Extractor Fan Specs

O.ERRE produce two major types of extractor fans, differing in power and method of installation.

AXIAL FLOW FANSaxial_flow_fan
These axial flow or helicoidal fans move large volumes of low pressure air. They are window or wall mounted when the duct is very short or direct to the outside.

These radial extractor fans move limited volumes of high pressure air through long centrifugal_extractor_fanducts, overcoming the resistance of bends, narrow areas, and internal irregularities. They are installed whenever the duct is not short and direct.

O.ERRE offers a choice from a wide and comprehensive range of extractor fans. When selecting an extractor fan, it is important that you select the model that will provide the correct number of air changes for corresponding intended use. By doing so, you will prevent excessive air extraction, which can lead to heat loss, whilst maintaining sufficient ventilation.

To work out the type and size of extractor fan required, make the following simple calculation

1. Calculate room volume in m3 by multiplying the room length (L) by it’s width (W) and height (H).
2. Calculate flow rate/hour by multiplying room volume in m3 by the suggested number of air changes per hour.
(Refer to Fig 1. below.)
3. Find the fan with the extraction capacity that is closest to this total. Refer to the ‘Technical Specifications’ section from page 8 onwards.


1. Room Size: 3m (L) x 3m (W) x 2.4m (H) = 21.6m3
2. Suggested Air Changes per hour: 15 – Multiply by Room Size: 15 x 21.6m3 = 324m3/hr
3. O.ERRE fan required: Ventilor 20/8 M or Ventilor 20/8 AR


Analysis Lab 7-8
Department Stores 7-8
Libraries 5
Rotisseries 20-30
Bakers 10-20
Dormitories 5
Living Rooms 5-6
Schools 5-7
Banks / Building Societies 5
Dressing Rooms 8-12
Medical Offices 2-4
Self Service 10-20
Bathrooms 6-10
Dry Cleaners 30-40
Medical Surgeries 6
Shops 12
Bedrooms 2-4
Factories 10
Motel / Hotel 10-15
Shower Baths 15-20
Body Shops 20-40
Foundry 20-30
Museums 5
Stables 8-15
Cafes 8-14
Galvanic Baths 25
Nightclubs 18
Stores / Warehouses 5-10
Canteens 6-10
Gymnasiums 8-15
Offices 5
Supermarkets 5-10
Car Parks 8
Hairdressers 10-15
Painting 25-40
Swimming Pools 7-8
Carpenters shops 10
Hospitals 5-10
Pet Shops 15-30
Tannery 10
Cellars 10
Household-Lounges 7-8
Pizza Restaurants 20-40
Toilets-Domestic 10-15
Cinemas 8
Household-Showers 15-20
Plants 4-10
Toilets-Public 10-15
Clinics 5
Kitchen-Domestic 15-20
Printers 10-15
Theatres 6-8
Conference Rooms 10
Kitchen-Restaurant 15-25
Pub Bars 8-14
Veterinary Surgeries 10
Copying Offices 12
Laundrettes 10-15
Repair Garages 10-15
Waiting Rooms 7-8
Craft Shops 6-15
Laundries-Underground 30-40
Restaurants 8-15
Woodworks 8

In addition to selecting the appropriate fan, it is also critical that the extractor fan be correctly sited. For an extractor fan to operate effectively and efficiently, the air that is extracted out must be replaced by another volume of air.

The three methods of extraction used are:

This is the most widely used method owing to its simplicity. The polluted air is not channeled into the adjacent rooms but carried outside by one or more extractor fans. Fresh air enters the rooms through cracks in the doors, windows and, if necessary, through appropriate air intakes covered with grills.

Grills are recommended when the room is airtight and powerful extractor fans are installed. It is better that air intakes and windows or doors that are often left open, are as far away as possible from the extractor fan, so that the incoming air does not immediately become outgoing air (and vice versa).

PRESSURE EXTRACTIONpressure_extraction
This fan lets new air go into the room by taking it from the outside and creating a higher pressure inside that forces the polluted air through the provided openings.

This system must see that the polluted air is carried outside and not into other rooms. Air currents are not created as the inside pressure is higher than that outside.

This guarantees greater ventilation, air emission and expulsion must be studied so as not to leave air pockets. The incoming air volume must be higher than the outgoing, so that the environment is slightly pressurized (15%).

Maintenance consists of periodically cleaning the impellers and all other parts in contact with the flow of air created by the extractor fan. Polluted air deposits grease and dust on the impeller and grill. This layer of dirt unbalances the impeller making the motor less efficient, putting it under excessive pressure and making it more noisy. Cleaning consists of removing the grease build-up with a damp sponge (not wet) and soap, after disconnecting the appliance and taking care not to wet and damage the electrical parts of the extractor fan.

It is better to have one or two grills to protect the extractor fan when it is not is operation. One outside, for manual or automatic operation, that does not allow air changes with the outside when the extractor fan is turned off. This grill is a part of the appliance and therefore should be obtained when purchasing. The outside grill is generally of the gravitational type. It protects the mechanism and circuits of the appliance against external atmospheric conditions, and prevents air changes when there is no internal grill.

To obtain the maximum performance out of your extractor fan, mount the fan as high as possible, but not directly, above a cooker hob or eye-level grill, in the shower cubicle, nor where temperatures exceed 40°C.

If there is an appliance in the room that uses solid, liquid or gas fuel (e.g. water heater, heater, boiler, etc.) that is not of the “balanced flue” type and that is airtight, sufficient air must be let into the room in order to ensure that the fuel appliance works properly and to compensate for the air extracted by the electric fan. The air taken in must not be let into existing ducts that are equipped to expel hot air when using ducted extractor fans. For example, combustion outlets of water and gas heaters.

NOTE: the appliance must expel the air through single outlets or directly outside.