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Using an APC battery backup for other things - help!

Discussion in 'PC Hardware' started by Blake Patterson, Nov 22, 2003.

  1. I recently converted a basement space into a finished, computer area.
    Part of the moistuer treatment was hacing a sump pit and two drain
    channels dug under the floor. The sump pump in the put activates
    rarely, but in really moist periods it comes on every 20 mins, for 3-4
    seconds, or so. I worry about what would happen if power went out.

    Rather than just having a standby generator, could I use a computer
    batter backup system, like these from APC:


    ....or would the load, even tho it only runs 3-4 seconds each time, be
    too much? It's a small pump - maybe it'd be ok.

    I'd feel better with one of these _and_ a generator vs. a standby
    generator alone. Thanks.

    Blake Patterson, Nov 22, 2003
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  2. :The sump pump in the put activates
    :rarely, but in really moist periods it comes on every 20 mins, for 3-4
    :seconds, or so. I worry about what would happen if power went out.

    :Rather than just having a standby generator, could I use a computer
    :batter backup system, like these from APC:

    Yes, generally speaking you can use "computer" UPSes for other
    purposes such as pumps. The trick is to size the UPS properly.

    There are [at least] four important considerations in choosing a

    1) Does the UPS do the kind of power cleaning that is important to you. The
    cheapest variety of UPSes pretty much just pass power through raw until
    the power fails, and then kick in the battery. There might be some
    power spike filtering, and there would be some amount of protection
    against brownouts and blackouts, but you can still end up with some
    pretty ugly power inbetween those limits. These are called "standby"
    UPSes. The kind of UPSes that clean the power up the most are called
    "online" or "double conversion" UPSes, but they are -much- more
    expensive. There is a third intermediate "single conversion" kind of

    2) Can the UPS handle the voltage and amperage you need in total?
    You can do a worst-case calculation by looking at the specifications
    of the devices, multiplying voltage by rated amperage and totalling the
    results over all of the devices, and buying a unit that handles
    that many VA (Volt-Amps); this will often come out noticably
    higher than you really need, but extra doesn't hurt [other than

    If the UPS is rated in Watts, then you have to be careful
    in how you do the VA to Watts conversion: there is a phase angle
    involved in the calculation and the angle is much more favourable for
    computer equipment than for motors such as pumps: you need a more
    powerful unit (in Watt terms) to handle motors than you do modern
    computer equipment that looks to have the same rating.

    3) If the UPS goes out, can the UPS handle the drain for as long
    as you need? In your case, the time the pump would be most needed
    would be during a storm, but a storm is the time the electricity
    would be most likely to go out. If you had a really bad storm,
    could the pump end up running effectively continuously? Take the
    highest expected load and look through the manufacturer's tables of
    how long the model could support that load, and figure out whether
    that's long enough for you. Are you trying to protect against power
    going out for 5 minutes? For 2 hours? For all day?

    4) How long is the unit going to last? How much is it going to cost
    to change the batteries a few years down the road [the batteries
    lose their effectiveness over time, depending how far down
    you draw them, and depending on how exactly they get recharged.]

    5) Does the UPS have enough of the right kind of outlets for all of
    your equipment? Examine all the specifications *very* carefully;
    it's very easy to end up with the wrong kind of receptacles
    if you don't make a list and check it four times. In the case of your
    pump, you might find that you need to "hardwire" the connection --
    the pump might not *have* a plug of any sort. If the unit you are
    looking at does not have exactly the right kind of connections, it
    is possible that the next one along will... but every once in awhile
    you find a plug type that a particular manufacturer just doesn't support.

    Four major UPS manufacturers that I can think of at the moment are APC,
    Powerware, Tripp-Lite, and Liebart. APC has more than half the market,
    but I would not say that they are always the best value for your
    money, and their lower-end equipment does not always last as long
    as some of the other manufacturers (but you would definitely
    want to look at APC if you were putting together a "911" call
    centre or other establishment combining high power with high
    availability.) There are hundreds of lesser-known UPS manufacturers,
    some of which produce excellent devices, and others of which
    don't. Shopping around can really pay off... but it can also take
    a long time to decide between multitudes of similar units with
    similar prices.
    Walter Roberson, Nov 22, 2003
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  3. Blake Patterson

    wesley Guest

    What are the current demands of the sump pump - both starting and running?
    (Starting current draw will be higher if shown as a separate item.) You
    would need a battery backup unit whose current abilities exceed the
    demands of the sump.

    From the APC web site:

    APC's Back-UPS line is designed for use with Computer-type loads only.
    They are not designed to be used with motor loads such as fish filters,
    air conditioning units, space heaters, vacuum cleaners or any other

    One potential issue is the start-up current draw for a motor can easily
    overload a UPS in the Back-UPS line. Secondly, these models of UPSs
    output a Stepped-Approximated sine wave when on battery. This waveshape,
    while ideal for computer-type equipment, is not particularly compatible
    with most motor loads. The result may be that motor runs very slowly,
    erratically, or not at all when the UPS is on battery.

    To protect this type of equipment, APC recommends first determining the
    appropriate size UPS for the motor load in question. Ensure that the Volt
    Amp rating of the UPS is sufficient to handle the start-up inrush current
    draw of the motor. Secondly, select a UPS which outputs a Pure Sine Wave
    when on battery, such as a Smart-UPS (minimum of a SU700), Matrix-UPS, or
    Symmetra Power Array.
    wesley, Nov 22, 2003
  4. Blake Patterson

    B'ichela Guest

    An electric motor takes 2 times the running current at start.
    so if it takes 2A at 120VAC during a normal run. the peak demand on
    each start is 4A at 120VAC. Therfere you need to rate your UPS for
    the inrush. not the normal run. Some people suggest basing at 3x the
    normal run current or 6A! which I feel is actuallly not a bad Idea for
    a UPS especially if the pump cycles often. Based on the rough numbers
    of V*A (Volt Amperes) we come out with 6 * 120 = 720va. A good UPS for
    this would be AT least 1400VA. to give plenty of runtime while your
    Natural Gas or Diesel generator is comming up to speed. (automated
    transfer switches assumed.) Another idea is to use a trace inverter
    that works very similar to a UPS without the nice casing. it produces
    the voltage from the seperate batteries but is charged from the genset
    or the mains when available, these have the advantages to synchronizing
    with the frequency of the genset/mains to provide good line control.
    These can be powerful enough to run your whole computer system during a
    bad blackout.

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    B'ichela, Nov 22, 2003
  5. Blake Patterson

    Al Dykes Guest

    (comp.sys.sgi.misc pruned from list)

    I suggest you look in a Marine (boating) supply place for a 12V sump
    pump, a big deep-discharge battery, and a battery charger (one designed to
    maintain charge, not a fast-charge model from the Automobile parts place.)
    This will be cheaper and the salesman may actually know how to calculate
    the optimal size pump and battery for you.
    Al Dykes, Nov 23, 2003
  6. Blake Patterson

    David Lesher Guest

    You are better off to buy a small marine sump pump and use it as

    The 13.8 vdc may come from an in-place battery or extended for car
    in the dtiveway.
    David Lesher, Nov 23, 2003
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