Retrotec Blower Door - Manual (Page 46)

Page 46 of 87
©Retrotec Inc. 2015
5. Avoid Common Sources of Error
Some level of error is unavoidable in all Door Fan testing. However, there are a number of common mistakes that are
made that can lead to grossly inaccurate results.
5.1 Wrong Range Configuration or Device
Always make sure that the fan in use, and the Range Configuration that is installed on the fan, is correctly reflected
in the settings on the DM-2. Each device, and associated Range Configuration, has a specific calibration. Selecting
the incorrect device or Range Configuration will lead to incorrect calculations of airflow and other results.
5.2 No Reference Tube when Pressurizing
When pressurizing an enclosure, the fan is pushing air into the same enclosure in which it is located. It is important
to make sure that the fan is referencing the correct pressure.
The DM-2 is capable of self-correcting when the fan flow is towards the fan operator, however, fans with an
additional reference port must be connected properly, as the DM-2 will not apply the correction when those devices
are selected.
5.3 Incorrect @ Pressure usage
Forgetting that @ Pressure is on can lead to all results being taken at the same pressure. If the flow doesn't appear
to be changing when multiple points are being taken at different pressure, check that the @ Pressure function is
turned off. Also, if the measurements indicate that the enclosure is far tighter, or leakier than expected, the @
Pressure setting could be converting the results to a vastly different pressure than the desired test pressure.
It is not advisable to use the @ Pressure function when the fan cannot reach a pressure that is even close to the
desired pressure reading. This can lead to highly inaccurate results.
5.4 Choose the Appropriate Test Direction
Selecting a test direction is heavily dependent on the type of test being
conducted. Consult the specific test procedure to ensure the correct
direction is chosen.
All Retrotec fans include an arrow on the Fan Top or control panel to
indicate which way the airflow will travel. Use the airflow arrow to
determine if the fan is pointed in the correct direction. Buildings often
leak exactly the same in both directions but occasionally a small increase
in leakage of 5 to 10% may be apparent under pressurization since this
test direction can open up flaps over exhaust fans.
5.5 Minimize effects of upstream Air Flow conditions
The calibration for all Door Fans is sensitive to upstream air flow conditions (e.g. orientation of walls, doors, stairs
etc…, relative to the fan inlet). This is particularly true when measurements are taken using the Open Range
configuration. To minimize problems, follow these rules whenever possible:
1. Install the fan in a doorway leading to a large open room. Avoid installing the fan in a doorway where
stairways or other major obstructions to air flow are very close (1-5 feet) to the fan inlet.
Figure 29: Airflow direction arrow on the Fan Top.