NuAire LabGard NU-581-400, Operation And Maintenance Manual

Page: 57 / 107

OM0302
Rev 2/December 2020 Page 57 of 107
7.5.3 Airflow Calibration
The NU-581 airflow calibration consists of adjustments to balance the airflow within the cabinet and the
calibration of the airflow monitor sensors.
THIS WORK SHOULD BE DONE ONLY BY A QUALIFIED TECHNICIAN
WHO CAN MEASURE THE AIRFLOW FROM THE FILTERS WITH A SUITABLE VELOMETER. Nuaire provides two
adjustments to balance the airflow within the cabinet. These are:
a. PWM signal adjusts via DC ECM motor control system
b. Exhaust filter choke
The blower speed control system adjusts the cabinet's total volume of airflow while the choke adjusts or balances
the exhaust airflow as well as makes up for filter resistance tolerances. Since it has been Nuaire's experience that
the filters may not "load" evenly, both adjustments are necessary for proper cabinet performance.
The cabinet is considered to be certifiable if the following airflow measurements are present:
a. Downflow average: 60 LFPM
±
5 LFPM (.30 m/s
±
.025 m/s).
b. Inflow average: 105 LFPM ± 5 LFPM (.53 m/s ± .025 m/s) using the
Direct Inflow Measurement (DIM) method, or alternate 3” constricted inflow velocity measurement
method.
The calibration of the airflow monitor sensors occurs during the cabinet airflow balancing procedure. The
calibration procedure consists using the downflow and inflow averages achieved and entry of those values into the
control system.