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UPS doesn't last long

Discussion in 'Networking' started by associates, Jan 16, 2007.

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  1. associates

    associates Thread Starter

    Joined:
    Jan 16, 2007
    Messages:
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    Hi,

    I was wondering if anyone might be able to help me here. I'm looking for a better UPS for my network. At the moment, i have a UPS called Powerware 3110 that connects a server, a PC and 2 routers. but it doesn't work the way i wanted it to. Yesterday, we had a power blackout in our area. It kept the server and the rest of the network running for less than 2 minutes when the sudden power blackout started. I dont think 2 minutes would be enough time to shut down the server and the other PC properly. Consequently, both server and PC were shut abruptly because of no more electricity running through. I was told that it may be because the server and the other PC draw too much power out of the UPS and it's true. I tested it. I unplug the server and the PC from the UPS and just left the routers connected to it. Then, i played the switch on the UPS on and off. It still gave a bit of power to run the routers and modem for a few minutes before it died.

    My question is if there are anyone who might have had the same experience and would like to share their ideas as to overcome this issue, I'd be very grateful.

    Thank you in advance
     
  2. johnpost

    johnpost

    Joined:
    Dec 17, 2005
    Messages:
    317
    that unit is good for one pc, monitor.

    putting the load that you did on it uses all its
    capacity in a few minutes or overheats
    and shutdown in a few minutes.

    get another unit for the server.

    you want to have the ability to safely shut
    down your system and not loose data.
    so run just your pc and monitor off the
    battery. run things like printers through
    the surge protection but not the battery.
    you get about 15 minutes time or less
    depending on your system load, you want to
    size your ups to get about 10 or 15 minutes.
     
  3. O111111O

    O111111O

    Joined:
    Aug 26, 2005
    Messages:
    894
    Powerware 3110 is 650-700va. You're probably exceeding that. Most deskop manufacturers shoot for 5-10 minutes of runtime at load.

    Generally you don't want a lower load ratio than 1.3:1. (That is ration of VA drawn per VA of capacity)

    Look at the power ratings for the equipment you plug in. Real quick and dirty PF determination is volts * amps (which gives you watts, which for this purpose is close enough for volt amp calculations)

    Add up your VA rating for all of the equipment that you're running off UPS. Divide VA capacity of UPS by summed VA of equipment connected.

    Example:

    Powerware 3110: 650va capacity.

    Desktop: 3A @ 110V = 330va
    Server: 5A @ 110V = 550va
    LCD monitor: 1.5A @ 110V = 165va
    Wireless router/etc: 1A @ 110V = 110va

    SUM: 1155va

    UPS capacity (650va) / load estimate (1155va) = load ratio of 0.562:1

    OOPS! You've cut your UPS runtime by at least half, if not more. On a larger scale, this would cook the inverter/rectifier in the UPS.

    The moral of the story is to add up your capacity needs and find either multiple UPS to split the load across, or purchase a larger UPS. (Of which, you'll find that you will probably only be able to find a 1100-1200va UPS that will run off a 15A 110VAC circuit)

    Hope this helps.
     
  4. associates

    associates Thread Starter

    Joined:
    Jan 16, 2007
    Messages:
    17
    Thank you all for your replies.

    Now, i'm getting to know what i'm doing here. Yes, it allows 650-700va capacity. However, if i may ask one more question. Is this for the whole unit?

    I mean I can see that the powerware 3110 provides 5 sockets for "continuous surge protection". Three of them are for "Battery Power Backup". Just want to check if I do the right thing here. If i were to use this UPS for the server only (since it can only support one PC), I could connect one socket of "Battery Power Backup" to the PC Box, 2nd socket to the monitor. Is this right? sorry for asking this silly question but i just don't want to get into unexpected problem again. This would leave me one more socket of "Battery Power Backup" and i can connect it to something else so long the total amount of loads does not exceed 650VA.

    Thank you in advance
     
  5. O111111O

    O111111O

    Joined:
    Aug 26, 2005
    Messages:
    894
    Yep, I have a Liebert UPS that's similar. 3 of the outlets are powered by the inverter, and 3 are simply powered by the surge protector.

    The VA rating is only for systems powered by the inverter. The other 3 outlets are parallel to the inverter, and your only limiting function is the circuit breaker or melting point of the UPS case :)
     
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