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Computer room static blowing server power supplies

Discussion in 'Electronic Basics' started by T, Apr 4, 2006.

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  1. T

    T Guest

    A raised floor server room with 6 servers, fiber optic patch panels, large
    control system cabinets and large UPS system, has been recently been plagued
    by computer power supply failures. The supplies fail when apparently many
    tens of thousands of volts jump from inside the PS around the switching
    regulators to the chassis of the supply taking out all the components. This
    has happened to 8 supplies so far. A visible blue flash has been witnessed
    several times by pewrsons in the room.

    The servers so far affected are all sitting on the raised computer center
    floor. What ususally happens seems to be when a person enters the 12x20ft
    room or gets near a server a large snap is heard and the server is on the
    backup redundant PS, if it has not already failed.

    We have been adding grounding bonding from all computer case to the bldg
    steel, raised floor structure, etc to try to stop this. Its still happening.
    The computers are various brands and varoious ages, from 1 week old to 5
    years old. The probelm began occuring 2 months ago. The data center was
    built 12 years ago.

    We are at a loss to figure out how the charge is building up on the inside
    of the power supplies. I am thinking about the common power source, via the
    power cords Hot, Neutral and Ground conductor.

    The green wire should be bonded to the PC case. Apparently the PS regulator
    board floats above chassis potential. Apparently a large potential differnce
    is building. It jumps a 1 inch gap to the chassis. Burn marks from repeated
    arc overs are evindent (the arc that makes it fail is not the 1st time it

    The Hot and could a charge be coming in on these conductors and
    getting past the MOVs to build a potential on the boards.

    Any ideas would be appreciated.
  2. GregS

    GregS Guest

    It sounds like your UPS's should take care of everything.
    I woulds have the UPS's checked out. I would have building electricians
    check things out. I would have installed whole circuit transient protection
    at the breaker box feeding the room.

  3. Ban

    Ban Guest

    Put a humidifier inside the room, the air is too dry and static electricity
    builds up.
  4. T

    T Guest

    This was th 1st thing we fixed. The RH was 15%, we raised it to 45% (its
    winter). The adjacent control rrom is around 15% .

  5. Is ground still connected to good old earth? You'll have to check to be
    sure. Suppose the metal of the floor and installation has been grounded
    carefully but you'll have to check this too. An open ground connection may
    be the cause of you problems. Especially an open connection that is closed
    again by someone entering the room.

    On all PCs and servers I know, the secondary of the power supply has been
    connected to the enclosure which in turn is grounded. So I assume the spark
    jumps from the primary of the power supply the the chassis. Looks like
    neutral and hot are floating which means that the neutral has not been
    connected to ground, at least not properly. (Don't know where neutral should
    be grounded in your place.)

    There are other possibillities. Did someone install a badly insulated neon
    sign near you? Some other renovation maybe? Something else I can't even
    imagine but not very likely. I'm pretty sure something is not grounded
    properly anymore, but what?

    petrus bitbyter
  6. Guest

    T wrote:
    A near identical situation was cured simply by spraying the carpet
    tiles in the computer room and access corridor, with anti static
  7. T

    T Guest

    We have ordered some conductive matting for walking on. Waiting for it while
    supplies are failing!

  8. T

    T Guest

    My technicians have been testing the grounds to the steel and they are
    intact. We have a new fiber pull coming into the room just today via and
    existing conduit. The failures have been occuring for almost 2 months but
    much more frequently these last 2 weeks.
  9. I would have the electrical system inspected. The power transformer
    for the building may not be properly grounded. The ground rod or wiring
    may be damaged, leaving the transformer floating above ground.

    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
  10. TJS

    TJS Guest

    An update; We are investigating "zinc whiskers" phenomina as a possible
    cause. The zinc filaments are produced from the plywood core floor panels
    supported by the zinc electrocoted support structure. When floor panels are
    lifted or disturbed the conductive dust can get into the power supply and
    lead to shorts between the modern closely spaced SMT devices.
    See here for a white paper

    The failures/arcs in our supplies have all arced from the 120vac chopper
    regulator collector to the PS case. If the zinc whisker problem is our case
    then the blue flash is just a 120/170p-p vac arc to ground, and not a static

    We are looking at replacing our floor tiles with the modern ultra low static
    floor tiles.

    I'm a little skeptical that this is the problem, but it is true that 2
    months ago we pulled floor tiles to look for fiber conduits and that about
    the time the problems began

  11. Is the air conditioning overhead supply or raised floor supply?
  12. Franc Zabkar

    Franc Zabkar Guest

    What are the chances of zinc whiskers causing *exactly* the same fault
    in *8* PSUs?

    - Franc Zabkar
  13. T

    T Guest

    I'm skeptical about zinc whiskers and the white paper does come from a
    cleaning service company, enough said. But still it is a consideration
  14. T

    T Guest

    AC is from overhead
  15. Franc Zabkar

    Franc Zabkar Guest

    I wonder why the arc jumps a 1" gap between the chopper and the
    chassis. Why not the much smaller (?) gap on the underside of the PCB?

    - Franc Zabkar
  16. GregS

    GregS Guest

    Identical or different?
  17. James Sweet

    James Sweet Guest

    I think static is highly unlikely as the cause here. My guess would be
    overvoltage on the line, transients, or inadequate cooling.
  18. .
    Call an exorcist. ;-)
    "If you find for your verse there's no call,
    And you can't afford paper at all,
    For the true poet born,
    However forlorn,
    There is always the lavat'ry wall."
  19. Rich Grise

    Rich Grise Guest

    Well, skeptical is good, but usually when troubleshooting, the first
    question is, "What changed?"

    This is a no-brainer. Start looking through your contract with the floor
    installer, to see if you can have him eat the cost of replacing the killer

    Good Luck!
  20. Rich Grise

    Rich Grise Guest

    Pretty good, considering that the tiles are the only thing that changed.

    I probably wouldn't say, "zinc whiskers", but I'm pretty sure that, except
    for galvanizing garbage cans, zinc is AWFUL! It gets all over everything.
    I once worked at a place where they had to scrap a $100,000.00 (or so)
    Ultra-High-Vacuum bell jar because someone had installed brass connectors -
    the zinc outgassed, and contaminated the whole thing.

    Maybe you could leach the zinc out of your tile by washing it down with
    muriatic acid. ;-) [1]

    I've also seen an installation where a bunch of boxes running off 277V
    lighting power started arcing, and the only conductive thing in the room
    was the dust from the desert setting, which could very well have been
    conductive - it was only about 100 miles from Great Salt Lake. We fixed
    it by putting furnace filters on top of all of the boxes, which the idiot
    designer had put all of the intake air vents on the top of. =:-O

    It was a pretty sweet TDY[2], though - $1000.00/week plus per diem plus
    expenses plus airplane ticket plus car rental. ;-)

    Good Luck!
    [1] That's a joke, by the way. If you do use muriatic acid on zinc, be
    sure that you're in a very very well-ventilated place, because it makes
    hydrogen gas. But then, you could use the zinc chloride for sunscreen;
    just mix it with yogurt. ;-)
    [2] Temporary DutY
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