ASHRAE Journal - April 2022 - 38

TECHNICAL FEATURE
seen as substantially different than design and originally
installed/TAB calibrated values.
The deficiencies caused a lot of control problems
because in many cases the controller was using
bad input airflow data, so it responded as it was
programmed:
1. Shutting off the OA damper completely because the
reading is way over its setpoint (AHU 4, 11, 15).
2. Excessive closing of the return air damper to help
compensate for the low OA flow readings (AHU 1/2, 3, 5,
6, 7, 9, 10, 12, 13, 16, 17).
Impacts to the owner caused by these deficiencies
include:10-13
* Inaccurate ventilation to affected occupied spaces,
due to erroneous readings;
* Additional costs due to ventilation quantities being
much larger than necessary or required;
* Potential of over- or underpressurization of the
building;
* If demand control ventilation (DCV) is being used,
these erroneous readings cause DCV to be compromised
because the reading being used is not accurate;
* Loss of beneficial use of the asset--the devices
themselves as well as building-related functions;
* Increased maintenance costs for early replacement
of airflow monitoring devices;
* Increased risk to occupant health impacts, illness or
disease propagation because of ventilation inaccuracies,
inadequacies and deficiencies;
* Drifting out of code compliance for ventilation
requirements;
* Increased energy use;
* Productivity loss; and
* Designer or installing contractor reputation/confidence
loss.
During the commissioning process, the contractor
followed the manufacturer's maintenance instructions
and tried to revive the devices by cleaning them with
an isopropyl alcohol solution. This cleaning did result
in an acceptable flow reading in five of the 13 airflow
monitor devices; the remaining airflow monitor devices
were nonresponsive after cleaning. The conclusion was
that the remaining airflow monitor devices failed due to
fouling and damage to their velocity sensing device.
Under warranty requirements, the contractor replaced
the eight malfunctioning airflow monitor devices at
zero cost to the owner, recalibrated all of them again
38
ASHRAE JOURNAL ashrae.o rg
A P R I L 2022
TABLE 1 Airflow data spreadsheet.
AHU NAME
OA cfm
DESIGN
AHU 1/2
AHU 3
AHU 4
AHU 5
AHU 6
AHU 7
AHU 8
AHU 9
AHU 10
AHU 11
AHU 12
AHU 13
AHU 14
AHU 15
AHU 16
AHU 17
775
2,185
700
7,565
785
2,370
2,500
2,040
3,115
2,685
3,050
2,690
2,445
2,225
3,195
3,035
OA DAMPER
FLOW cfm;
INITIAL
READINGS
437
706
2,505
3,845
661
2,327
No AFM
580
2,000
67,811
1,761
1,876
2,154
4,439
644
964
PERCENT
CHANGE
FROM
DESIGN
43
67
257
49
15
2
N/A
71
35
2,425
42
30
12
80
79
68
OA DAMPER
PERCENT
OPEN
100
100
100
100
100
N/A
100
100
100
100
57
100
100
RA DAMPER
PERCENT
OPEN
40
40
100
40
46
40
N/A
40
20
100
40
40
100
100
40
40
and the building was brought back into ventilation rate
compliance. Had it happened after the warranty period,
the owner could have paid close to $15,000 to perform
these corrective measures themselves by using a service
company. Since the root cause of the premature failure
at this project was not cured by adding filtration, there is
no reason to believe this situation will not repeat itself in
the years to come.
To avoid this situation in a future new construction
design, engineers proposed adding filtration to outside
air louvers to this owner's next similarly designed building.
The cost included outfitting the intake louvers with
filter racks at 14 locations. The cost for this added scope
of work was approximately $9,000. This work equates to
$643 per AHU or $0.23 per ventilation cfm.
Therefore, the cost of not providing adequate filtration
of the entering outside air is significant. If the building
is built to last 15 years without a major renovation,
conservatively these airflow monitors could need to be
replaced five to seven times. The payback for originally
installing these outside air filters and preserving the life
http://ashrae.org
ASHRAE Journal - April 2022

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