Retrotec Multi-Fan Blower Door - Manual (Page 4)

Page 4 of 37
©Retrotec Inc. 2015
1. When do you need more than one fan?
Multiple fans are required for testing an enclosure when the maximum flow generated by the power of
one fan (running at 100% Speed with Open Range) is not enough to reach the desired test pressure. For
example, you try to pressurize an enclosure to a target pressure of 75 Pa but even when the fan is
running at 100% Speed with Open Range, you can only reach a pressure of 25 Pa. This problem occurs
because there is too much leakage in the building to reach the target pressure. In this case, you will
need additional fans.
A large enclosure area (greater than 10,000 cu ft) usually suggests a large amount of leakage, and you
should investigate how many fans you’ll need.
1.1 Maximum flow capacity of Retrotec fans
The maximum flows generated by Door Fans depend on which Range Configuration the fan has installed
– a Range with a larger opening produces a higher maximum flow. They also depend on the induced
pressures generated in the enclosure, known as the “backpressure” imposed on the fan – if the
enclosure is being pressurized to a positive pressure, the higher the backpressure, the lower the flow
capacity. The voltage/frequency of the fan’s motor also affects the flow rate. Figure 1 illustrates the
flow capacities of DU200, and 1000, 2000, and 3000 series Retrotec fans, at 50 Pa back pressure, with
various Range Configurations:
Figure 1: Minimum and Maximum Fan Flow Rates per Installed Range