UPS for Abit mobo computer

Discussion in 'Abit' started by Guest, Jul 11, 2005.

  1. Guest

    Guest Guest

    How does one relate the UPS needs for a particular computer/power
    supply. I am upgrading to a 530W power supply for my Abit mobo and
    system. Does this mean that any UPS I may buy needs to support 530 Watts
    or higher ?
     
    Guest, Jul 11, 2005
    #1
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  2. Guest

    Vanguard Guest


    530 watts is its power output, not its power consumption. You never
    mentioned the efficiency rating of the power supply. If, for example,
    the efficiency was 70% then the power consumption would be 530 watts /
    0.70 = 757 watts. Are you actually drawing 530 watts from your power
    supply or actually expect to draw that much with later addition to your
    computer's components? What else are you going to connect to the UPS?
    Please explain what good is a workstation's system unit on a UPS if the
    monitor is not also connected to the UPS. A file server can run without
    a monitor but a workstation is for use by a *user* and that means you
    need to *see* what is going on.
     
    Vanguard, Jul 11, 2005
    #2
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  3. You don't, to a large extent. You choose the rating according to how long
    you want the load (i.e. PC, monitor and anything else connected via the UPS)
    to remain functional without mains power.
    Yes and no. You don't choose the rating of the UPS according to the peak
    power consumption of your PSU. You choose it according to the expected
    average power consumption of the entire load (i.e. everything that you'll
    connect to the UPS, monitor, external devices and so-on). Also, as mentioned
    above, once you know the average power consumption, you also need to decide
    for yourself how long you need to maintain the load in the absence of mains.

    UPS's are little more than big batteries with some circuitry to convert the
    low DC voltage back into AC mains. The more you pay, the larger the capacity
    of the battery you get, although of course some of the extra money is taken
    up with toys like remote management, modular batteries and so-on.

    There's little point, for example, in a typical home user investing in
    enough capacity to run the system for several hours - unless of course you
    live somewhere where power cuts of this duration are common and need to use
    your PC when the power is out. For most of these users a fairly low capacity
    UPS with USB or serial feedback will do fine. That way when the battery
    starts to run out, the UPS can order the PC to automatically and safely
    hibernate or shut down without any data loss - just like a laptop would
    under similar conditions.

    To work out how long the batteries on a particular UPS are likely to last,
    you first need to work out the *average* (not peak) power consumption of
    your load. Once you have done that you can use some fairly simple equations
    to turn the various VA ratings into a typical run time in hours and minutes,
    and from that you can choose the UPS that best meets your needs.
    --


    Richard Hopkins
    Cardiff, Wales, United Kingdom
    (replace nospam with pipex in reply address)

    The UK's leading technology reseller www.dabs.com
     
    Richard Hopkins, Jul 11, 2005
    #3
  4. Guest

    Guest Guest

    Let's say, just as an example, I do. Then what is the minimum UPS
    wattage I need to support my computer and its power supply ?


    What else are you going to connect to the UPS?
    Of course. I need to add in my monitor's usage also. But I am just
    looking for a good formula to determine what the minimum UPS wattage
    should be that I get. Also I do not understand the relationship between
    the UPS VA and the wattage. So I am looking for hints there also.

    If you or anyone else wants to point me to somewhere I can read about
    UPS in relationship to the wattage used on my system, and how to
    determine the wattage actaully used on my system, I will be glad to read it.
     
    Guest, Jul 11, 2005
    #4
  5. Guest

    Wes Newell Guest

    The simple as is no. About any 400va ups would work for a short period.
    But the real question is how much power the things you are going to plug
    into will draw and how long you want it to run (which equates to the ah of
    the battery). I'd suggest a 600va UPS with a 7ah battery as minimum.
     
    Wes Newell, Jul 11, 2005
    #5
  6. Did you read my original post? UPS's are usually sold via their capacity
    (VA) not "wattage" - although some smaller ones do have a maximum
    instantaneous power/current draw rating.

    Obviously in this latter case you need to make sure that the minimum
    instantaneous power rating of whatever you buy, if indeed it has such a
    rating, is at least 530W.
    See above and my previous post.
    Wattage is a measure of the amount of power drawn by the load. The "VA"
    rating of the UPS is a measure of the *capacity* of the batteries.
    APC have some good product info on their site, including tables that will
    give you an idea of the expected runtime off various loads for each of their
    UPS models. www.apcc.com
    You could use your mains electricity meter to gauge the mean power
    consumption of your system, albeit slightly inaccurately. Check the
    consumption level of your meter over, say, an hour, with the computer
    switched off. Then switch it on and measure the amount of power consumed
    over another hour. From this you'll be able to roughly ascertain the
    wattage. Of course you have to make sure that you don't turn any lights,
    ovens etc. on or off during this testing or you'll bugger the data.

    Alternatively it's relatively easy to reach a spec figure for the power
    consumption of your PC. You should be able to find out the thermal design
    power of your CPU, graphics card, hard disks, monitor and so-on from the
    manufacturers. Add all the in-system power ratings up, and add another 35%
    or so for PSU inefficiencies and expansion. Then add your monitor and other
    external devices.
    --


    Richard Hopkins
    Cardiff, Wales, United Kingdom
    (replace nospam with pipex in reply address)

    The UK's leading technology reseller www.dabs.com
     
    Richard Hopkins, Jul 11, 2005
    #6
  7. Guest

    Vanguard Guest


    You need to look at the specifications for the UPS in which you are
    interested. A 1000VA UPS that has a load of 1000VA wouldn't supply any
    time at that full load - except if the battery actually could produce a
    sustained output at the maximum load. A UPS with a tiny battery would
    go poof in no time at its maximum draw but a huge battery could deliver
    that sustained maximum output load for a lot longer. So it depends on
    the capacity of the batteries in the UPS. As another example, I can
    string ten 12-volt motorcycle batteries together which would then handle
    a 120VA load, but a series of ten much larger car batteries could also
    sustain the same 120VA load but for much longer. With batteries, size
    does matter.

    The maximum voltage output of the UPS will be 120 volts (since that is
    what the connected equipment is rated for). The maximum current will
    depend on how much and how fast it can be drawn from the battery (so
    quality of battery and its chemical composition matters) and the size of
    the conductors used to connect the equipment. The typical power cords
    can only handle 15 amp currents. So theoretically you could draw 1800
    VA from the tap except it is likely that the battery cannot supply that
    high a current load. So it all depends on the battery in the UPS, not
    the VA rating because that won't tell you the time.

    For example, the chart at
    http://www.apcc.com/products/runtime_for_extendedruntime.cfm tells you
    how much running time you have with THEIR products using whatever
    batteries they employ in their products based on the load. You say that
    you have a 530-watt power supply except you never mention its brand and
    model. Lots of PSU makers lie about their specs so figure you'll get
    60% to 70% of their rated wattage (before the PSU fries since many don't
    provide decent overload protection). At two-thirds of your PSU's
    claimed 530-watt capacity, you could suck out from it 353 watts. At 60%
    efficiency, and if loaded at 353 watts, it would be sucking in 589 watts
    from your UPS. Now add a 19-inch CRT monitor that consumes another 140
    watts. With just the system unit and monitor, you are consuming 729
    watts. From their chart, APC's BR800 wouldn't give more than a minute
    or two of up-time and you probably cannot close all your applications
    and properly shutdown the operating system and computer in that amount
    of time. If, however, you were loading your PSU much less, say only 200
    watts, and it was more efficient at 70% so it sucked in 286 watts at
    that load and your 19-inch monitor only consumed 80 watts for a total
    load of 366 watts on the BR800 then it would stay up for 12 minutes.

    I have a 2500 VA true-sinusoidal output transformer-isolated UPS that
    gives me 56 minutes of up-time (the two batteries weigh a total of 70
    pounds) with the system unit and a 19-inch monitor (the scanner and
    inkjet are also hooked up but they are in standby mode so they consume
    very little power for their indicator lights, and I also put the
    cordless telephone on the UPS since the telephone line is powered in an
    outage but not the cordless function of the base unit to the handheld
    unit). The 56-minute up-time was when the batteries were new. After 5
    years (and before I replaced them), I only got around 20 minutes of
    up-time. As to what up-time you can expect, you'll have to check the
    specs for whatever UPS you are looking at and actually know what type of
    load you are going to put on it.

    You could go to http://www.powerware.com/UPS/selector/, select your type
    of setup (probably a workstation), and walk through their wizard to
    figure out what size of UPS you need, but their runtimes are based on
    their efficiencies and battery capacity for their products, so the VA
    rating they show for their product may not equate to the same VA
    capacity for another vendor's product. Because you were vague in
    providing any details regarding your particular hardware setup, almost
    deliberately so, I choose some typical values and found that their $95
    low-end 700VA #3105 UPS (http://www.powerware.com/UPS/3105_UPS.asp)
    weighing 15 pounds might give you about 3 minutes of up-time whereas
    their $630 high-end 700VA #9120 UPS
    (http://www.powerware.com/UPS/9120_UPS.asp) weighing 29 pounds would
    give you 10 minutes (and a lots more features, too). Same VA rating but
    more time because of a larger battery, better efficiency, better shaped
    output voltage (sinusoidal or more granular stepped-wave), and other
    factors.
     
    Vanguard, Jul 11, 2005
    #7
  8. Guest

    paul diener Guest

    Try this link; you should find all your answers at their site:
    http://www.apcc.com/


    paul m diener, D.Sc. Information Technology
    Microsoft Windows XP Associate Expert
    diener & associates ltd
    small office network specialists
     
    paul diener, Jul 12, 2005
    #8
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