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25
13
B
ALANCING THE
A
IRFLOWS
Example:
This is an example for determining the airflow in a 6 in. (0.5 ft) duct.
•
The Pitot tube reading was 0.025 inches of water. From the chart, this is 640 ft/min.
The 6 in. (0.5 ft) duct has a cross sectional area of:
A =
πr
2
= [πd
2
] / 4
A = [3.14 x (0.5 ft)
2
] / 4
A = 0.2 ft
2
The airflow is then: (640 ft./min.) x (0.2 ft
2
) = 128 cfm
For your convenience, the cross sectional areas of some common duct sizes are listed below:
DUCT. DIAM.
(inches)
CROSS SECTION AREA
(sq. ft.)
5 (127 mm)
0.14
6 (152 mm)
0.20
7 (178 mm)
0.27
The accuracy of the air flow reading will be affected by how close to any elbows or bends the readings are
taken. Accuracy can be increased by taking an average of multiple readings as outlined in the literature
supplied with the Pitot tube.
Note:
Place pitot tube a minimum
of 18” from blower or elbows
Note:
Duct connections may
vary, depending on model.
Summary of Contents for 1230 ERV
Page 1: ......
Page 6: ...www lifebreath com 5 3 DIMENSIONAL DRAWINGS 330ERV Dimensions 530ERV Dimensions ...
Page 7: ...www lifebreath com 6 3 DIMENSIONAL DRAWINGS 730ERV Dimensions 1230ERV Dimensions ...
Page 32: ...www lifebreath com 31 18 WIRING DIAGRAMS 330ERV ...
Page 33: ...www lifebreath com 32 17 WIRING DIAGRAMS 530ERV ...
Page 34: ...www lifebreath com 33 17 WIRING DIAGRAMS 730ERV AND 1230ERV ...
