How To Choose An Extractor Fan
There are two basic models of the extractor fan.
The axial extractor fan is suitable for smaller rooms with less ducting, while centrifugal fans are used in rooms where the duct work can exceed 5 m or where higher rates of extraction is needed.
The formula for calculating the extraction rate is not difficult.
It is given as: the volume of the room x the number of air changes needed in each hr.
The designation is volume/ hr.
The typical number of air changes for bathroom would be 3-8, while that of a utility room would be up to 20.
In a typical bathroom where the dimensions are 3m x 3m x 2.
5m, the volume would be 22.
5, and the number of air room changes = 8.
The performance rated extraction rate would be calculated as 22.
5 x 8, which equals 180 m3/hr.
With this information, you can now choose a suitable extraction fan.
The rating on an axial fan with a diameter of 4 inches can range from 75m3/hr to 95m3/hr at the upper end of the range.
It is also extremely important to consider the level of noise generated by the fan, in addition to the extraction rate.
Although there is no rating for fan noise, good fans are virtually silent operating at no more than 25 decibels, which is almost inaudible.
The operation of the fan must also be considered.
There are several methods that can be used for turning the fan on and off.
The switch can be integrated with the operation of the lights, on a timer, a pull cord, with a humidistat that detects changes in the humidity or with Infrared sensors, that detects motion.
The method chosen, should suit our situation and needs of your lifestyle.
If for example you have a room that is exposed to a lot of heat and or sunlight, a fan integrated with a humidistat may be suitable as it can be preset to turn on -and off at predetermined levels.
In the UK there are special zone designations for bathrooms.
The zone determines the voltage of appliances used.
A Separated Extra Low Voltage is designated for use in zone 1, which cannot exceed 12V.
For zone 3, the standard mains can be applied.
The duct work is also critical for proper functioning of the extraction fan.
Bends and turns in the ducting should be kept to minimum, as they will increase the resistance, and undermine the operation of the fan.
You want a fan that also looks good, and the appearance and designs have changed dramatically over the last few years.
There are much more designs available to suit your decor, than just having horizontal or vertical grilles.
Fans that are integrated with humidistat, timers or pyroelectric sensors, will require three core and grounding cables, which includes both a permanent and live switch.
Power is always supplied to the fan, which is only operated when the switching mechanism is activated.
Wiring for new fans may be required a change to the newer cables.
The axial extractor fan is suitable for smaller rooms with less ducting, while centrifugal fans are used in rooms where the duct work can exceed 5 m or where higher rates of extraction is needed.
The formula for calculating the extraction rate is not difficult.
It is given as: the volume of the room x the number of air changes needed in each hr.
The designation is volume/ hr.
The typical number of air changes for bathroom would be 3-8, while that of a utility room would be up to 20.
In a typical bathroom where the dimensions are 3m x 3m x 2.
5m, the volume would be 22.
5, and the number of air room changes = 8.
The performance rated extraction rate would be calculated as 22.
5 x 8, which equals 180 m3/hr.
With this information, you can now choose a suitable extraction fan.
The rating on an axial fan with a diameter of 4 inches can range from 75m3/hr to 95m3/hr at the upper end of the range.
It is also extremely important to consider the level of noise generated by the fan, in addition to the extraction rate.
Although there is no rating for fan noise, good fans are virtually silent operating at no more than 25 decibels, which is almost inaudible.
The operation of the fan must also be considered.
There are several methods that can be used for turning the fan on and off.
The switch can be integrated with the operation of the lights, on a timer, a pull cord, with a humidistat that detects changes in the humidity or with Infrared sensors, that detects motion.
The method chosen, should suit our situation and needs of your lifestyle.
If for example you have a room that is exposed to a lot of heat and or sunlight, a fan integrated with a humidistat may be suitable as it can be preset to turn on -and off at predetermined levels.
In the UK there are special zone designations for bathrooms.
The zone determines the voltage of appliances used.
A Separated Extra Low Voltage is designated for use in zone 1, which cannot exceed 12V.
For zone 3, the standard mains can be applied.
The duct work is also critical for proper functioning of the extraction fan.
Bends and turns in the ducting should be kept to minimum, as they will increase the resistance, and undermine the operation of the fan.
You want a fan that also looks good, and the appearance and designs have changed dramatically over the last few years.
There are much more designs available to suit your decor, than just having horizontal or vertical grilles.
Fans that are integrated with humidistat, timers or pyroelectric sensors, will require three core and grounding cables, which includes both a permanent and live switch.
Power is always supplied to the fan, which is only operated when the switching mechanism is activated.
Wiring for new fans may be required a change to the newer cables.
