Smoke exhausters for boilers: description, principle of operation, installation and maintenance features

Smoke exhausters for boilers resemble fans. Even structurally they are similar.Both equipment options can be distinguished by their markings. For fans, the brand begins with the letter “B”, for smoke exhausters with the letter “D”. Moreover, the latter are made of heat-resistant steel, which increases their cost.

Purpose of the smoke exhaust device

The main task of the smoke exhauster is to remove carbon monoxides that are formed during the combustion of fuel inside the combustion chamber boiler. The equipment is installed after the last one, cutting into the chimney. Installation location - indoors or outdoors.

The model line of equipment includes smoke exhausters used in fire protection systems. Their task is to remove smoke from premises, toxic substances, fire extinguishing powders, gases, aerosols, and lower the temperature.

Design and principle of operation

Structurally, the smoke exhauster of a domestic or industrial boiler consists of:

• steel body;
• impellers, also known as the impeller;
• a shaft on which the impeller is mounted;
• electric motor;
• support frame.

The body is a welded structure consisting of a shell made in the form of a snail and two sidewalls. In the center of one sidewall there is a hole for the inlet pipe. Exhaust gases are sucked in through it.The cross-section of the hole corresponds to the performance of the smoke exhauster.

There is also a hole in the center of the second sidewall through which the device shaft passes. The snail ends with a pipe through which gases are removed from the boiler. The cross-sectional shape is usually square.

There are several versions of smoke exhausters:

1. The impeller is mounted on a shaft, which is connected to the electric motor shaft by a coupling or belt drive via pulleys. The first is installed in two bearings.
2. The impeller is mounted on the electric motor shaft. This model is more compact.
3. The snail relative to the frame can be rotated at a certain angle according to GOST.
4. The rotation of the impeller can be right or left.

The operating principle of boiler smoke exhausters is identical to the operation of centrifugal fans. Here it is important to create a vacuum, that is, to reduce the pressure inside the combustion chamber. Due to this, air and gases move from outside into the firebox and from the latter into the chimney. Air enters the firebox and supports combustion of the fuel. Exhaust gases and smoke move to the boiler chimney pipe and are discharged outside through it.

Inside the smoke exhauster, air masses move from the inlet located in the center to the center of the impeller (using centrifugal force). Afterwards, the impeller blades are thrown towards the inner surface of the volute and removed through the inlet pipe.

Technical characteristics and calculation of parameters

When choosing a smoke exhauster for solid fuel and other types of boilers, three technical characteristics are taken into account:

• equipment performance;
• pressure created to move gases;
• electric motor power.

It is necessary to take into account the fact that the choice is made towards a smoke exhaust unit, the performance of which exceeds the operating conditions of the boiler.

Calculations of smoke exhaust parameters are based on the technical characteristics of the boiler unit, such as:

• performance;
• fuel consumption;
• the amount of air required to burn the fuel;
• the amount of gases formed during fuel combustion and air oxidation;
• heat of combustion of fuel.

All these parameters are in the boiler passport. Based on them, the performance of the smoke exhauster is determined from the tables. And accordingly, so does his brand.

Varieties

Smoke exhausters do not have a wide range of models. There are two groups:

• for boilers;
• used for fire purposes.

The first group includes two models:

1. Marked "D". This is the simplest and most reliable equipment in which the blades on the impeller are tilted forward.
2. Under the brand name "DN". These are industrial-type smoke exhaust units with rear-facing blades.

An important criterion for increasing draft in a boiler is the type of fuel used. The more by-products the fuel releases during the combustion process, the stronger the draft the boiler should have. Therefore, centrifugal smoke exhausters are installed on solid fuel boilers. For gas engines, a flow-through version or a traction booster is suitable. The same applies to pyrolysis boilers.

Natural draft enhancers

The simplest device included in this category is a unit equipped with an axial-type fan. It is simply placed at the end of the chimney pipe and connected to an electrical network with a voltage of 220 volts. A canopy is mounted on top to protect the amplifier from rain and snow.

The performance of the devices is adjusted manually or using a control unit that is installed inside the house. Often both elements are included. But more often the fan and the unit have to be purchased separately.

Flow-through smoke exhausters for boilers

By design, this is a pure smoke exhaust unit - a housing, inside of which there is an impeller mounted on the electric motor shaft. But the method of mounting the device differs from classic models.

The impeller of the unit is installed so that it, together with the housing, becomes a continuation of the chimney. At the same time, the impeller does not reduce the cross-section of the pipe in any way. The electric motor is located outside the chimney structure.

Often, for flow-through models, a separate chimney is built, built parallel to the main one. That is, the boiler chimney system consists of two pipes. One constantly works on natural draft, the second with the help of a smoke exhauster. The convenience of this option lies in the fact that when the power goes out, which often happens in country houses, draft will always be present due to the main pipe.

Centrifugal duct smoke exhausters for solid fuel boilers

For boilers operating on solid and liquid fuels, there is no better option. This applies to both domestic and industrial boilers. This type of equipment works effectively if it is connected to the boiler control unit. It will independently respond to all changes in the fuel combustion process and, if necessary, quickly change its parameters.

Centrifugal models create a good vacuum in the firebox and high pressure inside the chimney pipe, on which the draft depends.

Advantages and disadvantages

There are four advantages on the basis of which you can install a smoke exhauster on the boiler:

1. Reduced fuel consumption.
2. Increasing the efficiency of the boiler.
3. The chimney does not become clogged - soot does not accumulate on its inner walls.
4. The smell of burnt fuel, much less its unburnt part, will never penetrate the rooms.

All these advantages do not depend on the weather. The boiler will work efficiently in snow, rain, and strong winds.

There are also disadvantages:

1. Smoke exhauster is an additional expense.
2. It is better to entrust its installation to specialists. And this is another expense.
3. Sometimes you have to pay for repairs and maintenance.

Features of choice

Before choosing a smoke exhauster for your boiler, it is recommended that you familiarize yourself with the five selection rules.

Rule #1

It is better to choose a model that has the ability to adjust. Manufacturers offer three options in this regard:

• standard devices connected to the electrical network and having only an “on-off” function;
• connected to the automation of a solid fuel boiler;
• with thermostats.

The latter belong precisely to the category of “best-functional smoke exhauster”. The device is connected to the electrical network. The temperature is set on it. Low boiler draft occurs at temperatures from +50 ℃ to +140 ℃. As soon as the temperature inside the chimney drops to a predetermined value, the smoke exhauster immediately turns on, increasing the boiler draft.

Rule #2

The smoke exhaust unit for the boiler must withstand temperatures of at least +250 ℃. The manufacturer indicates this parameter in the product passport. In this case, you should always pay attention to the performance of the device.

The high power of the smoke exhauster, much higher than the parameters of the boiler, reduces the technical characteristics of the latter:

• efficiency decreases;
• fuel consumption increases due to rapid burnout;
• frequent boiling of boilers;
• condensation forms in the chimney, which negatively affects the technical condition of the chimney system;
• strong drafts appear in the house.

Rule #3

Low productivity is also a minus. Therefore, it is recommended to choose units with a capacity of at least 500 m³/h. Otherwise, the efficiency of the equipment will decrease. This is especially true for solid fuel boilers, the fuel of which does not burn completely.

Non-combustible particles will be deposited on the walls of the heat exchangers and chimney, reducing the efficiency of the entire heating system.

Rule #4

The smoke exhauster should not greatly influence the natural draft of the boiler. This device is just an assistant, and not the main element that creates traction. Therefore, it is important to first accurately calculate the performance and then purchase the unit.

Another point related to power supply is that all smoke exhaust models operate on electricity, which is not always present in countryside villages. And if there are no problems with flow-through systems, then problems will definitely arise with traction amplifiers and centrifugal structures. Therefore, it is recommended to purchase an additional uninterruptible power supply (UPS) for them.

Rule #5

If you have a choice between purchasing an outdoor installation option or an indoor one, then it is better to give preference to the first one. Both options are structurally no different from each other. The only difference is in execution and degree of protection. Outdoor models can be installed inside the house, but indoor models cannot be installed on the streets.

If you install an additional canopy over the smoke exhauster, it will extend the service life of the device. Outdoor structures can easily withstand temperatures from -30 ℃.

Units for indoor installation are not always easy to install. Inside the house, the chimney pipe is short, hence the difficulty of installation.

Other selection criteria

Some tips from the experts:

• smoke exhausters for stainless steel boilers are a priority;
• if you bought a device made of carbon steel, then the thickness of the housing walls should not be less than 2 mm, and the impeller should be made of stainless steel;
• galvanized products should not be present in the design of the smoke exhaust unit for boilers.

Installation features

The most common smoke exhausters used for domestic boilers are flow-through or, in other words, overhead models. They are simply cut into the chimney without dismantling it.

First, you need to choose the right device. There are many criteria: productivity, amount of gases removed, etc. But it’s easier to select according to the diameter of the chimney. This parameter must match the diameter of the smoke exhaust pipes.

Then everything is simple:

• markings are applied to the pipe according to the template;
• A cut is made along the drawn lines with a grinder;
• a rectangular hole is obtained;
• its edges are coated with silicone sealant;
• a smoke exhauster is installed, which is attached to the pipe with two clamps.

If the boiler chimney is a sandwich structure, then first the rectangle of the outer pipe is cut out, then the heat-insulating material is removed, and then the rectangle of the inner pipe is cut out. Next, the unit is installed.

Draft amplifiers, also known as duct smoke exhausters, are installed differently. Since their location is inside the chimney, part of the latter has to be removed and the device installed in its place.This is not always easy, so it is recommended to install draft amplifiers for boilers at the end of the chimney structure, covering it with a visor. This means that you need to choose only the street option.

Smoke exhausters for gas and other boilers can be installed on vertical and horizontal sections of the chimney. The exception is street models. They are mounted only on vertical pipes.

For horizontal installation, the device must be installed so that its electric motor is located on top - above the chimney. This protects the motor from condensation and debris getting into it.

You cannot narrow the chimney pipe after the smoke exhauster. You can expand a little, but not much.

If the unit is installed inside the house, then after it there must be a section of the chimney no less than 1 m long without bends, tees or other obstacles. In this section, the exhaust of carbon monoxide from the boiler accelerates.

The closer the smoke exhauster is to the boiler, the more efficiently it works.

When you turn it on for the first time, you need to pay attention to which direction the impeller rotates. The structure must not be allowed to force air into the boiler.

Maintenance and operation

The internal surfaces of the smoke exhauster become covered with soot during operation. It needs to be cleaned several times a year, at least once. This is especially true for impeller blades. It's not that hard to do.

The blades are installed at an angle. You just need to reconnect the smoke exhauster so that its shaft begins to rotate in the opposite direction. This movement creates a vacuum inside the chamber, causing the soot to begin to flake off. A few minutes of spinning will keep the blades clean.

Technology and recommendations for self-production

You can make any technical device yourself if you have the necessary blocks, parts and materials. In the case of a smoke exhauster for a boiler, this is an impeller with an electric motor. This unit may also be used. The key here is balancing. The electric motor shaft should not have any play. If this is present, then the smoke exhauster will blow apart the first time it is turned on.

The second is the body. It is not difficult to make if you have welding skills. Making a snail is easy. The main thing is to follow the drawing and diagram. They are freely available. There are also dimensions of the unit. The only thing to consider is the thickness of the sheet metal used. This parameter should not be less than 2 mm, but not more than 5 mm. Thick material will make the structure heavier.

The finished blocks are connected to each other. After which they are installed on a previously prepared frame support. Fastening is done with bolts and nuts.

In this entire operation, it will be difficult to accurately maintain the dimensions of the smoke exhauster. Even small deviations to the smaller side will lead to incorrect operation of the unit. Therefore, it is recommended to buy such a device necessary for boilers in a store. In this case, the equipment must have a quality certificate.

Smoke exhauster - a unit that enhances the draft of the boiler. Therefore, the device is more popular today than ever. The main thing is to choose the right one in terms of performance, so as not to reduce the efficiency of the boiler equipment. It has a large number of advantages, one of which is simple installation. Any costs associated with its operation are covered by the good operation of the boilers.

Choosing a smoke exhauster for a boiler, fireplace and stove: video.

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