How high should the chimney be? What should be the height of the chimney relative to the roof ridge.
One of the most important parameters characterizing the chimney as a whole is the height chimney.
A properly designed chimney (i.e. a chimney that has the optimal configuration, diameter and height for the given conditions) provides the following advantages:
- Quality fuel combustion
- Ideal or close to ideal traction
- Rapid heating of the walls
- Rapid overcoming of the so-called dew point (temperature threshold at which condensation occurs)
In addition, the correct arrangement of the chimney should ensure that it is easy to maintain and thus guarantee its longevity.
Chimney Design Basics
The location of the chimney in the building
The chimney project must be developed in conjunction with the entire project heating system, which, in turn, is part of the overall design of the building.
The best way of accommodation is determined not only and not so much by your personal wishes (or the wishes of the customer), but first of all by the design features of the house itself.
Note!
When designing, it is imperative to take into account the location of the structural elements of the roof, in the first place - the rafters.
This is due to the fact that when crossing a pipe with some rafters, it is necessary to move the pipe to the side, which is quite difficult.
Where to lay the chimney?
As a rule, the chimney in the house is laid through the kitchen, corridor and utility rooms. But in the bedrooms and living rooms, chimneys should not be laid. This is due to the fact that at active work boiler or furnace in the chimney, quite a lot of noise is possible.
Chimneys
What affects the chimney
As we mentioned above, the height of the chimneys affects many aspects of the operation of the heating system. However, for us, the key points will be such as the efficiency of the boiler (if the design of the chimneys of the building was carried out with an error, it is possible to reduce the efficiency from 95 to 60%) and fuel consumption.
That is why, when starting the arrangement of the heating system, it is necessary to take into account not only the nominal height, but also the material from which it will be made, and its cross section, and configuration. Yes, and the location of the chimney should be determined by the project, taking into account which heating device is used - a boiler, stove or fireplace.
Choice of pipe height
And yet, speaking about the intricacies of arranging a chimney, one cannot get around the most important question - how high should the chimney be?
On the one hand, everything is simple: the higher the pipe, the more thrust. However, if the chimney is too high, the aerodynamic resistance to the movement of combustion products formed in the boiler or furnace will increase. The smoke moves up more slowly, gradually cools down, giving off its heat to the walls of the pipe.
As a result of a decrease in temperature, the mass of combustion products increases - and, accordingly, thrust decreases. That is why even the highest chimney is not a guarantee of sustainable draft.
You also need to consider exactly where the chimney is located. If the chimney is below the level of the roof ridge, then the draft will be inconsistent, as it will be very much influenced by the direction of the wind.
That is why SNiP 2.04.05-91 puts forward the following requirements for the height of chimneys:
- The height of the pipe, starting from the grate to the mouth of the pipe, must be at least 5 meters, and preferably - 6 meters or more
- Pipe located on a flat roof without a large parapet, must be at least 0.5 m high
- Pipe located at a distance of up to 1.5 meters from the ridge or parapet, should rise at least 0.5 m above their level
- When the chimney pipe is located at a distance of 1.5 to 3 meters from the ridge or parapet its mouth should be at the level of these elements of the roof
- If the pipe is located further than 3 meters from the ridge- its mouth can be located not lower than the line drawn from the ridge down at an angle of 10 degrees to the horizontal
Note! If a ventilation duct is located next to the pipe, its height should be equal to the height of the pipe.
However right choice pipe height is only half the battle. The pipe of the selected height must also be installed correctly.
The technique for erecting a chimney depends on the material that will be used, however, for any chimney, the following requirement will be true: if the height of the chimney above the roof level (from the foot of the chimney to its mouth) exceeds 1.2 m, it is mandatory to install stretch marks. To fix the stretch marks, a special clamp is put on the pipe itself, and the opposite ends of the stretch marks are securely fixed on the roof.
Estimated determination of the height of chimneys
So, we have come to the question that worries many novice builders - how to calculate the height of the chimney?
When calculating the height of the pipe, the following factors must be considered:
- Coefficient showing the level of dispersion of combustion products in the atmosphere
- Coefficient showing the settling rate of combustion products
- Mass of released combustion products per unit of time
- Number of pipes
An alternative to these calculations (by the way, professional heat engineers should still do them) can be the use of calculator programs to determine the height of chimneys.
There are many online and offline versions of such programs on the Internet that can produce in a few seconds and provide you with all the parameters you need to work.
As you can see, the correct determination of the height of the chimney is necessary condition optimal operation of the chimney, and of the entire heating system as a whole. Therefore, if you want your house to be warm and the chimney to work "like a clock" - pay close attention to the recommendations that are given in this article.
The question of how to calculate the diameter of the chimney is provocative in itself. Just want to ask in response - Why? But we won't do that. Any purchased boiler, fireplace, gas convector has an outlet for combustion products, which is really most often round. And here a chimney made of steel is already connected, or indirectly, made of ceramics, glass or asbestos cement. Therefore, in fact, the calculation of the diameter of the chimney is not required. It is already set by the device design itself. You can not take pipes smaller than the output size, but more - just not worth it. You will need a gearbox, and this is an extra waste, and no one needs it. Better make sure that the initial section above the heating device is vertical. In extreme cases, it is allowed to put the slope at an angle of about 45 degrees, which already enters the pipe, built into the wall or taken out.
When it may be necessary to calculate the cross section of the chimney
- oven ordering;
- fireplace arrangement;
- ordering barbecue and all in the same vein.
With a high degree of probability, something you need will be found. For example, that stove-maker from Izhevsk on his website osnovaremonta.ru lists hundreds of ready-made designs that are just waiting to be brought to life. We don't know why the resource has such a strange sounding address, but there are actually a lot of useful videos that will show you how to masonry in one case or another. Please note that the seams are neatly dressed, it is explained how to divide the brick, how many halves, quarters and other pieces are needed. This is just a great course. And the choice is really great.
We took from the resource the most interesting moments from our point of view so that readers bother to search, only having prepared in advance. The diagram below fully and completely indicates the rules for choosing the cross-sectional area of \u200b\u200bthe chimney of various designs. It does not apply only to closed systems where the air is supplied separately, for example, from the street. But in this case, the easiest way is to use forced oxygen injection, as in condensing boilers, or copy an existing factory design.
Three types of section are shown at the very top of the graph:
- Round.
- Square.
- Rectangular.
- On the x-axis, we see a certain ratio, which is obtained by dividing the chimney area by the portal area. To get a percentage, multiply the quotient by 100.
- On the vertical axis, the minimum height of the pipe is set, at which the structure will be consistent.
An example of calculating the cross section of a chimney and choosing its shape
Let's say we have a fireplace. The portal of which is 8 masonry high and 3 masonry wide. This is approximately 75 x 58 cm in centimeters. At the same time, the size of the channel is equal in area to just a brick. What is 12.8 x 25.8 cm. We draw your attention to the fact that the dimensions may be different for the products of individual factories, so check the data before laying, having thoroughly examined the order and taking the actual dimensions. Now let's do the math:
- The letter F denotes the area of the fireplace portal, it is equal to 75 x 58 \u003d 4350 square centimeters.
- The small letter f denotes the cross-sectional area of the chimney, meaning its inner passage. This will be 12.8 x 25.8 = 330.24 square centimeters.
For example, it is planned to build a two-story mansion, which has a height of 11 meters from the fireplace to the chimney cap. In this case, the ratio of areas as a percentage should not be lower than 8.4%. Since you hardly want to change the design, we select the appropriate diameter of the chimney for the fireplace. In particular, the area of the pipe will be equal to:
f \u003d Fx 0.085 \u003d 370 cm2, from where we already find the diameter:
D= √4 x f / P = √4 x 370 / 3.14 = 21.7 cm.
- Glass.
- Ceramics.
- Steel.
- Asbestos cement.
An example of a chimney design for a gas purchased fireplace
The optimal diameter of the chimney for the fireplace is already indicated in the passport. On the back wall or on top there is a branch pipe for installation of a standard section. But what about the height of the pipe? But no way, the manufacturer did everything to make the device work. Just follow the installation instructions in the user manual. Usually this concerns a straight vertical section above the heating device. Most often, the minimum length is regulated. If this rule is violated, then the craving will disappear. The products of combustion will go into the room. As for boilers, they most often have a combined hood. This is when there is a coaxial pipeline, usually air enters through the outer pipe, and combustion products are removed through the inner pipe.
Chimney diameter for gas boiler hardcoded. While oxygen is moving towards the furnace, it still has time to heat up a little, which generally increases the efficiency of the device. Condensing boilers operate somewhat differently. They have a separate hood most often. At the same time, air is forced from the street by a fan, and the combustion products are cooled on a heat exchanger, through which, for example, water flows, until it is removed from the flow most of condensate. It is believed that this occurs approximately at the border of 30 ºС. This does not mean that you can not insulate the pipe at all, but the danger of clogging the passage with an ice plug really drops.
Chimney diameter for solid fuel boiler calculated by designers and carries the least danger. Although the distillation of coal or wood (if they are raw) at low temperatures also gives little pleasure. We have already talked about what creosote is, and why it is better not to deal with it directly. What should be the diameter of the chimney, of course, but there is one more nuance: fluff should be done on the passage of floors chimney. This is a brick thickening that reduces the range of fluctuations and the temperature value at the point of contact with the ceiling. In the case of a steel chimney, a box is used, which is filled, for example, with expanded clay. It is allowed, using adapters, to insert one segment of an insulated version in this place, like a Volcano.
The diameter of the pipe for the chimney of the bath is not so important, because the firebox is usually closed (for safety reasons), and the supply channel goes outside. Much more attention should be paid to the correct connection of pipes. A narrow subsequent one is inserted into the wide upper part of the pipe. This ensures that no leakage of creosote into the tubular water tank is ensured. And it will just make breathing easier.
We hope that we have answered the question of how to calculate the diameter of the chimney pipe. When laying on floors, please note that with significant heat loss due to thin steel, condensate can form an ice plug at the outlet. At the same time, a chimney built into the wall is also not the best option, because a lot of heat is given off to the atmosphere. Apply rendered constructs. The distance from the chimney to the wall is about 40 cm, the material is asbestos cement or steel. See above for the limitations of either option.
That's all for today, ask questions in the comments. We say goodbye exactly until the next time!
The use of materials is allowed only if there is an indexed link to the page with the material.
AT country houses and baths of individual construction, various heating and air intake systems are provided. Each must be equipped with a device output of combustion products. The correct operation of the entire heating system to a large extent depends on the height of the chimney. Today we will decide chimney pipe calculation criteria.
Chimney calculation
Many believe that the size of the chimney does not play an important role in creating a comfortable temperature inside the house. The chimney pipe serves not only to remove the resulting smoke and combustion products, it has a major impact on the efficiency of heating appliances and energy consumption.
For the correct calculation of the chimney the following should be taken into account:
- Based on the fuel with which the house will be heated, the material for the manufacture of the chimney must be selected. For various energy carriers flue gas temperature is different.
- The elevation of the chimney above the roof ridge, the section inside the pipe and design features entirely affect the operation of the heating units of your home. Incorrect calculation and design can lead to breakage heating equipment.
- In some cases, for the correct operation of heating equipment and the removal of combustion products, it is necessary to have a separate ventilation for air intake. In many cases, the channel do together with a chimney.
The height of the chimney above the roof depends on:
- location pipes relative to the ridge
- from the angle of the roof
- from the presence of foreign objects near the pipe
- on the strength of the wind in a given place, as well as on the height of the snow cover
Minimum Height Dimension chimney is 50 cm, is being built provided that the pipe along the horizontal roof line is one and a half meters away from the ridge. This location is the most ideal. Less snow forms on the roof at this location, which reduces the risk of leakage during the melting period. The construction of any chimney relative to the ridge is based on the requirements SNiP41-01-2003 and SP 7.13130.2009.
General provisions
- The height of the pipe from to the outlet is about 5 meters. With a flat roof, the pipe is built with a height at least 50 cm
- When the pipe is located relative to the ridge at a step of one and a half meters, the height of the pipe can be 50 cm in relation to the last or enclosing obstacle, this applies to pitched roofs. At distance from 1.5 m to 3 m to the ridge, the height of the pipe must not exceed it. At a distance of more than 3 m from the ridge line, a line is drawn to determine the height of the pipe at an angle of 10 degrees relative to the horizon.
- If there are tall buildings nearby, the height of the pipe at wood heating built above the roof of a nearby building.
- Ventilation ducts for air intake, located near the chimney, must have the same height with it.
There are several location recommendations. chimney pipe and its installation. Chimneys should not be located near attic windows in order to avoid carbon monoxide and products from getting into the air during gusts of wind. burning in the room. The outer part of the stainless steel chimney should not be fixed rigidly to the roof or truss structure, in case of a strong gust of wind it may be damaged whole roof structure.
How does the diameter of the chimney affect its height
Height of all flue ducts regulated by SNiP, it is also important to take into account the cross section and the internal shape. These parameters greatly affect the operation of heating systems and efficiency.
Warm air, heating up, rises, the closer to the exit to the outside, the more it cools, as a result of which draft is formed. With very large dimensions of the internal sections of the chimney, the air cools faster, forming at the same time, which reflects badly on the traction itself.
What can be done? Perhaps increase the height of the pipe, by reducing its cross section. In this case, the draft will become so strong that it will lead to a loss in the efficiency of the heating boiler or stove, fireplace. Since the influx of cold air from below will be sharply increased, as a result of which the heater will be heated poorly. Because of this, an increase in fuel consumption and heating time will be required.
High chimney and small internal section too will not give good traction for the proper operation of the stove, fireplace. It is possible for carbon monoxide and smoke to enter the room itself. In order not to encounter such a situation, it is better to seek the help of a specialist or calculate the height of the smoke pipes with a calculator.
A large number of country houses does not manage only with a heating system, many people want to see fireplaces, stoves in their house, all these devices need their own smoke exhaust channel. maybe arrangement of separate chimneys. In practice, they build a common chimney with the required number of channels, taking into account their power, type of fuel and the volume of produced combustion products.
Such chimneys have a number of advantages:
- stable operation of all devices
- saving usable space, finances.
Which chimney is better
It is considered optimal in the form of a cylinder from. Even brick chimneys are built in metal pipes of the required diameter. The products of combustion move upward in a spiral, and the cylinder is the best options for formation of maximum thrust.
In square or rectangular brick pipes, turbulences occur inside, which. When burning fireplaces and stoves with wood, this form of chimney is especially convenient, as it allows you to slow down the release of heat and increases the efficiency of devices. One chimney can serve only two heating devices, but only when the size of its internal section allows work with them in parallel.
A stainless steel chimney for stoves and fireplaces is much stronger than a brick chimney and relatively inexpensive. Stainless steel chimneys are resistant to corrosion and temperature changes, unlike brick chimneys, which can crumble during operation. These chimneys are easy to operate, it is quite easy to replace any element, since the whole structure consists of modules. A stove or fireplace will be much easier to equip stainless steel chimney
The chimney discharges combustion products from fireplaces, stoves and other heating devices into the atmosphere. As a rule, chimneys are arranged vertically, however, inclined or gently sloping structures are also often found. Soot, ash and soot regularly accumulate in the chimney. This happens for several reasons: the builders made an incorrect calculation of the chimney or violated the technology for its installation.
Parameters affected by the length of the chimney
Construction practice has shown that the size of the chimney depends on:
- Efficiency of heating equipment (fuel and heating combustion efficiency);
- Traction formation;
- The rate of heating of the pipe walls. Rapid heating of the walls leads to the formation of condensate, which, when certain conditions can mix with soot and form build-ups that reduce the draft and efficiency of the fireplace.
In addition, the quality of the material also affects the performance parameters. The rough inner walls of the chimney contribute to the formation of soot and burning. For this reason, it is not recommended to finish the smoke exhaust pipe with clay mortar.
Effect of Altitude on Performance
Amateurs think that a long pipe will provide them with good traction for life. The height of the chimney affects the efficiency of heating equipment, but not in the way we used to think. Therefore, the length must be calculated taking into account aerodynamic resistance (air resistance and atmospheric pressure).
How to calculate the height of the chimney
A long chimney does increase thrust, however, it does not speed up the release of combustion products into the atmosphere. As a result, the base of the chimney above the roof heats up, which leads to the destruction of its foundation. The resulting cracks reduce the draft and burning rate of the fireplace.
Nearby buildings, especially multi-storey buildings, must also be included in the calculation of the height of the chimney. Skyscrapers can not only change the direction of the wind, but also completely block its breath.
Which chimney is better
Chimney pipes - ceramics
Experts unanimously believe that the cylinder is the optimal form for the removal of combustion products into the atmosphere. Even an incorrectly calculated chimney height has little effect on performance characteristics such a design. As for the material, it is better to stop your choice on asbestos-cement or metal cylinders. In such pipes, the diameter of the chimney does not greatly affect the speed of smoke movement above the roof.
They cannot do without such materials. modern boilers operating in stop and start mode. The peculiarity of this heating system is that it can switch to standby mode, while saving a significant amount of fuel.
As for rectangular or square structures, turbulence often forms in it, which causes a loss of traction. However, this shape is considered optimal for modern wood-burning boilers. The slow movement of smoke into the atmosphere and the low height of the chimney above the roof - all this helps to slow down the escape of heat and increase the efficiency of the heating system of modern fireplaces.
How to calculate correctly?
The international standards say:
- The height of the chimney from the grate to the edge should not exceed 5 m. World construction practice has shown that the optimal height of the chimney for smoke removal is a structure of 6 m;
- Above the plane of the roof, the building should rise at least 0.5 meters. How to calculate the optimal distance? Measurements are taken from the plane at the installation site of the chimney;
- When the pipe is at a distance of 2 m from the roof ridges or large fences, then it should rise above them by 0.5 m. Insufficient height of the chimney reduces the traction force and the rate of burning logs;
- When the smoke exhaust pipe is located at a distance of 2-3 m from the skates or parapets, then it can not be raised above them. Protruding objects must be in the same horizon. You can correctly calculate the horizon using the water level.
In a separate category, it is necessary to highlight the calculation of the height for a structure that is further than 3 m from parapets or ridges. In this case, the length of the chimney is calculated using a horizontal line, which is created by a building cord from the chimney to the ridges or parapet. The slope of this line should be 10 degrees. Practice has shown that a slight deviation of 2 degrees is allowed.
In addition to calculating the length of the pipe, attention should also be paid to the shape and cross section of the chimney. Experts have repeatedly noted that a properly selected shape and diameter can improve the operation of the device several times.
Selection of the section and shape of the pipe
Selection of insulation thickness depending on the temperature of the flue gases
For brick chimney models, it is necessary to carefully observe the proportion of a rectangular section in a ratio of 1: 1.5. It is worth noting that the inner corners take on a rounded shape. It is quite simple to calculate the rectangular shape of the pipe - during laying, it is only necessary not to exceed a cross section of 10 cm2. The chimney diameter for a round structure cannot be less than 15 cm. If the chimney layout includes a brick structure with a metal pipe, then its diameter in this case should not exceed 18 cm.
Results
Practice has shown that independent calculation of the cross section and height of the smoke exhaust pipe leads to a decrease in the efficiency of the fireplace. The fact is that an ordinary citizen does not have special equipment that will allow you to accurately calculate the required parameters. It is for this reason that it is recommended to contact specialists. However, you can only use the data provided if your situation is exactly the same as the cases described.
Video: Typical mistakes when installing stoves and chimneys
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In order to install the chimney correctly, it is necessary to carry out a series of design work, which includes both the calculation of the chimney and the choice of material for its manufacture. And if for industrial-scale work it would be best to attract professionals, then in private construction you can limit yourself. Below we will consider how to calculate the chimney.
Types of chimneys
The purpose of the chimney is to remove the products of combustion and smoke from the furnace or any other heating device outside the premises. Draft in any household chimney is formed naturally and does not involve the use of any additional devices.
Modern chimneys can be made:
- From brick. Since such a structure has a significant weight, it is necessary to build a solid foundation for it.
Advice! Experts advise adding lime to the composition of the mortar used for brickwork, which will avoid the formation of condensate, which has a detrimental effect on the walls of the building.
- From sandwich pipes, which are made of two layers of metal with a heater laid between them. The most commonly used material for the manufacture of such pipes is stainless steel. In most cases, basalt acts as a heater.
- from polymeric materials. Such pipes should not be subjected to excessive high temperatures, therefore, such chimneys can be used for geysers and small boilers. At the same time, polymer pipes are very durable, easy to install and have a low price.
- From ceramics. Such pipes are characterized by high strength, but they cost a lot. Therefore, they are most often used for arranging industrial-type chimneys. Due to their significant weight, such structures, like brick ones, require laying the foundation.
Important! In some situations, combinations of materials intended for the manufacture of chimneys are possible. For example, a polymer or metal chimney can be lined with bricks.
How is a chimney calculated
In order to calculate the dimensions of the chimneys, it is necessary to navigate in the parameters heater. The main dimensions of chimneys are the cross-sectional diameter and height. This data is in the accompanying documentation of the equipment.
How to calculate height
The performance of heating devices directly depends on this parameter, therefore, calculating the height of the chimney is very important. According to the SNiP documentation, the minimum height of the chimney is 5 meters. If the pipe is less than this value, then the necessary natural draft will not occur in it. However, a too high chimney is also bad, because in this case, the smoke will slowly pass through the system and cool down to reduce the draft.
A serious calculation of chimneys is used in industrial construction. It uses a very complex system of calculations. In private construction, the requirements are usually much less, and the calculation of the height of the chimney involves following the following rules:
The method of aerodynamic calculation of chimneys was developed to determine the resistance and selection of chimneys. A good aerodynamic calculation should take into account possible pressure drops in sections of the gas-air paths, also taking into account the resistance that occurs in a certain section.
How is the cross section of the chimney calculated?
In order to calculate the draft of a chimney, it is necessary to first determine its diameter. In order not to carry out complex calculations, you can use the following recommendations of experts:
- If the power of the heating equipment does not exceed 3.5 kW, then a chimney with dimensions of 0.14 by 0.14 meters will be enough for you.
- If the heating boiler has a power in the range of 4-5 kW, then in this case the optimal dimensions of the chimney will be 0.14 by 0.2 meters.
- When using powerful equipment with indicators in the range of 5-7 kW, the cross section of the chimney should be at least 0.14 by 0.27 meters.
Advice! If you know the power of the heater used, then you can safely use the recommendations of the experts above. If the power is unknown, then appropriate calculations will have to be carried out to determine the optimal cross section.
- The amount of fuel burned in the appliance per hour. Most often, this parameter can be found in the characteristics of the equipment.
- Indices of gas temperature at the inlet to the chimney. This parameter can also be found in the hardware specifications. Most often it fluctuates between 150-200 degrees Celsius.
- Chimney height.
- The speed of gas passing through the pipe.
Note: The default value is 2 m/s.
- Indicators of natural traction. Usually this parameter is taken as 4 Pa per meter of chimney length.
The main parameter in calculating the pipe section is the amount of fuel burned. When calculating the diameter of the chimney, you should use the following formula: F \u003d (π * d²) / 4. Thus, to find out the diameter, we derive a new one based on this formula: d²=4*F/π. Using it, you will already be able to determine the pipe section required for your heating equipment.
Conclusion
In order to ensure the correct operation of the heating system, it is necessary to make a competent calculation of the parameters of the chimney. Only in this case will an effective natural thrust be created. And if complex calculations are usually carried out in an industrial environment, then every home master will be able to independently determine the parameters of a domestic chimney.