[Seattle-SAGE] Q: EPO (Emergency Power Cutoff Switches), data center design question.

J. Nyhuis cabal at u.washington.edu
Wed May 25 14:07:39 PDT 2005

 	I am in the process of designing a small data center and am trying to 
spec out a EPO Switch (The big red button that kills all power to the racks in 
the case on an emergency).

 	The old fashioned method was to use a huge breaker-like device that 
physically cut the power to the racks.  The vendor I recently contacted is 
claiming that it's not done that way anymore.  The EPO they want to sell me 
triggers a circuit to each "EPO enabled device" telling the device (such as a 
UPS or smart PDU) to shut down nicely, without ever actually cutting the power 
to the racks.

 	I can foresee several problems with this system, such as:
If there is an emergency, (e.g. the PDUs are on fire), what's the likelihood 
that the "shut down nicely" circuit will still be operational and will work? 
(Usually there is a pull on the UPS to shut down the UPS in an emergency 
fashion).  According to the manual I downloaded, the communication between the 
EPO and "smart EPO enabled devices" is over cat5 or 24 gage wire, and I can 
tell you from experience that cat5 does not survive long in fires... ^_^

 	Has anyone designed a data center recently?  Would you share how you 
met this fire code requirement?  Is this vendor selling me a line of b#ll?

"***The EPO switch will not directly break the 208V circuits.  There is
too much power to run through the switch.  It is designed to operate a
contactor or other relatively low level device that in turn will control
the actual power equipment."

 	Sorry, as a sysadmin, I just see more single points of failure in an 
emergency situation... ^_^

 	Thanks in advance for sharing any advice,

John H. Nyhuis
Sr. Computer Specialist
Dept. of Pediatrics
HS RR349B, Box 356320
University of Washington
Desk: (206)-685-3884
cabal at u.washington.edu

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