TAB Journal

THE MAGAZINE OF THE ASSOCIATED AIR BALANCE COUNCIL • SUMMER 2024

Testing and Balancing

Variable Air Volume Boxes
• Office, School, and Health
Facility Case Studies
• VAV Troubleshooting
• Hardware and Software
Compatibility

Plus:
• Pressure-Critical Spaces
• Constant Volume Systems
• A Clean Room Balancing Earn AIA LUs
for reading...
Mystery Find Out
More
Inside!
 AABC

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Associated Air Balance Council | 1015 18th St. NW, Suite 603 | Washington, D.C. 20036 | (202) 737-0202
 CONTENTS

TAB Journal Troubleshooting Problems with VAV Boxes

Tim Sibinski, TBE
Systems Management and Balancing of Minnesota
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Associated Air Balance Council

BOARD OF DIRECTORS
Pressure Critical Pitfalls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
AND OFFICERS
Brian Trogstad, TBE
President Design Control, Inc.
Gaylon Richardson, TBE, CxA
Engineered Air Balance Co., Inc. VAV System Pressure Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Executive Vice President
John H. Gazo, TBS
Douglas R. Meacham, TBE
Accu-Air Balance Co. (1991) Inc.
Kahoe Air Balance Company
Case Study: Using Digital VAV Diffusers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Secretary/Treasurer Timothy J. Mahoney, TBE
Brian G. Venn, TBE, CxA Mechanical Test and Balance Corporation
Mechanical Testing, Inc.

Vice President/Eastern Zone-1

Seeing the Forest, Not Just the Trees: A Clean Room Balancing Puzzle . . . . . . . . . . 10
John A. Balanik, TBE
Jeremy Johnson, TBE, CxA
R.H. Cochran and Associates, Inc.
American Testing, Inc.

Vice President/Central Zone-2 Case Studies: Hardware and Software Improvements in VAV Systems . . . . . . . . . . . 12
Josh Green, TBE, CxA Todd Yates, PE, TBE, CxA, and Eric Jespersen
Environmental Test & Balance Company Synergy Test and Balance, Inc.
Vice President/Western Zone-3 Installing Pressure Independent Valves into a Constant Volume System . . . . . . . . . 16
Robert Kolnes, TBE, CxA Paul Mocny, TBE
TABITT, LLC MESA3 Inc.
Immediate Past President
Benjiman J. Link, TBE
United Testing & Balancing, Inc.

Director, Canadian Chapter

Tony Mohammed, TBS
Air Movement Services Ltd.

Executive Director
@TABCxEnergy @AABCtandb Associated Air
Raymond R. Bert Balance Council

Technical Advisor
Joe Baumgartner, PE, TBE, CxA Pass This Issue's Quiz to Earn 1 AIA LU!
Editor
Cassie LaJeunesse

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TROUBLESHOOTING
Problems with VAV Boxes
Tim Sibinski, TBE
Systems Management and Balancing of Minnesota

V
ariable air volume (VAV) systems are one of If the TAB team can spend a few minutes to diagnose
the most common systems that a testing and and possibly repair problems they encounter, it will often
balancing (TAB) agency works on, whether for save time, rather than requiring the controls or mechanical
new construction, a remodel, or rebalancing projects. The contractor’s involvement or writing up the issues and
main components in a VAV box are a motorized damper to waiting to complete the balancing after the problem has
vary the airflow and a pressure transducer to measure the been repaired. A lot of the problems encountered with VAV
airflow. Typically, VAV boxes modulate from a minimum to a systems could be found by the controls contractor if checkout
maximum airflow depending on the thermostat. was done, but it seems that more and more there is minimal
if any checkout done on the VAVs.

2 TAB Journal Summer 2024

There are still buildings that have pneumatic controls, but Flow sensor issues require inspecting the tubing from the
most of the time those are being removed and replaced with flow cross at the VAV inlet, which connects to the VAV
direct digital controls (DDC) with a building automation controller pressure transducer. For it to work correctly, the
system (BAS). Because of this, I will not get into actual tubes need to be connected on both ends, and if there are
pneumatic control problem diagnostics, t-fittings installed in the tubing, the
but a lot of the issues for VAVs will
apply to both types of controls.
ʼʼ caps need to be installed. Some VAV
boxes come with rubber caps on the
Depending on the application, some Some problems are t-fittings, which are fine when they are
standard VAV boxes have heating coils new but crack and leak as the rubber
and some are cooling only. The other system problems, gets old. When this happens, the VAV
types are fan-powered VAV boxes, cannot measure flow accurately. If
some of which are parallel and some of the VAV box has t-fittings installed,
which are series boxes.
and some are they can be used for checking the
integrity of the tubing. When using a
Some problems are system problems, issues with the VAV manometer connected to the t-fitting
and some are issues with the VAV box
with the VAV damper closed, the
itself. System problems require drilling box itself. System pressure should read zero. With the
a hole in the duct ahead of the VAV
damper open, the manometer should
box and measuring the static pressure.
problems require read pressure. If the manometer reads
If there is low or no static pressure and
pressure with the VAV damper closed,
the system is operational, then there is
a problem with the ducting. By drilling
drilling a hole in that indicates that there is something
wrong with the tubing.
holes and taking static pressure
readings, the TAB agency can find the the duct ahead of When looking at fan-powered VAV
blockage in the duct. boxes, the main thing to check is
the VAV box and whether the fan operates or not. With
Sometimes the mechanical contractor
parallel fan-powered VAV boxes, the
installs manual dampers ahead of the
VAV box and they need to be opened.
measuring the fan typically runs with a call for heat
and is off otherwise. With series fan-
If there are manual dampers ahead of
the VAV box that will not stay open,
static pressure... By powered VAV boxes, the fan runs
all the time. For the fan to operate
putting a sheet metal screw through
drilling holes and correctly, that VAV controller needs
the handle should hold it in place.
to be programmed correctly. If the
There are also fire/smoke dampers that
fan is not operating and it is a new
could be closed. These are typically taking static pressure
installation, there could be packing
found at risers to shut off airflow in
material in the fan that should have
case of a fire. On new construction, readings, the TAB been removed by the mechanical
they are often found not wired or not
contractor at the time of installation or
powered because of a breaker being agency can find the before it was powered up.
turned off. There should be an access
door to verify if the fire/smoke damper
is open.
blockage in the duct.
ʼʼ When VAV boxes are not operating
as intended, knowing these common
issues can help the TAB agency
The main problems found at the VAV
determine the problem as quickly
are either related to dampers or to flow
as possible. The quicker the problem can be diagnosed, the
sensors. The main damper issue is whether it functions as it
quicker it can be corrected by the appropriate party.
is supposed to. Does it go open when it is commanded open
and closed when it is commanded closed? If it is backward,
can it be reversed in a lot of the automation systems? If it AIA After reading the full issue, take what you’ve
does not move, the set screws that hold the actuator to the Continuing
damper could be loose. Education learned, visit www.aabc.com/TABQuiz and
Provider pass the quiz to earn 1 AIA LU.

TAB Journal Summer 2024 3

Pressure-Critical Pitfalls
Brian Trogstad, TBE
Design Control, Inc.

P
ressure-critical rooms have been around for decades. room that is achieving only slightly more than design airflow
These rooms are designed to maintain specific pressure and we cannot achieve desired differential pressure with the
differentials to ensure safety, control air quality, and design supply airflow, the supply will need to be reduced.
prevent the spread of contaminants. Positive pressure rooms Assuming there is no issue with room construction or finishes,
are used to prevent contaminants from entering the room, airflows may need to be reduced to a level that may impact
while negative pressure rooms are used to prevent hazardous heating and/or cooling performance. If anticipated room
materials or airborne pathogens from leaving the space. leakage is more realistic with appropriate offsets, heating and
Through the years, the standards and tolerances for pressure cooling for the room will be sized appropriately and the room
critical rooms have changed, becoming increasingly stringent. will remain comfortable and controlled.
Tighter tolerances require more complex controls and less
The third issue we have encountered is when the design of the
room for error in mechanical design and architectural finishes
exhaust CFM is equal to minimum air changes in the room.
around the perimeter of the space.
Often negatively pressurized rooms have a dedicated exhaust
There are many issues we encounter when testing and fan. If for some reason installation of ductwork was tight,
balancing newly constructed pressure-critical rooms. First, or ended up with more restriction than design, the fan may
the room needs to be properly constructed and finished. This achieve 90+% of design but still not achieve minimum air
includes walls, ceilings, lights, electrical outlets, medical changes required for the space. There should be some amount
devices, and any other items penetrating the perimeter of the of safety in the design of the ventilation to allow for the
room. In addition, final specified doors, glass, door handles mechanical installation problems that are common constraints.
and sweeps need to be installed prior to testing. We have had This issue can be compounded if there is HEPA filtration on
many projects where the specified door sweeps or astragals the exhaust system. If there are marginal exhaust flows during
were either not ordered, backordered, or forgotten. initial set up, the owner will not be able to achieve full filter
life before airflows drop below minimum air changes. Without
On a recent project, we were having problems achieving
remaining capacity on the exhaust, the filters will need to be
pressures after initial testing and balancing had started. We
changed prematurely, which is a large cost to the owner for
began to reduce supply CFM to the spaces to achieve proper
many years to come.
pressures when we were informed that there were door sweeps
specified but the general contractor had not ordered them Overall, testing and balancing pressure-sensitive rooms is a
to save costs. Often door glass is missing and replaced with critical process that ensures the safety and functionality of
cardboard to “get the balancing done.” All these items impact these specialized spaces. It requires careful design, accurate
the quantity of “leakage” of the space. The amount of final testing, and ongoing maintenance. By maintaining the proper
leakage in the space can dramatically affect the amount of offset pressure differentials, these rooms can effectively control air
required to keep the room at the required differential pressures. quality, prevent the spread of contaminants, and protect the
health of individuals inside.
The second item we have seen is not enough differential
pressure design. We see designs for pressure-critical rooms
with too low of an initial CFM design offset. Obviously, these AIA After reading the full issue, take what you’ve
designs are a starting point and can be adjusted and noted; Continuing
Education learned, visit www.aabc.com/TABQuiz and
however, in extreme cases, overall performance of the room Provider pass the quiz to earn 1 AIA LU.
can suffer. If we have an exhaust fan in a negative-designed

4 TAB Journal Summer 2024

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TAB Journal Summer 2024 5
 VAV System
Pressure
Issues
John H. Gazo, TBS
Accu-Air Balance Co. (1991) Inc.

W
e were contracted to balance a VAV system that • East branch: 14” round (1.07 sq. ft.) to 36” X 12”
had six main ducts that were serving two different (3.0 sq. ft.)
floors in an office building. We were only required • Center branch: 22” round (2.6 sq. ft.) to 40” X 16”
to balance the renovated area serving the first floor. There (4.4 sq. ft.)
were three main branch ducts — west branch, center branch, • West branch: 18” round (1.8 sq. ft.) to 30” X 16”
and east branch — that were serving air to the first floor (3.3 sq. ft.)
VAV boxes. The controls contractor advised that the static We located the static pressure controller in the west branch
pressure controller was set at 2.3” WC and was reading round duct before the renovated area. We took static
2.29” WC. He also advised that he was not sure where the pressures in the three ducts before the silencers, after the
static pressure controller was installed. After completing the silencers and at the inlet of the last box for each branch. At
balancing, we determined that several VAV boxes were low the same time, we obtained total air flow for the unit since
on airflow. We obtained the inlet and discharge pressures on the engineer for the project provided the new total design air
one of the low 4” inlet VAV boxes: for the system.

• Inlet SP: 1.2” WC • New design airflow: 33,092 CFM

• Discharge SP: 0.07” WC • As found airflow: 24,022 CFM (52.8 HZ)
• Static pressure set point: 2.3” WC
Further investigation determined that a piece of rectangular • SP read out from computer: 2.29” WC
metal was installed on the inlet of the VAV box, which • Actual static pressure in duct: 1.10” WC
appeared to be causing the excessive pressure drop. At this • SP west branch before silencer: 1.64” WC
point, we took the static pressure in each branch as the ducts • SP west branch after silencer: 1.32” WC
came through the wall of the renovated area. It was observed • SP west branch inlet last VAV: 0.75” WC
that the three main ducts going into the renovated area were • SP center branch before silencer: 1.9” WC
all round and then transitioned to rectangular ducts that served • SP center branch after silencer: 0.96” WC
the VAV boxes. The ducts also had sound attenuators installed. • SP center branch inlet last VAV: 0.33” WC

6 TAB Journal Summer 2024

• SP east branch before silencer: 1.82” WC There was still a large discrepancy in the static pressure for
• SP east branch after silencer: 1.33” WC the center branch. Further investigation revealed that the
• SP east branch inlet last VAV: 0.58” WC center duct split into north and south branches. The north
branch served an area not in our contract and the south
We determined that the static pressure controller was not
branch served the renovated area. We took the static pressure
operating correctly. The static pressure controller was
in the north and south branches to determine at what
replaced and reinstalled in a more suitable location in the
pressure they were operating.
rectangular duct on the west branch. The readings were
repeated to determine if the operating conditions improved. • SP center branch before silencer 2nd floor: 3.24” WC
• SP center branch after silencer north branch: 2.95” WC
• As found airflow: 32,201 CFM (60 HZ)
• SP center branch after silencer south branch: 1.64” WC
• Static pressure set point: 1.6” WC
• SP read out from computer: 1.62” WC We used an inspection camera to determine if there was
• Actual static pressure in duct: 1.72” WC any blockage in the ductwork. There were turning vanes
• SP west branch before silencer: 3.24” WC installed in the round duct, causing a larger pressure drop
• SP west branch after silencer: 2.94” WC for the south branch. We suggested to the engineer to remove
• SP center branch before silencer: 3.4” WC the turning vanes and rework the duct fitting to equalize the
• SP center branch after silencer: 1.63” WC pressure for both branches.
• SP east branch before silencer: 2.8” WC
As of publication date, we are waiting for direction from the
• SP east branch after silencer: 2.4” WC
engineer on the next course of action.
The static pressure for the west and east branches increased
enough for the VAV boxes to operate properly. We had AIA After reading the full issue, take what you’ve
the rectangular plates on the 4” inlet boxes removed and Continuing
Education learned, visit www.aabc.com/TABQuiz and
the airflow for these boxes increased to design. The center Provider pass the quiz to earn 1 AIA LU.
branch VAV boxes were below design.

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TAB Journal Summer 2024 7

CASE STUDY:
Using Digital VAV Diffusers

Timothy J. Mahoney, TBE

Mechanical Test and Balance Corporation

Our company was contracted to perform TAB work in an office building that is
remodeling the HVAC systems on individual floors. Each floor has dedicated
AHUs that are in good working condition. The system has fan-powered series
VAV boxes on the perimeter with standard grilles. The interior spaces are
served by standard VAV boxes with digital VAV diffusers.

T
he new mechanical drawings called for all controls to reheat coil) based on individual room thermostats. The VAV
be upgraded (the AHU and all the HVAC components). box controls to a static pressure setpoint downstream of the
The exterior fan-powered boxes and diffusers were box and upstream of the diffusers.
calibrated and rebalanced using standard AABC practices
The following procedure was used to balance and calibrate
with no issues. The interior VAV boxes and digital VAV
the interior VAV boxes and VAV diffusers:
diffusers were to control as follows per the new sequence of
operation: the individual VAV diffuser modulates airflow and 1) The VAV diffusers were indexed to 100% open to
temperature (each VAV diffuser is equipped with an electric simulate standard lay-in diffusers.

8 TAB Journal Summer 2024

2) The VAV box and the diffusers served were then balanced to .015” WC. In this condition, the VAV is still
using the individual take-off dampers, and the VAV box delivering the 400 CFM, as the static pressure did
was calibrated using standard AABC practices. not increase a significant enough amount to cause
the box to modulate. Now the diffusers are noisy
3) The static pressure downstream of the box was then
because the dampers are closed to 20%.
measured and recorded, and the static pressure sensor was
checked for calibration and adjusted as needed. To solve the problem, MTB worked with the controls
contractor and determined that the static pressure control
4) The VAV diffusers were then released to auto control,
needed to be removed from the sequence. The control system
and the VAV box was allowed to control to the pressure
should then look at the individual damper positions of the
measured.
VAV diffusers and the VAV box should adjust based on this
The issue arose after the diffusers were allowed to control in information. This eliminated the noise problem and allowed
auto. As the diffuser modulated the damper position based the boxes to modulate off of their maximum CFM setpoint
on temperature in the areas served, the VAV box never down to the minimum setpoint. This information was relayed
modulated because the static pressure in the duct was too to the design team, and after testing proved that the original
low to control. The following is an example of an individual sequence would not work as specified, an addendum to the
VAV: specification was issued for the remaining floors, changing
the sequence of operation for the interior VAV boxes and the
The VAV box is 400 CFM max., 100 CFM min.,
VAV diffusers.
serving 4 VAV diffusers at 100 CFM max. each.
When balanced in this condition, the static AIA After reading the full issue, take what you’ve
pressure in the duct was only .009” WC. When Continuing
Education learned, visit www.aabc.com/TABQuiz and
all 4 VAV diffusers are at minimum damper Provider pass the quiz to earn 1 AIA LU.
position (20%), the static pressure only increases

TAB Journal Summer 2024 9

SEEING THE FOREST, NOT JUST THE TREES:
A CLEAN ROOM BALANCING PUZZLE

John A. Balanik, TBE

R.H. Cochran and Associates, Inc.

Recently our company was hired to balance a small research and product
development facility. The building consisted of a small constant volume office
area, research and development lab areas, and a small clean room.
We were hired by the mechanical contractor to balance At this point there was quite a bit of head scratching going
everything except for the clean room. Our involvement for on. The mechanical contractor, the lab valve contractor, the
the clean room was only to establish the total flow on the clean room contractor, and our company were all present and
supply and exhaust systems. very confused.

The research labs were served by several make-up air units As any balancer who has worked on venturi valves will tell
and strobic exhaust fans. The supply outlets and fume hoods you, the first thing the lab valve guy will ask you when they
were controlled by venturi lab valves. We worked our way are not performing as expected is to test the pressure drop
through the whole facility with some minor glitches, which across the valve. This is to verify the pressure is within
are to be expected. In the end, everything balanced out fine. operating parameters. These readings were taken and found
to be well within range. I took this a step further and read
The owner hired a separate company to build and balance
the pressure at each end of the valve. That’s when something
the clean room. The room was served by a single packaged
really strange occurred. The negative static pressure at the
rooftop unit and exhaust fan. Multiple lab valves took care of
inlet to the valve was higher than the pressure on the leaving
five fume hoods and the make-up air above the ceiling. The
side. How could this be? The exhaust fan was pulling from
ceiling of the clean room contained thirty-nine fan filter units.
the leaving side. This shouldn’t be possible, right?
We finished up our work on the rest of the facility and
submitted the balance report thinking we were done.
Several weeks had gone by when we received a call from
the mechanical contractor. The clean room contractor was
unable to properly set the five fume hoods. The hoods were
designed to have a face velocity of 100 feet per minute.
These five hoods were measured between 160 to 190 feet
per minute. This caused the powdered product being tested
to be dispersed all over the inside of the hood. As you can
imagine, this was unacceptable for the owner.

We arrived onsite, and sure enough, we confirmed these very

high velocities. Fortunately, the clean room had a mezzanine
that allowed access to the duct work and valves. Our first
steps were to retest our traverse readings. All readings
appeared normal — even the traverse readings at the venturi
valves that served the fume hoods indicated the proper flow.

10 TAB Journal Summer 2024

To say I was confused is an extreme understatement. I was Once the filter units were slowed down, the face velocity on
taking readings and not really coming up with any answers, the fume hoods stabilized to the correct face velocity. At this
just more questions. On top of that, I had the contractors and point, all we needed to do was build a partition around each
the owner looking to me for the solution to this research- of the fume hoods. This isolated the hood from the ceiling
stopping issue. plenum and allowed proper operation.

We decided to go back down to the clean room to investigate After the partitions were installed, the clean room had to
further. Of course, everyone had to gown up to enter the be decontaminated again. However, at this point the owner
room. For some reason, I held off and walked into the was overjoyed to be back in business. I also suggested to the
corridor, which had observation windows looking into the clean room contractor that he relay this process to his design
room. As I was standing there watching these guys retake the team to prevent this from happening again.
same readings once again, it suddenly occurred to me that I
Many times, when things don’t operate as expected, we begin
knew what was happening.
to think that the problem has to be complicated. Quite often
I got the attention of the guys in the clean room, and I asked we find that the solution to the problem is the most obvious.
them to lift a ceiling panel near one of the fume hoods. There In this instance and many others, the old adage of not being
it was: the fume hood was installed between the mezzanine able to see the forest for the trees applies to our industry —
deck and the clean room ceiling. The fume hoods were open sometimes we can’t see the obvious solution because we’re
to the plenum where the fan filter units were pulling from. focused on the complex details.
Apparently, these particular hoods had a slight opening
between the sash and the hood itself. The suction of the fan
filter units combined with the suction from the exhaust fan
AIA After reading the full issue, take what you’ve
via the venturi valves created this increased velocity. Continuing
Education learned, visit www.aabc.com/TABQuiz and
To prove my theory, I had the clean room contractor decrease Provider pass the quiz to earn 1 AIA LU.
the fan speed on several banks of fan filter units. Success!

TAB Journal Summer 2024 11

 C A S E S T U D I E S

Hardware and Software

Improvements in
VAV Systems
Todd Yates, PE, TBE, CxA
Eric Jespersen
Synergy Test and Balance, Inc.

Case Study #1: Software Incompatibility just as quickly. We have seen major changes in the way that
systems communicate, but also in the hardware that operates
Modern technological advancement moves at a pace that the equipment we balance.
often requires rapid adaptation. Building system controls This case study looks at changes in certain variable
are no exception, which means test and balance must adapt air volume (VAV) technologies. While technological

12 TAB Journal Summer 2024

improvements are generally beneficial, the progress of device and algorithm to algorithm, but for most applications
hardware may outpace the software systems they are can be expected to remain consistent unless something major
integrated with and the procedures to install, start, and changes. In the process of troubleshooting the continuously
service them. This mismatch can cause moving venturi valves, we noted that
systems to appear to be malfunctioning
and hold back progress on a project.
ʼʼ their movements were reminiscent
of a poorly tuned PID loop. The
As equipment improves, it will become Modern technological installers reviewed their procedures
increasingly necessary for TAB and noted that the software that they
technicians and engineers to consider advancement moves had installed on each valve was the
the various points at which installation same as the software they had used
procedures may have been set for older on previous projects. We questioned
technologies.
at a pace that often
whether the new actuators were
compatible with the older software.
Consider a recent project we balanced requires rapid After more research, it was discovered
at a healthcare facility. It incorporated
that the installed software version was
a few dozen venturi air valves, which adaptation. Building indeed inappropriate for the hardware.
of course are expected to be factory
Installing new software corrected the
calibrated and operationally tested.
system controls are operational issues, but it also required
Upon arrival on the project site, we
recalibrating the air valves in the field.
noted that these valves were making a
great deal of noise. The linear actuators
no exception, which
seemed to be unable to settle and they
were readjusting constantly. As in means test and balance Case Study #2:
other venturi valves, the venturi control Timing Issues
mechanism used does not measure must adapt just as Another place where we see new
differential pressure or measure flow issues arise is in the speed with
in the traditional fashion; instead, it quickly. We have seen which devices communicate. In many
relies on a positional potentiometer for VAV systems, data is updated at a
feedback to their network for setpoints. major changes in the steady pace. In the past, this pace
In the previous fit-out projects in this was set based on the limitations of
facility, we had never encountered way that systems the connected devices. As the devices
venturi valves that did not move improve, their speeds increase. VAVs
expeditiously to their setpoint. Even communicate, but also themselves are, albeit somewhat
more infrequently did they not prove to simple, motion control devices that
match flows shown on the calibration in the hardware that use some form of feedback to change
sheets provided by the startup an output to position their damper.
technicians. The big difference on this operates the equipment In simple terms, this is a PID loop.
latest project was an improvement in When this loop is not performing
their technology. The linear actuators
on these valves were of a new design.
The installers on previous projects had
we balance.
ʼʼ optimally, there are several errors we
expect to see. As TAB technicians,
we calibrate the input feedback
a rotation servo/encoder which moved of flow to the controller to ensure
the armature and provided positional feedback. These servos/ that the VAVs are measuring flow
encoders were faster than what we expect in a traditional accurately and can therefore be expected to achieve the
VAV, but not as fast as the linear actuators. correct setpoint. However, dampers take time to move and
flow rate measurements take time to communicate back to
Any process to move an actuator to achieve a setpoint must
the controllers.
account for a certain amount of mechanical inaccuracy. This
is normally solved with positional feedback and a basic PID In a recent project at a school, we discovered that nearly
loop. The control values in that loop will vary from device to every VAV would move its damper to a position, then

TAB Journal Summer 2024 13

 C A S E S T U D I E S C O N T I N U E D

continue to open until the reported flow was far over Because people have a habit of doing what has worked
setpoint, and then close until it was far below the setpoint. before, the installation and programming methodology
The system provided to calibrate these specific VAVs gave was identical to the previous several installations and did
a live readout of the flow the VAV was reporting and the not account for the new, improved, and much faster main
damper position command. Every VAV seemed to make two controller.
or three changes to damper position command for every one
This improvement in the technology created a mismatch
update of flow input. For example, a VAV with a setpoint
in integrated systems that was observed somewhat
of 100 CFM would read 50 CFM at 20% command, then
uniformly on the system. While working with the controls
50 CFM again at 80% command, then 200 CFM at 90%
team responsible for these VAVs, we determined that the
command. Once the readout was over the setpoint, the cycle
symptoms matched a poorly tuned PID loop and could be
would reverse.
corrected by changing the speed at which command updates
The airflow measured by our flow hood would show a were made. Since then, a new method for setting up systems
relatively consistent sweep up and down when measured at with these controllers and VAVs has been adopted as their
intervals that matched the pace of the damper commands. No current standard.
amount of waiting for the system to settle resulted in steady
operation. On this system, the speed at which updates to
AIA
damper commands were made was set by a clock on the main After reading the full issue, take what you’ve
Continuing
controller and would be calculated based on the most recent Education learned, visit www.aabc.com/TABQuiz and
flow reading reported by each VAV. The main controllers Provider pass the quiz to earn 1 AIA LU.
were a new model that the installers had not used before.

14 TAB Journal Summer 2024

 MARK YOUR CALENDAR

2025 EXPO
Orange County Convention Center // Feb. 10-12

Orlando

TAB Journal Summer 2024 15

INSTALLING PRESSURE INDEPENDENT VALVES INTO A

CONSTANT
VOLUME
SYSTEM
Paul Mocny, TBE
MESA3 Inc.

A local hospital facility’s project to remodel an existing critical space

involved adding new supply and exhaust air valves into the existing
house supply and exhaust systems for the remodeled rooms. The
existing supply system served pressure independent constant air volume
boxes. The exhaust system, however, was a constant volume system
with ceiling-style registers and no pressure independent boxes.

T
he mechanical engineer for the project designed the ductwork to have any appreciable length of straight ductwork
remodeled space with venturi-type air valves for entering a valve. This issue is mitigated with these valves. The
both the supply and exhaust systems. These valves main requirement for the venturi valves to function is to have
have numerous benefits for critical room environments: they a minimum operating differential pressure across the valve.
have no velocity sensors that can gather lint, they are low
On this project, the supply system had enough static pressure
maintenance, and their recalibration is basically nonexistent.
and the valves were able to be successfully calibrated because
The internal controls for these venturi valves are mechanical. the original system already had a higher duct static pressure
By combining calibrated shaft positions with a spring-loaded to operate the pressure independent boxes. The real issue was
cone assembly that adjusts its shaft position to size the encountered with the exhaust system; it did not have enough
orifice accordingly, the airflow is maintained accurately — static pressure for the exhaust valves to function or calibrate
typically within +/-5% of the airflow setpoint. As the system properly. The exhaust system at the location of the valves
pressure changes, the valve responds as needed. They are had 0.25” static pressure, and per the startup contractor,
fast-acting and have quick response times for better control factory tech support wanted to see a 0.60” and ideally a 0.70”
of the room environment. differential pressure across the valve. Airflow was not an
issue, as we had higher than design airflow at the registers.
Due to the nature of the valves’ mechanical control and not The valve just could not control or function properly at the
utilizing a velocity sensor in the ductwork, these devices also current pressure differential. The exhaust fan was controlled
don’t require straight duct runs entering the valve. Ceiling by a VFD and had the capacity to be increased, but increasing
space is often very congested with piping, conduit, wires, the fan would have affected the existing registers outside of
structural supports, etc., and it becomes a challenge for the project boundary.

16 TAB Journal Summer 2024

 We considered many options, including a full system balance Another option was to replace the venturi-type air valves
that would involve speeding up the fan, installing branch with traditional constant volume exhaust boxes. These boxes
volume dampers to minimize the quantity of dampers needing would provide operator control of the airflow via the control
to be adjusted, and performing a system balance in an system if needed, and they can operate at low static & velocity
occupied facility, with the intent of increasing static pressure pressures. However, this scenario may also require future
in the main ductwork. The owner did not like this option calibrations, cleaning & maintenance, and these boxes are not
because of sound level concerns, duration of the work, and fast-acting. This would have been a good compromise but also
occupantNEBB-Half-Page-2022-Reporting&PM-FINAL.PRINT.pdf
impact in the existing areas.1 6/22/2022 2:18:22 PM was decided against, as a better option was found.

CM

MY

CY

CMY

TAB Journal Summer 2024 17

 Ultimately, a product was recommended that provides the
desired performance and would operate in a lower static
pressure system: an electronically operated airflow control
valve. The technology on this type of valve is not mechanical
based, as the venturi type of valve is. These valves measure
actual airflow, and they can operate at a design system
pressure as low as 0.05” WC.

The integral vortex airflow sensor is accurate to +/-5% over

the flow range and does not require maintenance. Additionally,
they can be mounted in any orientation, straight entering
duct runs are not required, and they are static pressure reset
compliant. Products are always advancing, and this technology
provides additional options for the industry.

AIA
After reading the full issue, take what you’ve
Continuing
Education learned, visit www.aabc.com/TABQuiz and
Provider pass the quiz to earn 1 AIA LU.

18 TAB Journal Summer 2024

 AABC
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TAB Journal Summer 2024 19
 AABC NATIONAL MEMBERSHIP Up-to-date listings always available at www.aabc.com/member-locator

ALABAMA Penn Air Control, Inc. Test and Balance Corporation LOUISIANA MISSISSIPPI
Performance Testing & San Diego, California Tampa, FL Coastal Air Balance Corp. Capital Air Balance, Inc.
Balancing Co., Inc. (760) 451-2025 (813) 909-8809 Metairie, Louisiana Terry, Mississippi
Cleveland, Alabama RSAnalysis, LLC The Phoenix Agency, Inc. (504) 834-4537 (601) 878-6701
(205) 274-4889 El Dorado Hills, California Lutz, Florida Tech-Test Inc. of Louisiana
Systems Analysis, Inc. (916) 358-5672 (813) 908-7701 Baton Rouge, Louisiana
MISSOURI
Birmingham, Alabama RSAnalysis, LLC Thermocline Corp. (225) 752-1664 Mechanical Testing, Inc.
(205) 802-7850 Fairfield, California Merritt Island, Florida St. Louis, Missouri
(707) 696-2444 (321) 453-3499 MARYLAND (314) 432-5100
ARIZONA Winaire, Inc. American Testing, Inc. Miller Certified Air, Inc.
Arizona Air Balance Company Huntington Beach, California
GEORGIA Ellicott City, Maryland St. Louis, Missouri
Tempe, Arizona (714) 901-2747 Addison Energy (410) 461-6211 (314) 352-8981
(480) 966-2001 Technologies, LLC Baumgartner, Inc. Precisionaire of the
ETB Arizona, LLC COLORADO Toccoa, Georgia Hunt Valley, Maryland Midwest, Inc.
Phoenix, Arizona United Test & Balance (706) 244-0383 (410) 785-1720 Grain Valley, Missouri
(602) 861-1827 Littleton, CO Augusta Air Balance Chesapeake Testing & Balancing (816) 847-1380
General Air Control, Inc. (720) 333-3601 Company, LLC Engineers, Inc. Testing & Balance Co. of the
Tucson, Arizona Martinez, Georgia Easton, Maryland Ozarks, LLC (TABCO)
(520) 887-8850 CONNECTICUT (706) 799-2254 (410) 820-9791 Republic, Missouri
CFM Test & Balance TAB Services, Inc. (417) 443-4430
Pangea Consulting Group Corporation CJ Weisman Balancing, LLC
Higley, AZ Norcross, Georgia Easton, Maryland
Bethel, Connecticut (404) 329-1001 NEVADA
(602) 708-6636 (203) 778-1900 (443) 496-0625
Test and Balance Corporation American Air Balance Co., Inc.
Phoenix Test and Balance, LLC James E. Brennan Company, Inc. Environmental Balancing Las Vegas, Nevada
Glendale, Arizona Alpharetta, Georgia Corporation
Wallingford, Connecticut (678) 393-9401 (702) 255-7331
(602) 708-6618 (203) 269-1454 La Plata, Maryland
(301) 868-6334 Mechanical Test and Balance
Precisionaire of Arizona, Inc. HAWAII Corporation
Cave Creek, Arizona FLORIDA Pacific Test and Balance, Inc. Mechanical Testing, Inc. Las Vegas, Nevada
(623) 580-1644 Absolute Balance, Inc. Waipahu, Hawaii (MidAtlantic Region) (702) 737-3030
Southwest Testing Oviedo, Florida (808) 488-2444 Hampstead, Maryland
(407) 402-3256 (410) 935-8249 Penn Air Control, Inc.
& Balancing, LLC Penn Air Control, Inc. Las Vegas, Nevada
Peoria, Arizona Air Balance Unlimited, Inc. Kapolei, Hawaii Performance Test and (702) 221-9877
(602) 370-6601 Altamonte Springs, Florida (808) 492-1640 Balance, LLC
(407) 383-8259 Chester, Maryland Raglen System Balance, Inc.
Systems Commissioning & Test & Balance Group Reno, Nevada
Testing, Inc. Air Proserv, Inc. (301) 809-0100
Pearl City, HI (775) 747-0100
Tucson, Arizona Boca Raton, Florida (630) 790-4940 Quality Test and Balance, LLC
(520) 884-4792 (561) 208-3882 Pasadena, Maryland RSAnalysis, LLC
(410) 647-1015 Las Vegas, Nevada
Tab Technology, Inc. Bay to Bay Balancing, Inc. ILLINOIS (702) 740-5537
Mesa, Arizona Lutz, Florida UBES, Inc. Test & Balancing, Inc.
(480) 964-0187 (813) 971-4545 Wheaton, Illinois Baltimore, Maryland RSAnalysis, LLC
(630) 790-4940 (301) 953-0120 Reno, Nevada
ecoTAB, LLC (916) 358-5672
CALIFORNIA Sarasota, Florida
Air Balance Company, Inc. (941) 822-9636
INDIANA MASSACHUSETTS TABITT, LLC
Covina, California Fluid Dynamics, Inc. Thomas-Young Associates, Inc. Las Vegas, Nevada
(626) 339-4700 Gregor Hartenhoff, Inc. Fort Wayne, Indiana Marion, Massachusetts (702) 912-5700
Pompano Beach, Florida (260) 490-8011 (508) 748-0204
Air Balance Company, Inc. (954) 786-3420
(San Diego) Synergy Test & Balance, Inc.
NEW JERSEY
Escondido, California JM Test & Balance Indianapolis, Indiana
MICHIGAN Airology
(760) 741-5401 Royal Palm Beach, FL (317) 222-1828 Aerodynamics Inspecting Co. Bridgewater, New Jersey
(561) 764-3895 Dearborn, Michigan (908) 722-1776
American Air Balance Co., Inc. (313) 584-7450
Anaheim, California Precision Balance, Inc. IOWA Effective Air Balance, Inc.
(714) 693-3700 Orlando, Florida Systems Management & Air Solutions, Inc. Hoboken, New Jersey
(407) 876-4112 Balancing, Inc. Lapeer, Michigan (973) 790-6748
Balance America Inc. Waukee, Iowa (810) 358-8644
San Marcos, CA Premier Energy Solutions, Inc. National Air Balance
(515) 987-2825 Airflow Testing, Inc. Company, LLC
(760) 798-9255 Naples, Florida
(239) 822-3640 Lincoln Park, Michigan Paramus, New Jersey
Los Angeles Air Balance KENTUCKY (313) 382-8378 (201) 444-8777
Company, Inc. Premier Energy Solutions, Inc. Synergy Test and Balance, Inc.
Upland, California (East Office) Lexington, KY
Palm Beach Gardens, Florida
MINNESOTA NEW YORK
(800) 429-6880 (270) 884-6706 Air Systems Engineering, Inc. Mechanical Testing, Inc.
(443) 458-8012
Matrix Air & Hydroponic Thermal Balance, Inc. Edina, Minnesota Clifton Park, New York
Balance Co. Professional Air Balancing, Inc. Nicholasville, Kentucky (952) 807-6759 (518) 450-7292
Torrance, California Clearwater, Florida (859) 277-6158
(727) 592-9666 Mechanical Data Corporation Mechanical Testing, Inc
(310) 320-9020 Thermal Balance, Inc. Bloomington, Minnesota Binghamton, New York
MESA3, Inc. Southern Balance, Inc. Ashland, Kentucky (952) 473-1176 (607) 722-1819
San Jose, California Milton, Florida (606) 325-4832
(850) 623-9229 Mechanical Test and Precision Testing & Balancing, Inc.
(408) 928-3000 Thermal Balance, Inc. Balance Corporation Mineola, New York
National Air Balance Co., Inc. Southern Independent Paducah, Kentucky Maple Plain, Minnesota (718) 994-2300
Fremont, California Testing Agency, Inc. (270) 744-9723 (763) 479-6300
(510) 623-7000 Lutz, Florida NORTH CAROLINA
(813) 949-1999 SMB of Minnesota
Penn Air Control, Inc. Blaine, Minnesota Airflow Experts, Inc.
Cypress, California (763) 398-3284 Graham, North Carolina
(714) 220-9091 (336) 229-1470

20 TAB Journal Summer 2024

 AABC CANADIAN CHAPTER

enTAB, Inc. WAE Balancing, Inc. PHI Service Agency, Inc. MANITOBA ONTARIO
Winston-Salem, North Carolina Mercer, Pennsylvania San Antonio, Texas A.H.S. Testing & Balancing, Ltd. Accu-Air Balance Co.
(336) 896-0090 (724) 662-5743 (210) 224-1665 Duguld, Manitoba (1991), Inc.
Palmetto Air & PHI Service Agency, Inc. (204) 224-1416 Windsor, Ontario
Water Balance, Inc. (Charlotte)
SOUTH CAROLINA Austin, Texas (519) 256-4543
Optimum Air & Water Air Movement Services, Ltd.
Charlotte, North Carolina (512) 339-4757 Winnipeg, Manitoba Air & Water Precision
(704) 587-7073 Rock Hill, South Carolina
(803) 728-6655 PHI Service Agency, Inc. (204) 233-7456 Balancing, Inc.
Palmetto Air & (Rio Grande Valley) AIRDRONICS, Inc. Toronto, Ontario
Water Balance, Inc. Palmetto Air & Alamo, Texas (647) 896-5353
Water Balance, Inc. Winnipeg, Manitoba
Greensboro, North Carolina (956) 781-9998 (204) 253-6647 Airwaso Canada, Inc.
(336) 275-6678 Greenville, South Carolina
(864) 877-6832 Precision Flow Engineering D.F.C. Mechanical Testing London, Ontario
Palmetto Air & Water Balance, Mansfield, Texas & Balancing, Ltd. (519) 652-4040
Inc. (Raleigh) Palmetto Air & (817) 453-8588
Water Balance, Inc. Winnipeg, Manitoba Climatech Services
Morrisville, North Carolina TAB Solutions, Inc. (204) 694-4901 Thunder Bay, Ontario
(919) 460-7730 Charleston, South Carolina
(843) 789-5550 Leander, Texas (807) 628-3636
Palmetto Air & (720) 220-1062 NEW BRUNSWICK Designtest & Balance Co. Ltd.
Water Balance, Inc. TENNESSEE TABFX, LLC Controlled Air Management, Ltd. Richmond Hill, Ontario
Wilmington, North Carolina Environmental Test & San Juan, Texas Moncton, New Brunswick (905) 886-6513
(910) 202-3850 Balance Company (956) 510-8022 (506) 852-3529
Dynamic Flow Balancing, Ltd.
TAB Services, Inc. Memphis, Tennessee Scan Air Balance 1998 Ltd. Oakville, Ontario
TAC Services, LLC
Charlotte, North Carolina (901) 373-9946 Dieppe, New Brunswick (905) 338-0808
Edinburg, Texas
(803) 517-8002 Mechanical Testing, Inc. - (956) 874-5889 (506) 857-9100
Kanata Air Balancing &
The Phoenix Agency (Southern Region) Source Management Limited Engineering Services
Technical Air Balance,
of North Carolina, Inc Knoxville, Tennessee Hanwell, New Brunswick Ottawa, Ontario
Texas
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Spring, Texas
(336) 744-1998 Systems Analysis, Inc. (281) 651-1844
NOVA SCOTIA Pro-Air Testing, Inc.
Hermitage, Tennessee Toronto, Ontario
NORTH DAKOTA (615) 883-9199
Texas Test & Balance Griffin Air Balance, Ltd.
Magnolia, Texas Dartmouth, Nova Scotia (416) 252-3232
Design Control, Inc.
United Testing & Balancing, Inc. (281) 460-0142 (902) 434-1084 Vital-Canada Group, Inc.
Fargo, North Dakota
Nashville, Tennessee Mississauga, Ontario
(701) 237-3037 Scotia Air Balance 1996 Limited
(615) 331-1294 UTAH (905) 848-1000
RSAnalysis, Inc. Antigonish Co., Nova Scotia
OHIO United Testing & Balancing, Inc. (902) 232-2491 VPG Associates Limited
Air Balance Unlimited, Inc. Knoxville, Tennessee Sandy, Utah
(801) 255-5015 King City, Ontario
Thornville, Ohio (865) 922-5754 (905) 833-4334
(614) 595-9619
TEXAS VIRGINIA
Kahoe Air Balance Company Atlantic Testing
Air Balancing Company, Inc.
Eastlake (Cleveland), Ohio Powhatan, Virginia
Fort Worth, Texas
(440) 946-4300 (804) 367-7126
(817) 572-6994
Kahoe Air Balance Company C&W-TESCO, Inc.
AIR Engineering and Testing, Inc.
(Cincinnati/Dayton) Midlothian, Virginia
Dallas, Texas
Liberty Township, Ohio (804) 400-0431
(972) 386-0144
(513) 248-4141
Air Technology Consulting, LLC Mid-Atlantic Test & AABC INTERNATIONAL MEMBERS
Kahoe Air Balance Company Balance, Inc.
Plano, Texas
(Columbus) South Boston, Virginia
(817) 442-5214
Gahanna, Ohio (434) 572-4025
(614) 694-2558 Austin Air Balancing Corporation
GUAM SAUDI ARABIA
Austin, Texas Palmetto Air & KMFNE, LLC Molden Technical & Consulting
Precision Air Balance Water Balance, Inc. Barrigada, Guam Projects Co. W.L.L. (Saudi)
(512) 477-7247
Company, Inc. Charlottesville, Virginia (671) 747-4646 Al Yasmeen, Saudi Arabia
Cleveland, Ohio Delta-T, Ltd. (919) 460-7730 +965 5098-5799
(216) 362-7727 Garland, Texas Penn Air Control, Inc.
(972) 494-2300 Penn Air Control, Inc. Tamuning, Guam
R.H. Cochran and North Chesterfield, Virginia (671) 477-0325 SOUTH KOREA
Associates, Inc. Delta-T, Ltd. (919) 460-7730 Awin ENC Co., Ltd.
Wickliffe, Ohio Austin, Texas ITALY Seoul, South Korea
(440) 585-5940 (512) 590-1051 Premier Energy +82-2-2117-0290
Solutions, Inc. (DMV) Studio S.C.S. Ingegneri
Energy Testing and Balance, Inc. Chantilly, VA Giancarlo Cuomo Energy 2000 Technical
OREGON Austin, Texas Pordenone, Italy Engineering Co., Ltd.
Northwest Engineering (239) 822-3640
(512) 266-2424 +39-0434-29661 Songpa-gu, South Korea
Service, Inc. TAB Technologies, Inc. +82-2-408-2114
Tigard, Oregon Engineered Air Balance Co., Inc. Sterling, Virginia
Richardson, Texas
KUWAIT Independent Commissioning
(503) 639-7525 (703) 319-1000 Molden Technical &
(972) 818-9000 Engineers Inc.
Consulting Projects Co. Gyeonggi-do, South Korea
PENNSYLVANIA Engineered Air Balance Co., Inc. WASHINGTON Sharq, Kuwait
Butler Balancing Company, Inc. San Antonio, Texas Eagle Engineering Company +82-31-853-8891
+965-22282020
Downington, Pennsylvania (210) 736-9494 Bellevue, Washington National Air Control, Ltd.
(610) 873-6905 (425) 747-9256 Shurouq Al Hamera Est. Seoul, South Korea
Engineered Air Balance Co., Inc. Al-qibla, Kuwait
Flood and Sterling, Inc. Spring, Texas TAC Services, LLC 2-982-4231
(551) 20185
New Cumberland, Pennsylvania (281) 873-7084 Bow, Washington Romon E&C
(717) 232-0529 National Precisionaire, LLC (360) 255-5306 QATAR Seoul, South Korea
Kahoe Air Balance Company Houston, Texas Penn Air Control, Inc. AJB Contracting, Qatar +82-2-2655-9100
(Pittsburgh) (281) 449-0961 Monroe, Washington Doha, Qatar
Canonsburg, Pennsylvania (714) 220-9091 97440075196 UNITED ARAB
Online Air Balancing Company EMIRATES
(724) 941-3335 Houston, Texas Jedi Middle East
Corniche, Doha Qatar AJB Hightech, Ltd.
(713) 453-5497
+974-44126651 Dubai, United Arab Emirates
+971 (0)4 424 0126

TAB Journal Summer 2024 21