In some data centers, an approach known as allowing data center humidity to "float" -- by shutting off the humidity controls in cooling units -- has gained traction as a way to save on data center power costs.
This method of data center cooling was also the topic of a session at last month's Data Center World conference hosted by AFCOM. The presentation was given by John Richard, the director of business development at Toronto-based Morrison Hershfield Group Inc., and Yogendra Joshi, a professor at the Georgia Institute of Technology in Atlanta.
In most modern data centers, air-cooling units such as computer room air-conditioning units, or CRACs in a raised-floor environment, overhead coolers or units nestled in a row of server racks, display a relative humidity reading that data center managers can adjust. Preventing data center humidity from climbing too high or dipping too low prevents condensation on your equipment and the possibility of electrostatic discharge (ESD), both of which can be harmful to computer equipment.
But in geographic locations where the weather doesn't get too humid or too dry, data center managers may not need to manually adjust humidity levels in their facilities at all, data center managers have discovered.
Humidity off equals energy savings
Instead of making manual adjustments, when data center managers allow humidity to float, it can translate into energy savings. By turning off humidification and dehumidification controls, the cooling units become focused only on blowing cool air. Trying to control humidity manually can be counterproductive, causing cooling units to fight one another when humidity levels differ throughout a room. If one unit, for example, is humidifying a room as another dehumidifies, the units cancel each other out and use extra electricity in the process.
Intel Corp. doesn't control the humidity in about 50,000 square feet of data center floor space. "We haven't really had any humidity issues," said John Musilli, data center operations manager for Intel and a board member of AFCOM's Data Center Institute. "We decided to turn off the [humidity] systems, disable them at the CRAC level, and we could always turn them back on if we needed them," Musilli said. "We've never had to turn them back on." About three years ago, Intel started experimenting with shutting off humidity controls in its California data centers. For those data centers, the company buys its CRAC units without the humidity controls attached, which also generates savings up front on capital costs.
About nine months ago, Shands HealthCare in Gainsville, Fla., shut off the humidity controls in its 3,500-square-foot data center, said Brad Kowal, Shands' associate data center director. Why? The company was running out of power in the facility and needed to stem the bleeding. Shutting off humidification and dehumidification controls – which, along with the main blower make up the three circuits for the CRAC units – has done that without putting the facility at risk.
"I ran into a power issue within my data center," Kowal said. "So I needed to rob Paul to pay Peter. That said, I still had to put that through a little rhyme and reason. The rhyme and reason was that I'm in Florida. I'm in a humid state. If I was in Arizona, I don't know that I would do that."
Kowal hasn't yet seen how the winter weather will affect his data center's humidity. Gainesville is in the northern part of the state, and in the months of December, January and February, temperatures outside can hit the freezing point and humidity levels can drop. Kowal's goal is to stay close to the guidelines for computer rooms set by the American Society for Heating, Refrigerating, and Air-Conditioning Engineers Inc. (ASHRAE).
ASHRAE's recommended range is 40% to 55% for relative humidity, but it says an acceptable range is 20% to 80%. Some manufacturers allow an even wider range than that – and there is ongoing industry debate about the proper data center humidity levels. Kowal said he would like to stay in the 30%-to-70% range.
No matter what happens this winter, Kowal knows he can keep the humidity controls off for at least nine months a year, and that will yield electricity savings. How much he's not sure of yet, but determining that is on his to-do list, he said.
"I think that with the greening of the data center, there is a larger push to get rid of the nonsense," he said. "If there's an area to be saved, data center engineers are OK with the ASHRAE guidelines."
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