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Home > Help > Axial Fans v Centrifugal Fans

Axial Fans v Centrifugal Fans

Should I use an axial fan or centrifugal fan?

Axial Fans

An axial fan is one in which the extracted air is pulled through the impeller, parallel to the shaft around which the blades rotate. Most domestic wall fans use an axial impellar and are ideal for bathrooms, toilets and smaller rooms where the fan is to be ducted straight through the wall or installed in a window.

Domestic axial fan impellars are usually four inch, or six inch for bigger rooms. However, in commercial situations, axial fans can be as big as nine or even twelve inch. Axial fans can be either mains (240v) or low voltage (12v) and are usually available with different switching options such as 'pullcord', 'timer', 'humidistat' or 'occupancy sensor'.

A cheap four inch axial fan will extract 70m3/hr or less, but the really good (4") axial fans extract between 90 - 95m3/hr. This is currently the technological ceiling for axial fans. Our most popular, (and we think best) axial extractor fan, is the Silent Tornado ST100: 
Silent Tornado ST100 - High Power 4 inch Axial Fan
Airflow Quiet Extractor Fan Vital Statistics: 97m3/hr / 26L/s : 25db(A) : 7.5w

- IP45 rated motor, so the fan can be installed in any zone in the bathroom without the need for a separate transformer.
- Most powerful 4inch axial fan on the market @ 97m3/hr 
- Low energy. On full power it uses only 7.5w! 
- Virtually silent. 25db(A)
- The best 4 inch axial fan we have ever tested. Click on the 'view item' buttons on the right to see the full specification and read our review.
Standard Model: ST100B
£41.40
Timer Model: ST100T
£48.60
Humidistat Model: ST100HT
£85.20
Pull Cord Model: ST100PC
£47.22
PIR Model: ST100PR
£90.00

Centrifugal Fans 

Centrifugal fans extract air at right angles to the intake of the fan, and spin the air outwards to the outlet by deflection and centrifugal force. The impeller rotates, causing air to enter the fan near the shaft and move perpendicularly from the shaft to the opening in the fan casing.
 
This allows the fan to produce more pressure for a given air volume, and is thus able to 'push' the extracted air along much longer duct runs. Indeed, such is their efficiency that some centrifugal fans, such as the Vent Axia Solo can be used in a duct run up to 50m! 

The wall mounted centrifugal fan looks just like a standard axial fan. Since the impellar is hidden by the front grille and casing it can be hard to differentiate the two but the price will usually give it away : Centrifugal wall fans are usually more expensive than axial fans.
 
Centrifugal fans are often seen in rooms which do not have exterior walls. Such rooms do not have windows or any natural ventilation and these circumstances usually require a long duct run to reach the outside of the building. Our two most popular wall mounted centrifugal fans are the Manrose CF200, a 240v fan, and the Vent Axia Solo Plus 12v fan, for installation in zone 1 or 2 of the bathroom.
 
240v Manrose CF200 Centrifugal Fan
Vent Axia Solo Extractor Fan Vital Statistics: 100 m3/hr / 31 L/s Noise: 45dB(A) : 17w

The CF200 range incorporates the latest technology and design in a powerful but very quiet centrifugal fan. This new range is fitted with a backward curved centrifugal impeller for a large airflow against the high pressures caused by longer lengths of ducting and resistance by grilles. 
Timer Version
£32.50
Humidistat Version
£85.68
PIR Version
£90.23

12v Vent Axia Solo - Centrifugal Fan for Long Duct Runs
Vent Axia Solo Extractor Fan Vital Statistics: 90 m3/hr / 25 L/s Noise: 42dB(A) : 21w

This centrifugal fan is great for longer duct runs up to 50m. Whilst it looks like a large bulky unit, it can in fact be recessed into the ceiling or wall, leaving only the front fascia visible. The Solo has washable filters.

The Solo also features a 'trickle function' which draws air even when not in use, at 25m3/hr - Great for bathrooms with poor natural ventilation.
Timer Version
£134.58
Humidistat Version
£202.06

 

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