Choosing a Bathroom Extractor Fan

You have a brand new bathroom, and building regulations require you to install a bathroom extractor fan; but which one should you choose? You will soon discover that the possibilities are almost endless: to start with, should you buy an axial fan, a centrifugal fan, or even an inline fan? Do you need a low voltage fan? What size should you buy: 4, 6, 9 or even 12”? What features do you need in a bathroom extractor fan? Surely a fan is just a fan I hear you ask? If only it were that simple! Humidistats, motion sensors, timers, trickle functions and pullcords all come into play. Have you thought about the noise the fan will make, or whether it fits flush to the wall, or the colour & style?

In this first article we are just going to deal with the first point above, and look at the type of extractor fan you require. This will also help you to think about what other aspects of an extractor fan are important to you.

The most commonly sold domestic bathroom extractor fans are axial. These fans suck the air in at the front and discharge it out of the back. They tend to be smaller and quieter than centrifugal fans, but not as powerful. They are suitable to be installed in walls and windows (window kits are normally required in addition), but should generally only be installed onto ceilings when you have a very short duct run. A duct run is the ducting that runs from the back of the fan to the eventual external outlet for the air, i.e. the outside wall or roof. You can connect flexible or rigid ducting to the back of the fan, which leads to the outlet, on which you install a grille. Axial fans can be installed into exterior walls and windows because the air is going straight outside……when you install into a ceiling, the duct run tends to be longer, and axial fans as a general rule loose power when ducted over distances. The advantage of axial fans is that they tend to be smaller, use less energy, and are usually quieter than centrifugal fans.

Centrifugal fans work by spinning the air through 90° inside the fan to increase air pressure and create a higher airflow rate. This means they tend to have higher extraction rates than axial fans, and can be ducted over longer distances, so are more suitable for ceiling installations. However, this means they are usually bulkier, noisier and use more energy.

Inline fans can be either axial or centrifugal, and are housed in the loft space above the bathroom between 2 lengths of ducting. The advantages of these are that as the motor is housed up in the loft the sound is dampened by the ceiling, meaning they can be more powerful than wall mounted fans but not any noisier. Obviously not all installations, due to space restrictions are suitable for inline fans.

Hopefully this has got you thinking about the main features required in your fan. In future articles, I’ll be discussing the other points raised in this article.

Please see Bathroom Extractor Fans for more information.

Paul Blythe writes about extractor fans for Gil-lec Electrical Wholesalers and kindly asks that all backlinks are retained.

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