ASHRAE Journal - March 2023 - 20

DATA CENTERS
Column
Thermal Guidelines' X-Factor IT Reliability Data
Data Center Energy
And Capital Cost
Considerations
BY DAVE QUIRK, P.E., MEMBER ASHRAE; HAMED YASSAGHI, PH.D.; TOM DAVIDSON, P.E., MEMBER ASHRAE
An underused portion of ASHRAE's Thermal Guidelines for Data Processing Environments,
5th Edition,1 is the analysis of server reliability data and the impact this can have on
both the energy consumption and the capital cost of a data center. This reliability
analysis is called x-factor and is the focus of Section 2.4.3, Server Reliability Trend
Versus Ambient Temperature, of the Thermal Guidelines' 5th edition.
What exactly is the x-factor reliability metric? It
first appeared in the 3rd edition of Thermal Guidelines.2
As stated in the document, " Since there are so many
different variables and scenarios to consider, the
approach taken by TC 9.9 was to initially establish a
baseline failure rate (x-factor) of 1.0 that reflected the
average probability of failure under a constant ITE inlet
temperature of 20°C (68°F). " Using manufacturer's
data, a table was then created to show the relative
failure rate (with lower, average and upper bounds)
at other information technology equipment (ITE)
inlet temperatures. This table has been previously
reproduced in ASHRAE Journal3 but is shown in Table 1 as
a refresher.
The purpose of this column is to reexamine x-factor
with an eye toward the potential energy and capital cost
savings.
20
ASHRAE JOURNAL ashrae.o rg M A R CH 2023
Alignment of Data Center Cooling System
With Local Climate
While designing with x-factor considerations can
yield significant capital and energy cost advantages,
it is important to understand that the intent of
operating without mechanical refrigeration does not
mean that one should operate outside of the allowable
operating range of the IT equipment. This means that
mechanical cooling (and possibly also humidification
and/or dehumidification) will be required in certain
climates to stay within the Allowable (A2, A3 or
A4 as applicable) range at all times. It may be that
partial cooling can be accomplished via integrated
economizer even during the worst-case design
David Quirk, P.E., is a managing principal at DLB and past chair of ASHRAE TC 9.9.
Hamed Yassaghi, Ph.D., is an energy engineer specialist and Tom Davidson, P.E., is a
senior mechanical engineer at DLB Associates.

http://ashrae.org

ASHRAE Journal - March 2023

Table of Contents for the Digital Edition of ASHRAE Journal - March 2023

Contents
ASHRAE Journal - March 2023 - Intro
ASHRAE Journal - March 2023 - Cover1
ASHRAE Journal - March 2023 - Cover2
ASHRAE Journal - March 2023 - 1
ASHRAE Journal - March 2023 - Contents
ASHRAE Journal - March 2023 - 3
ASHRAE Journal - March 2023 - 4
ASHRAE Journal - March 2023 - 5
ASHRAE Journal - March 2023 - 6
ASHRAE Journal - March 2023 - 7
ASHRAE Journal - March 2023 - 8
ASHRAE Journal - March 2023 - 9
ASHRAE Journal - March 2023 - 10
ASHRAE Journal - March 2023 - 11
ASHRAE Journal - March 2023 - 12
ASHRAE Journal - March 2023 - 13
ASHRAE Journal - March 2023 - 14
ASHRAE Journal - March 2023 - 15
ASHRAE Journal - March 2023 - 16
ASHRAE Journal - March 2023 - 17
ASHRAE Journal - March 2023 - 18
ASHRAE Journal - March 2023 - 19
ASHRAE Journal - March 2023 - 20
ASHRAE Journal - March 2023 - 21
ASHRAE Journal - March 2023 - 22
ASHRAE Journal - March 2023 - 23
ASHRAE Journal - March 2023 - 24
ASHRAE Journal - March 2023 - 25
ASHRAE Journal - March 2023 - 26
ASHRAE Journal - March 2023 - 27
ASHRAE Journal - March 2023 - 28
ASHRAE Journal - March 2023 - 29
ASHRAE Journal - March 2023 - 30
ASHRAE Journal - March 2023 - 31
ASHRAE Journal - March 2023 - 32
ASHRAE Journal - March 2023 - 33
ASHRAE Journal - March 2023 - 34
ASHRAE Journal - March 2023 - 35
ASHRAE Journal - March 2023 - 36
ASHRAE Journal - March 2023 - 37
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ASHRAE Journal - March 2023 - 63
ASHRAE Journal - March 2023 - 64
ASHRAE Journal - March 2023 - Cover3
ASHRAE Journal - March 2023 - Cover4
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