Bathroom Extractor Fan Motor
Definition: A Bathroom Extractor Fan is a ventilation appliance used to expel moisture and odours from domestic bathrooms. Almost always utilising a 4 inch (100mm) Axial Impeller, they should extract an air volume between 80 - 95m3/hr (cubic metres per hour or 22.22 to 26.39L/s (Litres per second). Most models are available in 5 different switching options: basic, over run timer, humidistat, pull cord and occupancy sensor.
Choosing a Bathroom Extractor Fan
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Electricity and water make for a dangerous combination so the UK Electrical Wiring Regulations divide the bathroom into three zones relating to their proximity to water sources. This determines the type of fan you may install in each zone.
Let us first look at the zones:
- Zone 1 is in the shower or the area vertically 2.25m above the bath.
- Zone 2 extends in all directions for 0.6m (60cm) from Zone 1.
- Zone 3 extends laterally for a further 2.4m from zone 2.
Anything outside this area, or outside the bathroom - for example the loft above, is outside the zones.
So where can I put my extractor fan?
Zone 1 and Zone 2
There are only two types of fan which may be installed in Zones 1 and 2. They are:
- ALL SELV fans (Safety Extra Low Voltage). Also known as 12v fans or LV fans, they require a transformer, (housed in zone 3 or outside the zones) to reduce the mains voltage (240v) to 12v. Usually, but not always, the transformer is supplied with the fan.
- Any fan, regardless of voltage, that has an IP45 rated motor. 'IP' means 'Ingress Protected' and a rating of IP45 signifies that the motor, and indeed all electrical parts, are 'resistant to jets of water from all angles'.
The important advantage an IP45 rated fan has over a SELV fan is cost. SELV fans tend to be expensive because of the extra cost of the transformer. Furthermore, installing a SELV fan is a bigger, and thus usually more expensive job, due to the fact that two electrical components - the fan and the transformer - must be installed separately.
Any fan rated for zones 1 and 2, by default, may be installed in zone 3.
Zone 3 and Outside the Zones
- Any extractor fan, regardless of voltage or IP rating may be installed here as these areas are deemed a safe distance from the principle sources of water, the bath and shower.
- Inline fans are another type of extractor fan which are installed in the loft space above the bathroom. A length of ducting connects the fan to the bathroom. Since the fan itself is housed remotely,outside of the zonal area, with only a plastic grille in the bathroom ceiling, they too are suitable for extracting 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.
Remember: all electrical works must be carried out by a fully qualified, professional electrician.
Impeller Size and Air Extraction Rate
Domestic fans come in two sizes: 4 inch /100mm and 6 inch / 150mm. In almost every case a 4 inch model will suffice. Six inch fans need only be considered in bathrooms greater than nine metres squared, or where special circumstances require a more powerful fan, such as those with no natural ventilation or particularly cold, north facing rooms.
Bathrooms with very intense usage - for example in households with large families who all use the shower in the morning, or wet rooms may also benefit from a larger six inch fan.
Measured in 'Litres per Second' (L/s) or 'Metres Cubed per Hour' (m3/hr), the air extraction rate is one of the most important considerations. The Building Regulations stipulate that a bathroom extractor fan must extract at least 15L/s in a standard domestic bathroom. Most 4 inch models far exceed this minimum requirement, and nowadays the standard is 85m3/hr.
However, all other considerations being equal (noise, power, cost etc) we would always recommend installing the most powerful fan available. The Silent Tornado, for example extracts at 97m3/hr - the highest extraction rate for an axial fan. While the Turbo Tube Pro - an inline fan - extracts a magnificent 245m3/hr. At this flow rate, steam is extracted before it even condenses.
Switching and Operation Options
All fans maybe wired into the lighting circuit, so that they turn on and off with your lights, or a separate remote switch, allowing them to be operated independently. Further to that, extractor fans have a range of extra switching options which suit different applications and requirements. Many fans are available in three versions - Basic, Timer and Humidistat, but some ranges also have pull cord and PIR versions.
- Basic models are operated by the light or remote switch only.
- Timer models feature a timer which keeps the fan running for a set period after the light or remote switch is turned off. This ensures all steam has been extracted from the bathroom.
- Fans with Humidistats will turn on automatically when humidity in the bathroom reaches a pre-set level and off when the humidity falls back to its preset level. These are great in bathrooms where the lights (and fan) are not always turned on manually and are popular with landlords, or in those installations where a fan is only required to extract steam.
- Fans with integral Pullcord are rarer these days, but allow for local operation.
- PIR (Passive Infra Red) sensors operate the extractor fan automatically when somebody enters the room.
Noise and Aesthetics
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Noise
Typical dB measurements for axial bathroom extractor fans range between 35dB(A) and 45dB(A) with the more powerful centrifugal fans between 40dB(A) and 55dB(A). In recent years however the trend has moved towards even lower decibel levels. The Silent Tornado, for example, (pictured left) is whisper quiet at 24dB(A).
Please note that manufacturers' quoted decibel levels are taken 'at 3 metres' - This is the industry standard. Furthermore, these measurements are taken in test environments which may not necessarily replicate your installation. Also bear in mind that any fan activated during the night - by a call to nature for example - will sound louder than during the day.
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Aesthetics
Remember that you are likely to see this fan every time you use the bathroom. The money you saved on it when purchasing will soon be forgotten, so don't install an ugly fan just because it's cheap.
Homeowners are spending more on making their bathrooms beautiful with cool lighting and funky fixtures and fan designs have improved immensely. The old 'box with grilles' is slowly being replaced by chamfered louvre type designs which sit comfortably with any bathroom aesthetic.
However, the most unobtrusive extractor fan is of course the one that can't be seen! Pictured to the left is an 'inline' fan - so called because it sits in the middle of the duct run in the loft above the bathroom. One end is ducted to the outside world, the other is ducted to a discreet four inch grille which sits flush on the bathroom ceiling. The flush grille, therefore, is the only part of the whole extraction system that actually appears in the bathroom!
Two Bathroom Fans which cover 95% of all installations
We stock the highest-quality, and highest-specification fans in the industry. The following two fans cover 95% of all the bathroom installations we specify and supply.
Ordered Silent Tornado ST100T extractor for bathroom, arrived promptly and fitted today by electrician. Great fan, very quiet.
- Krichana Ghera, TrustPilot
Silent Tornado ST100 High Power 4 inch Axial Fan
| Power | Sound | Installation | Watts |
|---|---|---|---|
| 97m3/hr / 26L/s | 25 dB(A) | Can be installed in Zones 1, 2 and 3 | 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 4 inch 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.
PLUS Next Day Delivery on this product. You'll even get a one-hour delivery window so you'll know exactly when the item will arrive.
Order within 3 hours 45 mins for delivery by Tuesday, July 3rd
Excellent stats on the fans in question, very helpful when choosing the right fan for the job. I always use the website to determine the type and style of fan needed.
- Chris Keeble, Trustpilot
Vents Turbo Tube Pro Inline Duct Fan
| Power | Sound | Installation | Watts |
|---|---|---|---|
| 245m3/hr /68L/s | 32 dB(A) | Duct from Zones 1, 2 and 3 | 25w |
- Installed above the bathroom in the loft or ceiling void.
- With a whopping 245m3/hr extraction rate it's the most powerful 4 inch fan on the market.
- Mounted in the loft above the bathroom, this inline fan can be ducted from directly above the shower or bath.
- Using only 25w it's very energy efficient.
- Incredibly quiet, particularly so considering its power.
- Extracts steam before it condenses.
- No electrics, impeller or fan casing in the bathroom - just a discreet, flush, circular grille.
PLUS Next Day Delivery on this product. You'll even get a one-hour delivery window so you'll know exactly when the item will arrive.
Order within 3 hours 45 mins for delivery by Tuesday, July 3rd
Centrifugal extractor fans
In your research you may have come across the term 'centrifugal extractor fan'. This is a special type of fan which uses a totally different impeller design to generate higher exhaust air pressures. In simplified terms - the old/stale/moist air extracted from the room is pushed harder down the length of ducting to the outside world.
This is particularly useful in situations where the fan sits at the end of a long duct run, over 10 metres, for example in internal, basement or en suite bathrooms. Whilst centrifugal and axial fans use consistent impeller sizes such as four and six inch for domestic installations, centrifugal fans are larger than axial fans. They also tend to look 'boxy' as they necessarily sit proud of the wall in order to accommodate the much deeper impeller.
Intermittent Extraction v Continuous Ventilation
Despite changes in trend in recent years, intermittent extractor fans are still by far the most common type of air movement device. Intermittent extraction is the movement of air at specific times of need when air is polluted or full of water vapour - for example when someone is cooking or taking a shower. Crucially, the ventilation unit, either manually or automatically, switches on and off - it does not run all the time.
Continuous ventilation has become more popular in recent years as the Building Regulations - particularly Part F (Ventilation) - have demanded greater control over the air coming into and out of properties. Specifically, as buildings have become better insulated and more air tight, in the drive for more efficient energy usage, they suffer more often from lack of fresh air. Before double glazing and precision engineering natural drafts kept our buildings ventilated and in the absence of this natural air movement we have turned increasingly to Continuous Ventilation.
Mechanical Extract Ventilation - MEV
MEV refers to extract units which simply expel stale air (continuously). Operating at low flow rates of between 50m3/hr and 65m/hr MEV units keep air flowing through a room or building, acting rather like a small window. This is known as Trickle. Some MEV units can switch to a more powerful setting - up to 80m3/hr for example, at times of specific demand. This is known as Boost.
Mechanical Ventilation Heat Recovery
MVHR is increasingly popular and the ventilation industry is investing heavily in this technology. MVHR units use a heat exchanger to bring warm fresh air back into the building to replace the warm heated air that was expelled. MVHR systems were developed to solve the problem that continuous ventilation causes - lost heat and energy wastage. Currently they are more common as 'Whole House Ventilation' units, in which a central, usually rather large, unit with multiple duct points, extracts and replaces air from multiple rooms. However, as the sector grows we are seeing more 'Single Room Heat Recovery' units which look a lot more like traditional extractor fans.
See our experts' choice of extractor fans
Author: DJ Treblig
Publisher: EFW
Date First Published: 1st September 2016
Source: https://www.extractorfanworld.co.uk/choosing-a-bathroom-extractor-fan-123-c.asp
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