Greenheck Fan Canopy Type Kitchen Hoods 452413 User Manual
Page 16
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Kitchen Hoods • Type I and Type II
High Velocity Cartridge Filters - Rotating Vane
Method
A. Exhaust
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. 10.
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. 11. 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.
1/4 Width
1/4 Width
1/2 Width
1/2 Height
Inlet
Height
Filter
Height
Fig. 10
Cartridge Filter Size
Imperial
Conversion
Factor
Metric
Conversion
Factor
16 in. (400 mm) high with 4 in. (100 mm) high inlet
1.63 1/
ft
3
5.35 1/
m
3
20 in. (500 mm) high with 4 in. (100 mm) high inlet
2.15 1/
ft
3
7.05 1/
m
3
16 in. (400 mm) high with 7 in. (120 mm) high inlet
1.24 1/
ft
3
4.07 1/
m
3
20 in. (500 mm) high with 7 in. (120 mm) high inlet
1.58 1/
ft
3
5.18 1/
m
3
Rotation Vane
Anemometer
2 in.
(50.8 mm)
Fig. 11
Hood exhaust volume =
CFM/linear foot (m
3
/hr / m)
x
Hood Length
(Imperial)
=
206.6
x
9 ft.
=
1859.4 cfm
(Metric)
=
1152
x
2.74 m
=
3156 m
3
/hr
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
=
Sum of Velocity Readings
Number of Readings
(Imperial)
=
5330
12
= 444.2 ft/min.
(Metric)
=
97474
12
= 8123 m/hr
CFM per linear foot
=
Average Slot Velocity
Conversion Factor
(Imperial)
=
444.2 ft/min.
2.15
= 206.6 cfm/linear ft.
(Metric)
=
8123 m/hr
7.05
= 1152 m
3
/hr
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
®