Choosing a Bathroom Extractor Fan
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Choosing a Bathroom Extractor Fan

Summary

We know that picking the right extractor fan for your bathroom or shower room can be tough. Therefore, we put together this complete guide to help you choose the best extractor fan for your chosen application. It can be quite difficult, especially due to the technical nature of extractor fans but don’t worry – we have done our best to ensure that this guide is very easy to digest.

What is an Extractor Fan?

It makes sense to first properly explain what an extractor fan is. A bathroom extraction fan is a ventilation device or appliance that is installed in bathrooms, shower rooms, toilets, washrooms etc, to expel airflow, moisture and odours. Their purpose is to ensure that your bathroom or toilet is constantly fresh and ventilated while also preventing the appearance of mould and damp.

Bathroom extractor fans extract upwards of 80m3/hr (cubic metres per hour) or 22.22l/s (litres per second),  usually using a 100mm (approximately 4 inches) Axial Impeller (the actual internal fan). Most fans on the market come in different switching modules: basic, pull-cord, over-run timer, humidistat (sometimes called humidity sensor), and occupancy sensor.

Types of Extractor Fan

For the sake of consumers’ convenience, fans are divided into three major types of extractor fans depending on their airflow mechanisms;

  • Axial fans
  • Centrifugal fans
  • Mixed Flow fans

Axial Fans

Axial fans are fans that extract the air and flow in an axis, parallel to its shaft rotates the blades. The pressure difference allows a flow of air through the fan. In domestic applications, the most commonly used fans utilise an axial impeller.

An example of an Axial Fan is the Airflow iCON 15 model.

Centrifugal Fans

As the name suggests, these fans make use of centrifugal force in order to expel airflow. The impeller’s rotation causes the air to circulate perpendicularly, which then moves toward the opening of the fan casing.

An example of a Centrifugal Fan is the Manrose CF100T model.

Mixed Flow Fans

Mixed flow fans, in a nutshell, combine features from both an axial fan and a centrifugal fan. The high volume flow aspect of the axial fans is combined with the pressure delivery system of the centrifugal fans to deliver a solid performance.

An example of a Mixed Flow Fan is the Manrose MF100T model.

Bathroom Zones and Extractor Fans

As you will likely know, water and electricity can make quite a lethal combo. Alongside the specific instructions published in the Wiring Regulations, bathroom zones are designed to keep installers or contractors of any kind safe from any potential dangers that could occur. This will therefore determine which fan you can install in which zone.

Electrical Bathroom Zones for Extractor Fans
  • Zone 1 refers to the area in the shower or vertically 2.25m above the bathtub.
  • Zone 2 refers to all directions from Zone 1 for 60cm (0.6 metres).
  • Zone 3 refers to 2.4m from zone 2, laterally.

Where to put your Extractor Fan

Zone 1 & 2

There are two extractor fan types that can be installed in both Zones 1 or 2;

Safety Extra Low Voltage (SELV) fans, which are sometimes called 12v fans or LV (Low Voltage) fans. These fans will require a transformer in order to reduce the mains voltage, from 240v down to 12v. Transformers are often provided with the extractor fan and will need to be housed either outside of the zones or in zone 3.

Any extractor fan with an IP45 rated motor. Any fan with a motor that has an ‘Ingress Protected‘ rating of IP45, confirms that the motor, and all electrical parts, are ‘resistant to jets of water from all angles‘. One great advantage of an IP45 rated fan is the cost. SELV fans are usually a bit more expensive – due to the extra cost of the transformer that’s required. In addition, the cost of the installation of a SELV fan is usually more expensive. This is because the fan and the transformer have to be installed separately.

Zone 3

As Zone 3 is deemed a safe distance from the main water sources (bath and shower), any extractor fan may be installed – regardless of its IP rating or voltage.

Inline fans can also be installed in Zone 3. Inline bathroom fans are usually installed in the loft space above the bathroom. A length of ducting will then link the fan to the bathroom. Since the fan itself is housed remotely and outside of these zones, they are also suitable for extracting air from any bathroom zone.

A number of fans, such as the Vent Axia Silhouette, Manrose XF range and Airflow Icon are available in both SELV and 240v versions.

Things to consider when choosing an extractor fan

Extraction Rate

The extraction rate of a fan is a very important thing to consider. This refers to the amount of air that is extracted and can be expressed in two ways:

  • l/s = Litres per Second
  • m3/hr = Metres cubed per Hour

Typically, the higher the extraction rate the more powerful the fan. This also means that it will also be noisier, more expensive and also more expensive to run, in terms of wattage.

But you may not require the most powerful fan, if you are trying to get an extractor fan for your small bathroom. It will all depend upon your application. The table below shows a rough guide of what the minimum requirement is on average for different applications, as seen in the Building Regulations – Ventilation: Approved Document F.

Keep in mind that this is the minimum required and will vary, depending on your unique requirements and circumstances. For example, if you have a larger bathroom then you will of course require a fan with a higher extraction rate. If however, you had a second bathroom that was not used very often, you would need to consider this.

Noise Level

Noise is also an important factor to consider. The noise level of extractor fans is measured in decibels (dB). In addition, any decibel figure mentioned was measured at 3 metres distance, indicated by “(A)” in product specifications or product listings.

As mentioned above, the higher the extraction rate, the more noisy the extractor fan will be, and this all comes down to personal preference. Some people don’t mind the noise too much where others might find it extremely annoying. Usually, for a fan to be found as quiet, it would need to be around or under 30dB(A).

With that said, when you think about it, we are rarely 3 metres away from the extractor fan and therefore it may be noisier than we expect when we finally install it and test it out. This is why it is important to read the product reviews carefully, as you can avoid making this mistake.

As well as picking a lower dB fan, some fans will naturally be quieter due to how they are installed. For example, inline fans are housed inside the area above the bathroom either in the loft or wall. As a result, less noise can get through.

Switching Modules

Switching modules refer to the modules or switches that activate the extractor fan. Most of the time we are used to them simply turning on when we turn on the light switch, but there are quite a few options available:

  • Basic models are activated by the light or remote switch.
  • Overrun Timer models keep the fan running for a set period after the light or remote switch is turned off. This will ensure all moisture has been extracted from the bathroom.
  • Humidistats, also known as Humidity Sensors, will turn on automatically when humidity in the bathroom reaches a pre-set level and similarly turn off when the humidity drops back down to its preset point. These are great in bathrooms where a fan is only required to extract steam. Landlords like these as they are quite efficient in that they only turn on at specific humidity, instead of every time the light is turned on.
  • While less common these days, Pullcord modules activate only the extractor fan.
  • Passive Infra-Red (PIR) sensors activate the fan automatically when someone enters the bathroom.

Going by the list above, you will be able to work out which one is suitable for your needs. Most of the time, the overrun timers or light/remote switches are chosen, mainly because they are more commonly available than some of the others. Some extractor fans come with their own module installed where for others you have to get them separately. For most Manrose fans, you will find the module number has a letter at the end, indicating T for Timer or H for Humidity Sensor, for example. The Airflow iCON range, for example, features snap-in functionality where you can plug and play your chosen modules. This has the benefit over those already a part of the fan because they are cheaper to repair.