Balancing
Technical Note:
Design with VAV/Constant Flow Boxes and Ducted Applications
In applications where the fan filter units will be ducted with upstream VAV, constant flow boxes, valves, or other airflow
devices that may have varying airflows, or modes, a constant flow program is not recommended.
In systems where two controllers are trying to compensate to adjust to a constant airflow, the system will be unable to
stabilize. This results in constant adjustment of both controllers until the Krown Fan Filter Unit motor shuts off. The ECM
with constant torque motor program or PSC motor is suggested for this type of application.
The Krown Fan Filter Unit is designed to overcome the pressure drop of the filter only. The motor is not intended to pull air
down supply ductwork, nor to experience a positive static pressure at the inlet forcing air through the fan. Krown Fan filter
units should be installed in a system where the inlet static will be neutral or slightly negative.
In ducted applications, it is critical that primary air be balanced prior to installing the Krown Fan Filter unit. The primary air
controls should be locked in position post balancing, and the is installed and running. Similarly, the Krown Fan Filter series
should be bench-set by using a flow hood and adjusting the speed controller, as required, to the same balanced, primary
airflow rate before the is mated with the duct. Alternatively, the Technical Note: Design with VAV/Constant Flow Boxes and
Ducted Applications can also be followedl.
To prevent a high static pressure build up at the Krown Fan Filter series during start up, the Krown Fan Filter unit should be
energized prior to the system. This helps to prevent the possibility of backwards rotations of the blower wheel, which will
eventually lead to the motor shutting off.
For any additional information, or troubleshooting assistance on systems and design with Krown fan filter units
used in sequence with a variable upstream air source, contact contact Keystone Clean Air Solutions help at
KeySupport@KeystoneCleanAir.com, or dial (470)-604-9938.
For more information visit
KeystoneCleanAir.com
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Fan Filter Units |
Balancing
