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- Should I use an UPS on my Laser Printer?
- A UPS unit’s main job is to provide back-up power in order to save valuable data. In the case of a laser printer, print jobs are readily re-queued, so there is no real loss of data should a power outage occur while printing. APC’s SurgeArrest is a cost-effective way to protect a laser printer. However, for a desktop publishing
application in which a large amount of time is invested to download fonts, a UPS may be required.
- What about the PC workstations on the LAN?
- According to Novell, “We strongly recommend that you use UPS protection for network workstations. Protecting network workstations has always been a necessity; however, until the introduction of APC’s Back-UPS, a cost-effective way to achieve these benefits was simply not available.” Now users who are interested in protecting their LAN workstations can benefit from:
- Complete local data protection
- Ability to work through outages
- Superior protection from surges and overvoltages
- Reception of important warning messages from the server
Since the most recent work on a file may be performed on a workstation, client PC protection prevents data files corrupted on the workstations from being written back to the server. For this reason alone, UPS protection on workstations is crucial.
- What about output waveform?
- A UPS unit’s output waveform must deliver proper Peak and RMS (a kind of average power) to the load. Ideally, this is accomplished with a sine wave identical to AC power, although a step sine wave can be designed to provide both proper Peak and RMS values.
Square wave output UPS units, in contrast, deliver output with Peak power identical to RMS power. This creates stress on components, premature failure, and hence, decreased reliability. Only purchase UPSs with sine wave or stepped wave output.
| Ideal sine wave power (under load) from APC Matrix or Smart-UPS |
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Stepped wave power from APC Back-UPS |
| Undesirable square wave power output from a competing brand which fails to provide proper Peak and RMS values for your computer |
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- A salesman is trying to get me to pay more for “on line” protection; what’s up?
- Of the three general types of UPS protection (on-line, standby and line-interactive), on-line is the oldest. If reliability is a concern, your choice should be line-interactive or standby. In fact, a study titled, “AC-UPS Reliability and Availability Performance: Comparison of Available Solutions,” presented by independent
researchers Mssrs Sunito, Uusitalo, and Jonsson at the 1989 INTELLEC conference, showed that from a computer users standpoint, all popular UPS solutions were equal in performance, but that using a standby UPS or a line-interactive system reduced downtime more than twice as much as using an on-line. In addition, the Mean Time Between Failures (MTBF) over a 10 year period for a standby UPS and line-interactive UPS
was twice that of an on-line.
A study by PC Magazine showed that on-line market share dropped precipitously (12%) over the last few years, while line-interactive share (which APC invented) has grown strongly. Furthermore, a recent article in PC Week, warned users to demand schematics whenever pressured to purchase an on-line UPS, as many so-called on-line UPS units incorporate switches and are “on-line” in name only.
- What do new PFC computers mean to my UPS choices?
- Modern computers incorporate a Switched-Mode Power Supply (SMPS) for converting AC to the DC required by the computer. Newer versions include power factor correction. While PFC eliminates dangerous harmonic currents, it is incompatible with some UPS designs, most notably ferroresonant based UPS units.
Federal standard, FIPS PUB 94, entitled “Guideline on Electrical Power for Automatic Data Processing Installations” addresses the ferro’s potential system instabilities. Lab tests have also shown:
- Stability is reduced when the DC load on the PFC supply is increased.
- Different PFC supplies reach instability at different loading points when fed from the same Ferro source.
While currently small, the number of PFC-equipped computers is expected to grow very rapidly as new legislation takes effect and computer manufacturers release new models incorporating PFC power supplies.
- Surge supressors are all the same - if it’s UL Listed I’m OK, right?
- “UL-listed” means a product has been submitted to Underwriter’s Labs for safety testing in a certain product category. However, the “surge suppressor” you paid $4.99 for may be “UL-listed” in the extension cord category.
The UL listing for surge suppressors is UL 1449. APC’s SurgeArrest products are the lowest priced surge suppressors to receive the best UL 1449 rating of 330V across all lines. Keep in mind that some vendors rate surge protection on the basis of joule energy. The IEEE specifically warns that such ratings are misleading. Instead, compare the IEEE surge Let-Through measure when shopping for a surge.
- Do I need to protect my laptop?
- While laptop computers spend a large part of their time disconnected from power problems happening at the outlet, they are highly susceptible to surges traveling along serial and modem lines right into the CPU. If you have an internal modem, you should protect your investment with an appropriate data line surge suppressor.
- Any myths or misconceptions?
- Perhaps the biggest myth (propagated by UPS manufacturers that will try to sell you more than you need for more than you should pay) is that so-called “on-line” or “no-break” are the only units appropriate for fileservers. In fact, both independent editors and third party vendors have endorsed standby and line-interactive designs for
their equipment for one simple reason: far greater reliability.
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Custom Networks, Inc.
www.CustomNetworks.net
P. O. Box 368 • 510 King Street • Littleton, Massachusetts 01460
(978) 952-2626 • (800) 535-5454 • Fax: (978) 742-9832
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