Retrotec Commercial 441 and 451 DucTester - Manual (Page 22)

Page 22 of 56
©Retrotec Inc. 2015
Setting up for pressurization
The advantage of pressurizing is that it makes
changing Range Rings on the fan easier so always
test in this direction first. Simply install the Flex
Duct on the outlet side of the Blower. Wiggle the
fitting inside the rubber collar on the Blower
Housing.
Setting up for depressurization
Install Range 47, since most systems can be tested on this Range Configuration. For more information
about selecting and changing Range Configurations, refer to section xx. Install the Flex Duct over the fan
inlet, covering the Range Rings and tighten the strap.
Figure 12: Install Flex Duct over the fan inlet, covering the Range Rings, for depressurization. Later systems had a 2.5 inch
connector instead of the 4 inch shown.
5.3.2. Install Range Configuration on fan
Each Retrotec Model 400 Blower includes three Range Configurations to maximize accuracy and
versatility: Range 74, 47, 29 and 18 as standard. The selected Range Configuration will determine the
range of air flow that the DucTester can measure. While it is easy to change the Range Configuration
when pressurizing, it is better to make your best guess at the correct Range Configuration when testing
in the depressurization direction since the Flex Duct Adapter must be removed to change Range
Configurations. The Flow Plugs must always go on the inlet of the fan.
Use a Range with a larger opening for leakier ducts and smaller opening for tighter ducts. Testing should
always be done at the highest possible fan speed, which means using the most restrictive Range
Configuration possible (the one with the smallest hole possible). Higher fan speeds lead to the highest
degree of accuracy. If the fan is running too slowly, “-----“will appear on the DM32 gauge display
indicating you must change to a more restrictive range.