ASHRAE Journal - May 2024 - 19
COLUMN DATA CENTERS
supply temperature of 68°F (20°C) CHWS. Table 4 shows
that Scenario 1 has a relatively high x-factor of 1.22
(higher than 1.00 because the cold aisle temperature
is above the x-factor baseline of 68°F [20°C]). It also
has a relatively high mechanical cooling energy use
(annualized MLC = 0.26). This complies with Standard
90.4-2016 for Climate Zone 2B (MLC 0.36), but is not
close to IECC 2021 (MLC 0.18). Not all chiller effi ciency
curves are the same, but this result indicates that ACCs
operating without economizers with a CHWS of 68°F
(20°C) will likely struggle to meet IECC 2021.
Scenarios 2-A and 2-B. Here, the ACC benefi ts from
an integrated closed-loop water economizer, with lower
annualized chiller energy use compared to Scenario 1
(Baseline). The MLC drops in both scenarios compared
to the baseline, but not suffi ciently to comply with the
IECC 2021 MLC.
Note that in Scenario 2-B, which allows chilled
water reset to 60°F (16°C) at lower ambient dry-bulb
temperatures, the x-factor is reduced by 0.07 compared
to Scenario 2-A. The total energy use, however,
increases, as the chiller is not as effi cient operating
at the lower CHWS, even though the ambient air is
relatively cold when the transition to 60°F (16°C) CHWS
setpoint is used.
Scenarios 2-A and 2-B represent a different set
of priorities. Scenario 2-A aims to reduce energy
consumption as much as possible, while 2-B aims
to improve server reliability by reducing cold aisle
temperatures for much of the year.
Scenarios 3-A and 3-B. These scenarios incorporate
the ACC from Scenario 1, but replace the chiller's
integrated economizers (Scenario 2-A) with direct
airside free cooling. Both Scenarios 3-A and 3-B were
able to comfortably meet the IECC 2021 MLC levels
with an MLC of 0.15. Scenario 3-A represents the codecompliant
case, as cold aisle temperatures are always
within ASHRAE's recommended temperature range of
64.4°F - 80.6°F (18°C - 27°C).3 Scenario 3-B was included
because it shows that in this instance, a signifi cant
increase in server reliability as defi ned by x-factor
can be obtained by dropping the minimum cold aisle
MAY 2 0 2 4 ashrae.org ASHRAE JOURNAL
19
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ASHRAE Journal - May 2024
Table of Contents for the Digital Edition of ASHRAE Journal - May 2024
Contents
ASHRAE Journal - May 2024 - Intro
ASHRAE Journal - May 2024 - Cover1
ASHRAE Journal - May 2024 - Cover2
ASHRAE Journal - May 2024 - 1
ASHRAE Journal - May 2024 - Contents
ASHRAE Journal - May 2024 - 3
ASHRAE Journal - May 2024 - 4
ASHRAE Journal - May 2024 - 5
ASHRAE Journal - May 2024 - 6
ASHRAE Journal - May 2024 - 7
ASHRAE Journal - May 2024 - 8
ASHRAE Journal - May 2024 - 9
ASHRAE Journal - May 2024 - 10
ASHRAE Journal - May 2024 - 11
ASHRAE Journal - May 2024 - 12
ASHRAE Journal - May 2024 - 13
ASHRAE Journal - May 2024 - 14
ASHRAE Journal - May 2024 - 15
ASHRAE Journal - May 2024 - 16
ASHRAE Journal - May 2024 - 17
ASHRAE Journal - May 2024 - 18
ASHRAE Journal - May 2024 - 19
ASHRAE Journal - May 2024 - 20
ASHRAE Journal - May 2024 - 21
ASHRAE Journal - May 2024 - 22
ASHRAE Journal - May 2024 - 23
ASHRAE Journal - May 2024 - 24
ASHRAE Journal - May 2024 - 25
ASHRAE Journal - May 2024 - 26
ASHRAE Journal - May 2024 - 27
ASHRAE Journal - May 2024 - 28
ASHRAE Journal - May 2024 - 29
ASHRAE Journal - May 2024 - 30
ASHRAE Journal - May 2024 - 31
ASHRAE Journal - May 2024 - 32
ASHRAE Journal - May 2024 - 33
ASHRAE Journal - May 2024 - 34
ASHRAE Journal - May 2024 - 35
ASHRAE Journal - May 2024 - 36
ASHRAE Journal - May 2024 - 37
ASHRAE Journal - May 2024 - 38
ASHRAE Journal - May 2024 - 39
ASHRAE Journal - May 2024 - 40
ASHRAE Journal - May 2024 - 41
ASHRAE Journal - May 2024 - 42
ASHRAE Journal - May 2024 - 43
ASHRAE Journal - May 2024 - 44
ASHRAE Journal - May 2024 - 45
ASHRAE Journal - May 2024 - 46
ASHRAE Journal - May 2024 - 47
ASHRAE Journal - May 2024 - 48
ASHRAE Journal - May 2024 - 49
ASHRAE Journal - May 2024 - 50
ASHRAE Journal - May 2024 - 51
ASHRAE Journal - May 2024 - 52
ASHRAE Journal - May 2024 - 53
ASHRAE Journal - May 2024 - 54
ASHRAE Journal - May 2024 - 55
ASHRAE Journal - May 2024 - 56
ASHRAE Journal - May 2024 - 57
ASHRAE Journal - May 2024 - 58
ASHRAE Journal - May 2024 - 59
ASHRAE Journal - May 2024 - 60
ASHRAE Journal - May 2024 - 61
ASHRAE Journal - May 2024 - 62
ASHRAE Journal - May 2024 - 63
ASHRAE Journal - May 2024 - 64
ASHRAE Journal - May 2024 - 65
ASHRAE Journal - May 2024 - 66
ASHRAE Journal - May 2024 - 67
ASHRAE Journal - May 2024 - 68
ASHRAE Journal - May 2024 - 69
ASHRAE Journal - May 2024 - 70
ASHRAE Journal - May 2024 - 71
ASHRAE Journal - May 2024 - 72
ASHRAE Journal - May 2024 - 73
ASHRAE Journal - May 2024 - 74
ASHRAE Journal - May 2024 - 75
ASHRAE Journal - May 2024 - 76
ASHRAE Journal - May 2024 - 77
ASHRAE Journal - May 2024 - 78
ASHRAE Journal - May 2024 - 79
ASHRAE Journal - May 2024 - 80
ASHRAE Journal - May 2024 - Cover3
ASHRAE Journal - May 2024 - Cover4
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