ASHRAE Journal - October 2021 - 60

COLUMN ENGINEER'S NOTEBOOK
FIGURE 4 The impact of different operating variables on the shape of the perfect load lines and cloud.
A. Economizer-equipped constant volume system and B. 100% OA constant volume
system operating as intended.
* A. vs. B. illustrates the impact of moisture for an economizer-equipped system
vs. a 100% OA system operating at a constant volume, 24/7.
* A. vs. C. illustrates the impact of setting the economizer high limit too high.
* A. vs. D. illustrates the impact of VAV operation vs. 24/7 constant volume
operation.
* A. vs. E. illustrates the impact of VAV operation plus a schedule vs. 24/7
constant volume operation.
A.
120
110
100
90
80
70
60
50
40
30
20
10
-10
B.
120
110
100
90
80
70
60
50
40
30
20
10
-10
D.
120
110
100
90
80
70
60
50
40
30
20
10
-10
10 20
30 40
The Perfect Chilled Water Load
Cooling Coil Leaving Air Setpoint: 51°F, No Reset
Variable Volume System, 24/7 Operation
Outdoor Air Temperature Dry-Bulb Economizer High Limit: 65.7°F
Design Cooling
Condition - Economizer
System, 25% MOA
Economizer High Limit
Design Heating
Condition
50 60 70
Design Cooling Coil LAT
80
Outdoor Temperature (°F)
scheduling or flow management opportunities.
* If there are economizers but no " bend " in the data
cloud in warm weather, then the economizer high limits
60
ASHRAE JOURNAL ashrae.o rg O CTO B E R 2021
90 100 110 120
10 20 30 40 50
60 70 80 90 100 110 120
Outdoor Temperature (°F)
E.
120
110
100
90
80
70
60
50
40
30
20
10
-10
10
20
The Perfect Chilled Water Load
Cooling Coil Leaving Air Setpoint: 51°F, No Reset
100% Outdoor Air
Design Cooling
Condition - 100%
OA System
C.
Design Heating
Condition
Design Cooling Coil LAT
120
110
100
90
80
70
60
50
40
30
20
10
-10
10
The Perfect Chilled Water Load
Cooling Coil Leaving Air Setpoint: 51°F, No Reset
Outdoor Air Temperature Dry-Bulb Economizer High Limit: 75°F
Design Cooling
Condition - Economizer
System, 25% MOA
Economizer High Limit
Design Heating
Condition
20 30 40
Outdoor Temperature (°F)
Design Cooling Coil LAT
50
60 70 80
90 100 110 120
The Perfect Chilled Water Load
Cooling Coil Leaving Air Setpoint: 51°F, No Reset
Variable Volume System, Scheduled Operation
Outdoor Air Temperature Dry-Bulb Economizer High Limit: 65.7°F
Design Cooling
Condition - Economizer
System, 25% MOA
Economizer High Limit
Design Heating
Condition
30 40
Outdoor Temperature (°F)
Design Cooling Coil LAT
50
60 70 80
90 100 110 120
are suspect.
* A flat (vs. inclined) cloud above the economizer high
limit setpoint can point to under-ventilating or incor10
20
30
The Perfect Chilled Water Load
Cooling Coil Leaving Air Setpoint: 51°F, No Reset
Constant Volume System, 24/7 Operation
Outdoor Air Temperature Dry-Bulb Economizer High Limit: 65.7°F
Economizer
High Limit
Design
Heating Condition
Outdoor Temperature (°F)
Design Cooling Coil LAT
40
50 60
70 80
90 100 110 120
Design Cooling
Condition -
Economizer
System,
25% MOA
Percent Full Load
Percent Full Load
Percent Full Load
Percent Full Load
Percent Full Load
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ASHRAE Journal - October 2021

Table of Contents for the Digital Edition of ASHRAE Journal - October 2021

Contents
ASHRAE Journal - October 2021 - Intro
ASHRAE Journal - October 2021 - Cover1
ASHRAE Journal - October 2021 - Cover2
ASHRAE Journal - October 2021 - 1
ASHRAE Journal - October 2021 - Contents
ASHRAE Journal - October 2021 - 3
ASHRAE Journal - October 2021 - 4
ASHRAE Journal - October 2021 - 5
ASHRAE Journal - October 2021 - 6
ASHRAE Journal - October 2021 - 7
ASHRAE Journal - October 2021 - 8
ASHRAE Journal - October 2021 - 9
ASHRAE Journal - October 2021 - 10
ASHRAE Journal - October 2021 - 11
ASHRAE Journal - October 2021 - 12
ASHRAE Journal - October 2021 - 13
ASHRAE Journal - October 2021 - 14
ASHRAE Journal - October 2021 - 15
ASHRAE Journal - October 2021 - 16
ASHRAE Journal - October 2021 - 17
ASHRAE Journal - October 2021 - 18
ASHRAE Journal - October 2021 - 19
ASHRAE Journal - October 2021 - 20
ASHRAE Journal - October 2021 - 21
ASHRAE Journal - October 2021 - 22
ASHRAE Journal - October 2021 - 23
ASHRAE Journal - October 2021 - 24
ASHRAE Journal - October 2021 - 25
ASHRAE Journal - October 2021 - 26
ASHRAE Journal - October 2021 - 27
ASHRAE Journal - October 2021 - 28
ASHRAE Journal - October 2021 - 29
ASHRAE Journal - October 2021 - 30
ASHRAE Journal - October 2021 - 31
ASHRAE Journal - October 2021 - 32
ASHRAE Journal - October 2021 - 33
ASHRAE Journal - October 2021 - 34
ASHRAE Journal - October 2021 - 35
ASHRAE Journal - October 2021 - 36
ASHRAE Journal - October 2021 - 37
ASHRAE Journal - October 2021 - 38
ASHRAE Journal - October 2021 - 39
ASHRAE Journal - October 2021 - 40
ASHRAE Journal - October 2021 - 41
ASHRAE Journal - October 2021 - 42
ASHRAE Journal - October 2021 - 43
ASHRAE Journal - October 2021 - 44
ASHRAE Journal - October 2021 - 45
ASHRAE Journal - October 2021 - 46
ASHRAE Journal - October 2021 - 47
ASHRAE Journal - October 2021 - 48
ASHRAE Journal - October 2021 - 49
ASHRAE Journal - October 2021 - 50
ASHRAE Journal - October 2021 - 51
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ASHRAE Journal - October 2021 - 53
ASHRAE Journal - October 2021 - 54
ASHRAE Journal - October 2021 - 55
ASHRAE Journal - October 2021 - 56
ASHRAE Journal - October 2021 - 57
ASHRAE Journal - October 2021 - 58
ASHRAE Journal - October 2021 - 59
ASHRAE Journal - October 2021 - 60
ASHRAE Journal - October 2021 - 61
ASHRAE Journal - October 2021 - 62
ASHRAE Journal - October 2021 - 63
ASHRAE Journal - October 2021 - 64
ASHRAE Journal - October 2021 - 65
ASHRAE Journal - October 2021 - 66
ASHRAE Journal - October 2021 - 67
ASHRAE Journal - October 2021 - 68
ASHRAE Journal - October 2021 - 69
ASHRAE Journal - October 2021 - 70
ASHRAE Journal - October 2021 - 71
ASHRAE Journal - October 2021 - 72
ASHRAE Journal - October 2021 - HR1
ASHRAE Journal - October 2021 - HR2
ASHRAE Journal - October 2021 - HR3
ASHRAE Journal - October 2021 - HR4
ASHRAE Journal - October 2021 - HR5
ASHRAE Journal - October 2021 - HR6
ASHRAE Journal - October 2021 - HR7
ASHRAE Journal - October 2021 - HR8
ASHRAE Journal - October 2021 - HR9
ASHRAE Journal - October 2021 - HR10
ASHRAE Journal - October 2021 - HR11
ASHRAE Journal - October 2021 - HR12
ASHRAE Journal - October 2021 - HR13
ASHRAE Journal - October 2021 - HR14
ASHRAE Journal - October 2021 - HR15
ASHRAE Journal - October 2021 - HR16
ASHRAE Journal - October 2021 - HR17
ASHRAE Journal - October 2021 - HR18
ASHRAE Journal - October 2021 - HR19
ASHRAE Journal - October 2021 - HR20
ASHRAE Journal - October 2021 - HR21
ASHRAE Journal - October 2021 - HR22
ASHRAE Journal - October 2021 - HR23
ASHRAE Journal - October 2021 - HR24
ASHRAE Journal - October 2021 - 73
ASHRAE Journal - October 2021 - 74
ASHRAE Journal - October 2021 - 75
ASHRAE Journal - October 2021 - 76
ASHRAE Journal - October 2021 - 77
ASHRAE Journal - October 2021 - 78
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ASHRAE Journal - October 2021 - 81
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ASHRAE Journal - October 2021 - 90
ASHRAE Journal - October 2021 - 91
ASHRAE Journal - October 2021 - 92
ASHRAE Journal - October 2021 - 93
ASHRAE Journal - October 2021 - 94
ASHRAE Journal - October 2021 - 95
ASHRAE Journal - October 2021 - 96
ASHRAE Journal - October 2021 - Cover3
ASHRAE Journal - October 2021 - Cover4
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