ASHRAE Journal - March 2021 - 47

COLUMN ENGINEER'S NOTEBOOK

FIGURE 3 Campus central plant industrial makeup water system sketches: existing (top) vs. solution implemented by owner (bottom).

Condenser
Evaporator
Condenser
Evaporator
Condenser
Evaporator
ET

CT Makeup Water
Solenoid

PRV

ICW
Campus
CHWS
Campus
CHWR

Existing Central Plant Makeup Water System

1

Condenser
Evaporator
Condenser
Evaporator
Condenser
Evaporator

caused the pressure in the CHW
lines to fall from the design pressure of ~30 psi or ~2.1 bar (207 kPa)
to as low as ~20 psi or ~1.4 bar
(138 kPa), per observations from the
plant operators on the day of our
hot call. Figure 2 includes our pressure analysis.
Per our analysis, an industrial
cold water makeup pressure of
~30 psi or ~2.1 bar (207 kPa) at the
central plant is sufficient to permit
the AHUs at the research facility to
bleed and burp lines to purge air
from the CHW piping. However,
when the makeup water pressure
at the central plant drops to less
than ~23 psi or ~1.6 bar (159 kPa),
then one of two conditions are
present for air to enter the lines
and degrade the chilled water coil
performance. (See the Expansion
Tank Buffer Failure section below
for the second condition.)
Our hydraulic model of the building also shows that under peak
flow conditions, AHU-1 requires an
additional ~1 psi or ~0.1 bar (7 kPa) of
distribution pressure in the pathway
from Node 2 to Node 2-A when compared to the pathway from Node 2
to Node 2-B, which may explain the
biased accumulation of air observed
within AHU-1.

CT Makeup Water
Solenoid
ET

2

PRV

ICW

PRV

ICW
Campus
CHWS
Campus
CHWR

Central Plant Makeup Water System Revision Implemented By Owner

Expansion Tank Buffer Failure
Why did the drop in CHW makeup water pressure
affect the system pressure? Shouldn't the expansion
tank have provided a buffer against those fluctuations?
Under normal circumstances, it is expected that a sudden or temporary reduction in available makeup water
pressure would not impact the operation of the closedloop chilled water system, because the expansion tank
would maintain pressure, and the backflow prevention
valve would prevent water from leaving the system
through the makeup line.
Discussion with the central plant operators

disclosed that an adjacent building project caused a
significant loss of chilled water volume on the day the
research facility suffered the loss of cooling capacity.
The combination of water volume loss with reduced
available makeup water pressure yielded the hydraulic conditions causing the symptoms observed in this
case study.

Recommendations
As described earlier, our interim solution to increase
chilled water pressure at the building is ill-suited to
a long-term resolution of the problem. Other taller
buildings are also on campus that will eventually
MARCH 2021

ashrae.org

ASHRAE JOURNAL

47


http://www.ashrae.org

ASHRAE Journal - March 2021

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

Contents
ASHRAE Journal - March 2021 - Intro
ASHRAE Journal - March 2021 - Cover1
ASHRAE Journal - March 2021 - Cover2
ASHRAE Journal - March 2021 - 1
ASHRAE Journal - March 2021 - Contents
ASHRAE Journal - March 2021 - 3
ASHRAE Journal - March 2021 - 4
ASHRAE Journal - March 2021 - 5
ASHRAE Journal - March 2021 - 6
ASHRAE Journal - March 2021 - 7
ASHRAE Journal - March 2021 - 8
ASHRAE Journal - March 2021 - 9
ASHRAE Journal - March 2021 - 10
ASHRAE Journal - March 2021 - 11
ASHRAE Journal - March 2021 - 12
ASHRAE Journal - March 2021 - 13
ASHRAE Journal - March 2021 - 14
ASHRAE Journal - March 2021 - 15
ASHRAE Journal - March 2021 - 16
ASHRAE Journal - March 2021 - 17
ASHRAE Journal - March 2021 - 18
ASHRAE Journal - March 2021 - 19
ASHRAE Journal - March 2021 - 20
ASHRAE Journal - March 2021 - 21
ASHRAE Journal - March 2021 - 22
ASHRAE Journal - March 2021 - 23
ASHRAE Journal - March 2021 - 24
ASHRAE Journal - March 2021 - 25
ASHRAE Journal - March 2021 - 26
ASHRAE Journal - March 2021 - 27
ASHRAE Journal - March 2021 - 28
ASHRAE Journal - March 2021 - 29
ASHRAE Journal - March 2021 - 30
ASHRAE Journal - March 2021 - 31
ASHRAE Journal - March 2021 - 32
ASHRAE Journal - March 2021 - 33
ASHRAE Journal - March 2021 - 34
ASHRAE Journal - March 2021 - 35
ASHRAE Journal - March 2021 - 36
ASHRAE Journal - March 2021 - 37
ASHRAE Journal - March 2021 - 38
ASHRAE Journal - March 2021 - 39
ASHRAE Journal - March 2021 - 40
ASHRAE Journal - March 2021 - 41
ASHRAE Journal - March 2021 - 42
ASHRAE Journal - March 2021 - 43
ASHRAE Journal - March 2021 - 44
ASHRAE Journal - March 2021 - 45
ASHRAE Journal - March 2021 - 46
ASHRAE Journal - March 2021 - 47
ASHRAE Journal - March 2021 - 48
ASHRAE Journal - March 2021 - 49
ASHRAE Journal - March 2021 - 50
ASHRAE Journal - March 2021 - 51
ASHRAE Journal - March 2021 - 52
ASHRAE Journal - March 2021 - 53
ASHRAE Journal - March 2021 - 54
ASHRAE Journal - March 2021 - 55
ASHRAE Journal - March 2021 - 56
ASHRAE Journal - March 2021 - 57
ASHRAE Journal - March 2021 - 58
ASHRAE Journal - March 2021 - 59
ASHRAE Journal - March 2021 - 60
ASHRAE Journal - March 2021 - 61
ASHRAE Journal - March 2021 - 62
ASHRAE Journal - March 2021 - 63
ASHRAE Journal - March 2021 - 64
ASHRAE Journal - March 2021 - 65
ASHRAE Journal - March 2021 - 66
ASHRAE Journal - March 2021 - 67
ASHRAE Journal - March 2021 - 68
ASHRAE Journal - March 2021 - 69
ASHRAE Journal - March 2021 - 70
ASHRAE Journal - March 2021 - 71
ASHRAE Journal - March 2021 - 72
ASHRAE Journal - March 2021 - 73
ASHRAE Journal - March 2021 - 74
ASHRAE Journal - March 2021 - 75
ASHRAE Journal - March 2021 - 76
ASHRAE Journal - March 2021 - 77
ASHRAE Journal - March 2021 - 78
ASHRAE Journal - March 2021 - 79
ASHRAE Journal - March 2021 - 80
ASHRAE Journal - March 2021 - 81
ASHRAE Journal - March 2021 - 82
ASHRAE Journal - March 2021 - 83
ASHRAE Journal - March 2021 - 84
ASHRAE Journal - March 2021 - 85
ASHRAE Journal - March 2021 - 86
ASHRAE Journal - March 2021 - 87
ASHRAE Journal - March 2021 - 88
ASHRAE Journal - March 2021 - 89
ASHRAE Journal - March 2021 - 90
ASHRAE Journal - March 2021 - 91
ASHRAE Journal - March 2021 - 92
ASHRAE Journal - March 2021 - 93
ASHRAE Journal - March 2021 - 94
ASHRAE Journal - March 2021 - 95
ASHRAE Journal - March 2021 - 96
ASHRAE Journal - March 2021 - 97
ASHRAE Journal - March 2021 - 98
ASHRAE Journal - March 2021 - 99
ASHRAE Journal - March 2021 - 100
ASHRAE Journal - March 2021 - 101
ASHRAE Journal - March 2021 - 102
ASHRAE Journal - March 2021 - 103
ASHRAE Journal - March 2021 - 104
ASHRAE Journal - March 2021 - Cover3
ASHRAE Journal - March 2021 - Cover4
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_VJKSRY
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_SDHUTC
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_JPPKRR
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_SDLTTH
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_CKLLES
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_SLDOX
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_HJETUK
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_OLUHGE
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2020october
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2020october_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_ZERDGH
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_QVMNEO
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_RTPOKE
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_BBATRE
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_STUBMW
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_TPEMPE
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_JNMKDS
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_FBTTPA
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_WQMMNE
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_TVBRYN
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_showguide2020
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_KTUZMA
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_ABEDGD
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201910
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201909
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2019septmeber_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2019september
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201908
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201907
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201906
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201905
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201904
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_2019april
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201903
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_2019march
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201902
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201901
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_showguide2019
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_2018december
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_2018november
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2018fall_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2018fall
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_2018october
https://www.nxtbook.com/nxtbooks/ashrae/ashraemexico_2018
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201810
https://www.nxtbook.com/nxtbooks/ashrae/ashraeinsights_201806
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201805
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201804
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201803
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201712
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201711
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201710
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2017fall_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2017fall
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201709
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201705
https://www.nxtbook.com/nxtbooks/ashrae/ashrae_meetinginsert_201610
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2016fall_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2016fall
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_acrexindia
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2015summer_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2015summer
https://www.nxtbook.com/nxtbooks/amca/2014summer2
https://www.nxtbook.com/nxtbooks/amca/2014summer
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_acma_2014summer
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201311
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201309
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_acmasupp_2013fall
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201305
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201303
https://www.nxtbook.com/nxtbooks/ashrae/pubcatalog_2013winter
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201211
https://www.nxtbook.com/nxtbooks/ashrae/achr_expo_mexico2012
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201209
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201208_v3
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201208_v2
https://www.nxtbook.com/nxtbooks/ashrae/pubcatalog_2012summer
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201205
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201203
https://www.nxtbook.com/nxtbooks/ashrae/pubcatalog_2012winter
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201111_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201109_v2
https://www.nxtbook.com/nxtbooks/ashrae/pubcatalog_2011summer
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201105
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201103
https://www.nxtbookmedia.com