[Beowulf] Re: Emergency Power Off

Robert G. Brown rgb at phy.duke.edu
Mon Mar 19 15:19:55 PDT 2007

On Mon, 19 Mar 2007, David Mathog wrote:

> After looking at the specs I believe that at least 4 of the 5
> can be wired to shut down instantly.  (Not sure about the one
> desktop size APC unit in the room, as it isn't mine so I don't
> have the manual). However it seems that turning off the
> tripp-lite UPS requires a positive voltage (12V) on the
> inverter shutdown line.  Which means, that even after the
> power has been killed (overtemp, red kill button,
> or building power shut down) the fireman entering this room would
> still need to smack another (not yet extant) red kill button, and
> that button is going to need DC power in order to work.  Googling
> turns up other EPO installations requiring much higher DC voltages
> than the tripp-lite needs, for instance here:
> http://nonstop.compaq.com/TechPubs/PDF/Power_Requirements/TPSEC04.pdf
> where they specify 56 volts for the EPO, but only 5mA of current when
> the switch closes.
> Clearly a second red kill button (EPO for the UPS units) would be a good
> thing.  Presumably somebody sells an EPO control unit that
> has all the pieces:

APC has a button -- it is spec'd somewhat in the pdf Jim and I passed
back and forth and you can look it up on their site.  There are some
other companies that sell them as well.

They don't look terribly easy to wire up, though, and say that they are
only to be installed by "professionals".  I asked our "professional"
electrician today if he'd ever installed an EPO button, and he said no
and slunk out.  The two professional consultants (I'm just an amateur:-) I
was working with -- nope, they only wire up server not-a-centers, even
if they have four or five racks in them and 20KVA in UPS.

Ultimately it comes down to your fire marshall and inspectors.  If they
say you need one, you need one.  If they say not, then not.  Unless you
get sued after a fire when somebody gets killed, in which case it will
almost certainly turn out that you needed one after all.

I'm still hoping to put one in "needed" or not.  If I can figure out
how, without spending a fortune.  How as in wiring and full parts
diagrams, including what we need at the UPS end.


> AC in
> AC to DC conversion
> battery or capacitor backup of the DC voltage
> a bunch of ports to plug in lines to control the EPO devices
> Who sells it?
> How much?
> Or is every EPO controller custom made???
> Thanks,
> David Mathog
> mathog at caltech.edu
> Manager, Sequence Analysis Facility, Biology Division, Caltech
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Robert G. Brown	                       http://www.phy.duke.edu/~rgb/
Duke University Dept. of Physics, Box 90305
Durham, N.C. 27708-0305
Phone: 1-919-660-2567  Fax: 919-660-2525     email:rgb at phy.duke.edu

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