Confused - UPS Solutions and who's Watts?

Discussion in 'Power cuts' started by ThaneF, 25 Sep 2010.

  1. ThaneF


    Posts: 165
    10 Jul 2010
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    Hi Guys,

    After not have water for 2 days the geyser decided it's time to burn out and tripped my house (you know, just to add to the experience)
    I got the hugest of frights with my tank and now looking for a UPS solution. I know that I need a pure sine wave device and looking at UPS's. My power usage is at worst case (all pumps, lights, heaters etc) 600w (rounded up) (300w heater, 2x 55w power compact, 4x pumps (30w each))
    I have found a 1000Va 700w UPS for R2500... would this be sufficient for my tank and what sort of uptime can i expect from it (assuming the heater isn't turned on all the time - then I'll have another problem on my hands) and is this a good price?
    Any advice would be much appreciated

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  3. lIghty


    Posts: 5,053
    3 Nov 2007
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    Westville, Durban

    hi Thane,

    I would not recommend running all your equipment, perhaps only 1 or 2 pumps and a heater if you live on a cold area (as they will chew up a battery very quick).

    Total all the wattage of the critical equipment and times it by 1.5 for safety, that will give you the size of the Invertor to get, from there you can calculate how many batteries and sizes you'll need to get to give you a certain back up time.
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  4. Reef Maniac

    Reef Maniac MASA Contributor

    Posts: 2,899
    15 May 2007
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    Sorry to hear about your problems - hope you have it all fixed by now :)

    Yes, it is best to have a pure sinewave inverter/ups, as the square-wave types can cause your pumps to run hot, or even fail prematurely.

    You don't really need to cater for your heaters unless you live in an area that is very cold, and even then one could make other plans for heating. You also don't have to allow for your lights (unless you want to...), as corals can easily survive unaffected for two or more days without lights - after all, serious tropical storms can leave the reefs quite dark for up to a week, or even longer, during the cyclone season.

    One must always allow for inrush current when using reactive loads such as lighting ballasts (which could more than double the current for the first second or two), but even so, your UPS should be OK.

    THAT would depend entirely on the capacity of the batteries. A "computer type" UPS that works off small, sealed lead acid batteries would NOT be ideal for a long-term outage. For 600W consumption, and assuming a total of 20% losses and a maximum depth of battery discharge (DOD) of 50% (which is pushing it...), you would need:

    600W x 1.2(allowing for losses) = 720W / 12V (assuming a single 12V battery) = 60A required input. Thus, for a 1 hour operation time, you would need a battery of minimum capacity or 60A / 50% (50% maximum DOD) = 120Ah. For a two-hour capacity, you need to double this, etc.

    This is just a very rough-and-ready calculation, and one would have to calculate it more accurately once all the parameters are known (such as the UPS's efficiency...). Also, one must consider the TYPE of battery used (deep cycle vs. common car battery) and the expected/required number of charge/discharge cycles over it's operational life - discharging a battery (even deep cycle) to 50% DOD would result in perhaps 200 charge/discharge cycles, whereas a DOD of only 20% would result in a battery life of perhaps 2000 cycles, so it's a matter of paying more for extra batteries at the start, or replacing the battery much more often over the years... Of cource, the inverter/UPS must also be able to charge the required batterie/s within a short enough time, and many of the cheaper UPS's cannot charge larger, external batteries, so that is something else to find out first.

  5. IMarine


    Posts: 1,512
    20 Oct 2007
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    walmer estate capetown

    Hi there i have ordered a back unit that comes completed in a black box with wheels and will run on my new system,to run 2 x 40 watt uplift pumps for the peroid of 4-6 hors @ total of 80-100 watts all you need is your up lift pump to run, for a cost of +- R5000,00-R6000,00
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