| Choosing the right Power UPS Guide to professional UPS selection |
The following steps will guide you through the process of specifying and selecting a professional UPS for your organization. For a
newcomer to the UPS field it is advised to start with UPS Basics article.
1. Decide the required UPS Size.
The Power Capacity of the required UPS should be the first thing to decide. Connect to the UPS only consumers which should be
protected. The UPS must back up servers, Communication items, preferably Personal Computers, and Emergency lights. Connect
monitors only if you need to provide service even if power fails. Avoid connecting printers, copiers, non-critical lights etc, even if
the UPS size permits.
Now calculate the total current drawn from the UPS, which is the total sum of the currents of every consumer connected to it.
Multiplying thus derived total current figure, by the local grid Phase to Neutral voltage, (normally 120V in North America or 230V in
Europe) provides the required VA Rating. Note the total current of a three-phase system is derived by the sum of all three phases.
The current demand of the consumers can be found in the users manual or read from the label attached to the instrument. To get
the final figure, reserve extra capacity for any expected additional future Loads. The VA figure so derived is in most cases 30% to
50 % above the current, which the equipment consumes. You will have to consult the manufacturer of the equipment or measure the
current for a more accurate figure.
The wattage rating is the second figure to consider. It represents the amount of real Power that the load requires. The Watts to VA
ratio, called Power Factor, is dictated only by the nature of the load. This ratio can theoretically be any number between zero to one,
but it is normally between 0.6 to 0.8. Unless you have the exact figure,Power Factor 0.7 should be OK for
Personal computers and 0.8 for large systems.
A personal computer (or server) including a monitor will normally require no more than 300 VA. Multiplying the VA rating by a
power factor of 0.7 renders 210Watt. The common presentation is 300VA/210W.Thus, any UPS with a VA rating equal to or above
300VA and Watt rating equal to or above 210W should be sufficient for a single computer.
2.Decide the required Autonomy time (Back-up time)
Autonomy time is the time that batteries are able to back-up operation and feed the load upon failure of utility power. Load
consumption and size of UPS batteries dictate the back-up time. UPS systems rated below 20-30 KVA come normally with internal
batteries. Medium and high power systems (above 3 to 5 KVA) are frequently designed to allow back-up time expansion by adding
external batteries.
Statistically, the duration of 90% of utility power outages is less than 5 minutes.The amount of utility grid outages in the Western
World is about 10 to 30 per year. If you are not located in a specific grid troublesome area, you may expect not more than three
power failures a year, lasting beyond 5 minutes.
The main reason to purchase a UPS is to protect data and hardware. Main causes of data failures happen due to short time
phenomena on the utility grid, such as spikes, sags, dips, and high frequency noise. Uncontrolled, abrupt power failure can harm
both software and hardware. Data in process or not stored on the Hard Disk is totally lost. In some cases, the Hard Disk may also be
entirely destroyed. The harm done to it, if power fails during the writing
period for instance, is like a scratch made by the needle of a phonograph record should you turn it off while it is playing.
Unless you provide real time service, or your equipment comprises part of a working industrial process, which can't be interrupted,
you might be happy with a system that backs up your loads for 5 minutes, and then turns off your computer in a graceful manner.
In most cases, mains outage is shorter than 5 minutes, and UPS turn off won’t be needed.
Therefore, 7-to 15 minute's back-up time should suffice for most applications. You should however make sure that the UPS is
supplied with a software suitable for your computer or network, and that the software exits the system, while storing on computers
hard disk all open files before turning down the computers, the way you would do it manually.
You should also take in account that back up time is strongly related to the size of your load. UPS systems sense the battery voltage,
emitting audible alarm, including load turn off signal to the computer, to allow orderly shut down, short time before the battery
discharges below a preset voltage level, at which the UPS will turn off. Lower load draws less current from the batteries, extending
the battery time.
APC's type LS 500 UPS for instance with 3.6 minutes backup time at full load, provides 14 minutes back-up time at half load.
Thus, over sizing the UPS by 20 to 30%, which good practice requires doing anyway, will enable you to protect your computer
network without purchasing a system with bigger battery.
In applications which require continuous operation, even during power absence, other and additional factors should be considered.
The battery should be sized according to the required autonomy time. The size of the UPS may have to be increased because small
units do not allow battery extensions. You may need to increase UPS size also in order to supply the charging current of an extended
external battery, or in order to decrease the charging time required by big battery bank. You might also consider installation of a
backup generator, to feed the UPS. Cost, availability of space, and reliability, should all be taken in consideration.
3. Decide the type of the UPS you need
UPS's are roughly divided to three main classes. The Off Line UPS is the simplest and the least expensive, then comes the Line
Interactive type, which overcomes the major disadvantages inherent to the off-line unit, finally the Double Conversion On-Line UPS
which provides the best power protection.
An off-line UPS, also called Stand-by or Back-UP, feeds the load continuously from Mains. Upon mains outage, the load
connections transferred to the inverter fed from the batteries. Most of the short term spikes surges and high frequency harmonics
are decayed by means of special filters. However, various phenomena of transient nature during mains existence, like over voltages
and deeps can harm protected data. These units are generally equipped with spike suppressors, aimed to protect the hardware from
high voltages on the utility grid.
Off-line systems are used mainly for low power installations, small offices, personal home computers and other less critical
application, where eliminating 85% to 90% of computer malfunctions caused by power failure, is satisfactory. In such applications,
this low cost solution, is a good value for your money, it decreases tenfold the probability of a harm to data and hardware from
utility Grid. The inverter output voltage in this class is usually non-sinusoidal, frequently called semi-sinusoidal. Personal computers
will probably work nicely with such waveform. You should however check with your vendor before using other types of loads.
Professional installations generally require better protection, Here comes the Line Interactive UPS, called sometimes Interactive
UPS, or On Line Interactive UPS. These systems are also based on stand-by principle, working directly from mains, switching to
battery (via the inverter) upon mains disappearance. Here however, additional circuits filter and correct output voltage, keeping it
within allowed tolerance band, thus providing conditioned power to the critical load. This UPS will probably have a sinusoidal type
inverter, therefore, special precautions as regards to type of load might not be required.
Line Interactive UPS units come generally in the range of 500 to 5000 watts, offering a popular solution for servers, personal
computers hubs and other loads in this power range. These units are used mainly for short backup times, sufficient to provide an
orderly shut down.
Like the Off-Line unit, also here the stand by behavior, is in most cases the major drawback of the Interactive UPS. Practically, UPS
operation is verified upon mains failure which is the most critical moment.Upon mains disappearance, the load is connected to the
inverter and batteries. Any dormant malfunction, such as loose internal connection or weak batteries might be revealed at the very
moment when it is called to action.
Neither off-line nor Interactive UPS systems are able to correct frequency. The output frequency of any stand-by unit is in normal
operation the same as the input utility grid. These units should therefore be avoided on sites equipped with small back-up generators,
exhibiting generally poor frequency regulation.
The Interactive UPS is a professional solution for business application where the main concern is to provide software protection
from about 90% to 95% of utility grid disturbances. These units may be utilized in relatively small networks, comprising 10-12
computers. They are applied in such locations as lawyer offices, accountants, sales agencies, engineering offices etc. Some prefer
to back up with Interactive UPS less critical equipment in the company, such as personal computers connected to LAN network,
whereas the severs are backed up by an ON -LINE UPS.
An On-Line UPS, also called Double Conversion UPS, or True On-Line UPS, is the ultimate solution for all applications from
one, or two kilowatts up to Megawatt sized consumers. Here, the load is constantly fed from the Inverter, providing conditioned,
stabilized sinusoidal voltage. The utility line in these systems forms a backup source in case of UPS malfunction. The
Transfer switch will automatically transfer the load to mains in case of overload or UPS failure.
The On-Line unit comprises two converting stages. The first stage converts the incoming ac power to DC, thus creating a dc-buss,
which is fed either from mains or from storage battery. A second stage converts the DC power back to conditioned ac in order to
feed the critical load. Filters on the DC buss and fast regulating circuits in the converters practically isolate the load from any
abnormal utility behavior.
In normal operation, load energy comes from mains, via the Rectifier and the Inverter. Upon mains outage the battery supplies the
energy, which the load requires (by the dc/ac Inverter). Should the mains voltage return before the battery was fully discharged, the
Rectifier will feed the load through the Inverter and start a battery recharge regime to compensate for the lost charge.
Otherwise, the UPS will turn off when battery becomes fully discharged. The UPS will resume automatically normal operation upon
mains restoration. Also here, the Rectifier will feed the load via the Inverter, recharging the battery.
The Output voltage of an On-Line UPS is generally stabilized within one percent tolerance. Output frequency is locked to input if it
is within preset tolerance band, otherwise a free running crystal controlled clock will dictate the output.
The merits of Double Conversion ON -Line system make it the preferred choice for business and industrial applications. It is the best
solution in spite of the added system and electricity costs.
4. Estimate the required Reliability
You can rely on the UPS to back-up your system and protect it from most power grid problems. You should however consider
Reliability issues if you provide real time service. Unfortunately,though the calculations are very simple, some basic mathematical
knowledge might be required, if you want to make the calculations yourself.
Reliability and Availability are the basic functions for measuring UPS non-failure probability. You should be acquainted also with
some additional interrelated terms, which describe different Reliability aspects.
MTBF (Mean Time Between Failures), represents the average time (generally in hours) between expected failures. The UPS
manufacturer should supply the MTBF Figure (Either by means of UPS data sheet or when requested.).
Failure Rate (λ = Reciprocal of MTBF) represents the average number of failures during a particular interval.
Reliability (R (t) = e ^ (- λt)) is defined as the probability of no failure before time t. For comparison purposes "t" refers normally to
one year (8760 hours).
Suppose the MTBF of a UPS is 100,000 hours. The Reliability figure becomes 0.9161(e ^ (-8760/100,000). We can therefore expect
that in a one year interval 91.6% of the time (totaling 334 days) the UPS will operate satisfactory and feed the load with conditioned
power, but during 8.4% of the time (totaling 31 days) the UPS will be down. In case of ON-Line system the load will be fed during
the down time from, the utility grid.
For high mission requirements, this Reliability figure is generally unacceptable. An additional, Redundant, UPS can be connected to
work in parallel with the first unit. Thus, normally both units share the load. Should one unit fail the second will continue to feed the
load. As long as one of the UPS’s works correctly, the load is supplied with conditioned voltage.
Evaluating the proper formula shows that the Reliability figure will increase to 0.993. Thus 99.3% of the time it will be fed from the
UPS. And only 0.7% of the time ( 2.5 days per annum ) it will depend on the reliability of the utility power. Adding additional
redundant units increases the Reliability to any desired value.
In practice however, no UPS is left incorrect during 31 days. Two Additional Figures are used to describe the real situation:
MTTR – Mean Time To Repair, expresses in Hours, the total time, which takes to restore the UPS to normal operation, starting
from the moment of its failure until the service personnel complete their work.
Availability = MTBF/(MTBF + MTTR), represents the degree to which the system is operational when required.
Assuming that the stand alone UPS in our example will be repaired on average within 24 Hours (MTTR=24), the Availability
becomes 0.99976 (100000/(100000+24)). Meaning that 99.976% of the time the unit will supply conditioned power. The down
time now decreases to 2.1 hours per annum. We can further proceed to improve this figure by adding additional redundant units.
Parallel connection of UPS systems is possible only if units operate at the same frequency, same voltage are synchronized and have
an ability to isolate a faulty UPS disconnecting it from the common output buss.
5. Refine the deal
At these stage you should already know the KVA rating of the UPS you intend to buy, the type of the UPS (Standby/Line
Interactive/On-Line) The autonomy time needed, and the configuration (Stand alone or Redundant).
Now you can contact a nearby dealer, or try choosing UPS system by yourself or by selecting a suitable unit on the Web.
Here are some tips to help you while concluding your Power UPS deal:
6. Purchase the UPS
Numerous manufacturers are probably able to meet your requirements. Most provide well designed and reliable systems. The top
producers are:
APC - American Power conversion, 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 Power 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
newcomer to the UPS field it is advised to start with UPS Basics article.
1. Decide the required UPS Size.
The Power Capacity of the required UPS should be the first thing to decide. Connect to the UPS only consumers which should be
protected. The UPS must back up servers, Communication items, preferably Personal Computers, and Emergency lights. Connect
monitors only if you need to provide service even if power fails. Avoid connecting printers, copiers, non-critical lights etc, even if
the UPS size permits.
Now calculate the total current drawn from the UPS, which is the total sum of the currents of every consumer connected to it.
Multiplying thus derived total current figure, by the local grid Phase to Neutral voltage, (normally 120V in North America or 230V in
Europe) provides the required VA Rating. Note the total current of a three-phase system is derived by the sum of all three phases.
The current demand of the consumers can be found in the users manual or read from the label attached to the instrument. To get
the final figure, reserve extra capacity for any expected additional future Loads. The VA figure so derived is in most cases 30% to
50 % above the current, which the equipment consumes. You will have to consult the manufacturer of the equipment or measure the
current for a more accurate figure.
The wattage rating is the second figure to consider. It represents the amount of real Power that the load requires. The Watts to VA
ratio, called Power Factor, is dictated only by the nature of the load. This ratio can theoretically be any number between zero to one,
but it is normally between 0.6 to 0.8. Unless you have the exact figure,Power Factor 0.7 should be OK for
Personal computers and 0.8 for large systems.
A personal computer (or server) including a monitor will normally require no more than 300 VA. Multiplying the VA rating by a
power factor of 0.7 renders 210Watt. The common presentation is 300VA/210W.Thus, any UPS with a VA rating equal to or above
300VA and Watt rating equal to or above 210W should be sufficient for a single computer.
2.Decide the required Autonomy time (Back-up time)
Autonomy time is the time that batteries are able to back-up operation and feed the load upon failure of utility power. Load
consumption and size of UPS batteries dictate the back-up time. UPS systems rated below 20-30 KVA come normally with internal
batteries. Medium and high power systems (above 3 to 5 KVA) are frequently designed to allow back-up time expansion by adding
external batteries.
Statistically, the duration of 90% of utility power outages is less than 5 minutes.The amount of utility grid outages in the Western
World is about 10 to 30 per year. If you are not located in a specific grid troublesome area, you may expect not more than three
power failures a year, lasting beyond 5 minutes.
The main reason to purchase a UPS is to protect data and hardware. Main causes of data failures happen due to short time
phenomena on the utility grid, such as spikes, sags, dips, and high frequency noise. Uncontrolled, abrupt power failure can harm
both software and hardware. Data in process or not stored on the Hard Disk is totally lost. In some cases, the Hard Disk may also be
entirely destroyed. The harm done to it, if power fails during the writing
period for instance, is like a scratch made by the needle of a phonograph record should you turn it off while it is playing.
Unless you provide real time service, or your equipment comprises part of a working industrial process, which can't be interrupted,
you might be happy with a system that backs up your loads for 5 minutes, and then turns off your computer in a graceful manner.
In most cases, mains outage is shorter than 5 minutes, and UPS turn off won’t be needed.
Therefore, 7-to 15 minute's back-up time should suffice for most applications. You should however make sure that the UPS is
supplied with a software suitable for your computer or network, and that the software exits the system, while storing on computers
hard disk all open files before turning down the computers, the way you would do it manually.
You should also take in account that back up time is strongly related to the size of your load. UPS systems sense the battery voltage,
emitting audible alarm, including load turn off signal to the computer, to allow orderly shut down, short time before the battery
discharges below a preset voltage level, at which the UPS will turn off. Lower load draws less current from the batteries, extending
the battery time.
APC's type LS 500 UPS for instance with 3.6 minutes backup time at full load, provides 14 minutes back-up time at half load.
Thus, over sizing the UPS by 20 to 30%, which good practice requires doing anyway, will enable you to protect your computer
network without purchasing a system with bigger battery.
In applications which require continuous operation, even during power absence, other and additional factors should be considered.
The battery should be sized according to the required autonomy time. The size of the UPS may have to be increased because small
units do not allow battery extensions. You may need to increase UPS size also in order to supply the charging current of an extended
external battery, or in order to decrease the charging time required by big battery bank. You might also consider installation of a
backup generator, to feed the UPS. Cost, availability of space, and reliability, should all be taken in consideration.
3. Decide the type of the UPS you need
UPS's are roughly divided to three main classes. The Off Line UPS is the simplest and the least expensive, then comes the Line
Interactive type, which overcomes the major disadvantages inherent to the off-line unit, finally the Double Conversion On-Line UPS
which provides the best power protection.
An off-line UPS, also called Stand-by or Back-UP, feeds the load continuously from Mains. Upon mains outage, the load
connections transferred to the inverter fed from the batteries. Most of the short term spikes surges and high frequency harmonics
are decayed by means of special filters. However, various phenomena of transient nature during mains existence, like over voltages
and deeps can harm protected data. These units are generally equipped with spike suppressors, aimed to protect the hardware from
high voltages on the utility grid.
Off-line systems are used mainly for low power installations, small offices, personal home computers and other less critical
application, where eliminating 85% to 90% of computer malfunctions caused by power failure, is satisfactory. In such applications,
this low cost solution, is a good value for your money, it decreases tenfold the probability of a harm to data and hardware from
utility Grid. The inverter output voltage in this class is usually non-sinusoidal, frequently called semi-sinusoidal. Personal computers
will probably work nicely with such waveform. You should however check with your vendor before using other types of loads.
Professional installations generally require better protection, Here comes the Line Interactive UPS, called sometimes Interactive
UPS, or On Line Interactive UPS. These systems are also based on stand-by principle, working directly from mains, switching to
battery (via the inverter) upon mains disappearance. Here however, additional circuits filter and correct output voltage, keeping it
within allowed tolerance band, thus providing conditioned power to the critical load. This UPS will probably have a sinusoidal type
inverter, therefore, special precautions as regards to type of load might not be required.
Line Interactive UPS units come generally in the range of 500 to 5000 watts, offering a popular solution for servers, personal
computers hubs and other loads in this power range. These units are used mainly for short backup times, sufficient to provide an
orderly shut down.
Like the Off-Line unit, also here the stand by behavior, is in most cases the major drawback of the Interactive UPS. Practically, UPS
operation is verified upon mains failure which is the most critical moment.Upon mains disappearance, the load is connected to the
inverter and batteries. Any dormant malfunction, such as loose internal connection or weak batteries might be revealed at the very
moment when it is called to action.
Neither off-line nor Interactive UPS systems are able to correct frequency. The output frequency of any stand-by unit is in normal
operation the same as the input utility grid. These units should therefore be avoided on sites equipped with small back-up generators,
exhibiting generally poor frequency regulation.
The Interactive UPS is a professional solution for business application where the main concern is to provide software protection
from about 90% to 95% of utility grid disturbances. These units may be utilized in relatively small networks, comprising 10-12
computers. They are applied in such locations as lawyer offices, accountants, sales agencies, engineering offices etc. Some prefer
to back up with Interactive UPS less critical equipment in the company, such as personal computers connected to LAN network,
whereas the severs are backed up by an ON -LINE UPS.
An On-Line UPS, also called Double Conversion UPS, or True On-Line UPS, is the ultimate solution for all applications from
one, or two kilowatts up to Megawatt sized consumers. Here, the load is constantly fed from the Inverter, providing conditioned,
stabilized sinusoidal voltage. The utility line in these systems forms a backup source in case of UPS malfunction. The
Transfer switch will automatically transfer the load to mains in case of overload or UPS failure.
The On-Line unit comprises two converting stages. The first stage converts the incoming ac power to DC, thus creating a dc-buss,
which is fed either from mains or from storage battery. A second stage converts the DC power back to conditioned ac in order to
feed the critical load. Filters on the DC buss and fast regulating circuits in the converters practically isolate the load from any
abnormal utility behavior.
In normal operation, load energy comes from mains, via the Rectifier and the Inverter. Upon mains outage the battery supplies the
energy, which the load requires (by the dc/ac Inverter). Should the mains voltage return before the battery was fully discharged, the
Rectifier will feed the load through the Inverter and start a battery recharge regime to compensate for the lost charge.
Otherwise, the UPS will turn off when battery becomes fully discharged. The UPS will resume automatically normal operation upon
mains restoration. Also here, the Rectifier will feed the load via the Inverter, recharging the battery.
The Output voltage of an On-Line UPS is generally stabilized within one percent tolerance. Output frequency is locked to input if it
is within preset tolerance band, otherwise a free running crystal controlled clock will dictate the output.
The merits of Double Conversion ON -Line system make it the preferred choice for business and industrial applications. It is the best
solution in spite of the added system and electricity costs.
- It offers the best power protection, covering all types of mains disturbances
- There is no size limit. Standard ON-Line UPS's are available to backup any
- With the right system, no practical limit exists on the available back-up time.
- Many systems allow power extension to satisfy the needs of a growing enterprise
- Units can be connected in redundant configuration to increase reliability or in parallel to enhance output power.
- In addition, this is the best choice, considering such issues as modularity, ability to work from generator, input power
factor correction, hot swapping, maintenance, fault clearing, supervising, and communicating.
4. Estimate the required Reliability
You can rely on the UPS to back-up your system and protect it from most power grid problems. You should however consider
Reliability issues if you provide real time service. Unfortunately,though the calculations are very simple, some basic mathematical
knowledge might be required, if you want to make the calculations yourself.
Reliability and Availability are the basic functions for measuring UPS non-failure probability. You should be acquainted also with
some additional interrelated terms, which describe different Reliability aspects.
MTBF (Mean Time Between Failures), represents the average time (generally in hours) between expected failures. The UPS
manufacturer should supply the MTBF Figure (Either by means of UPS data sheet or when requested.).
Failure Rate (λ = Reciprocal of MTBF) represents the average number of failures during a particular interval.
Reliability (R (t) = e ^ (- λt)) is defined as the probability of no failure before time t. For comparison purposes "t" refers normally to
one year (8760 hours).
Suppose the MTBF of a UPS is 100,000 hours. The Reliability figure becomes 0.9161(e ^ (-8760/100,000). We can therefore expect
that in a one year interval 91.6% of the time (totaling 334 days) the UPS will operate satisfactory and feed the load with conditioned
power, but during 8.4% of the time (totaling 31 days) the UPS will be down. In case of ON-Line system the load will be fed during
the down time from, the utility grid.
For high mission requirements, this Reliability figure is generally unacceptable. An additional, Redundant, UPS can be connected to
work in parallel with the first unit. Thus, normally both units share the load. Should one unit fail the second will continue to feed the
load. As long as one of the UPS’s works correctly, the load is supplied with conditioned voltage.
Evaluating the proper formula shows that the Reliability figure will increase to 0.993. Thus 99.3% of the time it will be fed from the
UPS. And only 0.7% of the time ( 2.5 days per annum ) it will depend on the reliability of the utility power. Adding additional
redundant units increases the Reliability to any desired value.
In practice however, no UPS is left incorrect during 31 days. Two Additional Figures are used to describe the real situation:
MTTR – Mean Time To Repair, expresses in Hours, the total time, which takes to restore the UPS to normal operation, starting
from the moment of its failure until the service personnel complete their work.
Availability = MTBF/(MTBF + MTTR), represents the degree to which the system is operational when required.
Assuming that the stand alone UPS in our example will be repaired on average within 24 Hours (MTTR=24), the Availability
becomes 0.99976 (100000/(100000+24)). Meaning that 99.976% of the time the unit will supply conditioned power. The down
time now decreases to 2.1 hours per annum. We can further proceed to improve this figure by adding additional redundant units.
Parallel connection of UPS systems is possible only if units operate at the same frequency, same voltage are synchronized and have
an ability to isolate a faulty UPS disconnecting it from the common output buss.
5. Refine the deal
At these stage you should already know the KVA rating of the UPS you intend to buy, the type of the UPS (Standby/Line
Interactive/On-Line) The autonomy time needed, and the configuration (Stand alone or Redundant).
Now you can contact a nearby dealer, or try choosing UPS system by yourself or by selecting a suitable unit on the Web.
Here are some tips to help you while concluding your Power UPS deal:
- Increase UPS capacity to allow for future expansion.
- Don't buy backup time that you don't need. Longer autonomy time does not mean better equipment.
- In case of Online units make sure you can add external batteries in future, and that you can increase power by adding parallel
units if expected
- If you do not see a clear advantage for your application, don't pay more. Higher price does not necessary mean a better or
more reliable unit.
- Don't buy any extras if you are not sure that they are needed for your application. Most can be added in the future whenever
required.
- Some manufacturers provide 6-figure guarantee to cover damage to your equipment.The enormous sums are seldom
meaningful, you won’t generally be paid above the value of your backed up hardware. The main items, such as loss of data,
or discontinuity of service to your clients are in most cases not covered
- Make sure that the UPS comes with software which shuts down gracefully and automatically all backed up computers.
- Make sure that the UPS includes surge protectors on input and on its communication lines.
- Make sure that the UPS performs automatic battery tests, 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 manually initiated test.
Nobody remembers to keep the routine.
- Avoid falling into a trap of misleading terms. Smart UPS should regulate output Semi-sinusoidal output is not sinusoidal. On -
Line must be double conversion and be able to regulate output frequency. Note that "Automatic self-test " does not always
mean battery test as well.
- Backup time has no meaning if you don't consider the amount of UPS loading. Partial load increases dramatically the time
the battery backs-up the equipment.
- Prefer hot swap-able Batteries. The batteries of some systems are not accessible by the operator and should be replaced by
qualified technician.
- When purchasing the UPS, make sure that after sales service is in good hands. Check who provides the service, how fast is
it, and whether it is provided in your premises.
- Check Guarantee. Duration, Where and When. It is not uncommon to get several years guarantee, 7 days per week at your
premises.
- Check the make of the UPS you are going to buy. Check that manufacturing company is at least ten years in the UPS
business. Get recommendation if the company is unknown.
6. Purchase the UPS
Numerous manufacturers are probably able to meet your requirements. Most provide well designed and reliable systems. The top
producers are:
APC - American Power conversion, 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 Power 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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