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© Retrotec 2017
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Be careful that no one steps on the tubes, or creates a kink in any of the lines while performing a
test. If this happens, wait a few seconds for the effects to subside before taking any readings from
the gauge.
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Use the metal tube provided with the gauge to pass tubes through tight spaces (such as under
closed doors) to prevent pinching.
8.13
Check if large fixed errors are caused by water in the tube
Water can also cause significant errors if a drop is pulled into the pressure tubes. It is very easy to get a
water drop inside the end of a tube. Simply drag it over a shallow puddle of water, and a drop of water will
get pulled into the tube by capillary action. Notice in the Figure 69 how one drop of water in the end of the
tube is creating 190 Pascal pressure. It is possible to complete a Blower Door test with a water drop in the
end of the tube. It will appear as if the fan is creating a pressure in the building, but in fact the results are
way off. Particularly unusual behavior in the gauge could mean that there is water in the end of the tube.
Water can cause either a positive or a negative pressure, based on which way the drop of water is pulling.
If a drop of water is facing downward, it pulls out of the tube, creating a negative pressure (as displayed in
Figure 69). Point the tube upward, and the water drop falls back into the tube, creating a positive pressure.
Figure 69: Water in the reference tube (left); high fixed pressure due to water (right).
To fix this problem:
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Whip the end of the tube around to remove excess water.
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If this doesn’t work (in extreme cases), water can be blown out from the other end. Be sure to not
have the gauge connected when blowing water from the tube.
8.14
Check if large fixed errors are caused by sun heating the tubes
If air inside the exterior heats up due to the Sun shining on it and if the tube end is above or below the
point where it leaves the enclosure, a stack pressure will build up inside the tube that will create a steady
pressure that may increase as the tube gets hotter.
8.15
Check if wind is causing fluctuating pressure
Wind blowing across the tip of a tube can cause significant error, even if the tube is not moving. High
fluctuations of bias (baseline) pressures on the gauge (greater than 2 Pa) are a good indication that wind
may be a large source of error.
