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Geny Output Vs Multiple or Single UPSs | Server Room & Data Center Design Best Practices

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Geny Output Vs Multiple or Single UPSs

Discussion in Server Room & Data Center Design Best Practices started by MikeP , 3/30/2009 2:39 PM
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Geny Output Vs Multiple or Single UPSs

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  • mlewis

    I need to replace 4 Smart-UPS-3000's with one older, used, unit. Like the 3000's with the sensitivity switch, the replacement unit needs to be able to sync with power from a geny.

    Here's the situation.

    I've got a server room which is using about 4000/5000Kva or so at the moment. This could go up to between 6000/8000Kva now and then as I turn storage on and off.

    I was using a single 12Kva UPS with custom external batteries for many years which worked great, gave me hours and hours of backup but maintaining the batteries was simply too much work. I then bought a 12KW generator only to find that it could not sync up with the UPS. I hoped that even though the geny was small, that because I wasn't using max power on the UPS, that I could get away with it. Besides, it's all I could afford at the time.

    I then found that the Smart-UPS 3000 with sensitivity switch would work with my geny. I ended up buying one at a time, testing each time and found that so long as I keep the loads down/balanced, that the geny can keep 4 units and everything up when there is a power failure. But that's the problem again, just barely, when I add too much load, then things aren't rock solid.

    So, the problem I have at this point, I think, is that I now have so much headroom being taken up just to power the UPS's that it's eating into the geny's total output. I can't count how many times I've been told this won't work because I need 2 or 3 times the output on the geny but it's not in the budget so need to find a solution with what I have on hand.

    The question is; What older, used, unit, which has the sensitivity switch, so geny ready, should I be looking for to replace all of these individual units. While I realize that the headroom on a larger UPS will be higher, I also suspect it'll be less than all of these individual units as well. I could use as much as 7000Kva/8000Kva at times so it sure would be nice to find a way of doing this with the geny that I have.

    I'm sure there are plenty of 'no, can't be done' answers but I'm looking for the out of the box thinking that gets me closer to it's not perfect but it works for now :).

    Mike

  • ipicKedawinna

    above 5kVA, you will need to look at a UPS with a topology of double online conversion.

    [this APC white paper goes over all the different topologies|http://forums.apc.com/spaces/11/netbotz-hardware-software/forums/general/4454/memory-management]

    the Smart UPS that have sensitivity settings are all line interactive topology. the double online conversion UPSs dont have sensitivity setting. the benefit to them is they have a 0ms transfer time to battery and also can accept a wider range of input power/frequency. if they cannot handle the dirty power coming from a generator, there is no setting you can adjust on them. if this happens, then the power must be AWFUL since they can handle side a wide range of crappy power.

    so in the 8kVA range you'd be looking at some type of single phase Symmetra UPS. we have different varieties of those..

    [Symmetra 8kVA Power Array UPS (discontinued)|http://www.apc.com/resource/include/techspec_index.cfm?base_sku=sy8k]
    [Symmetra 16kVA Power Array UPS (discontinued)|http://www.apc.com/resource/include/techspec_index.cfm?base_sku=sy16k]
    [Symmetra 6kVA Rackmount UPS (current)|http://www.apc.com/products/family/index.cfm?id=189]
    [Symmetra LX 8kVA UPS (current)|http://www.apc.com/products/family/index.cfm?id=180]
    [Symmetra LX 16kVA UPS (current)|http://www.apc.com/products/family/index.cfm?id=180]

    For smaller kVA requirements, there are [Smart UPS RT models|http://www.apc.com/products/family/index.cfm?id=223].

    hope this helps or at least gets us started in the right direction.

  • mlewis

    Thanks very much for the lead. As I said, I just need to survive until we can get our finances together and then I can buy what ever I'll need.

    I should have also asked, what about using two or three units, which the geny could power. I've got 6 racks, two on each side of a room. I use about 3Kva on one side and about 2Kva on the other. I try to balance that out by running a couple of extensions across and load evenly but that's a mess. While I'd love to get back to one single UPS, there is also the option of using the two Smart-UPS 3000's I have on one side and a larger single unit on the other.

    I was looking at a Smart-UPS 5000 which is 240input, has 240 out lines, is some 3700KW output as I recall. Any chance of knowing if the geny would be able to handle that? Does it have the sensitivity switch?

    Can you get a sense of how clean the geny power output is with the fact that it can run the UPS's when they are in medium sensitivity mode.

    Mike

    Message was edited by: mlewis

  • voidstar

    >
    Can you get a sense of how clean the geny power output is with the fact that it can run the UPS's when they are in medium sensitivity mode.

    Mike
    >

    Lets look at the big picture here. You have things set up so that when the power goes out, your UPSes keep the load up until the generator kicks in. At that point, you need your line interactive UPSes to sense good AC from the generator and switch from battery back to the AC line. The sensitivity switch allows you to desensitize your UPS so that it will consider the distorted output from the generator as good AC.

    However when your load is imbalanced or you've loaded the generator down too much, the generator's output no longer passes as clean AC under medium sensitivity. You could always try low sensitivity.

    The take-away is your generator's output regulation (or how clean it is) is dependent on how it's loaded.

  • mlewis

    However when your load is imbalanced or you've loaded the generator down too much, the
    generator's output no longer passes as clean AC under medium sensitivity. You could always
    try low sensitivity.
    The other day, we tried testing this again. Turned off the power and now none of the UPS's wanted to sync up to the geny. I think it was probably too much load on each UPS so I need to test again and find out what the max load can be on all units. It's near impossible to test since it's a production environment and we're trying to gather up customer trust. Hard to do that when running too many tests and yet, it's the only way to find out. Life is damned hard on a budget :).
    The take-away is your generator's output regulation (or how clean it is) is dependent on how it's
    loaded.
    It seems to have a pretty clean output but of course, as you say, that changes depending on the load. I almost need something in between, to clean up the geny's output, then feed it to the UPSs as more stable.

    I hope someone can let me know about the 5000 I'm asking about. I would then use two of the 3000's and one 5000 instead of four 3000's. Like I said in my first message, just wondering if running the overhead of so many UPSs is also cutting heavily into the geny's output.

    Mike

    Message was edited by: mlewis

  • voidstar

    I hope so too. Like i picKed a winna said, a double conversion online UPS like the SURT you just bought seems like the best bet. Let us know how it goes.

  • mlewis

    Would your SURT10000XLT be able to be run by my generator?

  • mlewis

    I'll update the thread for sure. If anyone has any input/thoughts on setting this up when I get it next week, geny output vs load, please let me know, thanks.

    Mike

    Message was edited by: mlewis

  • mlewis

    I don't know but I hope so since I've already bought it. Guessing I'll just have to keep the load down to what ever the geny can handle.

    Mike

  • mlewis

    So, got it installed but have another problem before I can test this. Not sure if I should post a new question of if someone can answer this.

    The unit has 3 wire input, two hots, one ground or neutral. The utility in the house has ground and common tied together. With the Powerware I was using, I had two separate wires for ground and common going into the machine. On the output, I had them separated in the panel. So, it was four wire out, two hots, one ground, one neautral, are separated.

    So, now I have a three wire input from utility, and have the output going into that 220 breaker box which has a number of 15amp fuses. The ground and neutral are separated in that panel.

    The Smart-UPS RT 10000 XL only has three wire output and is connected into that panel and since I have ground and neuatral separated in the panel, things don't work.

    So need to know how to deal with the three wire output into the breaker box. Do I tie ground and neutral together in the output panel that the UPS is feeding then? This seems to make sense but wanted to confirm.

    Mike

    Message was edited by: mlewis

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