35
15.
To convert the flow pressure measurement into flow in cfm, use this formula:
cfm = √
P
⁄
14.5
x
MaxRangeValue (Optimal Range Setting)
Where:
•
cfm
= Flow rate in cubic feet per minute
• P
= The flow pressure value recorded
• 14.5
= Maximum pressure drop across the test orifice
•
MaxRangeValue
= The full-scale range value for your specific SF-1020i obtained in step 5.
This is the maximum flow capacity of the flowbench at 25 inH
2
0.
Example:
If the Full Scale Range Value for Range 10 on your SF-1020i = 1000 and you measured a Flow
Pressure of 14.0 in/H
2
O at 25 inH
2
O test pressure, then:
Maximum Capacity
= √
14.0
⁄
14.5
x
1000 = 982.6(cfm)
You can create a capacity curve by repeating the process for as many data points as desired in 5 inH
2
O
steps of test pressure. "Figure 6.4: Typical SF-1020i Flow Capacity" shows a typical capacity curve for an
SF-1020i at 6,000 feet elevation and at sea level.
For best accuracy, move down one range when the
flow pressure drops below 7.0 inH2O.
NOTICE
Figure 6.4: Typical SF-1020i Flow Capacity
6.0 Maintenance
