I heard yesterday that a savvy data center operator on the west coast had surprisingly learned something at one of our recent energy efficiency classes, putting in practice a measure that saves wasted energy and recaptures cooling system capacity. (And I mean that in the most positive way - these guys know their way around a DC, and I hadn't expected to be able to share anything new with them!)
The facilities manager had managed to implement a number of airflow management measures, resulting in the ability to decommission a number of CRAC units.
In our section of the class covering airflow management we note that CRAC units don't typically feature back flow prevention dampers, so that when the unit isn't running air can flow through in either direction. Given that the underfloor plenum has a positive pressure, that means supply air is lost through the CRAC.
One solution to this problem is to install a temporary cover over the inlet plenum. Mark Hydeman of Taylor Engineering suggests going to a local boatyard to have a fabric cover made, because it is easy to install and remove by one person, compared to a sheet metal cover.
In this case, they had already installed "snorkels" on the CRAC inlets, extending them up to the dropped ceiling, which now serves as a return air plenum. So, installing back flow prevention dampers is the option they'll go with.
Oh, and here's the kicker: they measured the airflow from the underfloor supply up through the decommissioned CRAC at 2,200 CFM! That's a whole lot of wasted energy and cooling system capacity!
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