A NOTE ABOUT VAV BOXES AND DUCTED APPLICATIONS
In applications where the fan filter unit will be installed downstream of variable airflow devices such as
VAV boxes, air valves, or variable air handlers, proper care in unit set-up needs to be taken.
In these applications the unit should not be programed to run as constant airflow when ordered with the Airflow Sensor.
Two variable controllers trying to reach their respective set point will continuously adjust. This will cause issues such as
surging, starving, and eventual shut down of the fan filter unit. In these applications the unit should be placed into
"open-loop" control by turning off the S1-1dip switch (see pict below). This will no longer keep constant airflow
automatically. It will also remove the dirty filter ramp-up feature and the HEPA-lert dirty filter indicator (if applicable) will
be set as a static timer of 4400 hours (about 6 months). The set point will now be a percentage of motor speed instead
of CFM but it will still display CFM during normal operation. The unit in this setting is still preferable to a PSC system due to
the energy efficiency of an ECM versus a PSC motor and all control options are still applicable.
DUCTED APPLICATIONS
If ordered with the Airflow Sensor option the condition immediately before the inlet can impact the CFM reading. Use
the "C" up and down arrows on the face control to calibrate the airflow sensor to match the balancer's flow hood to
insure accurate airflow control. This calibration is best done as near to the operating point as possible. Recalibration may
be required if the setpoint changes more than 25%. In extreme cases the inlet conditions may not be able to be
compensated for using the caliberation adjustment. In these cases CFM controlled opperation may have to be forfit
and the unit run in open-loop mode.
S1-1
DRAWING NAME
DRAWN
CATEGORY
CHKD
APRVD
PRODUCT
SIZE
TAG
QTY
BRS/SLG
06/13/22
CRITI-CLEAN ULTRA INSTALLATION MANUAL
SSLFHFD-FFU-RF-MEA
REV # F
SHT
6 27
/
SCL
DO NOT
SCALE
1:10
STAINLESS STEEL
CRITI-CLEAN ULTRA
REVERSE FLOW - FAN FILTER UNITS
