• Excessive vibration or noise

The main reasons include:

(1) The impeller and the air inlet are different axes.

(2) The air inlet is damaged.

(3) The impeller is bent or damaged.

(4) The shaft and bearing are loose.

(5) Loose between impeller and shaft.

(6) The pulley is not fixed properly.

(7) The belt is loose or too tight.

(8) The motor or fan base is not fixed properly.

• Ventilation reduction

The main reasons are as follows:

(1) The fan turns incorrectly.

(2) Impeller and inlet ring are different axes.

(3) The fan speed is too low.

(4) ventilation pipe resistance is too large.

(5) Insufficient throttle opening.

(6) The filter screen is too dirty.

• Excessive fan power

The main reasons include:

(1) The backward tilting impeller is installed backwards.

(2) The fan speed is too high.

(3) The pipeline resistance is too small (centrifugal).

(4) Excessive duct resistance (axial flow).

(5) The filter screen is missing.