PC and workstation UPS

Five easy Steps to the right UPS

Specifying and Selecting the Right UPS for your PC or Work Station

1 Why do I need a UPS?

Radio rustle upon lights turn on, TV flicker when starting a washing machine, lights glitching in
stormy weather, lightning blackouts, power interruptions, all are line disturbances which might
erase data or damage permanently your computer or its hard drive. These visible incidents,
comprise only a fraction of various surges, spikes, dips and other phenomena of a transient
nature, too short to be seen, but by no means less harmful.

Some disturbances can be solved by suitable filters or surge arresters. UPS is however the sole
solution for almost all power disturbances.

A UPS protects your equipment from utility line disturbances, overriding short power outages,
by energizing the computer from batteries. In case of sustained power outage, the UPS will
signal the computer to start a graceful file saving and shut down Procedure thus, enabling to
resume normal operation without loosing data, when power is restored.

2. Sizing the UPS

Two figures are used to express UPS size. UPS capacity, expressed by Volt-Ampere (VA) is
calculated by multiplying maximum allowed UPS output current times its voltage (120V in
North America, 230V in Europe). The required capacity is derived by adding up the individual
VA ratings of all battery protected products.
The second figure, expressed in Watts (W) represents the real power delivered by the UPS.
Real power UPS rating equals the arithmetic sum of the Watt ratings of Individual consumers.
The ratio W/VA, called power factor, is generally 0.6 for computer loads in this power range.
Additional 20% should be allowed for future expansion, and to cover unaccounted for small
accessories.

VA and W ratings of the UPS, each should be above the corresponding figure of the total value
of battery protected equipment. The VA figure sets the allowed size of the equipment. The W
rating sets the backup time provided by the UPS.
500VA/300W UPS with 4 minutes Full Load (FL) rating, will protect a load equal or smaller
than 500VA (4.2 Ampere current for 120V line ), providing at blackout 4 minutes backup for
300W load. Backup time increases at lighter loads. Same UPS will probably provide 15 minutes
backup time at 150W (Half Load). Manufacturers generally state in product description the FL
and HL backup time ratings.

Labels on the protected items, contain generally the required information for calculating UPS
size. Alternatively the following list provides typical VA values:

Pentium P4 = 227VA including ATA 100 IDE Hard drive, IDE/EIDE or SAS/Ultra Hard Drive.
Add 20VA for each additional Hard Drive.
Pentium P4 = 247VA including DLT, Ultra, SAS, High RPM, or Serial ATA Hard Drive.
Add 40VA for each additional Hard Drive.

Pulsar = 272VA including ATA 100 IDE Hard drive, IDE/EIDE or SAS/Ultra Hard Drive.
Add 20VA for each additional Hard Drive.
Pulsar = 292VA including DLT, Ultra, SAS, High RPM, or Serial ATA Hard Drive.
Add 40VA for each additional Hard Drive.

Monitor 14"-15" = 79VA                Cable/DSC Modem = 31VA
Monitor 17" = 129VA                    Cable/DSC router = 39VA
CD/DVD = 14VA                          ICDN/Adaptor = 14VA

Scanner, Speakers, and Hub/switches are low consumption items accounted for in the 20%
allowance. Generally do not protect the printer. Never connect a Laser Printer to UPS.

Thus, typical UPS size requirement starts from 334VA (Pentium P4 with ATA 100 drive, 14"
monitor and CD), up to 639 VA ( Pulsar + everything included ). Accounting for 20% capacity
allowance, and 0.6 power factor results in UPS range from 400VA/240W up to 767VA/460W.

3. Specifying the UPS.

UPS types are described in our article Uninterruptible Power Supply Basics.
If your utility supply is generally fair and the computer serves personal use, you might be
satisfied with an OFF-Line UPS, that costs about 10US$ per 100VA and solves almost 95% of
power disturbances.
If however the power line in your location is relatively poor, and suffers from over or under
voltages you should have at least a Line Interactive UPS, in spite of its double price.
Line Interactive UPS should also be preferred for business applications, or if protection of
critical data is involved.

When selecting a UPS check that the following features are included:

Shutdown Software.
At least 4 minutes backup time at full load.
Battery replacement without tools.
Automatic self test including battery test.
At least 300 Joule Surge protection on all power outlets.
Surge protection on data lines.
Additional only surge protected outputs for noncritical equipment.
USB connectivity.
Data recovery warranty.

4. Selecting the UPS

Considerable number of UPS manufacturers offer UPSs which meet your needs. Most make
good and reliable systems. Bear in mind, that UPS is generally a long term investments and that
its main purpose is to protect sensitive data and expensive equipment, a reliable system from
trustworthy producer is therefore of utmost importance.

APC is THE main brand in these power levels, hereinafter suitable APC's product types:

BE500R: 500VA/300W: Off Line UPS. Outputs: 4 surge & battery backup, 4 Surge only
protected. 4 minutes backup 300W load, 365Joule Surge protection,
3 year warranty.

BE750BB:750/450W: Off Line UPS. Outputs: 5 surge & battery backup, 5 Surge only
protected. 6 minutes backup 300W load, 365Joule Surge protection,
2 year warranty.

BR900: 900VA/540W: Line Interactive UPS, 4 surge & battery backup, 3 Surge only protected
outputs. 5 minutes backup at 540W load, 320 Joules surge protection,
2 year warranty.

These are North American 120V types. Check APC site in your country for local equivalents.

5. Buying the right UPS

Finding the right store is the last mission. In the Pre-Internet era we had to make a market
survey, visit stores, compare prices, ask recommendation from friends etc. Today, with the
right link, we are able to perform all these exhausting and boring operations with a stroke of a
finger.

Shopzilla, the largest online rating service, developed a comparison-shopping search engine,
which enables buyers see the major stores selling the product, compare prices, see store rating,
and read clients' reviews.

Follow the following steps in order to make the right purchase from the best tore at the best
price:

Link to Shopzilla.com and Enter the selected UPS in the search window.
A new window shows the UPS picture and price range. Click on "compare prices"
button.
A new window shows list of stores, prices, store rating, customer revues, shipping cost,
including smart choice recommendation.
Link to the selected store to complete the transaction.