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Putting UPS's in series?

Discussion in 'Intel' started by YKhan, Jun 1, 2010.

  1. YKhan

    YKhan Guest

    I'm wondering if there are any dangers or precautions to putting a
    couple of UPS's in series to increase their power-on time?

    Yousuf Khan
     
    YKhan, Jun 1, 2010
    #1
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  2. In comp.sys.ibm.pc.hardware.chips YKhan <> wrote in part:
    > I'm wondering if there are any dangers or precautions to putting
    > a couple of UPS's in series to increase their power-on time?


    Even presuming sufficient VA (=W/PF), few UPSes produce
    nice sine waves on their outputs while most expect them on
    their inputs. There may be problems [overheating] with the
    second UPS. UPS should be able to handle poor powerfactor
    draws since most computing devices are miserable.

    It would be vastly preferable to put them in parallel
    where you can split loads, like one for the CPU,
    one for monitor & wallwarts.



    -- Robert
     
    Robert Redelmeier, Jun 1, 2010
    #2
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  3. YKhan

    YKhan Guest

    On Jun 1, 5:46 pm, Robert Redelmeier <> wrote:
    > In comp.sys.ibm.pc.hardware.chips YKhan <> wrote in part:
    >
    > > I'm wondering if there are any dangers or precautions to putting
    > > a couple of UPS's in series to increase their power-on time?

    >
    > Even presuming sufficient VA (=W/PF), few UPSes produce
    > nice sine waves on their outputs while most expect them on
    > their inputs.  There may be problems [overheating] with the
    > second UPS.  UPS should be able to handle poor powerfactor
    > draws since most computing devices are miserable.
    >
    > It would be vastly preferable to put them in parallel
    > where you can split loads, like one for the CPU,
    > one for monitor & wallwarts.
    >
    > -- Robert


    That's what I was afraid of. I remember hearing something about that
    sometime back, but I couldn't remember if I heard it right or what the
    reason was, so I asked here.

    Yousuf Khan
     
    YKhan, Jun 1, 2010
    #3
  4. YKhan

    Strobe Guest

    On Tue, 1 Jun 2010 07:50:50 -0700 (PDT), YKhan <> wrote:

    >On Jun 1, 5:46 pm, Robert Redelmeier <> wrote:
    >> In comp.sys.ibm.pc.hardware.chips YKhan <> wrote in part:
    >>
    >> > I'm wondering if there are any dangers or precautions to putting
    >> > a couple of UPS's in series to increase their power-on time?

    >>
    >> Even presuming sufficient VA (=W/PF), few UPSes produce
    >> nice sine waves on their outputs while most expect them on
    >> their inputs.  There may be problems [overheating] with the
    >> second UPS.  UPS should be able to handle poor powerfactor
    >> draws since most computing devices are miserable.
    >>
    >> It would be vastly preferable to put them in parallel
    >> where you can split loads, like one for the CPU,
    >> one for monitor & wallwarts.


    If you do this, don't forget to put a small lamp on one of them.
    Bad enough coping with a power outage without having to do it in the dark.

    >That's what I was afraid of. I remember hearing something about that
    >sometime back, but I couldn't remember if I heard it right or what the
    >reason was, so I asked here.


    Have you looked into replacing the UPS battery with a larger capacity one?
    This is the preferred (and more elegant) way to get longer power-up time.

    --

    Terry V.
     
    Strobe, Jun 1, 2010
    #4
  5. YKhan

    Rick Jones Guest

    In comp.sys.intel Strobe <!beep!.com> wrote:
    > If you do this, don't forget to put a small lamp on one of them.
    > Bad enough coping with a power outage without having to do it in the dark.


    That's what all the blinking lights are for - all real computers have
    blinking lights right?-)

    rick jones
    --
    oxymoron n, Hummer H2 with California Save Our Coasts and Oceans plates
    these opinions are mine, all mine; HP might not want them anyway... :)
    feel free to post, OR email to rick.jones2 in hp.com but NOT BOTH...
     
    Rick Jones, Jun 1, 2010
    #5
  6. YKhan wrote:
    > I'm wondering if there are any dangers or precautions to putting a
    > couple of UPS's in series to increase their power-on time?
    >

    In general it's more effective to split load or use a bigger UPS. With few
    exceptions the output of a UPS is ugly with high frequency harmonics, resulting
    on a bunch of losses.
     
    Bill Davidsen, Jun 1, 2010
    #6
  7. On Tue, 1 Jun 2010, Rick Jones wrote:

    > In comp.sys.intel Strobe <!beep!.com> wrote:
    >> If you do this, don't forget to put a small lamp on one of them.
    >> Bad enough coping with a power outage without having to do it in the dark.

    >
    > That's what all the blinking lights are for - all real computers have
    > blinking lights right?-)


    Absolutely. Anyway, we have a nice illuminated EXIT sign which is on
    emergency power and so stays on when the power is out. The computers are
    not, because the emergency power is turned off once every month for
    "testing". Really.

    Steve
     
    Steve Thompson, Jun 1, 2010
    #7
  8. YKhan

    LSMFT Guest

    YKhan wrote:
    > I'm wondering if there are any dangers or precautions to putting a
    > couple of UPS's in series to increase their power-on time?
    >
    > Yousuf Khan


    Series would double the voltage and blow your stuff up.

    --
    LSMFT

    I haven't spoken to my wife in 18 months.
    I don't like to interrupt her.
     
    LSMFT, Jun 1, 2010
    #8
  9. YKhan

    Bryce Guest

    Sam E wrote:

    > On Tue, 01 Jun 2010 18:45:10 -0400, LSMFT
    > <> wrote:
    >
    >>YKhan wrote:
    >>> I'm wondering if there are any dangers or precautions to
    >>> putting a couple of UPS's in series to increase their
    >>> power-on time?
    >>>
    >>> Yousuf Khan

    >>
    >>Series would double the voltage and blow your stuff up.

    >
    > That's funny. I hadn't thought of connecting the OUTPUTS
    > in series.


    In 'normal' mode, most consumer-grade UPS devices just pass
    through the input mains power. Any attempt at connecting the
    outputs in series would either result in total output
    voltage equaling mains voltage, or zero and an immedite
    shutdown by either unit's short-circuit protector.

    When operating off-line (i.e., during a line power failure)
    it would be possible to obtain much more than rated voltage
    with the series connection, but it would be weird. The two
    UPS units would not be phase synchronized and probably would
    not even operate at exactly the same frequency. Output
    voltage would vary unpredictably.
     
    Bryce, Jun 7, 2010
    #9
  10. YKhan

    Rick Jones Guest

    William R. Walsh <> wrote:
    > This does not always work, especially if the UPS manufacturer never
    > intended for larger batteries to be used.


    Doesn't that then also imply that the UPS is being used in a context
    for which the UPS manufacturer never intended?

    rick jones
    --
    firebug n, the idiot who tosses a lit cigarette out his car window
    these opinions are mine, all mine; HP might not want them anyway... :)
    feel free to post, OR email to rick.jones2 in hp.com but NOT BOTH...
     
    Rick Jones, Jun 7, 2010
    #10
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