Retrotec Commercial 441 and 451 DucTester - Manual (Page 13)

Page 13 of 56
©Retrotec Inc. 2015
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Figure 4: Retrotec Model 400 has a speed control knob and two Ethernet style Speed Control Ports for daisy chaining
speed controls for running many fans together. The yellow and green color coded tubing connections to the gauge are
shown.
The Model 400 has 4 Flow (Fan Pressure) sensors located inside the fan inlet, and 4 self-referencing
pickups located just above and below the fan inlet which are connected to the single green and yellow
ports. The End Plate is permanently taped on so you normally don’t get this view. The tape may be
removed for cleaning: is the long lasting tape that comes with your system to reinstall the End Plate.
Figure 5: Fan Pressure sensors are located in the fan inlet.
The 4 Flow sensors are located just inside the fan inlet, behind the protective grill. Together, they
measure the Fan Pressure, from which the fan airflow is calculated in the gauge. If the sensors become
blocked, it is possible to clear them by attaching a pressure tube to the yellow Ref B port, and blowing
air through the tube gently.
The exterior of the inlet has the 4 self-referencing pressure pickups. They are connected to the green
Input B port, and are used as the reference for the Flow (Fan Pressure) Sensors. Self-referencing
ensures that the measured pressure difference is always accurate, no matter what the direction of flow
is with respect to the location of the gauge and operator and whether or not a flex duct is attached to
the inlet of the fan or not.