Greenheck Fan 452413 - Manual (Page 21)

21 Canopy Hood
®
14 in.
17.25 in.
10 in.
2.75 in.
6 in.
2.75 in.
14 in.
Fig. 32
Fig. 33
Fig. 34
Nominal Filter Size (H x L)
Imperial
Conversion Factor
Metric
Conversion Factor
Inches Millimeters
16 x 16 400 x 400 1.66 .154
16 x 20 400 x 500 2.10 .195
20 x 16 500 x 400 1.96 .182
20 x 20 500 x 500 2.40 .223
Testing Hood Air Volume
10 in.
10 in.
Baffle Filters Style Hoods with the Shortridge Meter
A. Exhaust
With all the filters in place, determine the total hood exhaust
volume with a Shortridge meter 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. Measuring Velocities
• Set up the Shortridge meter.
• For 20 in. (500 mm) wide filters, position the grid as
shown in Fig. 32 and 33. Average two measurements.
• For 16 in. (400 mm) wide filters position the grid as
shown in Fig. 34.
• Take velocity readings for each filter.
3. *Calculate each filter’s volumetric flow rate by summing
the flow rate of each individual filter in the hood.
4. *Calculate the total hood’s volumetric flow rate by
summing the flow rate of each individual filter in the hood.
*Note: For best accuracy multiply the velocity of each filter by its
conversion factor and sum the flow rates. Averaging the velocity
measured for all filters may cause error.
Example: Measured velocities for 20 x 20 filter = 185 and 189 fpm
Average Velocity =
Sum of Velocity Readings
Number of Readings
(Imperial) =
185 + 189
2
= 187.0 fpm
(Metric) =
3383 + 3456
2
= 3420 m/hr
Flow rate for one filter = Conversion
Factor
x
Average
Velocity
= 2.40 x 187.0 fpm = 448.8 cfm
= .223 x 3420 m/hr = 763 m 3 /hr
Total hood flow rate =
(Filter 1
Flow Rate)
+ … +
(Filter X
Flow Rate)
= 448.8 + 457.8 + 437.5 + 444.8 = 1788.9 cfm
= 763 + 778 + 743 + 756
= 3040 m 3 /hr
Fig. 31