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Appendix F: Tables to correct Flow if range selected did not
match the installed range
If the range installed was different than the range selected on the gauge then the following tables can be
used to determine the correct flow, as long as the fan was blowing Away from the operator, which is
depressurizing from the inside or pressurizing from the outside.
The gauge converts the fan pressure to CFM based on the Range Configuration selected on the gauge. If
you realize that you have recorded results while the selected Range Configuration is different than what
was installed in the fan, look up the recorded flow on the Flow Conversion tables for the Device and read
across to the correct range column to determine what the result would have been if you have put the
gauge on the correct Range.
Use the Flow Conversion Chart for your fan to locate the correct results as follows:
In this example you were testing with a DU200 DucTester with “Range/Device” on the gauge set to “Mid”.
Later you remembered your DucTester actually had the Low Range Ring attached. You recorded 33 CFM.
Find the 33 CFM you recorded under the “Mid“column for Range on the Flow Conversion Table. Then, just
move over to read the correct result under the “Low” column for Range. In this case it will be 7.1 CFM.
Here is where to find those tables depending on the type of system you are using:
For Blower Doors see: Door Fan Operation Manual, Appendix D: Flow Conversion Tables
For DucTesters see: DucTester Operation & Testing Manual, Appendix C: Flow Tables
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