What sort of UPS would I need for these specs?

Posted on 2014-08-27
Last Modified: 2014-09-10
Hi guys,

These are the things that will need connecting to a UPS:

5 PC
12 laptop
1 QNap NAS (Network Attached Storage)
1 Drytek Vpn Router Modem
1 Thomson  Modem
1 Cisco Router
1 Powerswitch Gigabit Network Switch
1 Photocopy&Scanner(Black&White)
3 Printer
1 Colour Printer &Scanner

Do you know what sort of UPS would suffice for this?

Thanks a lot
Question by:Yashy

    Expert Comment

    by:Prakash Gupta
    provide your psu spec
    LVL 18

    Assisted Solution

    by:Andrew Davis
    There are lots of UPS calculators around (example ).

    you really need to supply more information.

    i would guess that you are not wanting to hook everything above to a single UPS, if so then you need to get an electrician in to quote for you.

    if they are all going to be hooked to seperate UPS's (with some grouping, router/modem/switch) then you need to look at what the wattage of each group is, and then consider how long you need to sustain power to it.

    Then you can start to get an idea of what you need.

    LVL 1

    Author Comment

    What PSU?
    LVL 18

    Expert Comment

    by:Andrew Davis
    PSU = Power Supply Unit, This will give the wattage of the device.

    That is just a small part of the question, as we then need to know how they will be grouped, and how long do you want it to sustain power for.

    LVL 25

    Accepted Solution

    You've received some good advice already.  Here is a "process" if that helps:

    1) Survey all the equipment that will be hooked up.  Determine, in some fashion, how much power each one takes.  NOTE: This is not a matter of "worst case" analysis that one might use in designing a power supply for a single device; it's a matter of determining how much energy storage is required for your application.
    - How long does the UPS system have to keep the devices powered up?
    - Which devices can be turned off in the event of a main power failure?
    - How much power does each device *draw* in normal operation?  Just because a PSU has a 350 watt rating does not at all mean that it will draw 350 watts in normal operation.  One reason is that it's conservatively overrated and "350W" is a *rating* and not an indication of power draw.  (Then, to be picky, you could presume that it's only 90% efficient and could draw 390 watts before it hits its rated capability).  One might be tempted to add up all the PSU numbers and divide by 2 for this purpose.  Some may be low and some may be high but the sum of them could be a useful number for starters.  For laptops, the duty cycle of the display is a driver here - are they on all the time or what?  Probably the easiest / quickest way is to plug each device through a metering device like:
    You can get some good ideas from websites like:

    2) Determine how long the system has to continue to operate.

    3) Knowing the power requirement you also know the current requirement: Power/Voltage=Current.
    Presumably everything is running off 115vac so if a device dissipates 100 watts that's 100/115=0.87amps.
    Add them up.

    4) In general, battery backups are rated in both amps and in something like amp-hours.  So, a simple view of how long a system will run is amp-hour capacity divided by amps from above.

    5) A couple of things determine how devices might be assigned to individual UPS devices:
      - you should not exceed the current capacity of the UPS
      - You should load the UPS so that its amp-hour capacity and the devices connected will yield the endurance time you require.

    If you decide you need 1 hour endurance and you size everything for 2 hours then you will likely be spending quite a bit more money than is warranted.  But, only you can decide on the cost-benefit for overdesign.
    LVL 91

    Assisted Solution

    you can either read the power spec on each device, or measure it with a kill-a-watt

    the easiest to have them all running on 1 line, and measure the AC line then
    if you have a total of 1KW, and you need to power it for1 hr, you need a 1 KVA at least (i would add 10% for safety margin - , eg when it is aging )

    don't forget to test the ups regularly (2x per year), and the batteries also!

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