Choosing an Extractor Fan

Published: 18th November 2011
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There is no room in the average household where it is more important to install an extractor fan than the bathroom. Preventing condensation build up, damp, mould and odour, a simple 4 inch model will help to keep your bathroom beautiful! The choice of bathroom extractor fan has never been greater, including those with timers, those with PIRs, those with humidistats, low voltage fans, low energy fans, slimline fans, and inline fans. This huge choice of extractor fan can be bewildering. The following article is intended as a guide to help the domestic buyer choose the right bathroom fan.

1. Wiring regulations and Bathroom Zones
2. Extractor Type
3. Size
4. Air Extraction Rate
5. Operation
6. Noise
7. Aesthetics

1. Wiring regulations

Since electric and water can make for a fatal combination, strict regulations were introduced dividing the bathroom into 4 zones: 0, 1, 2, 3. Zone 0 is in the bath. Zone 1 extends vertically 2.25m above the bath. Zone 2 extends in all directions for 0.6m from zone1 and zone 3 extends laterally for 2.4m from zone 2.

It is essential that you install the correct fan in the correct zone. Bathroom fans come in two voltages; Mains voltage (240v) and SELV or Safety Extra Low Voltage (12v). Mains voltage bathroom extractor fans may only be used in Zone 3 of the bathroom. In Zones 1 and 2 SELV bathroom fans (12 volt) ONLY must be used, with the transformer being housed in Zone 3. The only exception to this rule is the Airflow QuietAir: A mains voltage bathroom extractor fan that has been specifically designed with an IP45 rating to be used in all 3 zones. Inline fans are another special type of 240v bathroom extractor fan which are housed in the loft space above the bathroom in the middle of two lengths of ducting. Since the motor, impellars and all electrical parts are out of the zonal area, with only the duct and grille in the bathroom ceiling, they too are suitable for use in zone 1 or 2 above the bath or shower.

2. Types of bathroom extractor fan

There are two main types of bathroom extractor fan: Axial and Centrifugal. Axial fans are the ones that you are used to seeing on walls and ceilings and tend to have air extraction rates of between 85m3/hr and 95m3/hr on the 4 inch models. These are suitable for standard installations where the fan is intended to be ducted through the wall. Centrifugal fans tend to be (but not always) inline duct fans. (see previous section). Centrifugal fans are usually much more powerful than axial fans with air extraction rates of bewteen 110m3/hr and 220m3/hr on the 4 inch models. Centrifugal fans are particularly well suited to installations where long duct lengths are required. The Vent Axia Solo Plus, for example, can be used in duct runs up to 50m!

3. Sizes of bathroom fans

Domestic bathroom extractor fans come in two sizes: 4 inch /100mm and 6 inch / 150mm. In almost every case a 4 inch bathroom extractor fan will suffice. Six inch fans need only be considered in bathrooms greater than three metres squared, or where special circumstances require a more powerful fan,...such as bathrooms with no natural ventilation or particularly cold, north facing bathrooms.

4. Air Extraction Rate

Measured in 'Litres per Second' (L/s) or 'Metres Cubed per Hour' (m3/hr), the air extraction rate of a bathroom extractor fan 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 bathroom extractor fans far exceed this minimum requirement, and nowadays the standard is 85m3/hr. Any bathroom extractor fan with an extraction rate of 90m3/hr or above may be considered powerful.

5. Operation

Bathroom extractor fans have a range of operational features to suit different applications. The most simple is on/off via the bathroom light switch or integral pullcord. Bathroom fans with integral timers are great in bathrooms where large build ups of steam cause condensation problems, as the over run timer will keep the fan running for a desired period after it has been turned off....particularly useful if the fan is wired into the lighting circuit. Parents may prefer a bathroom fan with a PIR sensor which will operate the fan automatically when anybody enters the bathroom, whilst Landlords like those with humidity sensors, which switch on automatically when the relative humidity reaches a set level. This means that tenants are not relied upon to manually operate the bathroom fan.

6. Noise

Typical dB measurements for axial bathroom fans range between 35dB(A) and 45dB(A) with the more powerful centrifugal bathroom fans between 40dB(A) and 55dB(A). Whilst centrifugal fans are louder, it should be remembered that they are housed in the loft space and so are insulated and further away, lessesning the volume somewhat.

7. Aesthetics

Remember: you are likely to see this fan everytime 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 in 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 with unobtrusive and subtle 'tile' type designs which sit comfortably with any bathroom aesthetic.

More information on bathroom fans and extractor fans can be found at Gil-lec.

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