Duct fans for round air ducts: features and operation

Forced air extraction may be necessary in many cases. This is relevant when it comes to rooms in which it is necessary to create a certain microclimate or are characterized by high humidity, and for this purpose special exhaust fans are used. There are many varieties of them, but one of the most popular are duct fans for round air ducts.

Features and varieties of duct domestic fans and industrial models

A duct or direct-flow fan differs from other variants of devices for forced air circulation in that the fan itself and the electric motor for rotating it are located in the same housing. In addition, this system is mounted directly into the air vent, which greatly improves its efficiency. Duct fans 250 mm and other types can differ in the material of which the case is made, in the principle of operation and a number of other characteristics.

The following types of fans are distinguished by shape:

1. Round - mounted in round ventilation shafts. They are the most popular option, they are often used not only in residential, but also in industrial premises.
2. Rectangular - most often they are installed in rectangular ventilation shafts in warehouses and manufacturing plants. Such models are characterized by increased work power.
3. Square - also commonly used for industrial purposes, they are mounted in square ducts.

Also, there are axial and radial or centrifugal devices. The technical characteristics of axial industrial fans and household models differ from radial ones in that they consume less energy due to their design features. In an axial exhaust fan, air masses move along the axis, so the air resistance during operation of the device is quite small.

It is worth buying a radial fan if you need to maintain a microclimate in a room with a large area. This type of drafting device differs from the axial one in that its blades have a spiral shape.Due to this design, the outgoing air flow is directed perpendicular to the incoming one. In addition, radial fans have more air intake power than axial fans, so they are more profitable to use in warehouses and industrial premises.

Duct fan casing 200 mm and other sizes can be made of plastic or metal. The first option is designed for a small volume of air, so it is better to use it to organize ventilation in an apartment. The steel case is perfectly suited to work at high power, so the fan in it will be effective for use in industrial premises. In addition, the price of a radial fan in a plastic case will be much lower than in a metal one.

Selection parameters for inline centrifugal fans and axial models

When choosing a device for air extraction, you must pay attention to its following characteristics.

Maximum air flow - the higher this indicator, the more air volume the fan draws from the room for a certain period of time. Accordingly, if the device is needed to serve a large area, then the maximum volume of air flow should be as high as possible. For a domestic fan for a bathroom or toilet, this parameter is up to 350 cubic meters, and for an industrial fan - up to 17000. In addition, there are models with a maximum flow rate of up to 50,000 cubic meters, but the price of an industrial exhaust fan with such a power of work will be very high.

Blade type - they can be straight or curved. If an industrial exhaust fan has forward-curved impeller blades, then the efficiency of its operation is noticeably improved. But it is necessary to pay attention that along with this, the amount of noise produced by the device during operation increases. Also, the blades can be bent backwards, which makes the operation of the device virtually silent.

Helpful advice! A fan with forward-curved blades is best installed in an industrial building, where the noise level is not critical, but power is very important. But the backward curved blades are good for models used for hoods in the bathroom or toilet.

Outlet diameter - must correspond to the diameter of the ventilation duct in which the device is installed. So, channel fans 160 mm should be chosen for large ventilation openings in industrial premises, and for domestic purposes, models with a nozzle diameter of up to 100 mm are most often used.

Air flow rate - the recommended parameter here is 11-14 m / s. If the speed is lower, then it will not be enough for efficient air extraction, and if it is higher, the noise level will be too high.

If you are going to mount the device in a residential area, and the noise level is a determining factor for you, then you should purchase silent model, which has a number of advantages due to its design features:

• The case of the silent radial centrifugal fan is well insulated, due to which condensation accumulates on it much less than on other models. This, in turn, reduces the risk of short circuits and increases the life of the device;
• noise suppression is carried out by sandwich panels, which also actively suppress vibration, which is especially important for ducts with weak walls.

The purchase of an industrial low-noise axial fan is relevant for shopping centers, cafes and other premises where a high level of exhaust efficiency is required, but noise is undesirable.

Also, to reduce the noise level, you can purchase flexible joints for the radial fan. They serve to dampen vibrations, can be installed at the fan inlet and outlet and can be used at air temperatures from -50 to 50 ° C.

Reversible duct fans and models with a non-return valve

A separate modification of duct fans is reversible. They are characterized by the fact that they can simultaneously perform two functions - air extraction from the room and the inflow of air masses into it. This is realized by changing the direction of movement of the fan blades.

The features of 12 Volt reversible radial fans, which can be bought in many specialized stores, include the fact that they are poorly suited to work in humid or dusty environments. This means that it is not recommended to use them for hoods in bathrooms or other areas with high humidity.

Some industrial centrifugal exhaust fans can be equipped with a non-return valve. This design feature does not allow air from the street to enter the room when the device is turned off and will be relevant if your house is located in an area with a high level of air pollution. There are three options for the check valve:

• passive - closes solely due to gravity, can only be used in vertical type air ducts. Recently, a hood with a passive check valve is not in great demand due to its low efficiency;
• controlled - works from the mains, opening and closing is controlled by a special sensor;
• self-closing - opens by the movement of the air flow and closes as soon as the flow of air stops. Good option for toilet or kitchen use.

Helpful advice! Any type of fan valve should be cleaned regularly, as it is where dirt, dust and condensation usually accumulate.

Industrial Axial Exhaust Fan Selection

The devices used for forced air extraction in industrial buildings are also called snails. Radial fans of this type differ in a number of parameters.

Duct fans 150 mm low pressure - these are exhaust devices focused on one-way air intake and can operate with air masses with temperatures up to 80 ° C. Such a fan is designed to work with air without solid impurities, as well as non-aggressive gas mixtures, and is used in various types of industrial premises.

Explosion Proof Axial Fan designed to work in an explosive environment, used for drawing gas mixtures without fibrous materials, solid particles and sticky substances. Explosion-proof devices are often used in industries where work is carried out with flammable and explosive substances.

Medium pressure radial fan can be used for drawing and moving various gas mixtures with a temperature not exceeding 80 ° C and without solid impurities. A design feature of this type of model is a spiral rotary housing. They can be used in explosive production and operate on the one-way suction principle.

High pressure radial fan works on the same principle as the low and medium pressure models, but is characterized by greater efficiency and productivity. The fan design has 12 backward-curved blades that effectively handle the movement of air and gas mixtures without particulate matter.

Dust fans are used in rooms where the air contains a large amount of solid particles and impurities.

Roof-mounted radial smoke exhaust fans are designed to quickly remove smoke from the room in the event of a fire, can work in combination with an air duct network or without it. Explosion-proof roof-type duct fans can be used in an explosive atmosphere and move flammable gas mixtures.

When choosing high pressure radial fans and other models, the installation location and the functions that the device will have to perform should be considered. For example, if we are talking about organizing the removal of air from a room in which work is carried out with explosive substances, then it is better to give preference to explosion-proof models. And if you want to save energy, then you should buy an industrial axial fan with forward curved blades.

Installation and prices of duct-type axial industrial fans

As a rule, a device for forced air extraction is installed at the inlet to the duct. The device is fastened using dowels, which are threaded through the holes on its body. When installing, it is very important to fix the fan as tightly as possible. This can be done using silicone sealant or polyurethane foam.

Useful advice! When installing a duct fan, the electrical wiring is best routed through a special duct.

Prices for air extraction devices depend on factors such as power, size, body material and many others. Estimated cost of fans for round ducts:

• the price of a 315 mm duct fan is about 6,000 rubles;
• the price of a 250 mm duct fan is about 4500 rubles;
• a fan with a diameter of 200 mm costs 4000 rubles;
• the price of a 100 mm fan is 3000 rubles.

At the same time, the price of a 200 mm duct fan in a plastic case can be significantly lower than a device with the same diameter, but in a steel case.

Related article:

Plastic ventilation: using plastic pipes for ventilation

DIY ventilation from plastic pipes: PVC, polyurethane, polypropylene, polyvinyl chloride, ventilation system for plastic windows.

Duct fans for round air ducts: increasing the efficiency

In order to extract air as efficiently as possible, the following requirements are recommended:

• the wall closest to the air intake opening should be at a distance of no less than 0.75 from the diameter of the air duct;
• the length of the suction duct must not be less than its diameter;
• the difference between the channel diameter and the inlet section should not exceed 8%;
• if a ventilation duct system is used, then the straight section of the duct should be no shorter than three of its diameters;
• instead of turning the ventilation system by 90 degrees, it is better to use 45 ° turns.

Review of popular models

There are several variations of 150 mm duct fans and other models that are in great demand among customers.

Duct fans Silent - a line from the popular Spanish brand Soler & Palau. It differs in almost complete noiselessness during operation, can be used both in residential and industrial premises, where there are increased requirements for the noise level. Available in various sizes, body material - plastic.The design features of the Silent models allow you to efficiently move air masses characterized by high humidity, as well as containing various impurities, which makes them especially effective for installation in a bathroom or kitchen. Low noise level is the merit of a special fiberglass layer, rubber seals on clamps and a number of other modifications.

Duct fans Vents - domestic equipment that can be effectively used in high pressure ventilation systems. It is characterized by increased strength and moisture resistance, and from the design features, a built-in timer can be distinguished, which allows you to set a delay for turning off the device. Vents fans have a low noise level during operation, and are also equipped with a built-in speed controller and speed switch.

Systemair duct fans - products of a Swiss company, distinguished by a wide selection of models and modifications. The fans of this line are perfect for installation in ventilation systems of various types, are available in a galvanized steel case and boast high indicators of durability and resistance to all kinds of adverse influences. They can be mounted both directly into a round duct and on a wall, they are distinguished by increased resistance to humidity, compact dimensions and low noise level during operation.

Useful advice! The good thing about Systemair devices is that they can be mounted at any angle, so these fans can be installed both on walls and on the ceiling.

By purchasing a BP 80 75 radial fan or any other model, you provide efficient air removal from the room. This allows you to get rid of high humidity, remove dust, combustion products or an unpleasant odor from the room. Various models of duct fans can be installed in residential and industrial premises, require minimal maintenance and have a long service life.