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Thread: UPS woes

  1. 24th September 2008, 08:15 PM #1
    Grizzly_Adams's Avatar
    Grizzly_Adams
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    UPS woes

    G'day all,

    Got a problem with my UPSessss....

    I have an Eaton Powerware 5110 for my main PC which so far has run all fine and dandy.

    Lately I purchased a APC Back-UPS RS 500 to protect my NAS box (because the NAS box doesn't recognise the Powerware so it doesn't support the automatic shut-off feature, but it supports the APC).

    In order for everything to shutdown in the correct order I connected the APC to the Powerware so that - in theory - the Powerware will handle the majority of the work during a blackout and then shut the PC down when it runs out of battery.

    Once the Powerware runs out of battery the APC will keep the NAS box running until it to automatically shuts down the NAS box.

    Alas when we actually had a blackout on Saturday the APC died suddenly and in a bad way - overload lights flashing as well as replace battery lights. I managed to get everything back ok but was concerned on why the APC died. I've done some investigation and the APC works fine on mains AC, it also tests fine using it's software.

    However when I connect it to the Powerware and run system tests on the Powerware UPS it simulates the same failure on the APC I experienced last Saturday - the overload lights start flashing as well as the replace battery lights. Also it clicks between on battery and main several times before dying....

    I didn't think that daisy chaining a UPS off another would be such an issue - is this really such a bad idea (we've done it before at work sights but with somewhat larger main UPS's) or do I just have a bad combination?

    Like I said individually they both work fine... I have a work-around in that I connect the UPS's to their own individual mains AC, but that wasn't my plan.. can anyone shed any light?

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  2. 24th September 2008, 08:37 PM #2
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    Blknight.aus
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    switch mode power supplies...

    your getting interferance and back EMF from one to the other. If you cro the output of the UPS when its running I bet its not a true sine wave but a modified sine waved or "chopped" AC

    BAD ju ju.

    try it with them seperated from each other to eliminate the possability of the first one having a dying battery

    Ive seen this sort of stuff happen when UPS equipped hardware (mil stuff) gets pluged into those new eco generators which are essentially a sinewave inverter hanging off an alternator.. They work fine off of mains and an old school genny but crap out on the ecos.
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  3. 24th September 2008, 09:08 PM #3
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    Powerware UPSs are crap, replaced way to many of them, they were used for PLC processor backup where I worked, but unfortunately it was easier to go to the store and req out a new one, than fiddle around, so that's all I can help..........well, didn;t really help

    Every power failure we'd kill atleast one, average life span<2years
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  4. 25th September 2008, 05:04 AM #4
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    Bummer

    The Powerware has lasted me well so far (it's over 2 years old now) but I agree it was definitely cheap when I bought it - but it's all I could afford then. If / when it does die I'll replace it with something a little more flash.

    Thanks for the feedback Blacknight.aus, that sounds a distinct possibility. I have isolated both and run tests on both and as I said they both react fine when their not plugged in to each other. I guess the Powerware is sending out that modified sinewave you mentioned... equipment seems fine but the other UPS is more sensitive.

    Bummer bummer bummer.

    Oh well I'll just have to run them both off the mains instead of daisy chaining them.

    Thanks all for the feedback.
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  5. 25th September 2008, 06:39 AM #5
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    Quote Originally Posted by Grizzly_Adams View Post
    I didn't think that daisy chaining a UPS off another would be such an issue - is this really such a bad idea (we've done it before at work sights but with somewhat larger main UPS's) or do I just have a bad combination?
    i was always taught it is very bad practice.
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  6. 25th September 2008, 11:28 AM #6
    WhiteD3
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    Glen,

    You never nest UPS'. Technically I doubt it'd work as you're no doubt mixing technologies and standards ie true online, double conversion, switch mode, etc.

    The other more important issue is earthing and protection. I think you'd find your breakers and RCBs would be degraded.

    Also loading could cause you issues. ie the load power factor and what the UPS' are rated at re pf, and also the charging current of the downstream UPS has to be added to the load on it when considering the upstream UPS.

    Proper practice is to parallel smaller UPS, but only if they're capable of it.
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