OT: CRAC

Jerry Feldman gaf at blu.org
Fri Nov 4 09:03:01 EST 2005


On Friday 04 November 2005 3:45 am, Jon maddog Hall wrote:
> >Since we are on AC war stories.
>
> Now you have done it. :-)
>
> When I was at Hartford State Technical College we had a REALLY LARGp1dY3bIIAP+hogOHijhFiLYzeWsV4yS8AACR+CDHqAg
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IAepsHpKEC1YkwMiEJdCBBDqcB4i4AL5EQ/HYiqJIQKOZQype immediate trouble, but it will shorten
the lifespan of components.

  You will need a commercial-duty unit that can run constantly.  You
don't want something you buy a Wal-Mart, as they're consumer-grade and
will break down quickly if run constantly.  Check the specs for the
duty cycle.

  Set the AC so the fan runs all the time.  If the room needs it,
boost air circulation in the room with additional fans.  You want the
air moving around.  The AC only cools the air flowing through it.  The
idea here is to make sure the temperature distribution is uniform. 
You don't want it to be freezing right under the AC and hot on the
other side of the room (or behind the server rack).

  Use two identical units, set to the same temperature, running in
parallel, for redundancy.

  Make sure you can shut the heat in the computer room off separately
from the heat in the rest of the building.  Ideally, put a separate
heat zone with a separate thermostat in the computer room, and set it
a few degrees below the AC setting.  That keeps things from getting
*too* cold.  If you can't do that, at least make sure you can turn off
the dampers/values/whatever for the room.  Otherwise, the computer
room will be fighting the rest of the building constantly in the
winter.

  Make sure you can isolate air exchange, too.  Otherwise, your fancy
computer AC will be trying to cool the whole building in the summer. 
This is especially bad when the office people want it at 73 degrees
and the CRAC wants 68.

  HTH,

-- Ben



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