Retrotec DucTester 200 Series Residential Applications - Manual (Page 26)

Page 26 of 91
©Retrotec Inc. 2015
8. Connect the Control Cable to the fan, unless you wish to use the Manual Speed Control
Knob. When the Control Status light is illuminated solid green, this means the fan is
connected to the gauge and is ready to perform automated testing. Having the Speed
Control Cable connected disables the manual Speed Control Knob. To enable the manual
Speed Control Knob, disconnect the yellow Speed Control Cable and turn the knob on, off
and on again.
9. Connect the yellow and green tubes on the fan.
10. Insert the blue tube into the duct system, typically through a supply register closest to the
air handler or into the supply plenum itself. Attaching a Static Pressure Probe to the blue
tube is mandatory when connecting to the plenum to avoid the effects of the moving air
(velocities) to be found there. While not necessary when connecting to registers since there
is almost no velocity there, it makes a handy method to pierce the tape and hold the blue
tube in place.
Figure 20: Insert the blue tube into a supply register closest to the air handler
11. If the rechargeable batteries in the DM-2 are below one quarter power, the battery charger
should be connected to the “DC Power” port on the DM-2. Charge them fully overnight.
12. To test control of the fan, press [Set Speed] [20] [Enter] on the DM-2. This sets the fan to
20% speed. The preferred method is using [Set Pressure] [25] [Enter] . (Some standards
require 50 Pa).
13. Press [Exit] to stop the fan.
3.7 Blue Tube location matters when testing leaky
ducts
When measuring extremely leaky duct systems (where the leakage is
over 500 CFM), the location of the test measurement point has a
significant influence on the measured results because the test pressure
induced in the duct system will vary throughout the system.
The highest leakage results will likely be measured when the blue tube
is put into the supply register that is furthest from the air handler.
Conversely, putting the blue tube into the main supply trunk line, or
supply plenum, will measure lower leakage results. Measuring with
the blue tube at the return ducting, where the DucTester is normally
attached, will show the lowest possible leakage results.
Figure 21: A Static Pressure Probe attached to a
pressure tube allows the measurement of
pressure without flow interference (e.g: inside a
supply register)