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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