Greenheck Fan Canopy Type Kitchen Hoods 452413 - Manual (Page 17)

17 Kitchen Hoods • Type I and Type II
High Velocity Cartridge Filters - 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. Measure 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. Refer to Fig. 12
• Take velocity readings for each filter.
3. Calculate each filter’s volumetric flow rate as follows:
Calculate each filter’s average velocity by summing
the velocity readings and dividing by the number of
readings for each filter.
Multiply the average velocity by the conversion factor
to obtain the volumetric flow rate for each filter.
4. Calculate the hood’s total volumetric flow rate by
summing the volumetric flow rate of each individual
filter in the hood as calculated in Step 3.
1/2 width
1/2 height
Fig. 12
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
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 = 282 ft/min. (5157 m/hr)
Flow rate for one filter =
Conversion
Factor
x
Average
Velocity
(Imperial) = 1.50 x 282 ft/min. = 423.0 cfm
(Metric) = .139 x 5157 m/hr = 717 m 3 /hr
Total hood flow rate = (Filter 1 Flow Rate) + … + (Filter X Flow Rate)
(Imperial) = 423.0 + 421.8 + 420.7 + 418.2 = 1683.7 cfm
(Metric) = 717 + 717 + 715 + 711 = 2860 m 3 /hr
Edge of outlet/inlet
active face area
Maintain 1½ inch
(38.1 mm) margin
Maintain 1½ inch
(38.1 mm) margin
Place standoff spacers against
face of outlet or inlet grill,
filter, coil, etc.
Tubing harness
Neckstrap
External read jack
Extension rods
Swivel bracket
Tubing connectors
Pushbutton handle and plug
Handle bracket
Captive knob screws
Pressure input ports
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