A fireplace in your own home is the dream of any romance. Which of us did not try to find ourselves in a comfortable armchair on our own little stove on a winter evening in order to blissfully absorb with our whole body the heat spread by a living fire.
But the smoke that fills the room and does not want to go into the chimney does not fit into this idyllic picture. Back draft in the chimney - this is the name of this unpleasant phenomenon. Why does it arise and how to deal with it? We have collected information about this for you and provided in this article.
We also paid attention to methods for checking draft in the chimney and examined in detail the best options for solving draft problems.
What is backdraft?
Before you understand the causes of this phenomenon, you should understand the essence of what is happening. The heating device installed in the house, together with the chimney, forms an exhaust structure.
The air pressure inside and outside the device is not the same. Because of this difference in pressure, thrust arises - an aerodynamic directed flow of flue gases.
Safe and efficient operation of the heating device implies that the combustion products will move from the burning fuel along the flue ducts. The air masses in the chimney have a lower density, as a result of which they tend upward. In their place comes cooler outside air. This is exactly what the change of flows should ideally be.
Backdraft is not only an unpleasant, but also a dangerous phenomenon, the consequences of which can manifest itself in a deterioration in the health of people and pets
But sometimes a phenomenon called reverse traction occurs. In this case, the smoke resulting from the combustion of the fuel is not directed out through the chimney, but into the room.
The occurrence of backdraft is not only unpleasant, but also a dangerous phenomenon. Penetration of combustion products into the room leads to serious poisoning, and carbon monoxide carries a mortal danger.
The first signs of failure during the movement of air masses can be not only smoke entering the room, but also a quickly smoked glass window in the furnace door. At first, the thrust may just be weak, but if you do not take action, it will become inverse over time.
Sometimes there is another phenomenon associated with the movement of smoke - the air flow for a multiple time changes its direction to the opposite. So there is a rollover traction.
Causes of Backdraft
There are several reasons for reverse thrust. The main of them can be considered the mistakes made during the design of the heating system. Perhaps, during its construction, the rules for the use of building materials were violated.
A problem of this kind will not arise at all if the chimney is constructed in compliance with existing standards: the rotation must be done by 90 °, and the outlet should be placed at an angle of 45 °. Particular attention should be paid to the shape of the cross section of the chimney.
The most suitable shape is a circle. If angles are present in the structure, turbulence may occur which impedes the discharge of gases.
The profession of a chimney sweep, as you see, has not lost its relevance, but, with an increase in the number of private cottages, has even become even more in demand
If we compare brick and metal chimneys, then the draft in the latter will always be less quality. The problem is that the metal heats up pretty quickly, but just as quickly it cools down. And cold air, as you know, goes down.
Frequently encountered include the following reasons why there is no draft in your chimney:
- Chimney obstruction. It may well be that it is simply clogged with garbage or smoked as a result of prolonged use. Quick smoking can also occur if the chimney is composed of pipes of different diameters. In no case should this be done.
- Errors in the calculation. Incorrectly calculated cross section for smoke passage. Quite often, when designing a design by non-specialists, imbalances arise in the size of the elements of the device: the combustion chamber and the chimney. A powerful stove, for example, can produce more combustion products than a narrow chimney can remove. Therefore, you need to carefully perform the calculations of the chimney.
- Design Errors. The height of the smoke exhaust system is insufficient for its effective operation. The small length of the chimney can cause insufficient pressure differences. The optimum height of the chimney pipe is five to seven meters.
- The narrowing of the smoke channels. Smoke paths have narrow and horizontally directed sections. In such places, soot accumulates especially actively, which interferes with the free movement of smoke.
- Wind support. The chimney is located in the area of "wind backwater". The cause of backwater can be, for example, a high structure located next to the chimney.
- Improper ventilation. Lack of ventilation or its illiterate device leads to a lack of the required volume of supply air. Therefore, it is important to pay special attention to the proper organization of ventilation in a private house.
If the ridge of the roof is located above the level of the chimney, then the draft can overturn when a strong wind occurs.
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Reverse draft is a significant indicator of a malfunction not only of the smoke exhaust system, but also of the heating unit directly connected to it
The appearance of backdraft may indicate the formation of soot outgrowths inside the smoke channel, which can ignite
The main danger is associated with the entry into the room of carbon monoxide, which threatens serious poisoning to households
In order for the removal of flue products of combustion to be carried out regularly and correctly, it is necessary to observe the requirements of building standards during the construction of the pipe
Before the construction of the chimney, it is necessary to make a project and choose a standard section of the chimney. It should ensure the full removal of toxic substances outside the home.
The height of the smoke channel is determined in accordance with the distance from it to the ridge ridge of the pitched roof. Reverse thrust is inevitable if it is less than 1.5, and the pipe below the ridge
If, due to soot outgrowths, the smoke channel is greatly narrowed, the discharge will be slowed down. As a result, traction can fall completely
The location of the chimney should be planned so that it does not appear in the area of wind backwater. It can be created by large trees, tall buildings nearby, structural elements of the house itself
The catastrophic effects of reverse thrust
Ignition of sediment on the walls of the chimney
Carbon monoxide intake
Rules-built chimney
Smoke too narrow
Insufficient chimney height
Sooty smoke channel
Chimney in the area of wind backwater
Atmospheric indicators should also not be excluded from the list of reasons for the formation of reverse thrust. High humidity of the external air, as well as strong gusts of wind can cause the formation of reverse smoke movement.
The same phenomenon can be observed in the case when the air at home is colder than on the street. Due to the difference in pressure, a strong burning odor may occur.
To prevent poisoning, it should be well ventilated. At the same time, it will warm up at least a little. Wind is also capable of breaking traction, which forms turbulence of air flows on the roof. This phenomenon contributes to the incorrect direction of the tip relative to the ridge of the roof.
During the construction of the bath, it is necessary to arrange the furnace so that the chimney is indoors, because if you place it outside, condensation will form in the pipe
The installation location of the chimney also matters. For example, if we are talking about heating the bath, this part of the structure can be located in the inner part of the building.
Such a solution will allow to warm the room better, providing decent traction even in severe frosts. If the pipe is placed along the outer wall, heating will take longer, and condensation may form in the pipe itself.
Methods for checking chimney draft
The presence of backdraft can be detected even at an early stage of the problem before smoke begins to fill your house.
Let's start with folk ways. You can tear off a piece of toilet paper and bring it to the heater. Toilet paper is thin enough to respond well to air movement. Look in which direction the leaf deviates. If it oscillates towards the room, then there is a reverse thrust.
You can check the draft in different folk ways, including using a candle: the direction of the flame of the candle will tell you the thrust vector
Exactly the same experiment can be done with cigarette smoke. It looks even more clearly. Cigarette smoke will unmistakably show you the direction of traction.
The quality of the draft can be determined by observing the flame in the heating system. The white flame and the buzz in the chimney indicate too strong draft, which is also not good, since it leads to an excessive consumption of fuel. A good work result looks like this: the flame has a golden yellow color, combustion occurs stably and evenly.
An anemometer (wind meter) is a popular device used by specialists who, due to their profession, check the draft of a functioning chimney
For scientific verification, we need to arm ourselves with equipment. The most accessible device for ordinary users is an anemometer (wind meter). The appearance of the device, its variants are presented in the video, which is posted in the final part of this article.
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Normal operation of the furnace and the smoke channel
Smoked Firebox - Indicator of Traction Impairment
Dark red flame while burning
Deflector against traction drop
Traction Problem Solutions
As it turned out, the reasons for the occurrence of reverse thrust can be different. Therefore, standard solutions do not exist. You need to look for an option that matches the problem in each case.
If the exit paths are blocked by debris or soot, you will need to clean the pipe. If the paths are incorrectly designed, the structure will have to be completely dismantled and reassembled.
If the defect is the slow evacuation of the combustion products, there are several ways to improve the direct draft in the chimney. There are devices to help activate this process.
Option # 1 - deflector and its variants
In solving the problem, how to further increase the draft of the chimney, a deflector can help. It is mounted on top of the chimney. This device “draws in” smoke located in the chimney shaft, using wind power to achieve this.
Deflectors are a number of devices that have a single functional purpose: improving traction, preventing the reverse movement of fuel combustion products
Several functions are assigned to the deflector at once:
- protection of the mine channel from external clogging and precipitation;
- increased draft in the chimney;
- suppression of sparks arising from incomplete combustion of fuel.
The operation of this device is based on the laws of physics. When gas moves through a tapering pipe, its flow accelerates. In this case, the pressure that he exerts on the walls of the shaft decreases. There is a vacuum zone.
A deflector mounted on the chimney creates this discharge zone when air passes inside the tapering duct in its structure. Gases flow into the discharge zone located at the mouth of the chimney, and, with the help of traction, reinforced by wind, are removed from the pipe.
The materials for the manufacture of the most popular deflectors are aluminum, stainless steel and galvanization, although there are also expensive copper products that resist corrosion well
Even the simplest deflectors can increase smoke removal efficiency by 20%. The presence of such a device creates huge advantages for the heating system, as it contributes to the complete combustion of fuel and better heat transfer. Therefore, it is deservedly popular and in demand.
Typically, the deflector consists of two cylinders - the upper and lower, as well as a pipe connected to the lower cylinder, a protective cap and brackets designed to fix the parts.
The upper cylinder is not a mandatory element of the device. A model without it consists of the following elements:
- lower cylinder mounted on a smoke exhaust pipe;
- diffuser - an element that cuts air streams;
- two caps - direct and reverse.
The most expensive deflectors are made of copper. In general, to create them, use ceramics and plastic, stainless steel, aluminum and galvanization. Aluminum and steel products are considered the most popular.
Despite the commonality of functions, deflectors are very different. They differ not only in their appearance, but also in the device, as well as their sensitivity to air flow.
Difficult to manufacture, but very attractive spherical deflector looks very futuristic, although it is a wonderful functional device
The following deflector models are considered classic:
- dish-shaped;
- ventilation TsAGI;
- Grigorovich's device;
- H-shaped;
- spherical "Volper".
In addition to all the recognized classics, there are relatively new models that differ in unusual constructive solutions. This is a rotating model and a weather vane product. The basis of their work is all the same laws of physics, which were already mentioned above.
Don't want to splurge on a deflector? And it’s not necessary - it’s quite possible to make it with your own hands, using improvised materials. And how to do it right, we examined here.
Option # 2 - Special Gate Valve
If there are problems with the stove, check the position of the gate. The gate is a flap that is designed to regulate traction. They usually install it on the uninsulated first meter of the chimney pipe. This damper allows you to make the operation of heating equipment as efficient as possible.
This device has several functions:
- after burning fuel with it, they block the pipe, which allows you to save heat for a long time;
- as a draft regulator, the gate is used to change the cross section of the chimney: with excessive draft, for example, the smoke channel can be narrowed;
- with his participation, it is possible to control the quality of fuel combustion.
The material for the manufacture of the gate is, as a rule, stainless steel, the thickness of which is 1 mm. Thanks to the polished surface of the product, soot is easily removed from it.
The temperature that such a valve can withstand does not exceed 900 ° C. It is quite durable and has a low coefficient of thermal expansion.
The retractable shutter should not completely block the chimney door: 85% is the indicator that ensures safety standards when operating heating appliances
Shiber is presented by two models:
- horizontal pull-out plate, which is most often used in brick chimneys;
- rotary gate or throttle.
The throttle valve is called the same plate, which is fixed on a rotating axis, placed inside the chimney or pipe.
The contours of the swivel plate repeat the cross section of the chimney, which allows it to almost completely block the pipe when the heater is not working
In view of the simplicity of the design, it is easy to make a damper for the pipe with your own hands. Such homework in operation will be no worse than the purchased product.
Option # 3 - chimney stabilizer
A product with such a speaking name is otherwise called a breaker. This is a mechanism that automatically and metered supplies air to the chimney, allowing you to optimize the operation of the heating system without attracting a person to it. To prevent overpressure, the circuit breaker is equipped with a safety shutter.
Stainless steel is used to produce a chimney draft stabilizer. The maximum temperature that this device can withstand is 500 ° C.
The draft stabilizer installed on the chimney must be adjusted in accordance with the recommendations that you will find in the manual for your heating boiler
The essence of the stabilizer is that it automatically adds cold air directly to the chimney. In this case, the temperature and gas velocity inside the pipe are reduced. As a result, the efficiency of using combustible fuel is increased without any changes in the operating mode of the heater itself.
A breaker is installed, usually on the chimney pipe. At the same time, the distance from it to the heating device (boiler) should be at least 0.5 meters. The breaker should only be indoors.
Since its functioning is based on a system of precisely balanced weights, the influence of natural factors on the operation of this device must be excluded.
The stabilizer setting can be considered complete when the minimum draft is set on its regulator in accordance with the data specified in the operating instructions for your boiler. Either the exact parameter should be set, or a division higher than recommended.
In addition to the use of these devices, to prevent back draft, you can extend the chimney pipe by straightening it as much as possible. Bends and sharp turns of the shaft increase cavitation when gases are removed to the outside.
If the problem with draft is not manifested by puffs of smoke in all rooms, this does not mean that it does not exist. A device will help to identify it, the device of which can be found by watching this video here.
This product may save your life by paying attention to the problem in time, because carbon monoxide, for example, has no color or smell.
This video contains information about the appearance of the TsAGI deflector and its components. You can see how to build this device yourself.
If you feel the strength in yourself for the manufacture of a traction stabilizer, then this video will be for you a real guide to action.
Any device that operates in your home should work properly and not pose a threat to human life and health during its operation. Heating in this sense is no different from other useful devices. Deflector, gate and stabilizer will help to make its work stable and efficient..
Do you have a problem with draft in the chimney and are you trying to solve it on your own? Did you find the answers after reading our article? Or do you still have unresolved issues that we have missed? Feel free to ask them in the comments section, and we will try to clarify these points.