Retrotec Blower Door - Manual (Page 41)

Page 41 of 87
©Retrotec Inc. 2015
1. Determine the highest test pressure you will require during the test, for example 70 Pa. With the fan blowing
away from you to depressurize while you are inside the building, increase fan speed using Set Speed or the control
knob so pressure on Channel A rises above 70 Pa but not above 80 Pa. If you cannot reach the desired target
pressure (70 Pa in this example), change to a more open range to get more flow. Getting more flow means the open
area of the fan inlet must be increased so you are not looking for a higher Fan Pressure but a more open fan. If you
can easily achieve 70 Pa, try a less open range that will give less air flow and try again.
2. Determine the lowest test pressure you will require during the test, for example, 15 Pa. Leaving the fan as it was
at the end of the previous step, running and achieving the maximum pressure with the most restrictive possible
range, decrease fan speed using Set Speed or the control knob so pressure on Channel A falls to just below 15 Pa.
There will be times you cannot reach the lowest target pressure (15 Pa in this example). Either you cannot run the
fan slowly enough (reach 0% speed before the target pressure reaches 15 Pa), or the flow on Channel B will not
show a value (not enough fan pressure is being developed). In either case, you need to change to a more restrictive
range to develop more fan pressure. Since you already determined the smallest range that will let you reach the
maximum target pressure (in step 1), you now know that you will have to change range once during your data
collection.
4.13.4. Measure the Baseline (Zero Flow) Pressure before the test
Commonly, test procedures require that the pre-existing pressure across the building be measured. That value is
subtracted from the test pressure to uncover how much change occurred in the building pressure due to Test Fan
operation. Baseline is sometimes called Bias Pressure or Zero Flow Pressure or even Static Pressure but we will
primarily use “Baseline” here.
Note that there are two main components of Baseline: one is caused by stack pressures and the other by wind.
Stack is a building phenomenon which produces a steady pressure and is simply subtracted from the test pressure.
Wind may also cause some steady pressure which can be subtracted. However, wind generally also causes a
pressure that fluctuates over time. This fluctuation will distort the induced (applied) pressure difference when the
Blower Door is collecting data unless the measurement period is long enough to reduce the effect of the
fluctuations.
The length of time the Baseline must be taken varies from Standard to Standard but mostly is not specified exactly
which is why this guidance is being provided. EN13829 states “over a period of at least 30 seconds” but does not
state the required number of test points.
Recommended procedure to take the pre-test Baseline:
When manually entering data into FanTestic, set the Time Averaging on the gauge to 5 seconds for Baseline
readings. Start at 5 second averaging for manual readings since it will take you at least this long to write them down
anyway. There is a Baseline feature on the gauge but do not use it for this purpose since it was designed for single
point readings.
4.13.5. Measure each of the target points required for the test
Use either the fan speed control knob, the gauge Set Speed control, or the gauge Set Pressure control to capture
data for each of the target induced pressure points you need for the test.
When manually entering data into FanTestic, set the time averaging on the gauge to at least 20 seconds for induced
pressure and flow readings. This must be done in order to compensate for the effects of wind and to ensure that
you get an average reading. On windy days you will have to take readings for a longer period of time. To determine
if it is windy, set your gauge to 5 second averaging and check if the pressure fluctuation is above 2 Pa. If so, double
the time averaging for the induced pressure and flow readings to 40 seconds.