The roof fan is installed on the roof for air ventilation. Due to the particularity of the installation environment, the material and structure of the fan are determined. The roof fan is set to prevent the air from flowing backward after stopping. Because the fan rotates at a high speed under the action of hot pressure, the wind speed in the air cylinder increases a lot. The fan reversal is unfavorable to the starting of the motor and may be damaged due to excessive starting current.
Roof fans should be designed with reliable rain, snow and sand resistance. Wind and sand are not like rain, because snow and sand will not only enter the fan from the top, but also when the outdoor wind speed reaches a certain level. It is also possible to enter the fan from the bottom.