Musings on IT, data management, whitewater rafting, and backpacking

Friday, August 20, 2010

More on our new Data Center HVAC

I had more time to digest the HVAC proposal for our new data center and wanted to explain the new design.



Background


During design discussions with our mechanical sub-contractor, he was not sure our radical requirements could be met with off-the-shelf equipment. The initial design was overengineered using traditional requirements. After further discussions, he got excited about solving our problem, and came up with a better design.


Design
  • Two variable-speed blowers with bypass, will supply outside air 99% of the time, mixing data-center-warmed air when the temperature drops below 60°F, varying speeds as our CFM requirements change.
  • Two package air conditioners, will cool 1% of the time, when outside temperatures exceed 90°F. These could be downsized because air conditioners run much more efficiently at high temperatures
Simple. Not as simple as a custom or packaged solution that does both outside air and air-conditioning. But a custom solution would cost much more, and a packaged solution isn't available.

Why two units? Redundancy. Each unit is about half the required capacity. If one unit needs maintenance or fails, we still have half capacity until repairs are completed.

As I wrote this, got the idea to suggest we install just one larger blower and one larger air conditioner. We'll still have redundancy! Should be cheaper, simpler, and more efficient using larger fans. That's if larger units are available that will work with this design.

Note that HP designed their POD containerized data center to run at 90°F. This YouTube tour explains why this works, starting at 2:50. Our design also maintains strict separation between hot air and cold air using chimney cabinets, while using larger, more efficient fans on the roof.


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