Josip Loncaric josip at
Wed Apr 24 08:56:53 PDT 2002

Steven Berukoff wrote:
> We just purchased ~150 dual AMDs, and are cooling them with 4 Fujitsu
> ceiling-mounted air-conditioners: about 50kW of AC cost us about $25k,
> which is about 10% of the cost of the machines.

Your setup also has the advantage of redundancy.  We've got a large AC
(a 5-ton unit) plus two smaller/self-contained AC units for those
inevitable times when the large unit is not performing properly.

AC typically breaks down when you need it the most (i.e. on the hottest
day when it has to work the hardest).  We try to have some redundancy
and the ability to stage 1-2-3 AC units as needed.  Oversized AC to
handle event the hottest days is not as efficient, and when it breaks
down, most of the computers have to be powered off...


P.S.  Temperature alarms are a highly recommended.  One can even wire
the temperature sensor to kill the computer power at the circuit breaker
box when the temperature exceeds dangerous levels.  Automatic handling
of overheating is needed because when AC fails, the temperature in a
small room (heated by 5-10KW dissipated by the computers) can go above
100 deg F within ~30 minutes.  This may be faster than a system manager
can drive in on a weekend -- so automated shutdown may be needed even if
the temperature alarm pages someone.

Dr. Josip Loncaric, Research Fellow               mailto:josip at
ICASE, Mail Stop 132C           PGP key at
NASA Langley Research Center             mailto:j.loncaric at
Hampton, VA 23681-2199, USA    Tel. +1 757 864-2192  Fax +1 757 864-6134

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