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FOCUS on COOLING


RADICAL CHANGES TO COOLING


temperature weighted Net X-Factor of 0.86) based on keeping everything else constant except inlet temperature.


Climate 3 is essentially the opposite of Climate 2. It identifies the consequences if the baseline of 20°C (68°F) occurs for 50% of the time and the remaining 50% is at a higher temperature of 25°C (77°F). It shows that the annual server failures would increase by 12% (Net X-Factor of 1.12) based on keeping everything else constant except inlet temperature.


Climate 4 is a hybrid example with a


disproportionate amount of the operational hours being below 20°C (68°F). It shows that the annual server failures would be reduced by 4% (X-Factor of 0.96) based on keeping everything constant except inlet temperature.


NET X-FACTOR: US & GLOBAL CITIES The Net X-Factor is somewhat unintuitive but essentially identifies that the key to temperature related server failures is the total operational hours at each temperature. Figure 4a (page 14) shows the Net X-Factors for US cities and Figure 4b (page 15) Net X-Factor for global cities using


Constant 15 °C Inlet (Below The 20 °C baseline)


Climate A


Climate 1 Climate 2 Climate 3 Climate 4


X Factor B


0.72 0.72 0.72 0.72


Annual Server Failures C


0%


50% 0%


40% Baseline (Constant 20 °C Inlet Temperature)


X Factor D


1.00 1.00 1.00 1.00


Figure 3. Server Failure Rates (using Figure 1 Applied to Different Inlet Temperatures) © DLB Associates 15 °C ≤ Inlet Temperature ≤ 20 °C City A


San Francisco, CA Helena, MT Denver, CO Seattle, WA Madison, WI Boston, MA Chicago, IL


Washington, DC Phoenix, AZ


Los Angeles, CA Atlanta, GA Dallas, TX


New York, NY Miami, FL


X Factor % Annual Hours B


0.865 0.865 0.865 0.865 0.865 0.865 0.865 0.865 0.865 0.865 0.865 0.865 0.865 0.865


C


87.4% 83.6% 75.9% 88.0% 76.1% 75.2% 72.5% 61.6% 34.1% 67.1% 52.4% 45.5% 66.7% 9.5%


20 °C < Inlet Temperature ≤ 25 °C X Factor % Annual Hours D


1.130 1.130 1.130 1.130 1.130 1.130 1.130 1.130 1.130 1.130 1.130 1.130 1.130 1.130


E


10.7% 8.5%


11.8% 8.4%


13.6% 15.2% 14.6% 17.5% 14.9% 28.2% 23.2% 18.5% 17.2% 24.5%


25 °C < Inlet Temperature ≤ 30 °C X Factor % Annual Hours F


1.335 1.335 1.335 1.335 1.335 1.335 1.335 1.335 1.335 1.335 1.335 1.335 1.335 1.335


G


1.6% 5.1% 7.2% 3.0% 8.1% 7.2% 9.5%


14.6% 15.6% 4.2%


16.8% 19.7% 12.3% 48.6%


30 °C < Inlet T emperature ≤ 35 °C X Factor % Annual Hours H


1.482 1.482 1.482 1.482 1.482 1.482 1.482 1.482 1.482 1.482 1.482 1.482 1.482 1.482


I


0.4% 2.9% 5.1% 0.6% 2.2% 2.4% 3.5% 6.3%


35.4% 0.4% 7.7%


16.4% 3.8%


17.4% Average Figure 4a. Time Weighted Failure Rate Net X-Factor Calculations for US Cities for Class A2 and Air Side Economization - ASHRAE Table C-2. (modified) © ASHRAE Table reformatted by DLB Associates Using ASHRAE Weather Data Viewer


J = ( B X C) + ( D X E ) + ( F X G ) + ( H X I )


0.90 0.93 0.96 0.91 0.95 0.95 0.97 1.02 1.20 0.96 1.05 1.11 0.99 1.27 1.02


Net X-Factor


Annual Server Failures E


100% 50% 50% 30%


historical climate data from ASHRAE’s Weather Data Viewer software. These two figures highlight the opportunity to use full time economizers with a minimal increase in server failures or, in some cities, even a reduction in server failures.


In Figure 4a, there are 15 US cities that combine for a combined Net X-Factor average of 1.02. In Figure 4b there are 23 global cities that combine for a combined Net X-Factor average of 1.00. The Net X-Factor average for the 38 cities listed in Figure 4a and 4b was very close to 1 (1.02) which means an annual operating temperature


Constant 25 °C Inlet (Above The 20 °C baseline)


X Factor F


1.24 1.24 1.24 1.24


Annual Server Failures G


0% 0%


50% 30%


Net X-Factor H = ( B X C) +


( D X E ) + ( F X G ) 1.00


0.86 1.12 0.96


14 www.datacenterdynamics.com


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