NER Data Corporation White Paper
Thermal Monitoring Best Practices
Benefits gained through proper deployment and utilizing sensors that
work with evolving monitoring systems
Data centers are dynamic environments that change based on evolving business requirements. Monitoring your
physical infrastructure is key ensuring business continuity, preventing disruption of service, meeting compliance
requirements, reducing costs and increasing ROI. Decisions made today affect your ability to monitor and
manage your future state. Monitoring and management requirements change over time, so best practices use the
deployment of tools that meet the needs of today while allowing for changes in the future.
Best Practice: Monitor Temperature at Multiple Rack Level Points
The 2013 Uptime Institute Data Center Industry Survey reported “..only 15% of the data center managers
responding to the survey said they were measuring and controlling air temperatures from the server inlet, which is
the most accurate location. Nearly a third of the respondents are managing inlet air temperature at the room
level, which is the least accurate method. Obviously there is room for some further cooling efficiency
Thermal monitoring should be conducted at the rack and key points
within the data center to properly protect equipment and to gather
data for cost saving optimization.
A goal in data center cooling is to maintain server rack exhaust temp
under 100*F and a Rack Delta temperature of around 20*F while
targeting the highest efficiency. In order to do this you must monitor
rack intake and exhaust tempertures at various heights. Rack inlet
and exhaust temperatures can vary over 10*F within just 8". The
American Society of Heating, Refrigerating and Air-Conditioning
Engineers (ASHRAE) recommends at least 6 temperature sensors
per rack (top, middle, bottom / front and back).
Monitoring return air temps at the CRAC unit provides valuable
information but only measures intermixed air. This method leaves
gaps for hot (under provisioned) areas and cold (over provisioned)
areas at the rack level. Measurements taken at multiple points at the
rack as described above and at the CRAC feed and return provide you with actionable information:
1. Divide each individual CRAC unit return air temperatures to the average rack exhaust temperature to
determine the return path efficiency. Example: CRAC unit 1 return air temperature average is 76°F. The
average server rack exhaust temperature is 88°F. There is a 12°FΔT so the return air path back to CRAC
1 is 86% efficient.
2. Next determine the cooling delivery efficiency. Divide the CRAC unit feed temperature by the average
rack inlet temperature for each CRAC unit. Example: CRAC unit 1 feed air temperature average is 52°F.
The Average server inlet temperature is 58°F. There is a 6°FΔT so the cool air distribution is 89%
3. Finally determine the overall airflow distribution efficiency by averaging the efficiency rating for distribution
and return together. Example: CRAC unit 1 return airflow efficiency is 86% and the cool air distribution is
89% efficient. The overall airflow distribution efficiency for CRAC 1 is 87.5%.
By measuring at the rack and key points within the data center you will know what is changing in your data center
and you can clearly see:
· where the highest capacity exist in the rack
· where available cooling capacity exist
· cooling effectiveness at the rack and data center levels
· whether you are over/under provisioning cooling per rack
· problem alerting
· seasonal and weather impacts on server cooling
· cooling policy and SLA enforcement
· local problem solving such as blanking panel placement
· proof of concept pre and post deployment
Temperature is Just Part of the Cooling Equation
There are four values which affect the cooling properties of air:
Temperature, Humidity, Pressure, and Flow
A change in any one of these values will effectively alter the air’s ability to cool an electrical heat load as
illustrated in the examples below:
Baseline server rack with a 12kW load is introduced cooling air with the following values:
Temperature: 70°F, Relative Humidity: 50%, Pressure, Sea Level @ 14.7 psi, Flow: 1900cfm = exhaust
temperature of 90°F and 20 Δ°F temperature
(Note: changing the temperature also changes the relative humidity)
· Example 1: Lower Temperature to 55°F, Relative Humidity: 50%, Pressure, Sea Level @ 14.7 psi,
Flow: 1900cfm = exhaust temperature of 74.3°F and 19.3Δ°F temperature rise.
Example 2: Temperature:70°F, Relative Humidity: 50%, Pressure, Sea Level @ 14.7 psi,
Reduce Flow to 1500cfm = exhaust temperature of 95.3°F and 25.3Δ°F temperature rise.
Example 3: Increase Temperature to 77°F, Relative Humidity: 50%, Pressure, Sea Level @ 14.7 psi,
Reduce Flow to 1750cfm = exhaust temperature of 99°F and 22Δ °F temperature rise.
Example 4: The same server rack and airflow values as the Baseline, only this time we reduce the air
pressure by placing the rack in Denver Co. with an elevation of 5,280 feet. The result is an exhaust
temperature of 94.3°F and 24.3 Δ °F temperature rise.
These cooling examples show that monitoring temperature at the rack intake is just a piece of the puzzle and a
change in any variable can affect cooling. Through continual monitoring and measuring it may be possible to
adjust temperature (and corresponding humidity) and flow while still staying within a desired server exhaust
temperature. Benefits come in cost savings through reduced compressor and fan energy usage.
To optimize monitoring and management, temperature sensors should be positioned along the front and rear of
each priority rack. Also barometric and humidity sensors should be placed within the aisle where these racks
Aurora High Resolution Temperature Strip Enables Best-Practice
Rack Level Thermal Monitoring
The Aurora consists of innovative patent-pending technology that couples a series of 8 thermally
isolated temperature sensors with an array of high intensity LEDs. Aurora visually displays
temperature reading similar to a CFD through a range of cool (blue) to hot (red) and a blend of 129
colors in between.
With 8 sensors per strip, temperature is monitored over the entire height of the cabinet; perfect for
meeting ASHRAE recommendations, aisle containment and areas susceptible to temperature
stratification. Sensors start 4.5” from bottom of unit and end at 60.5” to provide measuring of
temperature fluctuations within 8” increments. Used as self-policing, real-time troubleshooting tool, it
clearly identifies potential cooling or heat-related issues and provides instantaneous feedback that is
invaluable when monitoring changes or validating best-practice improvements.
Aurora is extremely accurate because it measures air temperature, not surface temperature. Three
User-Selectable Sensitivity Settings allow for fine tuning of the monitored temperature range over the
full 129-color spectrum.
Low setting concentrates the color spectrum towards the colder end of the temperature
scale. The 129 colors will vary between 25 degrees F (50°F/10°C to 75°F/23.8°C). This
setting offers more color resolution for colder data centers such as cold aisle containment.
Medium setting closely reflects the ASHRAE standards for acceptable equipment inlet
temperatures. The 129 colors will vary between 25 degrees F (65°F/18.3°C to 90°F/32.2°C).
High setting concentrates the color spectrum towards the
hotter end of the temperature scale. The 129 colors will vary
between 25 degrees F (70°F/21.1°C to 95°F/35°C). This
setting offers more color resolution for data centers with
hotter temperature settings. This setting is also suitable for
positioning the Aurora Temperature Strip in the hot aisle.
Benefits of Visual Alerting
Studies on human behavior show that warnings are most effective
when they are presented proximate (in time and space) to the
hazard. By visually indicating the issue in both a Management
System interface and at the exact physical location, time to
remediation can be decreased. With automated alerts and easy to
comprehend alerts at the point of hazard,
every team member can insure that no
issue goes unnoticed.
Centralized management systems provide a way to capture,
manage, and effectively use sensor data. Down-time causing
events can be avoided or minimized through monitoring systems
that allow IT staff to quickly respond to environmental changes
and alerts. In advanced systems, alerts can trigger automated
response such as adjusting VFD controllers for target areas
based on alert thresholds.
Through the use of real-time data, Monitoring Solutions take the
guess-work out of decision making and planning processes.
Sensors provide important inputs for establishing baseline
conditions, trending, capacity planning, validating best-practice
improvements, monitoring changes, and confirming compliance
with company mandates.
According to the Uptime Institute 2013
Data Center Industry Survey:
“Data center infrastructure management
(DCIM) software adoption seems to have
skyrocketed. An astounding 38% reported
that they have deployed DCIM software.”
“That’s not to say that the companies
have fully installed the tools, or are
reaping the rewards of the software’s
capabilities. For many companies, it’s just
the beginning of a long cycle of
implementation and maintenance of the
Best Practice: Use Adaptable Sensors and Systems
The Aurora Strip is designed to work in any data center environment – from basic server rooms without
monitoring applications to Tier 4 data centers that deploy sophisticated DCiM systems. For data centers with
existing monitoring and DCiM solutions, Aurora can be integrated to provide data to these systems. Data from
the strips can interact with systems to provide automated remediation such as adjusting VFD controllers. In
addition, Aurora’s resource-saving communications require just one port to capture up to 800 different sensor
For data centers without existing monitoring systems, the Aurora strip can be used as a stand-alone visual
monitoring tool. However, a centralized monitoring system allows administrators to respond quickly and truly reap
the benefits of the sensor data. Deploying such a system can be costly and overwhelming, but the Aurora
Wireless Management Application (cloud-based and enterprise) is an easy avenue for data centers to move to the
next level of monitoring and management. The system provides for monitoring of additional sensor types
(humidity, fluid detection, airflow, etc.), automated alerts, powerful visual mapping tools, data trending/reporting,
and API commands for integrating with 3rd party applications.
Aurora Wireless Management Application Features
Complete configuration and customization at a sensor, local network, or client wide level
Notifications via SMS text and email
Unlimited sensor data storage and trending
Unlimited user accounts for system configuration, monitoring and notifications
Sensor heartbeats (check-ins) down to 10 minutes:
o Timed sensors (i.e. temperature) can be user-set to check against alert thresholds up to 256
times between heartbeats
o Triggered sensors (i.e. motion, door/window, etc.) record data as it happens, regardless of
Advanced sensor configuration options:
o Automatic sensor recovery attempts
o Sensor inactivity alerts
o Sub-heartbeat assessments with alert thresholds
o Sensor aware state reporting
Advanced Thermographic Sensor Mapping tool
Sensor Grouping feature allows onscreen sensors to easily be arranged to exactly match physical strip
API commands for integrating into 3rd party applications