3. Box C provides an indication of what the pressure of you system may be when the measurement is taken with a vane anemometer. Box B provides the actual likely pressure of the system which can be plotted on the  curve below to provide the installed performance. If the pressure in Box C is higher than the fan can develop then if it is near the fans stall point the airflows measured may vary greatly and cannot be relied upon. We would also note that these are the pressures likely if installed inline with the best practice above. Installation has a large impact on the pressures developed and as such can vary greatly. Click here for an example.

4. To define accurate system resistance, chose from one the following products