Previously, traction and blast fans were used only in industrial boiler plants. The first are placed inside the chimney channel and create a vacuum, the second - inject air into the furnace. Gradually, the units migrated to the domestic sphere - manufacturers began to equip heaters with a closed combustion chamber in turbines. The idea was picked up by home craftsmen, because a smoke exhaust for the boiler helps to solve the problem of poor draft in the chimney pipe. Let's see if forced extraction of combustion products is always necessary.
Design and principle of operation
The exhaust fan for a factory-made boiler includes the following elements (the device is shown in the diagram, the positions coincide with the points):
- Metal heat-resistant impeller with blades bent at 90 ° relative to the impeller.
- Mounting plate.
- Low-performance electric motor (20 ... 50 W).
- Power cable connector.
- Remote control and control.
- Flask and capillary tube of a temperature sensor connected to an emergency thermostat.
- Power cord with plug.
Note. As an example, the boiler smoke exchanger DM-01 from Kalvis was taken. The design of other types of fans differs in the shape of the case - a snail, duct, hemispherical landing site. The set of parts is similar.
The unit is attached to a special box located on the rear panel of the household TT boiler next to the chimney pipe. The flask of the temperature sensor is inserted into the immersion sleeve of the water jacket, the remote control is placed separately.
The principle of operation of the smoke exhauster is the forced removal of high-temperature gases from the boiler tube heat exchanger into the chimney. The algorithm looks like this:
- The firebox is filled with firewood, ignition is performed.
- The loading door is locked, the blower door opens. The fan is turned on by a button on the remote control, then the performance is tuned.
- When the heating system and the chimney are warmed up, the impeller speed is manually reduced to a minimum. If the heat generator has enough natural draft, it is recommended to turn off the smoke exhaust.
- When the coolant is heated to a critical temperature of 100 ° C or more, an emergency thermostat is triggered by a sensor command, which turns off the fan automatically.
Reference. On TT boilers equipped with an automatic draft regulator, the ash pan door does not need to be opened. The thermostat through a chain will open the air supply flap to the desired angle.
Large or small performance of the traction fan is set individually depending on the quality of the solid fuel, the combustion mode and the degree of heating of the chimney. The main thing is to avoid the accumulation and seepage of smoke into the room.
It is also impossible to overdo it with turns - the lion's share of heat will go into the pipe. Before opening the door and reloading it is better to increase the rotation speed to the maximum.
Varieties of traction fans
For solid fuel boilers and wood-burning fireplaces, several types of smoke exhausters are sold:
- boiler room (design discussed above);
- centrifugal duct;
- overhead;
- chimney / stove (aka roof).
Various nozzles that improve natural traction should not be classified as smoke exhausters - deflectors, circular rotary elements and rotating weather vanes. The effectiveness of these caps depends on the wind speed, which changes with the weather.
The duct fan has its own case with two connecting flanges or nozzles. The unit is installed vertically or horizontally in the gap of the chimney channel.The device and principle of operation is similar to the operation of a boiler smoke exhaust.
The laid on smoke exhauster for a domestic boiler is equipped with a semicircular platform and clamps-couplers. Installation is made on a vertical section of a chimney (not warmed):
- A hole is cut out on a paper template in a pipe.
- The impeller of the traction machine is inserted into the hole, the platform with an electric motor is pressed against the surface by clamps.
- The connection is sealed with an asbestos cord glued to the inside of the installation site of the exhaust fan.
Note. The patch element is selected according to the diameter of the flue pipe. The installation process is demonstrated on video.
Electric hoods for fireplaces are mounted on the tip of a brick chimney and are fastened with spacer bolts. The power cable is laid through the pipe and inserted into the room next to the home stove.
To choose a traction machine, you need to be guided by 3 criteria:
- heat generator capacity, models of smoke exhausters are designed for boiler performance up to 20, 30, 50 and 100 kW;
- mounting point - on the boiler itself, pipe or head;
- for overhead models - the diameter of the insulated duct.
When do you need a smoke exhaust
Manufacturers of heating equipment complete their products with traction fans because of the increased resistance of the heat exchanger, where the gases several times change the direction of movement through the heat pipes. The goal is to select the maximum heat from the combustion products and increase the efficiency of the boiler plant.
Nuance: the operation of the smoke exhauster in a factory-fitted boiler is coordinated with the combustion process and is controlled by an electronic unit. When mounting the fan assembly on a “brainless” heater, such a consistency is excluded, you need to buy an automation unit or adjust the speed manually.
We list the situations when the smoke exhauster will help improve the operation and maintenance of a solid fuel heat generator:
- traction problems - wind blowing, air congestion in the gas duct, many turns, narrowing of the diameter;
- due to the design features, the boiler smokes into the room when the door is opened;
- the chimney height is insufficient or the pipe cut fell into the area of the wind support behind the roof ridge or another building;
- cracks appeared in the brick pipe, from where smoke seeps.
An important point. Not a single fan will save the situation if there is no influx from the street in the boiler room. At first, the working impeller will create a small vacuum, but then the blades will mix the air in place. Supply ventilation is a prerequisite for the normal operation of any heater.
Some designs of wood-fired boilers (such as shaft type) tend to emit smoke through an open loading hatch. A similar picture is observed in heat generators with a three-pass fire-tube heat exchanger of increased resistance. The solution to the problem is the installation of a traction or blasting machine controlled by a controller.
Strengthening natural traction with a smoke exhauster has a downside. If, after warming up the pipe, the natural hood has not recovered, the unit must not be turned off - you can burn. Now imagine that in the middle of the night the power supply stopped, the fan stopped. While the chain thermostat covers the damper, smoke will fill the boiler room.
Recommendation. A smoke exhauster should not be a panacea. Be sure to take measures to restore traction - repair or remodel the flue according to the requirements prescribed in the boiler instructions.
Which is better - a smoke exhaust or a supercharger?
When the traction turbine is integrated into the heat generator by the manufacturer, no such questions arise. Another thing is the addition of an exhaust fan to a conventional direct-burning boiler. It must be understood that in this case, the smoke exhauster solves only 1 problem - creating a vacuum in the furnace and enhancing traction. Here are a number of negative points:
- Without an electronic control unit, performance will have to be manually adjusted.Automatic maintenance of the temperature of the coolant is excluded.
- When air is supplied through the open door of the ash chamber, the fan will cause the boiler to operate at maximum. Setting up a long burning mode will not be easy.
- In the event of an emergency stop of the impeller, the combustion of fuel will not stop, since the gases freely pass through the scroll or the body of the exhaust fan. Air enters the furnace, the likelihood of overheating increases.
- The impeller and internal surfaces of the unit are covered with soot, which must be removed. Sticking speed depends on the moisture and resin content of the wood.
Comment. We do not mention the consumption of electricity by the fan. The consumption is relatively small and will not have a significant impact on the total cost of heating.
The disadvantages described in paragraphs 1 and 2 are eliminated by switching the smoke exhaust with a controller that controls the impeller speed and the temperature of the water jacket. Electronic components can be bought at a price of 50-100. e.
Blowing machines always work together with the controller, so the above problems are absent:
- the supercharger changes performance and turns off at the command of the control unit, the coolant is heated to a predetermined temperature;
- during combustion, the ash pan door is hermetically closed, air is supplied through a separate channel;
- when a power outage occurs, the air channel is automatically blocked by a gravity damper;
- impeller blades do not come in contact with hot smoke and soot.
Reference. In pyrolysis boilers, supercharging is always used, since the operation of this type of heater is built on forced air injection.
Now compare the cost of traction and blower fan, not taking into account the price of the controller. A smoke exhaust for a TT boiler up to 30 kW will cost 90 oz. e., supercharger - 60-65 at. e. The difference is due to the design features of the exhaust unit - the hot gases should not overheat the electric motor plus the impeller is made of metal (with supercharging - from plastic).
By the complexity of installation, the units are approximately the same. Installation of a discharge snail involves sawing an opening in the ash pan door, a smoke exhaust - disassembling or cutting a pipe. It is easier to install a roof hood, but you have to pull a long cable.
A brief conclusion: put the smoke exhauster only if necessary, and better - correct the mistakes made during the construction of the flue. Add electronically controlled turbocharger as desired - the system will automate and secure the combustion process.
How to make an exhaust unit
The main difficulty in assembling a smoke exhauster with your own hands is the manufacture of a balanced impeller, the remaining details are not difficult for a home craftsman who owns welding. If the impeller blades vary in weight, the normal fan noise will crash due to vibration.
In addition to the blades, you will need such elements:
- electric motor with power up to 150 W, maximum shaft speed - 1400 rpm;
- a snail or homemade box shown in the drawing;
- a shaft with ventilation holes or an additional cooling impeller;
- studs with M8 nuts and other fasteners;
- power cable.
For ordinary homeowners, we offer the least thorny way - buy a factory electric motor with an impeller and a cooling impeller, weld a box and assemble a fully functional duct exhaust for a TT boiler. How to do it right, look at the video.
Conclusion
The creation of artificial vacuum using a smoke exhauster is rarely practiced in household solid fuel boilers. The technical solution leads to a rise in the cost of construction and creates problems in operation. Before putting the traction fan in the chimney, remember what fuel you used before.If you plan to burn wet wood, agricultural waste or low-quality briquettes, forget about the boiler exhaust fan, you will have to clean the impeller weekly. It is better to install a supercharger with a control unit.