[Beowulf] Emergency Power Off

Robert G. Brown rgb at phy.duke.edu
Sun Mar 18 10:36:50 PDT 2007

On Sun, 18 Mar 2007, Jim Lux wrote:

> At 06:52 AM 3/18/2007, Robert G. Brown wrote:
>> To answer my own question (GIYF, after all:-) there is a white paper
>> here:
>> HOWEVER, if you love your local firemen and want them to live (or love
>> yourselves and the other employees who sit near the data not-a-centers),
>> the same white paper says that an EPO switch is still a very good idea
>> for small server rooms and wiring closets that are not "data centers"
>> but are just "data closets" or "data rooms that aren't quite centers".
> Do not underestimate the power of lobby...  e.g. The front matter of the IEEE 
> Emerald Book, (which used to be called "grounding for sensitive electronic 
> equipment") explains why the "sensitive" was removed.  Mfrs didn't want their 
> particular piece of equipment to be referred to as sensitive.
> There's a huge "small office and retail" sort of market for middling sized 
> UPSes, and APC and the like would like to sell into that market as a "plug 
> and play" product.  Also, this is where the local AHJ can play a role.  THEY 
> can say, we don't care if your installation isn't in a room that meets ALL of 
> the requirements of 645, we want you to provide a disconnecting means anyway.

I could wish that they made this a whole lot simpler.  And perhaps
standardized so it would be cheap as well as easy.

> Another way that folks avoid the code is by putting the UPS into a rack with 
> the equipment being powered.  That puts it on the other side  the "line of 
> demarcation" between that which is subject to code and that which is 
> "internal to the equipment" and subject to different rules.  And, here, the

Hooo.  Right.  So the firefighters won't get electrocuted by big UPS's
IN a rack, only by smaller UPS's on the floor.

Makes perfect sense.  Sure.

I'm going to try to figure out how to put an EPO in this room for less
than a fortune, even though I'm pretty sure that it isn't strictly
required.  Even if it is just one that controls the UPS's -- so that
the building power can be cut externally and one can bop off the UPS's
on entering the room.

The building power is tricky enough as it is -- they have a gas
generator that kicks in transparently on loss of grid power (it's a
medical clinic).  That is not my thing, though.


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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