Appendix B
Calibration and Measurement Accuracy
8
The
ENERGY
CONSERVATORY
DIAGNOSTIC TOOLS TO MEASURE BUILDING PERFORMANCE
Appendix B Calibration and Measurement Accuracy
B.1 Exhaust Fan Flow Metering Box Calibration Formula
Door Opening
Formula
E1
Flow (CFM) = 43.73 x (Metering Box Pressure in Pascals)
0.5
E2
Flow (CFM) = 20.72 x (Metering Box Pressure in Pascals)
0.5
E3
Flow (CFM) = 10.07 x (Metering Box Pressure in Pascals)
0.5
B.2 Specifications
Flow Accuracy:
+/- 10% when used with a 1% pressure gauge (DG-700, DG-3 or DG-2).
Flow Range: *
System Weight:
4 lbs. including the extension pole.
Dimensions:
Inside opening (13” x 16” x 8” deep).
* The upper flow range limit of 124 CFM is based on the assumption that back pressures greater than
8.0 Pascals will start to restrict air flow through typical residential exhaust fans. The Metering Box will accurately
measure flows above 124 CFM, however the measured flow may be less than the actual flow through the exhaust
fan under normal operating conditions. Referring to the manufacturer's published fan curve for the exhaust fan being
tested will allow you to estimate how much the back pressure added by the Metering Box has reduced the air flow
through the exhaust fan.
Door Position
Flow Range (CFM)
E1
44 -124
E2
21 - 59
E3
10 - 28