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Ceiling Sweep Fans

Extractor Fan Guide

Choosing the right fan

The choice of wall, ceiling or window fixing is available to suit your application. Decide the fixing you require which will determine the ducting length and therefore the choice between an axail or centrifugal fan.

Example
Air changes per hour (ACH)

Where to site your fan
Incorrect siting of an extractor fan can severely impair it's efficiency.

It is therefore important that the fan is correctly sited using the following principles:

To ensure maximum airflow through the whole room, mount in the window, wall or ceiling furthest from the air inlet point and at high level
Do not position a fan where temperatures ate likely to exceed 40°C (for example above a cooker hob or eye level grill)
When installing in a room with an open fire or stove without a balanced flue, ensure that there is sufficient replacement air to prevent the fan drawing air back down the flue.
A 230 volt fan installed in a bathroom must not be within reach of a person using the bat or shower.
Always use an Induct or Low Voltage Fan (SELV) to ventilate a shower cubicle.
As it is potentially dangerous to install even a splashproof electrical appliance close to a shower head, Silavent recommends an Induct fan or Low Voltage Fan (SELV) for this application.

Many fluorescent lamps emit power pulses (spikes) when turned on and off. Some of these pulses can be substantial (in excess of 2KV)

Silavent products are tested to accept the occasional high voltage pulse as part of standards requirements but these are taken as exceptional circumstances and not as an operational norm.

Repeated high voltage pulses can cause premature ageing of electronics and in some circumstances actually destroy components.

If a specification requires fans fitted with electronic controls to be installed in conjunction with fluorescent lamps we recommend that a power filter (ANC 811A) be fitted to the fan power supply. Fan without electronics are unaffected by fluorescent lamps.

The above apples to all extractor fans known to us that are currently available.

There are two basic fan types to choose from:

Axial
These fans are designed to move air over short distances only, and are therefore suitable for window fixing or "through the wall" applications. They are not suitable for ducting runs in excess of 2 metres or in an exposed or high rise position where wind can create extra resistance. If in doubt fir a centrifugal type.

Centrifugal
These fans are designed to move air over longer distances, and will perform well against the resistance presented by longer lengths of ducting. Traditionally fitted with higher specification motors, they also provide longer life.

Performance

to calculate the performance required you need to establish the following:
Situation Changes Situation Changes
Bakeries 20-30 Meeting rooms 4-8
Bathrooms & shower rooms 3-8 Offices 6-8
Bedrooms 2-4 Restaurants & Bars 6-10
Cafeterias 10-12 School rooms 2-3
Canteens 8-12 Shops 8-10
Cellars 3-10 Sports facilities 6-8
Changing Rooms with showers 15-20 Store rooms 3-6
Conference rooms 8-12 Toilets-domestic 3-10
Garages 6-8 Toilets-public 10-15
Glasshouses 25-50 Utility rooms 15-20
Hairdressing Salons 10-15 Workshops 6-10
Halls & Landings 3-5 Hospital rooms 4-6
Kitchens-domestic 10-15

Use the higher figures incrowded conditions or where heat, fumes, odours or moisture are prevalent.

Kitchens – commercial 15-20
Laundries & Launderettes 10-15
Living & Other domestic rooms 3-6


Room volume:
(Multiply length x width x height)

Number of air changes requires:
(See table below)

Performance required:
(Room volume x number of air changes)

Then check this exceeds the minimum requirements of the Building Regulations . Note: In certain circumstances more than one fan will be required.

Example:
Room Domestic Kitchen
Volume (size) 3 x 3 x 2½ = 22 ½m³
Air changes/hr 10
Performance 22½ x 10 = 225m³/h
Fixing ceiling
Fan Type centrifugal
Fan required 225m³/h – kitchenaire 2000

Ceiling Sweep Fans