Rotating Vane Anemometer | Greenheck Fan PN 458294 specification

Measure the velocity of each location.

A digital 2.75 in. (70 mm) rotating
A digital 2.75 in. (70 mm) rotating
vane anemometer or equivalent		Rotating Vane Anemometer
is suggested. The center of the	Airﬂow
anemometer should be held 2 in.	Airﬂow
anemometer should be held 2 in.
(50 mm) from the face of the filters
as shown in Fig. 22. It is helpful		2 in.


to make a bracket to keep the
anemometer at the 2 in. (50 mm)
distance and parallel to the filter.			Fig. 22
distance and parallel to the filter.
Both squareness and distance are
Both squareness and distance are
very important for accuracy.
very important for accuracy.

Calculate the average velocity for the filter.

3.Determine the filter’s conversion factor from the table.

4.Calculate the filter’s volume in CFM (m3/hr) by multiplying the average velocity by the conversion factor.

5.Calculate the hood’s volume by repeating the process for the remaining filters and summing the individual filter volumes.

Nominal Filter Size (H x L)		Imperial	Metric
Inches	Millimeters	Conversion Factor	Conversion Factor

16 x 16	400 x 400	1.63	.157
16 x 20	500 x 400	2.13	.198
20 x 16	400 x 500	1.90	.177
20 x 20	500 x 500	2.48	.230

Example: Exhaust Only Hood with three 20 x 16 Filters

255

250

(4663.44 m/h)

(4572 m/h)

Measured velocities in fpm for one 20 x 16 Filter

256

Sum of Velocity Readings

(4681.73 m/h)

Average Velocity

248

240

Number of Readings

(4535.42 m/h)

(4389.12 m/h)

(Imperial)

255 + 250 + 256 + 248 + 240 = 249.8 fpm

(Metric)

4663 + 4572 + 4681 + 4535 + 4389

= 4568 m/hr

For a nominal filter size of 20 x 16, the conversion factor is 1.90 Imperial (.177 Metric)

Volume for one filter

Conversion Factor

Average Velocity

1.90

249.8 fpm

474.6 cfm

.177

4568 m/hr

809 m3/hr

Total hood volume

(Filter 1 Volume)

(Filter 2 Volume)

(Filter 3 Volume)

474.6

455.4

470.1

1400.1 cfm

809

880

799

2488 m3/hr

17 Proximity Hood