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Thread: A UPS behind a UPS??

  1. #1
    Join Date
    Mar 2004
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    A UPS behind a UPS??

    I work at DTE ENergy in Network Engineering and am responsible for all Telephone Room Builds. We typically run all our transmission and switch equipment on 48vdc (industry practice). This allows us to hold our voice systems for at least 2-4 hours pending generator deployment.

    As we are looking to migrate to the new VoIP switch structure our vendor AVAYA indicates they cannot (read will not) support a 48vdc based server to control the guts (brains) of the machine. Instead they are providing a small 1/2 hour UPS to support the server (brain)on.

    My concern is that within the telephone room I already have a BEST 3.1kVA UPS minimum provisioned to provide clean AC for my Data groups routers and switch hubs. My concern is a lack of raw AC and the suggested solution to just plug the new little UPS in to outlets fed from the BEST.

    I can't find a reference to this other than maybe neutral heating. IS there something in the Code which would prohibit this practice.

    Sorry to be so long winded, and I hope this makes some sense.

    Thank you all,

    Dennis D. Hock

  2. #2
    Join Date
    Aug 2004
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    Re: A UPS behind a UPS??

    I don't believe its prohibited, but I have heard of cases where the second UPS sees the choppy waveform from the first UPS as a problem and goes into UPS mode all the time.

    The Best UPS units have voltage regulating transformers on the output as I recall, so it may not be as much of an issue with them.
    Bob

  3. #3
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    Re: A UPS behind a UPS??

    I am very familiar with telephone office power design. Nothing in the code to prevent you from doing so, but I wouldn't dare try it.

    There are special UPS that operate in a manner similar to what you are asking called "parallel redundant", but they are made to work with each other by design.

    Good luck with your AVAYA VOIP switch, you are going to need it. Doesn't play well with others.

  4. #4
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    Re: A UPS behind a UPS??

    Rather than a seperate UPS, would you consider using your existing DC infrastructure, to supply inverters?
    Ron

  5. #5
    Join Date
    Mar 2004
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    Re: A UPS behind a UPS??

    First let me say thank you all for responding so quickly.

    As to your suggestions I will be contacting Power ware to see if they do have a good regulating output on the current UPS we have.

    I would prefer to run on a straight DC powered server but AVAYA claims to not be able to support their software yet on such and can only provide the UPS.

    As to Rons suggestion I would definitley consider an inverter to run off my existing battery. Do you have an suggestion as to who you might look to use? My only concern here again is AVAYA stating that their UPS has a bus type connection to the server to tell it when to power down. Some of their folks claim this should be able to be loaded onto other folks UPS but can't of course produce any results.

    Derek I would like to discuss with you further if you've a minute. I take it you have implemented severl of these 8700s from yopur comment/ What else doen't it play with. We are all AVAYA G3s running 11.3 and relatively happy. I too am form a CO background.
    Thank you all you have me thinking and I appreciate the help.

    Dennis Hock

    Dennis I removed your phone number for your protection... Dereck

    [ January 05, 2005, 10:55 PM: Message edited by: dereckbc ]

  6. #6
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    Re: A UPS behind a UPS??

    Dennis using a inverter from battery is quite common. Most switch manufactures use them to supply AC power to the MAP area as a means to integrate with the isolated ground plane used by most switch manufactures.

    The one I see used the most by Nortel, Lucent, and Erricson is made by Lorain/Reltec (now called Marconi) out of Lorain OH.

    The big advantage of using a inverter over a UPS is backup time. By using the battery approach you can get several hours of reserve compaired to the relatively small amount of time compaired to a UPS. However I am not sure there is a shutdown feature AVAYA may require.

    I will give you a shout tommorow at the phone number you listed.

  7. #7
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    Mar 2004
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    Re: A UPS behind a UPS??

    Thank you. I will look for you to call. I should be in all morning and most of the early afternoon.

    Thank you all once again this forum is a great resource.

    Dennis Hock

  8. #8
    Join Date
    Jul 2007
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    All I have to say, is good luck with VoIP. I think it's way before it's time for most networks to handle. (not that the network and phone guys don't talk)

  9. #9
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    I assume the brain is just a PC, do Avaya supply the PC or can you use any PC? If so, then you can simply get a white box PC and swap the standard 110V PSU for a -48V PSU available from several suppliers.

    As to chaining the UPSs, with a following wind it will work, the likely problem is if either of the units are simple ferro-reasonant units, which small UPSs often are; these boxes are often very touchy about what they'll run off.

  10. #10
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    better have a look at what type UPS they will be using. if the first UPS (the BEST one) is a stand-by type, then the second UPS will be OK. If the BEST is the online type, there could probably be problems for the second one.

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