Optimize the supply air temperature
For years, data centers have operated under the premise that the cooler, the better. Today that's not always the case, even in the summer. However, due to an increase in the solar load, data center operators tend to decrease the set points in the AC units in the summer months.
"The reason many do this is that they want to have a supply air temperature of 70 degrees, so as the temperature drifts up towards 75 degrees, they turn on the AC higher," Capes says. The most recent guidelines from ASHRAE (the American Society of Heating, Refrigerating and Air-Conditioning Engineers) recommend a supply air temperature of up to 81 degrees, yet many data centers continue to operate at much cooler temperatures.
"All too often, engineers or facilities operators run their data centers based on the return air temperature of the CRAC unit," says Capes. And while there might be plausible reasons to do that, "all server manufacturers and ASHRAE care about is the supply air temperature to the inlet of the server."
In addition to raising the temperature on your CRAC units, Capes says it may be possible ? and certainly is simpler ? to turn some of them off altogether. A data center that has 300 kW of cooling installed with a 400 kW UPS system running at 25 percent of capacity has three times the amount of cooling that is needed. "In some cases, you can put units on standby and have no effect on the environment at all," Capes says.
Maximizing cooling efficiency also requires regular maintenance and perhaps a few interior changes.
If a data center has a raised floor, make sure the space under the floor is as clear as possible. Often when IT disconnects cables, they drop them below the floor where they may inhibit air flow to the point where fans have to work extra hard. And to reduce the overall work an AC has to do, it makes sense to locate cooling as close to the workloads as possible, whether this means moving perimeter units to the end of a rack row or adding supplemental localized cooling.
Air conditioning units themselves also won't function efficiently when dirty, so make sure to clean the outdoor heat exchanges and the filters on indoor units. And if a data center has windows, drawing blinds or installing a room darkening film can reduce solar load. Lighting typically contributes about 4 percent of the total heat load of a data center, Capes says; adopting LED lighting is an easy way to achieve a quick pay back.
"It is astonishing how many data centers I go into that haven't done some really simple things and best practices to improve cooling efficiency," Capes says. By following just a few tips now, data centers can achieve noticeable cooling improvements before summer's end.
Megan Santosus is a business and technology writer based in Natick, Mass.