[c-nsp] Data Center cooling

[Joel Snyder]

 >   Has anyone looked at using outside air to provide data center
 > cooling during the winter season ?
 > I am aware of Google and Intel research into
 > this area but how about on a smaller scale ?
 > How about raising ambient
 > temperatures as well - do you keep your data centers at 65 or 80 ?

We do this and we have had mixed success.  We have Liebert A/C units 
which have something they call an "economizer."  Essentially, when the 
outside temperature falls below a certain point as measured by a simple 
thermostat, the A/C unit moves a damper and instead of sucking hot air 
from the room to cool, it sucks cold air from the outside, filters it, 
and blows it in.  At the same time, it turns off the compressor (because 
the air is, in theory, already cold).

In the sales presentations and talking to A/C gurus, it all sounded very 
smart and economical, but we've found that the actual management of the 
damper and the temperature that it shifts are very delicate settings. 
Depending on the time of the day (i.e., is there sunlight on that side 
of the building or not?) and the season of the year (i.e., is this just 
a little cold snap or an extended period?), as well as the outside 
humidity level (is it very different from the humidity in the room or 
not?), the temperature has to be adjusted a bit in each direction.  Our 
units don't have a computer control for that, so that means someone goes 
out every few weeks with a screwdriver and manually fiddles the 
economizer thermostat settings.

We can compensate a bit on the computer control side by changing the the 
system thermostat around a few degrees, but there is no direct linkage 
between the economizer part of the system--it's completely independent, 
essentially an add-on--and the rest of the cooling system.

I honestly can't tell whether we are saving any money on this or not, 
but for our latitude and climate, I would not recommend it to anyone 
else.  We have had to replace the thermostats and damper controllers, 
and that eats up $300 to $500 for every service call.  Plus, while we 
were learning about it, we had some midnight room-got-too-hot moments, 
which also cost us.

I think that if you lived someplace where it was in the 5C/40F range or 
below day-round for weeks at a time, this would probably work (assuming 
that you have physical ability to install this kind of unit).  In our 
climate, where it is 5C/40F for 8 hours at night and 20C/70F the rest of 
the day, for our 3 month winter, it was probably not the right decision.

jms

-- 
Joel M Snyder, 1404 East Lind Road, Tucson, AZ, 85719
Senior Partner, Opus One       Phone: +1 520 324 0494
jms at Opus1.COM                http://www.opus1.com/jms