have the more robust power supplies.
What all of this means is that good upstream protection is required. In an ideal world everyone would have full online uninterruptible power supplies that would filter out harmonic distortion, transients, and other hardware life shortening power events. The reality is that we all have budgets to live within.
But just as we do our daily/weekly backups (similar to buying car insurance) we also need to protect the system from catastrophic failure with a power bar (similar to car bumpers and crush zones).
All power bars are not created equal.
Prices for power bars range from under $10.00 to $200.00+. At the low end they are little more than power splitters with a switch and a 15-amp breaker. A $10.00 power bar will not protect your equipment.
As you increase the amount you spend the sales language changes, and for the uninitiated becomes quite confusing. In fact there are some simple things to look for in choosing a power bar that take some of the mystery out of the purchase.
Look for a UL1449 designation.
UL 1449 is an Underwriters Laboratory specification that requires the surge suppressor to meet certain specifications. Any power protection device that you plan to use with your computer should have this designation at the minimum.
The specification requires that plug in surge suppressors be rated in three categories based on the “Let Through Voltage”. The LTV sometimes listed, as Clamping Voltage is the voltage level allowed before the unit begins shunting the excess to ground. UL calls this the MLV rating or Measured Limiting Voltage. Only the best two categories are of interest to the computer user. In the $50.00 to $75.00 range there are units rated at 400 volts. In the $75.00 to $105.00 range are units rated at better than 330 volts.
Given the weakness in most modern desktop power supplies the 330-volt level is a better choice.
This is only one of the criteria needed to make an informed decision. The other variables that should be added to the mix are the maximum amount of current that the unit can handle, and the length of time that it takes to respond to an over voltage situation.
A Spike isn’t a Surge.
A voltage spike is considered to be an over voltage transient of 2 nanoseconds or less. A surge is 3 nanoseconds or more. Some units claim a 0.0 nanosecond response time, which physics say just can’t be although if they are reporting the response time of the shunting component inside the unit it is almost instantaneous. This shunting component is called a Metal Oxide Varistor or MOV. Realistically times range from <5 down to <1 nanosecond.
Maximum current handled is also an area that varies somewhat. Levels handled in the price ranges being discussed here were from 20,000 Amps to 58,000 Amps.
When you take the various criteria in combination you begin to see that each of the companies has a different approach and philosophy on how best to protect your equipment.
The following three examples illustrate this point.
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APC Network Surge Arrest 8 - NET8N $ 89.00 8 outlets + RJ45 |
Current Handled - 26,000 Amps (Surge and Spike) |
| Response Time - 0.0 Nanoseconds (claims whole unit response time) | |
| Voltage Rating - 330 Lists a let through voltage of 40 over nominal (Clamp at 150) | |
| Blue DiamondBB-09-9B $ 59.009 Outlets + Cable + Telephone | Current Handled - 58,500 Amps (Spike) 6,500 Amps (Surge) |
| Response Time - <1 Nanosecond (MOV Response time) | |
| Voltage Rating - 400 Clamps at 400V | |
| SyCom SYC-8TAC2
8 Outlets + Telephone $ 79.00 |
Current Handled - 52,000 Amps (Surge) |
| Response Time - <5 Nanoseconds (Full Power Bar response time)
<1 Nanosecond (MOV Response Time) |
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| Voltage Rating - 330 Clamps at 130V |
The lowest clamping voltage is the Sycom, which also has the slowest response time. The thinking is to start shunting off the excess voltage long before the danger level on the protected devices.
All three of these units protect line to neutral, line to ground, and neutral to ground. They all have rudimentary filtering in the form of an inexpensive toroid coil. A toroid coil is an iron ring wrapped in copper wire. Cheaper units do not always have these features.
In use these units are taking the hit for your equipment. In a major surge situation the unit will self-destruct saving your equipment. In day-to-day use on smaller surges the unit will be diminished with every hit, saving your computer. When you buy the unit remember that it will wear out and have to be replaced.
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