Retrotec DucTester 200 Series Residential Applications - Manual (Page 73)

Page 73 of 91
©Retrotec Inc. 2015
Flow Conversion Table for Duct Test Pressures greater than 50 Pa
The preceding tables can be used for much higher back pressures. The fan pressure must be at least
50% of the back pressure or 25 Pa, whichever is greater. When using the gauge, this is taken care of
automatically. If you are taking manual readings you must control this yourself or use the calculation
spreadsheet that Retrotec can provide.
Example: your Model 200 is blowing into 200 Pa on Mid Range which has a K2 value of 0.5 meaning the
Fan Pressure must be at least 0.5 x 200 = 100 Pa. Simply read directly off the chart as long as your Fan
Pressure is greater than 100 Pa.
For the Low Range for example, there is back pressure compensation in the flow formula that makes
these readings more difficult but if this is ignored, the results will still be within 6%. Use the gauge or
calculation spreadsheet or formulae to get the correct result.
When testing at high back pressures, over 200 Pa, this limitation on the minimum fan pressure will
reduce the width of each flow range meaning for some flow rates, you will not be able to get a reading.
These gaps between ranges are a limitation of the Model 200 which is not as apparent in the Model 300
that has many more ranges.
Whenever testing over 250 Pa, we recommend using the new Model 451 that will test up to 2500 Pa
with up to 260 CFM of flow, or even 5000 Pa at 100 CFM of flow.