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.
The unit should not be programmed to run as constant airflow in this application.
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. The units should be ordered with a constant torque
program. This will remove the dirty filter ramp-up feature and the CFM display will no longer be accurate.
However, this is still preferable to a PSC system due to the energy efficiency of an ECM versus a PSC motor.
Ducted applications
While the fan filter unit can handle some positive or negative static pressure, optimal
performance and reliability will be acheived with an inlet static pressure of 0.0" WC or slightly negative.
To reach an accurate 0.0"WC inlet static, it is recommended that the primary air balancing of the duct system
be done before installing the fan filter unit. When the duct is at optimal static, install the unit per these
instructions and adjust the airflow to the design setting. Verify the airflow with an airflow hood.
It is recommended that all FFUs in the system be energized before any upstream devices to prevent the FFU blower
wheel from spinning backwards. While the motor can generally overcome this, if the airflow needed to overcome
high static is too great, it may not. This will cause the motor to shut down. Continual running of the motor backward
may result in reduced reliability of the EC motor.
DRAWING NAME
DRAWN
CATEGORY
CHKD
APRVD
PRODUCT
SIZE
TAG
QTY
BRS/SLG
01/24/22
CRITI-CLEAN ORIGINAL INSTALLATION MANUAL
SSLFHFD-FP, SSLFHFD-FP-MEA
REV # F
SHT
6 29
/
SCL
DO NOT
SCALE
1:10
STAINLESS STEEL
CRITI-CLEAN ORIGINAL
FAN FILTER UNITS
