Extractor Fans: Axial, Centrifugal or Mixed Flow?

Extractor fans perform a very crucial function in the home. They facilitate the removal of fumes and stale air from rooms. Extractor fans may be set on a window or a wall and come in various forms. They vary according to size, low voltage and regulatory ability. Fans that need low voltage power are ideal for bathrooms.

Others have inbuilt mechanisms to switch on when certain levels of humidity are achieved in specific rooms. There are 3 types of extractor fans: axial, centrifugal and mixed flow. Although most extractor fans are affixed on windows and walls, the best location would be directly opposite the source of air.

Axial Extractor Fan

Axial extractor fans may be mounted on walls or ceiling boards, while others prefer to mount the extractor on windows. Those mounted on the wall facilitate the pumping out of condensed air through ducts connected to wall caps. The moist air is expelled into the atmosphere through the wall caps. Where ducts are used there is usually some resistance to air flow, which slows down the performance of the fan.

For the fan to function effectively the ducts must be straightened out and remain at uniform level. Also, ensure that you maintain uniform diameter between the fan opening, the ducts and wall cap. Failure to maintain consistency at any point leads to a significant loss of efficiency. Axial extractors have three classifications. Class C fans allow the adjustment of the blades as the fan is running, while Class A can only allow adjustment when the fan is not in operation. Class K fans do not allow the adjustment of blades. Axial extractor fans are the most common among the three listed above due to their low cost and compactness.

Centrifugal Extractor Fan

These are mounted on ceiling boards. They have similar abilities and characteristics to those of a centrifugal pump. They are stronger than axial fans and have the ability to operate at optimal levels, even where there is strong air pressure resistance from the ducts. Due to their strong capacities, they easily function in large bathrooms. Alternatively, one has the option of installing three units to cater for the shower, the toilet and the bathtub separately.

The centrifugal extractor fan also allows the installing of a system that has the ability to extract moist air from several rooms. The fan is durable and does not produce much noise during operation. Centrifugal extractor fans have three categories: straight steel plate paddle wheel, the forward multi-vatic and the backward turbo blade

Mixed Flow Extractor Fan

Mixed flow fans allow air to flow in axial and radial direction in relation to the shaft. These fans are widely used in kitchens and bathrooms. It is common to find them on duct systems, which are characterized by high pressure, good air flow and very little noise. These fans are mountable at the beginning, the middle and the end of the duct system. Installation of this type of fan is simple, and so is the removal.