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Five steps to select a small network UPS
Following steps provide guidance for protecting a small network of up to ten computers from
grid disturbances and short outages. If however your network is larger or in case you need to
continue working at extended outages, please refer to a more detailed Guide to professional
UPS selection.
1. Decide the required SIZE of the UPS
Uninterruptible power supplies are rated according to their output VA rating, derived by
multiplying mains voltage times the total current drawn by the equipment. The resulting figure
expresses the capacity, by means of a unit called Volt -Ampere (VA) or KiloVolt-Ampere (one
KVA equals 1000VA).
The Voltage in the VA figure, is the device voltage (mains utility,or line voltage in your
country, 230 Volt in Europe, 120 Volt in USA ).The Ampere term is the total sum of the
individual input currents of all products connected to the UPS.
The Ampere (A) rating of each consumer is indicated on its nameplate. If only VA is indicated
divide it by device voltage to get the Amperage. If only Watt rating is indicated divide it by
device voltage and multiply the result by 1.5 .
After adding up the individual ampere ratings, multiply the resultant figure by the voltage to get
the required VA capacity.
Input current derived from product nameplates is generally 40% above the measured current
drawn by the UPS. This additional margin is however required for future expansion.
Connect the UPS only to critical equipment. You should back-up the computer, the
modem (if external), the communication devices,emergency back light, and the monitor if
preferred Do not generally connect the printer. Never connect a Lase printer.
2.Decide the required Backup Time.
Upon Blackout, the internal Inverter feeds the critical consumers deriving its energy from
internal or external batteries. When mains voltage is restored it will feed the loads from mains,
via the inverter while recharging the batteries to replenish the charge withdrawn during the
outage.
In case of sustained outage the unit will turn off when the charge in the battery is
withdrawn. Before turning-off, it should automatically send a shut down signal, to your
computer or network, thus initiating with the aid of special software supplied with the UPS,
a file saving procedure and graceful shut down of all computers.
Backup time depends on the amount of Real Power drawn by the load, which is expressed by
a Watt (W) unit. The ratio Watt/VA called Power Factor (PF) is dictated entirely
by the type of the Load. The PF of a resistive load like heaters or lamps is 1, the PF of
computer type loads equals generally 0.6-0.7
Thus an Uninterruptible Power Supply rated 500VA/350W with 10 minutes Backup, will
protect any load with VA rating less than 500VA and Wattage rating less than 350W. It will
backup 350W load for 10 minutes before turning off. Partial load increases dramatically the
back-up time. Manufacturers generally provide full load and half load backup time figures.
3. Decide the TYPE of the UPS you need
UPS systems have two main functions. First, they protect the essential consumers from
utility mains phenomena, which might harm consumer's hardware or its sensitive information.
Second, they enable to back-up the critical loads upon mains outage with conditioned voltage,
initiating graceful turn off, in case the battery is depleted before the mains is restored.
It is the quality of protection that makes the difference between the types. UPS's are roughly
classified into three main categories. The Off Line is the simplest and the least expensive,
then comes the Line Interactive type, which overcomes major drawbacks inherent to the off-
line unit, finally the On-Line which provides the best possible power protection.
An off-line UPS, also called Stand-by or Back-UP feeds the load continuously from Mains.
Upon mains outage, the load is fed from batteries through an Inverter, an internal device that
converts the battery voltage to alternating waveform of the same magnitude and frequency as
the mains.
The off-line units include surge arresters and internal filters, thus protecting the critical load
from Utility Failures, Sags and Surges, which comprise three out of nine mains related
disturbance types, but constitute about 95% of measured disturbances which might cause
computer failures.
Due to the affordable price, these systems are generally used for protecting personal
computers and workstations where overcoming the nuisance involved with utility outage
seems to be the main issue.
The Line Interactive UPS, called sometimes Interactive, On Line Interactive or Smart,
also works directly from mains, switching to battery (via the inverter) upon mains
disappearance. Here however, additional Automatic Voltage Regulating (AVR) circuit corrects
also Undervoltage and Overvoltage power problems thus solving five out of nine possible grid
disturbances. By continuously monitoring the input voltage, and keeping the output within
allowed tolerance band, it provides. Constant conditioned power to the critical load, solving
almost 99% of measured disturbances.
Line Interactive units come generally in the range of 500VA to 5000 VA, offering a popular
and cost effective solution for servers, hubs and other loads in this power range. These
systems are applied in relatively small networks, comprising 10-12 computers, in such
locations as lawyer offices, accountants, sales agencies, engineering offices etc.
An On-Line UPS, also called Double Conversion , or True On-Line , is the ultimate solution
for all applications from one kilowatt up to Megawatts sized consumers. Here, the load is
constantly fed from the Inverter, providing conditioned, stabilized sinusoidal voltage, isolating
it from any abnormal utility behavior. This system solves also such disturbances as Switching
transients, Line noise, Frequency Variations and Harmonic distortions, thus providing protection
to all nine disturbance types.
The merits of an ON -Line system, make it the preferred choice for critical business, industrial
applications and real time service providers.
4. Optimize your selection.
The said decision steps specify the right Uninterruptible Power Supply for your application,
some additional items should however be considered at the procurement stage. These, are
generally found in line Interactive and On-Line units. You might consider upgrading to line
interactive type if the following requirements are not available in the off-line unit.
5. Buy the right UPS
Ordering the right make from the right supplier, is a key issue to finalize the right selection.
At this stage you already know the Size in VA (or KVA), the Backup time and the Type.
Now you need to find the right product at the best price offered by a reliable seller.
Please note that previous steps provide general guidance about the system you might
need. The presented information however does not serve as a substitute to a professional
consultation. Unless you have a professional consultation, we strongly advise to make
sure with the supplier that his equipment works properly with your specific
computers and other loads, and that you are covered against any possible
malfunctions due to inadequacy of the offered UPS to your critical hardware.
Numerous manufacturers are probably able to meet your requirements. Most provide well
designed and reliable systems.
Following are the top brands, distributed all over the world:
APC , Powerware- Eaton, Liebert- Emerson, MGE UPS Systems, Delta Electronics,
Tripp-lite, Chloride Power, Toshiba, Belkin.
To start you will need only one Right lead. Shopzilla.com is a Rating Site which enables you
to find a proper product, see a list of stores that offer the product, compare prices see store
rating, shipping information and more.
Link to Shopzilla.com, Enter in the search window the required VA and Voltage (for instance:
1000VA 230V ). Upon selecting the UPS a new window opens with main product information,
prices and stores. More details if required may be found in the specific store.
grid disturbances and short outages. If however your network is larger or in case you need to
continue working at extended outages, please refer to a more detailed Guide to professional
UPS selection.
1. Decide the required SIZE of the UPS
Uninterruptible power supplies are rated according to their output VA rating, derived by
multiplying mains voltage times the total current drawn by the equipment. The resulting figure
expresses the capacity, by means of a unit called Volt -Ampere (VA) or KiloVolt-Ampere (one
KVA equals 1000VA).
The Voltage in the VA figure, is the device voltage (mains utility,or line voltage in your
country, 230 Volt in Europe, 120 Volt in USA ).The Ampere term is the total sum of the
individual input currents of all products connected to the UPS.
The Ampere (A) rating of each consumer is indicated on its nameplate. If only VA is indicated
divide it by device voltage to get the Amperage. If only Watt rating is indicated divide it by
device voltage and multiply the result by 1.5 .
After adding up the individual ampere ratings, multiply the resultant figure by the voltage to get
the required VA capacity.
Input current derived from product nameplates is generally 40% above the measured current
drawn by the UPS. This additional margin is however required for future expansion.
Connect the UPS only to critical equipment. You should back-up the computer, the
modem (if external), the communication devices,emergency back light, and the monitor if
preferred Do not generally connect the printer. Never connect a Lase printer.
2.Decide the required Backup Time.
Upon Blackout, the internal Inverter feeds the critical consumers deriving its energy from
internal or external batteries. When mains voltage is restored it will feed the loads from mains,
via the inverter while recharging the batteries to replenish the charge withdrawn during the
outage.
In case of sustained outage the unit will turn off when the charge in the battery is
withdrawn. Before turning-off, it should automatically send a shut down signal, to your
computer or network, thus initiating with the aid of special software supplied with the UPS,
a file saving procedure and graceful shut down of all computers.
Backup time depends on the amount of Real Power drawn by the load, which is expressed by
a Watt (W) unit. The ratio Watt/VA called Power Factor (PF) is dictated entirely
by the type of the Load. The PF of a resistive load like heaters or lamps is 1, the PF of
computer type loads equals generally 0.6-0.7
Thus an Uninterruptible Power Supply rated 500VA/350W with 10 minutes Backup, will
protect any load with VA rating less than 500VA and Wattage rating less than 350W. It will
backup 350W load for 10 minutes before turning off. Partial load increases dramatically the
back-up time. Manufacturers generally provide full load and half load backup time figures.
3. Decide the TYPE of the UPS you need
UPS systems have two main functions. First, they protect the essential consumers from
utility mains phenomena, which might harm consumer's hardware or its sensitive information.
Second, they enable to back-up the critical loads upon mains outage with conditioned voltage,
initiating graceful turn off, in case the battery is depleted before the mains is restored.
It is the quality of protection that makes the difference between the types. UPS's are roughly
classified into three main categories. The Off Line is the simplest and the least expensive,
then comes the Line Interactive type, which overcomes major drawbacks inherent to the off-
line unit, finally the On-Line which provides the best possible power protection.
An off-line UPS, also called Stand-by or Back-UP feeds the load continuously from Mains.
Upon mains outage, the load is fed from batteries through an Inverter, an internal device that
converts the battery voltage to alternating waveform of the same magnitude and frequency as
the mains.
The off-line units include surge arresters and internal filters, thus protecting the critical load
from Utility Failures, Sags and Surges, which comprise three out of nine mains related
disturbance types, but constitute about 95% of measured disturbances which might cause
computer failures.
Due to the affordable price, these systems are generally used for protecting personal
computers and workstations where overcoming the nuisance involved with utility outage
seems to be the main issue.
The Line Interactive UPS, called sometimes Interactive, On Line Interactive or Smart,
also works directly from mains, switching to battery (via the inverter) upon mains
disappearance. Here however, additional Automatic Voltage Regulating (AVR) circuit corrects
also Undervoltage and Overvoltage power problems thus solving five out of nine possible grid
disturbances. By continuously monitoring the input voltage, and keeping the output within
allowed tolerance band, it provides. Constant conditioned power to the critical load, solving
almost 99% of measured disturbances.
Line Interactive units come generally in the range of 500VA to 5000 VA, offering a popular
and cost effective solution for servers, hubs and other loads in this power range. These
systems are applied in relatively small networks, comprising 10-12 computers, in such
locations as lawyer offices, accountants, sales agencies, engineering offices etc.
An On-Line UPS, also called Double Conversion , or True On-Line , is the ultimate solution
for all applications from one kilowatt up to Megawatts sized consumers. Here, the load is
constantly fed from the Inverter, providing conditioned, stabilized sinusoidal voltage, isolating
it from any abnormal utility behavior. This system solves also such disturbances as Switching
transients, Line noise, Frequency Variations and Harmonic distortions, thus providing protection
to all nine disturbance types.
The merits of an ON -Line system, make it the preferred choice for critical business, industrial
applications and real time service providers.
4. Optimize your selection.
The said decision steps specify the right Uninterruptible Power Supply for your application,
some additional items should however be considered at the procurement stage. These, are
generally found in line Interactive and On-Line units. You might consider upgrading to line
interactive type if the following requirements are not available in the off-line unit.
- Make sure that it comes with shut down software to enable automatic load shut down
in case of prolonged outage.
- Verify that it includes surge protectors on its input and on its communication lines.
- Make sure that it performs automatic test warning whenever the batteries should be
replaced. Otherwise you will discover that your computer goes down when the lights
turn off. Don't be tempted to buy systems with manually initiated test. Nobody
remembers to keep the testing routine.
5. Buy the right UPS
Ordering the right make from the right supplier, is a key issue to finalize the right selection.
At this stage you already know the Size in VA (or KVA), the Backup time and the Type.
Now you need to find the right product at the best price offered by a reliable seller.
Please note that previous steps provide general guidance about the system you might
need. The presented information however does not serve as a substitute to a professional
consultation. Unless you have a professional consultation, we strongly advise to make
sure with the supplier that his equipment works properly with your specific
computers and other loads, and that you are covered against any possible
malfunctions due to inadequacy of the offered UPS to your critical hardware.
Numerous manufacturers are probably able to meet your requirements. Most provide well
designed and reliable systems.
Following are the top brands, distributed all over the world:
APC , Powerware- Eaton, Liebert- Emerson, MGE UPS Systems, Delta Electronics,
Tripp-lite, Chloride Power, Toshiba, Belkin.
To start you will need only one Right lead. Shopzilla.com is a Rating Site which enables you
to find a proper product, see a list of stores that offer the product, compare prices see store
rating, shipping information and more.
Link to Shopzilla.com, Enter in the search window the required VA and Voltage (for instance:
1000VA 230V ). Upon selecting the UPS a new window opens with main product information,
prices and stores. More details if required may be found in the specific store.
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