Retrotec Commercial 441 and 451 DucTester User Manual
Page 31
Page 31 of 56
©Retrotec Inc. 2015
1. Tape the Field Calibration Plate to the Flex Duct Flange, and attach the blue tube to the pressure
pickup (or into the small cut hole if using a homemade one).
2. Install Range 74 Flow Plug and set same Range on the Gauge.
3. Attach the Flex Duct to the outlet side of the fan to pressurize the Flex Duct. If depressurizing ducts
normally, you can also check the DucTester in that direction by attaching the flex to the inlet of the
fan where you must connect the green reference tube.
4. Stretch the Flex Duct to its full length. Set the “Mode” to “Flow”.
5. Set % Speed until 1 in WC (250 Pa) is reached. The flow should read 68 CFM (32 l/s)
6. Compare this value with the reading on the DucTester.
The calibrated fan and flex duct has now been checked as a system, removing that major source of
error.