NuAire LabGard NU-560-400, Operation & Maintenance Manual

Page: 62 / 103

OM0295
Rev 2 September 2020 Page 62 of 103
Table 7.0
Recommended Measurement Methods for Cabinet Downflow & Inflow
A. Downflow Measurement
a. Instruments: TSI 8355 Thermo anemometer
b. Procedure: Supply filter efflux is measured on a grid, in a horizontal plane defined by 4 inches (102mm) above the
bottom edge of the window. No reading should be taken closer than 6 inches (152mm) from the inside perimeter.
c. Test Data - Inches (mm):
Model Size
Window Access Height
400
7.0
(178)
12.396
(315)
17.792
(452)
23.188
(589)
28.584
(726)
33.980
(863)
39.375
(1000)
600
7.5
(191)
15.410
(391)
23.320
(592)
31.230
(793)
39.140
(994)
47.050
(1195)
54.960
(1396)
62.870
(1597)
7.0
(178)
7.5
(191)
12.5
(318)
12.5
(318)
18.0
(457)
17.5
(445)
Number of Readings: Average Velocity ft./min.(m/s)
d. Acceptance Criteria:
1. Average downflow velocity = 55 to 65 fpm (.28 to .33 m/s)
2. Individual readings must be 20% or + 16fpm (+ 0.08m/s) whichever is greater (factory test) or + 25%
or + 16fpm (+ 0.08m/s) whichever is greater (field test) from the average downflow velocity.
B. Inflow/Exhaust Volume Measurement
a. Instrument: Shortridge Flowhood ADM-870 or TSI 8355 Thermo anemometer.
b. Procedure: The exhaust airflow (customer supplied) shall draw air from the cabinet. Any one of a number of airflow
controlling and measuring means may be used to establish inflow/exhaust volume. The inflow/exhaust volume is
established for the cabinet having the workzone downflow average velocity at its nominal value. To measure the inflow
volume, the internal blower should be turned on, thus, the inflow volume balanced with the downflow volume can be
measured to set the desired average inflow velocity.
The inflow/exhaust volume is measured by using a Direct Inflow Measurement (DIM) instrument (i.e. Shortridge
Flowhood). The DIM instrument can be used directly on the cabinet with NO CORRECTION FACTORS REQUIRED.
The DIM instrument should also be duct taped to the cabinet’s front work access opening to prevent any sneak air
paths from occurring. The DIM instrument will read inflow volume (i.e. CFM). Use the area table to calculate the
inflow velocity and referenced exhaust volume (Certification values listed in Table 7.1) based upon the DIM
measurement.
Alternate Procedure:
The alternate procedure to determine inflow velocity uses a thermo anemometer in a constricted window access opening
of 3 inches (76mm) with the downflow blower on and the armrest removed. Inflow air velocity is measured in the center of
the constricted opening 1-1/2 inches (38mm) above the work access opening on the following specified grid. Use the area
correction factor table to calculate the inflow velocity and reference exhaust volume.
(Certification values listed in Table 7.1)
NOTE : Since NuAire cabinets use a full supply diffuser, resulting in uniform airflow velocities, NuAire has found
that the average supply velocity and the average downflow velocity are typically found to be the same
value or can be related with a small correction factor. Using the average downflow velocity or a corrected
average downflow velocity (see individual model numbers below) to calculate the supply volume if
desired to evaluate cabinet airflow value.
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