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Types of Duct Fans and Their Principle of Operation

2021-06-07 hqt

Today, the most popular way to ventilate rooms is to install a duct fan, the principle of which is to move air through the pipes of the ventilation system. This article will discuss what a duct fan is, where it is used and how it works.

Where are they used?

Duct fans are widely used due to their simple design, low noise level and long service life. Such units are installed in office and residential premises, as well as in shops, restaurants, cafes and large enterprises.

Principle of operation and device

The principle of operation of duct fans is as follows: air flows through the ventilation ducts pass through the fans built into these ducts.

The duct fan consists of a special impeller, which is located in the housing. The wheel is powered by an electric motor, which is also part of the product.

The design of the duct fan allows the device to operate in the temperature range from -15 to +30 degrees. The thermal protection technology built into each device is responsible for the correct operation of the fan, and also monitors its temperature and prevents overheating. The body of the device is made of galvanized steel, which not only provides the entire structure with resistance to corrosion but also allows the unit to withstand heavy loads. The body is connected using self-tapping screws and spot welding, after which the body is covered with protective paint in order to further protect the equipment.

Reviews: pros and cons

  • Owners of duct fans note the following advantages of such devices:
  • High efficiency - the channel type of the unit reduces the cost of its operation;
  • Versatility - you can mount a model of this type in any room;
  • Ease of installation;
  • Silent work;
  • Reliability and simplicity of design;
  • Continuity and continuity of work.

In addition, modern duct fans are equipped with the function of protecting the electric motor from voltage surges and other temperature / electrical changes, and some models are even equipped with a recuperator, which makes the use of the device more economical.

Types and technical characteristics


Circular duct fans (VKK) are used for installation in round ducts of ventilation systems of buildings for various purposes. The features of such devices are:

  • Galvanized body;
  • Anti-corrosion treatment;
  • Effective noise reduction.

VKK fans are equipped with single-phase asynchronous motors with an external rotor and backward-curved blades. Built-in thermal contacts with automatic restart function provide the fan motor with reliable overheating protection. In addition, it is possible to adjust the speed by adjusting the applied voltage.

Attention: Duct fans of VKK type are designed to move non-explosive gaseous media with temperatures from -40 to +60 degrees, containing aggressive impurities within 100 mg / m3 and not containing viscous substances, fibrous and abrasive materials, in moderate climatic conditions at ambient temperatures not higher than +40 degrees.


To organize effective ventilation of all rooms, a supply and exhaust ventilation system is installed, the main elements of which are duct supply fans. The devices are mounted directly into long ventilation ducts to provide additional air supply to the network.

As you know, any ventilation functions on the basis of the inflow of air masses on the one hand and the hood on the other. However, in more modern ventilation systems, a reversible duct fan is used, the main functions of which are the flow of air into the manned room and the removal of the exhaust air by adjusting the direction of movement of the rotor and impeller.


The main difference in the operation of duct fans from other fire-fighting systems is the ability to operate them as conventional drives for everyday climatic ventilation, which in turn puts forward special requirements for the motors of the devices, namely:

  • Noiselessness;
  • Profitability;
  • Sufficient resource of work;
  • Large calculated number of switching cycles.

In addition, the motors of duct smoke exhaust fans must be equipped with reliable protection against overheating and be mounted in a housing made of materials that do not deform or decompose when heated above +600 degrees. Despite the fact that the features of the duct ventilation system do not allow the engine casing to be heated to the temperature of the ventilated environment, the safety margin must correspond to certain parameters.

Attention: In fire conditions, the duct smoke exhaust fan must be able to work for an hour at a temperature of the removed working environment not lower than +600 degrees, since even the most efficient cooling system will not be able to significantly reduce its temperature.

The peculiarity of the impeller lies in the blowing of the flow of hot gases by the channel without direct interaction with the motor housing. In this case, the large diameter impeller sleeve helps to protect the motor housing from flow.

Heat resistant

The heat-resistant duct fan has a fairly wide range of applications and is used in both household and industrial premises.

The main objectives of installing such equipment are:

  • Effective removal of steam from baths / saunas;
  • Control of the movement of hot air masses in air exchange heating systems;
  • Full-fledged removal of heated air masses from the serviced premises with fireplaces and stoves installed in them;
  • Removal of combustion products from industrial premises.

Heat-resistant duct fans can be installed both in walls and in the ceiling (suspended or conventional). Fixation of products is carried out using special hangers and brackets. The output of the working environment can be carried out into a centralized duct system or directly to the street.

In addition, fans of this type must have two operating modes: with active steam generation, the device must operate in a low-power mode, and at the end of steam production, activate the maximum power mode.


As you know, any fan emits aerodynamic or mechanical noise during its operation. In the first case, the noise is created by the movement of air masses, and in the second - by the work and vibration of the electric motor.

Silent duct fans include models whose sound pressure does not exceed 25 dB, which makes it possible to install such equipment even in a residential area.

In order to make the silent duct fan even quieter, it is necessary to install a special muffler immediately behind its casing and finish the ventilation shaft with noise-absorbing material.

For round ducts

Round fans have a wide consumption, as they can be easily installed in air ducts of any size. They are the most popular option and are used both in residential and industrial premises.

For rectangular ducts

Rectangular duct fans are most often installed in ventilation shafts of manufacturing plants and warehouses. They can be mounted both wall-mounted and suspended. They are characterized by increased power.