Retrotec Commercial 441 and 451 DucTester - Manual (Page 11)

Page 11 of 56
©Retrotec Inc. 2015
stable in both the pressurization and depressurization test directions, where it offers equivalent
accuracy in both directions.
A Flow Conditioner is not needed with Retrotec fans for depressurization testing. Some duct testing
fans require a flow conditioner when depressurizing a duct system, in order to get correct readings. The
Retrotec DucTester does not require a flow conditioner because it uses a flow nozzle, which is
intrinsically stable in either direction because the flow gets compressed as it goes through the nozzle.
All Retrotec models comply with ASTM E1554-07, ANSI/ASHRAE 152, ASTM E779-10, EN 13829, ATTMA
TS-1, CGSB 149.10, ASME and RESNET standards.
3.1.1. Range Configurations
Open cannot be used for
ducts
74 47 29 18 11 7 3
Figure 3: Range 74 is for the leakiest ducts while the smaller ranges are for progressively tighter ducts.
All Retrotec calibrated fans have multiple Range Configurations in order to measure a wide range of air
leakage flow rates. Select the correct Range Configuration by running the fan speed up to ensure it is
running at over 50% speed and the gauge is giving a flow result. If not change to a lower range and
repeat.
A calibrated fan measures flow by measuring the pressure developed inside the fan, which is often
called Fan Pressure. As the fan speeds up, a suction pressure develops at the inlet of the fan that causes
air to flow. By measuring this Fan Pressure, airflow is calculated using flow equations that are inside the
Retrotec gauge and FanTestic software.
When the fan slows down, the Fan Pressure can become too small to accurately measure flow. To
increase the Fan Pressure, a restriction plate is placed in front of the fan. The fan, consequently, has to
turn faster to maintain the same room or duct pressure, which creates a larger, more accurate Fan
Pressure. By providing a set of flow restricting plates with calibrated holes, Retrotec DucTester fans can
measure flows from 0.01 to 1400 m
3 /h.
The Model 450 has 4 standard Range Configurations: 74, 47, 29, 18. The numbered Ranges are 100 mm
Plugs that snap into the End Plate 300 and will restrict the flow to allow you to measure lower flow
rates. The numbers refer to the approximate hole diameter in millimeters. Most ducts can be tested
using Range 47.