Centrifugal Fan

An axial fan is located at the end of a vent and pushes the air through itself and out into the ducting. Most family wall fans use an axial impellar and are ideal for bathrooms, toilets and littler rooms where the moving air is to be ducted directly through the wall or installed in a window.

Axial fans are not capable of pushing air through particularly long vents. If a pipework is particulalry extensive or twisty, this will increase the air pressure present in the ducting and will mean a fan other than an axial fan will be reqiured. If the ducting is less than 5m, make sure it is is as straight as possible as too many twists and turns will decrease it's efficiency and may cause it to not work. If you are not able to use an axial fan due to the length or complexity of the pipe work, a centrifugal fan should be used.

In a centrifugal fan, centrifugal force is used to propel the air down the ducting at high pressures. The air enters the fan where the shaft is and is moved from the vent to the fan shell when the impeller rotates.

When you need move air through ducting that is more than 5 metres long, a centrifugal fan would be used. In fact it is general for a standard centrifugal fan to be employed in situations where the installtion is up to 50 meters long.

There are two main types of centrifugal fan, inline duct fans and wall mounted fans. Visually, a standard wall mounted type will look almost identical to a wall mounted axial fan. When shopping for a fan, because of the similar look between the two, it might be problematic to tell the difference between the two, you will usually find it will be stated on the packaging.

If you have a room near the centre of your property, this is the most likely place you will need to put in a wall mounted fan. Such rooms do not have windows or any natural ventilation and these situation normally need a long duct run to reach the outside of the house. One of the most widespread problems experienced with extractor fans is when the wrong type of fan is used in this situation. Sadly, an axial fan is unable to create the air pressure necesarry here.

Inline extractor fans, as the name suggests are located in the length of ducting. Because of this fundemental difference, the look and style of these fans are very different from their wall mounted counter parts as they are not designed to be set in the room requiring extraction. Ducting will run from one end of the fan to a roof grill in the extraction zone and from the exhaust end of the fan to the exterior grill. Inline fans are fantastic for use above bathrooms or kitchens where extra extraction power is vital.