Greenheck Waterwash (458292) - Manual (Page 33)

33 April 2005
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Supply (If Applicable):
Example for Perforated Face Supply
1. Hood set up
If the make-up air unit has a temperature control, it should be used to keep the supply air a the desired room
discharge air temperature.
2. Measure Velocities
Divide the perforated face panel into a grid of equal areas, each approximately 4 in. square.
Measure the velocity at the center of each grid area. A digital 2 3/4 in. rotating vane anemometer or
equivalent is suggested. The center of the anemometer should be held tight to the face of the panel, and
parallel to the filter. Both squareness and distance are important for accuracy. Calculate the average
velocity of the panel.
3. Measure the length, height, and width of the perforated face panel.
4. Calculate the perforated face panel volume in CFM by using the following formula:
Volume = Avg. Velocity * Length (in.) * Height (in.) * .005
5. Calculate the system’s volume by repeating the process for the remaining panels and adding the individual
panel volumes together.
Example: GWFW Hood with (3) 28 in. Perforated Panels
• Measured velocities in FPM for one perforated panel
• Average Velocity= Sum of Velocity Readings
Number of Readings
=260+250+ ... +290+295 = 270.7 FPM
28
260 250 255 260 250 255 265
270 275 270 280 265 265 270
290 285 280 280 275 290 295
285 275 280 260 270 265 260
• Measure = 28 in. long perforated panels x 16 in. high
Length and Height
• Volume for = 0.005 x ( Average Velocity) x (Length) x (Height)
one panel = 0.005 x 270.7 x 28 x 16 in. = 606.4 CFM
• Total System = (Panel 1 Volume) + (Panel 2 Volume) + (Panel 3 Volume)
Volume = 606.4 + 614.3 + 593.8 = 1814.5 CFM