The backward curved centrifugal fan design uses the centrifugal force generated by a rotating disk, with blades mounted at right angles to the disk, to impart movement to the air or gas and increase its pressure. The assembly of the hub, disk and blades is known as the fan wheel, and often includes other components with aerodynamic or structural functions. The centrifugal fan wheel is typically contained within a scroll-shaped fan housing.
Backward curved centrifugal fans have a smaller number of large blades which curve away from the direction of rotation. The air or gas inside the spinning fan is thrown off the outside of the wheel, to an outlet at the housing’s largest diameter. This simultaneously draws more air or gas into the wheel through the central hole.
Our supplier partner, Rosenberg, offer high speed operation and a robust construction which makes the backward curved fan suitable for applications with higher static pressure requirements, where a forward curved fan cannot be used. They are available in single and double inlet design or motorised impeller without a scroll, giving flexibility in designing your system. This construction and capability gives you more reliability and flexibility over a forward curved fan as if there are inconsistencies in the system pressure the fan will result in a greater first cost versus the forward curved fan, however, this cost is most often offset by the higher backward curved fan’s operating efficiency.
An attractive feature of the backward curved impeller is the non-overloading characteristic of its performance curve. Maximum power and minimum speed coincide at a point near the middle of the fan curve and as long as the motor is sized to operate at this point, the fan is said to have a non-overloading characteristic. This means that a motor selected to deliver at peak airflow will not overload, overheat or burnout, if there are variations in the flow due to ducting or dirty filters.
Rosenberg offer backward curved fans with AC and EC external rotor motors and standard motor formats. This means we are able to offer fans with high airflow and good pressure ranges. The energy-saving EC fans offer the advantage of constant airflow (ideal for filtered applications) and constant pressure (ideal for ducted applications). This gives the customer the flexibility to specify a fan to work at a set point and still have the room to add additional ducting, change out filters and not have to manually slow or speed up a fan.
A wide range of casing designs allow us to service an array of applications. We can supply the impeller only, a motorised impeller, a fan module (for applications such as fan walls or fan grids) or a fan module on skids / mounting stand (for larger fans and motors).