What determines whether the fan is suction or blowing?

The determination of whether a fan is operating in suction or blowing mode primarily hinges on the pitch and direction of the fan blades. When the blades of a fan are angled in a specific way, they can either pull air in (suction) or push air out (blowing).

In the case of a blowing fan, the blades are designed to push air forward, effectively creating a flow in the direction the fan is facing. Conversely, when positioned for suction, the blades are angled to draw air into the fan. This is a crucial principle in various applications, such as HVAC systems and cooling mechanisms, where the control of air movement is essential for efficient operation.

The other factors, such as engine speed, blade size, and the material from which the fan is constructed, may have roles in performance and efficiency, but they do not directly influence the fundamental action of whether the fan is designed for suction or blowing. Thus, the pitch and direction of the fan blades are critical in establishing the operational mode of the fan.