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Technical Brief Mastering Data Center Environmental Controls to Help Drive Your Bottom Line1

TECHNICAL BRIEF

Mastering Data Center Environmental Controls to Help Drive Your Bottom Line

ChallengeMany data centers waste energy using inefficient temperature and humidity controls within their computer rooms.

At StakeProper temperature and humidity control can extend the life of hardware and deliver significant cost savings to data centers.

Solution Data centers can closely follow temperature guidelines recommended by ASHRAE and use an air containment strategy to become more energy efficient and save money.

Running Your Data Center Under Ideal Temperature Conditions

Data centers are non-stop energy hogs. They require vast

amounts of power to run 365 days a year. The primary source of

consumption is server hardware stacked in racks in computer

rooms. The other major energy gluttons are refrigeration systems

and fans used for cooling and air circulation. Responsible for

almost a third of a data center’s energy consumption, these

systems fall under the larger umbrella of climate control. The

following recommendations offer simple, practical steps you can

take to lower cooling costs while maintaining your hardware.

Technical Brief Mastering Data Center Environmental Controls to Help Drive Your Bottom Line2

Raise the Thermostat Level

Did you know that increasing room temperature by one degree

Celsius can save on average between two to four percent of a

data center’s energy bill? Updated thermal guidelines set by the

American Society of Heating, Refrigerating, and Air-Conditioning

Engineers (ASHRAE) for data processing environments have

recommended raising room temperatures higher than 26.6

degrees Celsius (80 degrees Fahrenheit).

“Most of our control strategies at CenturyLink revolve around

ASHRAE TC 9.9 Thermal Guidelines for Data Centers,” said Doug

Florek, Senior Lead Engineer at CenturyLink. “We utilize the Class

A1 recommended ranges for control of our cooling systems as

well as humidity control, however most service level agreements

(SLAs) are written to the allowable temperature and humidity.”

ASHRAE guidelines reinforce the idea that servers can perform

effectively at higher temperatures. The problem is getting

data center managers to buy into this concept. “Equipment

manufacturers all do their own independent testing to find the

mean time of failure for their equipment,” said Florek. “Those

numbers are much higher than that of the actual recommended

control range.” Nevertheless, if you’re a data center manager and

your job depends on server availability, the last thing you want

to do is take chances. That’s why many data centers stay in the

low to mid 70 degrees range. It’s better than the frozen tundra

temperatures of years gone by, but it would be optimal for data

centers managers to program their computer rooms to match

current recommendations.

Technical Brief Mastering Data Center Environmental Controls to Help Drive Your Bottom Line3

Air Containment

One of the most effective ways to improve cooling efficiency

in the data center is to employ a containment strategy. With

containment, you separate cold airflow from the hot exhaust

air that comes from hardware. This simple separation creates

a consistent temperature at the supply intake and prevents hot

exhaust air from passing back through the front of the equipment.

In a cold aisle, cooling equipment blows cold air (usually through

a raised floor) into the front of computer racks situated to face

each other. The hot air from the servers gets discharged to the hot

aisle and is returned to the cooling equipment (commonly through

return grilles in the ceiling). Orienting rows in such a configuration

utilizes energy better. “Our best practice for containment is getting

the hottest air possible back to the cooling equipment,” said

Florek. “But that might not be possible if your computer room air

conditioning equipment is situated around the perimeter.”

If you’re not using a roof over a row or enclosing a space,

you can use vinyl strip or hard-walls to maintain the integrity

between rows. The vinyl material is easy to modify to

accommodate various mounting conditions.

Also, you should seal off all cable penetrations within the

floor and containment systems and install blanking plates in

unoccupied areas within and around racks. If there’s an area

where someone moved out, such as in a colocation facility, pull

those perforated tiles out of the floor completely. This is much

more efficient than using a damper or dialing them down. Only

cold aisles should contain supply registers or perforated floor

tiles for cold air supply; all supply air should be removed from

areas outside of the cold aisle.

A hot/cold aisle rack/cabinet with containment. A hot/cold aisle rack/cabinet without containment.

Sensors

A common challenge with containment is maintaining temperature

consistency within rows. Older rooms use sensors that hang from

the ceiling several feet above the equipment, and the readings fail

to accurately reflect the temperature of the rack below.

More and more companies, such as CenturyLink, deploy

wireless sensors that can be placed directly on a rack and

provide an infinitely more precise reading of the server inlet air

temperature. “Eighty percent of our sites have wireless sensors

on every third rack on the inlet,” said Florek. “It lets us better

control our systems and have more consistent temperature

coming into each rack.”

For full coverage, the sensors should be equidistant from one

another in areas where the equipment is actively drawing air

(avoid placing sensors on inactive sections of a cabinet). Florek

Technical Brief Mastering Data Center Environmental Controls to Help Drive Your Bottom Line4

also recommends placing each sensor slightly closer to (four to

five feet above) the floor because racks tend to be loaded from

the bottom and such positioning keeps them closer to the supply

side of the air flow and the higher off the floor, the more likely it

is you’ll have high inlet temperature issues.

Traditionally, data center temperatures are based on the air

returning to cooling units. This isn’t very practical. The returning air

is often warmer, which leads to wasted energy trying to cool down

spaces that don’t need it. By placing the sensor on the supply

side, a manager gets a reading of the air flow in front of a piece of

equipment, which is the temperature that needs to be controlled

most. “The idea used to be to make a data center as cold as

possible,” said Florek. “We’ve learned over the course of the last

ten years that having a computer room too cold can be just as

harmful to the life of equipment as too hot a temperature.”

Similar to the Internet of Things, wireless sensors collect and

monitor information. They are automated to identify data center

temperature fluctuations outside of the desired range and

send messages to the cooling systems to increase or lower

temperatures accordingly. Such automation means energy is

consumed only when needed.

An example of sensor placement in hot/cold rows.

Humidity

Humidity concerns the moisture in the air. You need to control the

humidity in your computer room in order to prevent issues — such as the

potential buildup of electrostatic discharges or fluctuations in temperature

— that can have a negative impact on the life of your hardware.

Measuring humidity in data centers really means talking about

relative humidity, which is directly impacted by the temperature

in the air. Percent Relative Humidity (%RH) is a humidity

measurement that varies with the temperature entering the rack. By

raising supply air temperatures, you can reduce the dehumidification

effect and use less energy. ASHRAE recommends a humidity level

of 60%RH and an allowable range of between 20-80%RH.

One of the biggest challenges with humidity is taking the uncontrollable

outside air and converting it into controllable interior air flow.

Humidifiers in data centers offer high capacity, low cost evaporative

cooling. The best way to choose a humidifier is to pick a cooling system

reflective of the climate of the data center building’s location.

Depending on the region, humidifiers may be needed minimally

or not at all. In most climatic regions, humidifiers are not a critical

component of a data center. If you utilize them, you do not need to

install them in each of the air conditioning units. A more efficient

practice would be to place one humidifier in your central air unit.

A lot of data centers also use outdoor air economizers.

Economizers use controllable dampers to increase or decrease

the amount of air drawn into the data center, depending on the

temperature outside. These tools come with high limit switches

that are meant to determine if the outside air is appropriate for

cooling. If not, the switch disables the dampers.

You would think that cooler outdoor temperatures would signal the

ideal scenario for using the economizer. But this is not always the

case. In some cases the outdoor air might be too cold, and lack

the required humidity to maintain ideal operating conditions calling

on humidification systems and wasting both energy and water.

Conversely there may be times when the return air is hotter than the

outside air, but the outside air would require more cooling because of

the moisture content. Humid air puts a dehumidifcation burden on

the cooling coils making them work harder and waste energy.

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Conclusion

There is no one-size-fits-all method for achieving data center

energy efficiency. Data center managers can, however, utilize

temperature and humidity controls that deliver consistent

readings and save energy by utilizing higher thresholds. Best

of all, you can achieve these savings without buying new

equipment or building new structures. Investigate your options

and make the move to improve the climate within your data

center structure and lower your energy consumption.

• Follow ASHRAE guidelines for temperature control.

• Be fanatical about containment. Keep the cold supply air

separate from the hot return air to increase cooling efficiency

and assure proper operating temperatures for the IT kit.

• Place more sensors closer to the equipment to monitor

server inlet temperatures.

• Manage humidity to provide a stable and efficient operating

environment in the data center.

• Research whether an outdoor air economizer makes sense

in your situation.

• Master your environmental management to maintain IT

equipment and improve energy efficiency.

About CenturyLink

CenturyLink, Inc. is the third largest telecommunications

company in the United States. Headquartered in Monroe, LA,

CenturyLink is an S&P 500 company and is included among the

Fortune 500 list of America’s largest corporations. CenturyLink

Business delivers innovative private and public networking and

managed services for global businesses on virtual, dedicated

and colocation platforms. It is a global leader in data and voice

networks, cloud infrastructure and hosted IT solutions for

enterprise business customers.

For more information visit www.centurylink.com/enterprise.

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