Looking for an UPS Expert

Discussion in 'TiVo Coffee House - TiVo Discussion' started by atmuscarella, Sep 9, 2007.

  1. atmuscarella

    atmuscarella Well-Known Member

    Oct 11, 2005
    Rochester NY


    Hello All,

    I recently purchase 2 new UPSs both are APC Back-UPS XS-1300s. I had 2 APC Back-UPS CS-500s before and thought I would be able to daisy chain a CS-500 off a XS-1300 and utilize both batteries.

    However when I plug a CS-500 into a XS-1300 and pull the XS-1300's plug, the CS-500 also goes to battery and the XS-1300 shows no load. For some reason the CS-500 will not draw power from the XS-1300's when it is on battery power.

    I also have a APC Smart-UPS 1400. When I plug either the XS-1300 or CS-500 into it and pull the 1400's plug both the XS-1300 and the CS-500 both act like the power is still on and appear to be drawing power just fine from the 1400's battery.

    Can someone explain why it appears a Smart-UPS 1400 can power another UPS but a Back-UPS XS-1300 can not?

    Also my parents put in a auto backup generator and the UPS they had act like there is no power (go onto battery) when the generator is running. The person who put in the generator said the UPSs would not work with the generator's power again can someone explain why?

  2. JimSpence

    JimSpence Just hangin'

    Sep 19, 2001
    Binghamton, NY
    I can't say for sure, but it is probably because the power supplied by the UPS or generator isn't a pure sine wave that the second UPS is expecting on it's input. It all depends on the quality of the UPS output.
  3. patonenow

    patonenow New Member

    Jul 22, 2005
    JIM, you are right because on all mine they all say NOT to do that. The original poster should not try that as they or his equipment will be damaged. Don't have time to explain the technical end of it now.
  4. kdmorse

    kdmorse Well-Known Member TCF Club

    Jan 29, 2001
    Germantown, MD
    The short version - Never chain UPS's like you're trying to do - it's bad. It's specifically documented as "Don't Do it!" by all UPS manufacturers. And for some manufacturers, it will void the warranty.

    The long version is twofold. (It's documented at length in several APC knowledgebase articles which I cannot find right now as APC's web site is not cooperating).

    A) The downstream UPS may not recognize the artificial power of the upstream UPS, and go on battery - just as you're experiencing. If the SmartUPS creates a standard sine wave, it may make the downstream UPS happy. If the BackUPS creates a modified square wave, the downstream ups may not like it.

    B) Even if the downstream UPS is happy, unless the upstream UPS is creating a 100% perfect regulated sine wave, the downstream ups may spend all it's time attempting to correct minute flaws in the upstream UPS's output. It's power stabilization circuitry may be constantly alternating between correcting for undervoltages, overvoltages, wave distortions, frequency shifts, etc... from the artificially generated power. This is *extremely* hard on a UPS, and can lead to premature death.

    Of course given a perfect setup, it could work without incident. But the general rule is - Don't do it. If you do do it, don't be terribly surprised if your UPS's wear out far sooner than they should - and not in a way where replacing the battery will bring them back to life.

  5. atmuscarella

    atmuscarella Well-Known Member

    Oct 11, 2005
    Rochester NY


    Thanks for the responses.

    Guess I will have to figure out the best plan to use all the UPS individually. Regarding my patients backup generator, is there any other solution other than removing the UPS and replacing them with surge protectors?

  6. BL

    BL Member

    Oct 15, 1999
    Falmouth, Maine
    I have some experience with trying to use electronics off a generator, and it appears that the quality of the power can vary widely, and the power can also fluctuate in ways that don't affect normal appliances, but do affect UPS's. When I tried to use mine off a generator, it kept switching back and forth, on and off battery, and it really made me nervous to watch. I also blew a surge protector that I have a small television plugged into while using the generator. So, I stopped trying to run anything delicate I cared about. It ran the fridge, well pump, furnace, lights, microwave, etc., all without problems.

    Unfortunately, I decided that the safest thing is to not use delicate electronics such as computers or Tivos while the generator is on line.

    It may be that some of the higher-end generators, such as Hondas, may work better in such situations.
  7. rbreding

    rbreding TiVo Nutjob

    Dec 12, 2004
    Oklahoma City

    Alot of it has to do with the quality of the UPS. The cheaper ones aren't able to "boost" or "trim" the power without goin on battery fully. The better UPS's (I.E. APC's Smart UPS line) are able to compensate for this. Running all our HT equipment (and RPLCD) off a SU1400 at the lake works fine. Even ran it during the ice storm where we were without power for 6 days. The generator is a midrange one (9000) and they all have swings in their power output so.... Neighbors came over to watch HD programming (extra bodies made cheap heaters in the house since it was 20degrees outside :))

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