Thread: UPSs & printers

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    UPSs & printers


    Can anyone give me the bottom line re connecting a printer to a UPS?

    I know connecting UPS & laser printer is a big no-no, but can't find a clear answer re what could happen if I did. I've read that it could overload & fry the printer's power supply circuitry; ditto some UPS circuitry or the inverter; or that a circuit breaker in the UPS might go, leaving the PC without backup power…………..

    Any comments....are any/all of the above correct & are there other reasons too?

    Also, is it ok to connect UPSs & other types of printer e.g. inkjet or dot matrix?

    TIA,
    Jeff
    Last edited by jifjaf; November 7th, 2011 at 04:54 PM.
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    The only relevant piece of knowledge I have is that laser printers draw a huge amount of power when they're warming up for a print job. The instantaneous power requirements of even a small laser printer would probably exceed the limits of most UPS's, although obviously if you purchased a UPS with sufficient capacity to handle the laser printer then there would not be a problem with connecting them.

    In all likelihood if you did connect a laser printer to a UPS the worst that would happen is you would blow a fuse in the UPS. As far as I know, you're not likely to damage either device.

    Unless it's defective, a UPS is not going to have a failure condition where it overloads and feeds too much power to the printer's power supply. They are designed to prevent that from ever happening. The only way you could damage the printer is if having it lose power while operating was bad for it, which might be the case for some printers, but you would have to consult the manual or vendor for your specific model to determine whether or not that is the case. (Plus in this case, that would actually be a reason to use a UPS with it.)

    The bottom line is that you should review the power requirements of the printer and compare them against the power capacity of the UPS, and if the power requirements of the printer exceed the power capacity of the UPS you should not connect them. Beyond that, the type of printer is irrelevant.
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    In general, you shouldn't attach anything with motors to a UPS, at least not without some compelling reason to do so. As far as I know the heavy current draw can actually damage the ability of the battery to charge properly.
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