Accurex XB Installation, Operation And Maintenance Manual page 18

High Velocity Cartridge Filters - Rotating Vane
Method
With all the filters in place, determine the total hood
exhaust volume with a rotating vane anemometer as
follows:
1. All cooking equipment should be on. If the hood has
internal short circuit make-up air, it should be turned off.
2. Measure velocities.
Velocity measurements should be taken at three
locations per filter. These must be over the inlet
opening as shown in Fig. 11.
Measure the velocity of each location. A digital
2.75 in. (69.85 mm) rotating vane anemometer
or its equivalent is suggested. The center of the
anemometer should be held 2 in. (50.8 mm) from
the face of the filters as in Fig. 12. It is helpful to
make brackets to keep the anemometer at the 2 in.
(50.8 mm) distance and parallel to the filter. Both
squareness and distance are important for accuracy.
3. Calculate the average slot velocity.
4. Calculate the CFM per linear foot by dividing
the average velocity by a conversion factor
listed in the following table.
5. Calculate each filter's volumetric flow rate in
CFM by multiplying the average velocity for
each filter by the conversion factor.
Example:
Measure the slot velocities in ft/min. for a 9 ft. (2.74 m) hood with four 20 x 20 in. (500 x 500 mm) filters with the
standard 4 in. (101.6 mm) opening, three readings per filter.
Average Velocity =
=
(Imperial)
=
(Metric)
CFM per linear foot =
=
(Imperial)
=
(Metric)
Hood exhaust volume =
=
(Imperial)
=
(Metric)
18 Kitchen Hoods • Type I and Type II
Sum of Velocity Readings
Number of Readings
5330
= 444.2 ft/min.
12
97474
= 8123 m/hr
12
Average Slot Velocity
Conversion Factor
444.2 ft/min.
= 206.6 cfm/linear ft.
2.15
8123 m/hr
= 1152 m
7.05
3
CFM/linear foot (m /hr / m)
206.6
1152
Fig. 11
1/4 Width
Fig. 12
Rotation Vane
Anemometer
Cartridge Filter Size
16 in. (400 mm) high with 4 in. (100 mm) high inlet
20 in. (500 mm) high with 4 in. (100 mm) high inlet
16 in. (400 mm) high with 7 in. (120 mm) high inlet
20 in. (500 mm) high with 7 in. (120 mm) high inlet
3
/hr
x Hood Length
x 9 ft.
x 2.74 m
1/2 Width
1/4 Width
2 in.
(50.8 mm)
Imperial
Conversion
Factor
3
ft
1.63 1/
3
ft
2.15 1/
3
ft
1.24 1/
3
ft
1.58 1/
Filter Readings (ft/min.)
470 440 425
482 430 453
455 431 441
399 439 465
Filter Readings (m/hr)
8595 8047 7772
8815 7864 8284
8321 7882 8065
7297 8028 8504
= 1859.4 cfm
3
= 3156 m /hr
1/2 Height
Inlet
Height
Filter
Height
Metric
Conversion
Factor
3
m
5.35 1/
3
m
7.05 1/
3
m
4.07 1/
3
m
5.18 1/