Retrotec DM-2A Manual de usuario descargar pdf (Pagina 50)

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©Retrotec Inc. 2012

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 13 how one drop of water in the

end of the tube is creating 190 Pascal pressure. It is possible to complete a Door Fan 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.

 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 DM-2.

 Whip the end of the tube around to remove excess water. 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. 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 13). Point the tube upward, and the water

drop falls back into the tube, creating a positive pressure.

Figure 13. Water in the reference tube (left); high fixed pressure due to water (right).

7.7 Wrong Flow Range or Device selected

If the results just don't make sense, check to make sure the correct Flow Range and device are

selected. Each Device and Flow Range configuration has its own individual flow curve that is used to

convert fan pressure into flow, and into the results selected under the Mode menu. If a test is

completed with the incorrect Device and/or Flow Range selected, it is possible to salvage the data by

using the customized flow charts provided in Appendix A.

To determine correct flow if wrong Flow Range/device was selected:

1. Select the fan pressure for which a corrected flow value is needed.

2. Find this fan pressure value in the left column of the flow conversion tables in Appendix A.

3. Move across the row and record the flow value beneath the column heading with the actual

Flow Range that was used.

Note: Retrotec 2000 and 3000 series fans have the same flow curves.

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Retrotec DM-2A Manual de usuario Pagina 50