ASHRAE Journal - April 2022 - 39

of the airflow monitors is on the approximate order of
magnitude of one-half year.
Other Considerations
As a veteran contractor for a variety of commercial
buildings including schools in Southwest Florida,
Nathan Carr states, " having completed several large
projects with chilled water and extensive outdoor air, I
have witnessed first-hand the negative effects unfiltered
outside air can have on airflow measuring devices. We
were both the contractor on the old school referenced in
this study (without filtered outside air intakes), and the
new school that changed the design to add them into the
new project. We fully supported the change to add filters
on the outside air intake louvers for the betterment of
the new project overall for our customers. " 14
There are problems sometimes caused by an overcompensation
(closing) of the return air damper closing
to " force " more air through the OA duct, increasing
the OA flow amount. Many engineers allow the return
air damper to close some to force more flow through
the OA duct if needed to meet design values; traditionally
this is maxed out at 50%; more than this limit can
become problematic. For example, when the return air
damper is allowed to close more than 50%, what it does
is increase the velocity of the mixed airstream entering
the cooling coil, potentially causing " coil moisture
carryover " if the coil is wet.
Care should be taken to keep the coil velocities below
its " beginning point of water penetration (BPWP), which
is approximately 1,000 fpm [5.1 m/s]. AMCA defines " the
point of beginning water penetration as the free area
velocity at which the AMCA water test has yielded 0.01 or
fewer ounces of water per square foot of louver free area
during a 15-minute test period. " 15
The increased velocity across the cooling coil can
diminish the effectiveness of the cooling coil to perform
its cooling or dehumidification process since coil
velocities are important to maintaining optimum heat
transfer. Higher velocities in the outside airstream assist
its " suction pressure component " and can bring in more
contaminants from the outside air source. It is advisable
to restrict return air damper modulation to not close
more than 50% in most cases.
Many reputable manufacturers sell/market airflow
measuring devices. The sensor devices use
many technologies to measure velocities. The
A P R I L 2 0 2 2 ashrae.o rg ASHRAE JOURNAL
39
Bu i l d i ng Be t t e r A i r
THE
ROOFTOP
REVOLUTION
CONTINUES . . .
Model L
was just the beginning.

http://ashrae.org

ASHRAE Journal - April 2022

Table of Contents for the Digital Edition of ASHRAE Journal - April 2022

Contents
ASHRAE Journal - April 2022 - Intro
ASHRAE Journal - April 2022 - Cover1
ASHRAE Journal - April 2022 - Cover2
ASHRAE Journal - April 2022 - 1
ASHRAE Journal - April 2022 - Contents
ASHRAE Journal - April 2022 - 3
ASHRAE Journal - April 2022 - 4
ASHRAE Journal - April 2022 - 5
ASHRAE Journal - April 2022 - 6
ASHRAE Journal - April 2022 - 7
ASHRAE Journal - April 2022 - 8
ASHRAE Journal - April 2022 - 9
ASHRAE Journal - April 2022 - 10
ASHRAE Journal - April 2022 - 11
ASHRAE Journal - April 2022 - 12
ASHRAE Journal - April 2022 - 13
ASHRAE Journal - April 2022 - 14
ASHRAE Journal - April 2022 - 15
ASHRAE Journal - April 2022 - 16
ASHRAE Journal - April 2022 - 17
ASHRAE Journal - April 2022 - 18
ASHRAE Journal - April 2022 - 19
ASHRAE Journal - April 2022 - 20
ASHRAE Journal - April 2022 - 21
ASHRAE Journal - April 2022 - 22
ASHRAE Journal - April 2022 - 23
ASHRAE Journal - April 2022 - 24
ASHRAE Journal - April 2022 - 25
ASHRAE Journal - April 2022 - 26
ASHRAE Journal - April 2022 - 27
ASHRAE Journal - April 2022 - 28
ASHRAE Journal - April 2022 - 29
ASHRAE Journal - April 2022 - 30
ASHRAE Journal - April 2022 - 31
ASHRAE Journal - April 2022 - 32
ASHRAE Journal - April 2022 - 33
ASHRAE Journal - April 2022 - 34
ASHRAE Journal - April 2022 - 35
ASHRAE Journal - April 2022 - 36
ASHRAE Journal - April 2022 - 37
ASHRAE Journal - April 2022 - 38
ASHRAE Journal - April 2022 - 39
ASHRAE Journal - April 2022 - 40
ASHRAE Journal - April 2022 - 41
ASHRAE Journal - April 2022 - 42
ASHRAE Journal - April 2022 - 43
ASHRAE Journal - April 2022 - 44
ASHRAE Journal - April 2022 - 45
ASHRAE Journal - April 2022 - 46
ASHRAE Journal - April 2022 - 47
ASHRAE Journal - April 2022 - 48
ASHRAE Journal - April 2022 - 49
ASHRAE Journal - April 2022 - 50
ASHRAE Journal - April 2022 - 51
ASHRAE Journal - April 2022 - 52
ASHRAE Journal - April 2022 - 53
ASHRAE Journal - April 2022 - 54
ASHRAE Journal - April 2022 - 55
ASHRAE Journal - April 2022 - 56
ASHRAE Journal - April 2022 - 57
ASHRAE Journal - April 2022 - 58
ASHRAE Journal - April 2022 - 59
ASHRAE Journal - April 2022 - 60
ASHRAE Journal - April 2022 - 61
ASHRAE Journal - April 2022 - 62
ASHRAE Journal - April 2022 - 63
ASHRAE Journal - April 2022 - 64
ASHRAE Journal - April 2022 - 65
ASHRAE Journal - April 2022 - 66
ASHRAE Journal - April 2022 - 67
ASHRAE Journal - April 2022 - 68
ASHRAE Journal - April 2022 - 69
ASHRAE Journal - April 2022 - 70
ASHRAE Journal - April 2022 - 71
ASHRAE Journal - April 2022 - 72
ASHRAE Journal - April 2022 - Cover3
ASHRAE Journal - April 2022 - Cover4
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_ATMAHK
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_VHQRAW
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_XGMDXI
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_YELQLJ
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_QJLWMC
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_MCDEBX
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_WNYSQY
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_XATVOD
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_FJSHSS
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_CCBZDS
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_XDEFVG
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2023november_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2023november
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_VHGNBL
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_WPKBNJ
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_UUVCDE
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_RTGDEW
https://www.nxtbook.com/nxtbooks/ashrae/ashraemexico_2023
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_LKRFXS
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_AZSOFG
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_ERCDBH
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_QWDFRV
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_JHGVDF
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_OPUYHG
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_SREIBM
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_LRTGLK
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_OKRFGH
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2022november_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2022november
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_TZSERA
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_LVRUIX
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_RPTVYZ
https://www.nxtbook.com/nxtbooks/ashrae/mini_pub_catalog
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_XIYTGD
https://www.nxtbook.com/nxtbooks/ashrae/ashraemexico_2022
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_RFGDOB
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_PABXNU
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_REMKLS
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_PICVBT
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_AOYTVW
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_JQOPLS
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_IOYTBC
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_SGAJJF
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_IGHYER
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_PDRKLS
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2021november
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2021november_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_XCODFR
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_QSLFGO
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_ILKVNM
https://www.nxtbook.com/nxtbooks/ashrae/ashraemexico_2021
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_OPDJKD
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