Q: Building a small machine room? Materials/costs/etc.

Jim Lux James.P.Lux at jpl.nasa.gov
Thu Sep 18 12:18:37 EDT 2003


At 08:50 AM 9/18/2003 -0400, Robert G. Brown wrote:
>On Wed, 17 Sep 2003, Jim Lux wrote:
>
> > You also don't want the thermal kill to shut down the power to the blowers,
> > now, do you?
>
>You don't but ours does, I'm pretty sure.  I'm not certain what the
>precise motivation was -- I believe it was the issue of those firemen,
>not knowing what circuits in the room were on and what were off.
>

I suppose this is why you want someone who has done this sort of design 
before... There's no real electrical reason why you can't have a thermal 
kill separate from the Emergency OFF kill.  All a matter of relays, 
subpanels, etc.

There IS a reason to shut down blowers when overtemp hits.. Most fire alarm 
systems (in big installations) are tied to the forced air ventilation 
system to prevent a fire from being pushed by the HVAC. This was generally 
motivated by the experience in the MGM fire disaster a few decades back 
(which is also responsible for things like "plenum rated" cabling, etc.)

So, what you probably want is a sort of staged setup.. moderate overtemp 
shuts down computer power, bigger overtemp (i.e. a fire) shuts down the 
blowers, pressing the big red button next to the door shuts down all the power.



James Lux, P.E.
Spacecraft Telecommunications Section
Jet Propulsion Laboratory, Mail Stop 161-213
4800 Oak Grove Drive
Pasadena CA 91109
tel: (818)354-2075
fax: (818)393-6875

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