Rosewill Computer Case 422 Informações Técnicas Página 74

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Line Conditioners
157
Disassembly
and Power
4
Tech
Tip
Tech
Tip
Feature Explanation
Energy absorption/
dissipation
The greater the number of joules (a unit of energy) that
can be dissipated, the more effective and durable a surge
protector is. This feature is sometimes called energy
absorption. A surge protector rating of 630 joules is more
effective than a rating of 210 joules.
TVS (transient voltage
suppressing)
rating
This is also known as response time. The lower the rating
the better. For example, a 330 TVS-rated surge protector
is better than a 400 TVS-rated one.
UL rating UL (Underwriters Laboratories) developed the
UL 1449
VPR
(voltage protection rating) standard to measure the
maximum amount of voltage a surge protector will let
through to the attached devices. The UL 497A standard is
for phone line protection, and the UL 1283 standard is for
EMI/RFI.
The federal government designates surge suppressor grades—A, B, and C. Suppressors are
evaluated on a basis of 1,000 surges at a specific number of volts and amps. A Class A rating is
the best and indicates tolerance up to 6,000 volts and 3,000 amps.
Which surge strip to buy?
When purchasing or recommending a surge protector, be sure it conforms to the UL 1449
standard and has an MOV status lamp. Also, check to see if the vendor offers to repair or
replace the surge-protected equipment in the event that they are damaged during a surge.
Surge protectors are not the best protection for a computer system because most provide
very little protection against other adverse power conditions. Even the good ones protect only
against overvoltage conditions. Those with the UL 1449 rating and an MOV status lamp are
usually more expensive. Unfortunately, people tend to put their money into their computer
parts, but not into the protection of those parts.
Line Conditioners
An alternative for computer protection is a line conditioner. Line conditioners, sometimes
known as power conditioners, are more expensive than surge protectors, but they protect a com-
puter from overvoltages, undervoltages, and adverse noise conditions over electrical lines. A line
conditioner monitors AC electricity. If the voltage is too low, the line conditioner boosts voltage
to the proper range. If the voltage level is too high, the line conditioner clamps down the volt-
age and sends the proper amount to the computer. Figure 4.32 shows a line conditioner.
Be careful not to plug too many devices into a line conditioner
A line conditioner is rated for a certain amount of current. Some devices, such as laser
printers, can draw a great deal of current (up to 15 amps). Some line conditioners are not
rated to handle these devices. Because laser printers draw so much current, if a computer
and a laser printer are on the same electrical circuit, that circuit should be wired to a 20-amp
circuit breaker. Most outlets in today’s buildings are on 20-amp breakers.
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