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21
Proximity Hood
®
High Velocity Cartridge Filters
1/2 width
1/2 height
Fig. 30
Nominal Filter Size (H x L)
Imperial
Conversion Factor
Metric
Conversion Factor
Inches Millimeters
16 x 16 400 x 400
1.22 ft
2
.113 m
2
16 x 20 400 x 500
1.67 ft
2
.155 m
2
20 x 16 500 x 400
1.21 ft
2
.112 m
2
20 x 20 500 x 500
1.50 ft
2
.139 m
2
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. Leave all holes of
Velgrid open. Do NOT tape over holes that are not
over openings. The conversion factor takes this into
account.
• Position the grid over each filter as shown.
• 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.
Fig. 29
Total hood flow rate = (Filter 1 Flow Rate) + … + (Filter X Flow Rate)
= 423.0 + 421.8 + 420.7 + 418.2 = 1683.7 cfm
Flow rate for one filter =
Conversion
Factor
x
Average
Velocity
(Imperial)
= 1.50 x 282 fpm = 423.0 cfm
(Metric)
= .139 x 5157 m/hr = 717 m
3
/hr
Example: Measured velocities for 20 x 20 filter = 282 fpm (5157 m/hr)
= 717 + 717 + 715 + 711 = 2860 m
3
/hr