Deflector for a chimney pipe: making it yourself

Author: Yuriy Fedorovich Kolesnikov, thermal power engineer

If you take a closer look at the chimneys and ventilation pipes of residential buildings, the variety of chimneys on them (deflectors, weather vanes) is amazing. But the main task of the deflector is not to decorate the chimney, but to increase and stabilize draft depending on the weather, and thereby improve the efficiency of the heating device and reduce heating costs. A deflector on a ventilation pipe can provide energy-independent (and free) supply and exhaust ventilation, see below. But at the same time, there are also plenty of opponents of installing deflectors on the pipes of residential buildings, and they provide compelling arguments in their favor. The purpose of this article is to help the reader understand in what cases it makes sense to install a deflector on a chimney or ventilation, and then how to choose the right one or make it yourself.

Deflectors on chimneys of residential buildings

The most important question

Before selecting or making a deflector for a pipe, you need to decide - is it needed at all? The deflector may freeze, be covered with soot or carbon deposits (coked), clogged with fallen leaves, wind-blown debris or dust. In any of these cases, if the deflector is on the chimney, the inhabitants of the house are at risk of getting burned. The deflector does not increase the efficiency of a furnace or boiler much, but it requires regular inspection and cleaning. At least once every 3 months for solid fuel stoves and at least once every six months for gas, liquid fuel or pyrolysis stoves and boilers. For more information on the dangers that can result from installing an unsuitable deflector on a pipe, see the video:

Video: what are the dangers of deflectors, umbrellas and weather vanes on a chimney?

Therefore, if you have an old wood or coal stove, but the draft is not good and the wind is blowing into the chimney, instead of a complex deflector it is better to install a simple chimney, for example. umbrella or tent. And in other cases, you need to thoroughly understand which deflector is needed for this particular stove/boiler with this particular chimney. It is also important not to confuse a smoke deflector with a ventilation one - small traders and the authors of some popular publications do not see or do not make the difference between them.

Operating principle of deflectors

The standard device includes three main elements - a cylinder, a diffuser, and a protective cap (umbrella). Additionally, the design is equipped with ring bumpers, which are located in the lower part and around the diffuser. There are several types of deflectors that differ in shape, size and number of elements, but all of them, regardless of type, work on the same principle.

Deflectors

The structure is installed at the very top of the chimney and creates an obstacle to air flow. When the wind hits the walls of the cylinder, it loses its strength and breaks up into many small air currents of low intensity. Some of them rise up the body and capture the smoke coming out of the chimney. This is what increases draft in the chimney duct.

Due to the absence of turbulence, smoke and carbon monoxide do not fall back into the pipe, but are completely removed outside. In addition, the deflector prevents the pipe from clogging through the top and performs decorative functions.

Decorative deflectors

It has been proven that after installing the deflector, the efficiency of the heating device increases by 15-20%. Of course, the deflector itself will not give anything if the chimney is not installed high enough or the cross-section of the connecting pipe is incorrectly selected. The location of the pipe on the roof also matters.

Evolution of the deflector

Deflectio in Latin means “I reflect” in the sense of “throwing away.” Not directed in a certain way, like a reflector, but just to the side. A cap for a chimney pipe made of skins, large shells, etc. It was already installed by primitive people to avoid wind blowing into the chimney.

The role of the deflector in creating thrust, its stabilization despite the vagaries of the weather and the ability of the deflector to increase the efficiency of heat-generating devices was first seriously thought about at TsAGI almost 100 years ago on the instructions of the newly hatched Soviet government. Before that, heating engineers tried to improve chimneys for this purpose. Have you seen in old photographs the huge pot-bellied pipes of American steam locomotives, like an inverted pear, or the long thin ones of English ones with a rosette at the top?

At TsAGI, the venerable aircraft designer D. P. Grigorovich worked on deflectors in creative collaboration with A. F. Volpert, who was fluent in mathematical apparatus. The latter is also, and even more, known for his work in the field of radio engineering (Wolpert-Smith diagram, etc.). Together and separately, Grigorovich and Volpert developed several types of deflectors for various purposes, therefore, various deflectors of Grigorovich, Volpert and Volpert-Grigorovich are described in the specialized literature.

Stages of evolution of the smoke deflector from a simple umbrella to the TsAGI deflector

Grigorovich began by aerodynamically correctly calculating an ordinary smoke umbrella, pos. 1 in Fig. This has already significantly improved the performance of the device; Grigorovich cone - remember, it will be very useful. Wolpert proposed to equip the umbrella deflector with an aerodynamic skirt-diffuser (item 2), but the deflector remained aerodynamically imperfect, see below. It was supplemented with a streamlined body of rotation instead of a cap and a cylindrical body-shell. In the end, after repeated blowing in a wind tunnel, the government commission was presented with a TsAGI deflector (item 3), which fully satisfied the issued technical specifications and far exceeded it.

The TsAGI deflector is still the most common in the world due to its technical excellence. There are modifications of them for different purposes, see below. But other developments of Grigorovich and Volpert were not in vain - most models of modern smoke deflectors are developed on their basis. Which one is more suitable for what, we will talk about this further.

Why do you need a deflector?

The main purpose of the deflector is to strengthen and stabilize draft in a chimney or exhaust ventilation unit.

Due to the rarefaction of the air inside the device, there is always a fairly strong draft, which removes smoke, ash, carbon dioxide, carbon monoxide and other by-products of fuel combustion.

In addition to creating draft, the deflector prevents the backflow of exhaust gases down the chimney into the room. Sometimes the wind on the roof is so strong that the natural draft of the chimney cannot overcome the wind resistance, causing the exhaust to be retained in the chimney or enter the room.

We recommend that you read: How to build a columnar foundation from asbestos pipes with your own hands

This contradicts the safety standards for the operation of residential buildings and structures. The deflector, powered by the force of the wind, directs it in the right direction, preventing the effect of suppressing draft.

Another important function of the deflector is to protect the chimney pipe or exhaust unit from the ingress of atmospheric precipitation, dust, leaves and other pollutants. The device works as a cap or visor, covering the chimney opening.

Some owners also use deflectors for decorative purposes, decorating them or making them in various shapes (animals, birds).

Types and schemes

The entire variety of trade names of smoke deflectors fits into a limited number of design types and aerodynamic designs. First of all, according to their interaction with the natural draft of the chimney, deflectors are divided into:

Active - with a built-in working smoke exhauster. To ensure the specified characteristics of the deflector, the smoke exhauster must operate continuously while it is burning in the firebox.
Active-passive - a low-power smoke exhauster for extreme cases: complete calm, storm, excessively intense fire, etc. The minimum permissible technical characteristics of the chimney are ensured even when the smoke exhauster is turned off.
Passive-active - the deflector creates a small amount of its own thrust in a non-volatile way.
Passive – there is no deflector’s own draft.

We do not further consider active deflectors as energy-dependent and not optimal for low-power home heating devices. Of the active-passive ones, we will consider one, designed for a low-power 12 V fan and suitable for DIY manufacture.

Aerodynamic designs of chimney deflectors

According to the aerodynamic design of the chimney deflector, it is possible to make a trace. way (above in the figure):

Aerodynamically imperfect (incomplete) - in the space occupied by the deflector there is a “pocket” - a weathering area in which accumulation of air, flue gases or a mixture of them is possible;
Aerodynamically fully open - there is no wind pocket, but the wind has free access to the working space of the deflector;
Aerodynamically perfect closed - there is no wind pocket, the wind does not have free access to the working space;
Deflector-vane (see below);
Vortex deflector.

An aerodynamically perfect closed deflector is the most complex structurally and technologically, but has a huge advantage: due to heating of the shell, almost all aerodynamically perfect closed deflectors provide their own energy-independent thrust. This is the only passive type of deflector that can increase the natural draft of a chimney in complete calm.

Note: an aerodynamically perfect closed deflector is the TsAGI deflector mentioned above. This aerodynamic design was invented precisely at TsAGI.

Vortex deflectors are easily recognized by their “ragged” design with sharp protrusions. There is still much that is unclear in their aerodynamics, as in vortex aerodynamics in general (the Navier-Stokes equation was solved in general form only 2 years ago). It is absolutely impossible to predict the behavior of a vortex deflector under any external conditions with any chimney. Therefore, vortex deflectors are not considered further. Whether or not to believe their manufacturers is your own business.

Aerodynamics

There are enough diagrams of flue gas flow in deflectors in publicly available sources. But from the point of view of the homeowner and the craftsman, the nature of the interaction of the deflector with the natural draft of the chimney and the wind in the wake is more important. aspects:

Will the deflector worsen the original draft?
Is the deflector capable of increasing the initial thrust in calm conditions?
How much and how does the deflector increase wind loads on the pipe?
How prone is the deflector of this design to icing/clogging and is it easy to clean?

Then it is better to consider the wind not according to the meteorological scale, but according to the rough gradation of force and the dynamics of the velocity field:

calm;
weak/medium (moderate) – up to 6 points on the weather scale;
strong – 6-8 points;
very strong – over 8 points;
gusty - the wind of any strength is really gusty, or sharp (strongly sloping up or down), or turbulent.

An idea of the aerodynamic properties of passive smoke deflectors is given in Fig. higher.

Simple cap

An ordinary chimney smoker in the form of an umbrella, if it is made in the form of a Grigorovich cone, is not so bad:

Chimney with a tent-shaped chimney-umbrella.

With a massive heat-intensive chimney, it keeps the draft within the permissible limits for a wood/coal stove in even winds up to a severe storm (10 points).
In any wind, up to hurricane force, it does not create destructive loads on the pipe; It's more likely to break loose and fly away.
Structurally simple.
It is slightly coked and clogged, and is easy to clean as part of the annual inspection and maintenance of the chimney.
Due to imperfect aerodynamics, it is little sensitive to the configuration of the umbrella. If the house is in the wind, the chimney-umbrella can be made into a tent (see figure on the right), which simplifies the work and provides greater opportunities for its design.
With a 2-3 channel chimney (see below) it provides technical performance (except for increased draft in calm conditions) no worse than an aerodynamically perfect closed deflector.

The disadvantages of an imperfect smoke deflector are also quite serious:

In calm conditions, the initial draft decreases the more strongly, the more intensively the stove is heated. What is especially dangerous in the harsh, quiet winter: the stove can choke and puff out fumes.
In strong winds it can create excess draft, which sharply reduces the efficiency of compact channel stoves (for example, Dutch ones with 2.5-3.5 bricks) and fireplaces.
In very strong/gusty winds, blowing into the pipe and causing reverse draft cannot be ruled out.

In general, an imperfect deflector-umbrella is the optimal smoke vent for a brick chimney of a properly built and well-maintained solid fuel house stove, operated in places where hurricanes and storms are extremely rare. There are ways to make a smoke umbrella uninflated (see below), but they complicate it to the point that most often you have to choose an aerodynamically complete or perfect deflector.

Open

The aerodynamically open deflector does not reduce the initial draft and, in any wind, keeps it within the limits acceptable for stoves and boilers using solid, liquid fuel and gas. It freezes quite heavily, becomes coked and littered, but is easily accessible for cleaning. Its disadvantages are:

A streamlined body of rotation instead of a cap is a technologically complex unit.
The resulting vector of wind loads is such that an aerodynamically open deflector tends to collapse the pipe, while an umbrella tends to fly off it.
In winds stronger than force 8, the lateral load on the pipe increases sharply and then grows according to a power law.
It does not absorb dynamic loads from gusts of wind well, so an open deflector cannot be installed on a brick pipe.
Unsuitable for pyrolysis heat-generating devices: in a strong wind it immediately sucks out the pyrolysis gases and the stove/boiler goes out.
Not very suitable for design: blotches and figures spoil the overall aerodynamics. The only places where it is possible to place decorations are the upper pole of the body of rotation and the lower edge of the diffuser (see below).

Note: at one time, we and the USA conducted experiments on the use of open deflectors on steam locomotives to increase efficiency at low speed. The result was disastrous - at mid-speed a tongue of flame appeared from the pipe, and none of them could accelerate to the design speed.

In general, an aerodynamically open deflector is suitable for all types of heating devices, except pyrolysis ones. Provided that the deflector is inspected and cleaned at least once every 2 months, and the draft is checked before each firebox. Very well suited for chimneys with insufficient draft and, especially, for sauna stoves: there have been no cases of fires in saunas due to an open deflector. Properly heating a bathhouse is not an easy task, and checking the deflector will not significantly complicate it.

Note: there are types of open deflectors that create virtually no lateral loads on the pipe and are suitable for fragile ceramic and glass chimneys, see fig. on right. However, dust, debris and soot accumulate in the open rotating body, which spoils the aerodynamics of the device and makes it difficult to clean. Therefore, manufacturers recommend such products only for gas boilers in places with not very dusty air.

Perfect

The advantages of an aerodynamically perfect closed deflector are partially indicated above. Besides:

The aerodynamically perfect closed deflector ensures stable draft in any external conditions, sufficient for any household stoves and boilers.
It does not clog or freeze inside, and ice and dust outside have little effect on its operation.
With minor modifications it is suitable for use as both smoke and ventilation non-volatile, see below.
It perfectly absorbs dynamic loads from wind gusts and is therefore suitable for installation on pipes made of any materials.
2-3-4 chimneys can converge into one oval, triangular or square shell in a bundle.

The disadvantages of a closed deflector are not so significant:

The lateral force on the pipe in a strong wind gives more than an open one, but then with increasing wind it increases linearly, i.e. the pipe under the open deflector can always be reinforced or reinforced with guy wires.
Quite complex structurally and technologically.
Unsuitable for design: any blotches and figures spoil the overall aerodynamics, and the coloring only enhances the utilitarian appearance of the deflector.

Design and types of deflectors

Despite the existence of many models of deflectors, they are basically built using the following structural elements:

inlet pipe with nipple or flange connection;
an outer cylinder, which is called a diffuser;
housings;
a cone-shaped cap called an umbrella;
brackets for attaching an umbrella.

Some deflector designs may use two cones—direct and reverse. The first serves as protection against precipitation, and the second serves to redistribute the flow of combustion products.

Various deflectors have common structural elements

For making deflectors with your own hands, galvanized sheet or stainless steel is best suited. In addition to these materials, the industry has mastered the production of devices with a protective enamel layer or a coating of heat-resistant plastic.

Among the many deflectors that you can make with your own hands, there are several of the most popular designs.

Deflector-vane

This reflector has a rotating part (wind vane), which rotates when the wind direction changes. In this case, the deflector curtain shields the chimney from incoming air masses and contributes to the appearance of vacuum on the leeward side. Thanks to this, active suction of combustion products is carried out, which eliminates backdraft and the formation of sparks.

The deflector with a wind vane can be rotated, orienting the reflector exactly across the direction of the wind

TsAGI deflector

The TsAGI deflector is a universal device that can be installed on any pipe - stove, exhaust or ventilation. Developed at the Central Aerohydrodynamic Institute named after. Zhukovsky device has a simple design with an open flow path and protection against reverse draft. There are two types of TsAGI reflectors, designed for external or internal installation. Thanks to its many advantages, this type of deflector has gained wide popularity among home craftsmen. However, the design is not without its drawbacks. The “weak link” is the narrow passage section, which can be blocked by a layer of ice on the inner cylinder. In addition, the TsAGI deflector is not effective enough in low winds and calm conditions - in these conditions its design creates little resistance to natural draft.

The TsAGI delector has a simple design and excellent performance characteristics

Disc-shaped

This deflector got its name because of several cones (plates) in its composition and refers to devices with an open flow path. The reflector has a protective umbrella combined with a cone and a lower part in the form of a cap with a hole for smoke exit. The vacuum occurs due to the plates directed towards each other, which form a narrowing channel for incoming air flows.

In a disc-shaped deflector, vacuum occurs in the gap between the cones directed towards each other

Round "Volper"

The device has a design similar to the TsAGI reflector. The differences concern only the upper part of the deflector. A cap that protects the inside of the chimney from debris and precipitation is installed on top of the diffuser, which eliminates some of the shortcomings of the device developed at TsAGI. Zhukovsky.

"Volper" has minimal differences from the TsAGI traction amplifier, which provide it with advantages in the absence of wind

Grigorovich deflector

One of the most repeatable designs is the improved TsAGI deflector. The smoke that comes from the chimney passes through the narrowing channel of the diffuser, thereby increasing its flow rate. The Grigorovich deflector is best suited for chimneys installed in lowlands and areas with weak air flow, since it is able to provide good draft even in complete calm.

The Grigorovich deflector is an ideal solution for areas with weak air currents

H-shaped

Deflectors, the silhouette of which resembles the letter “H”, are designed to equip chimneys of powerful stoves and boiler plants. In such devices, the exhaust gas flow is divided into two parts and accelerated out through two side diffusers. The advantages of the design include a significant improvement in traction when air masses move in any direction. In addition, the H-shaped deflector does not require the installation of a canopy, since the mouth of the chimney is protected by the transverse pipe of the device.

H-shaped draft amplifiers are designed for installation on chimneys of powerful heating units

Rotating

The device is made in the form of a sphere with many curved side blades. The presence of blades allows the device to rotate in a certain direction and work like a turbine. Rotary deflectors are best suited for gas boilers and do an excellent job of protecting the chimney from debris and precipitation. The disadvantages of devices of this type are their low efficiency in icing conditions and lack of wind.

Numerous rotating deflector blades create thrust like a turbine

Technological tricks

Incorrect design of chimney hood

The first rule is not to make chimneys like a gable roof or barrel vault (see figure on the right). These are suitable for their intended purpose only for mobile devices, when the axis of the umbrella can be arbitrarily oriented with the wind. Or as decorative for a false chimney. There is such a fashion in houses with bio-fireplaces. And in other cases, the craving will follow the will of the elements, even to the contrary.

Next, to make a chimney deflector with your own hands, you need to master some tinsmithing techniques. First of all, connecting the sheets into a fold (fold), or folding, see fig. below. Most often, the parts of the deflectors are connected with a single standing seam, but for umbrellas of imperfect deflectors, a double standing seam is sometimes used for decorative purposes.

Joining sheets of thin metal into a fold (folding)

Next, you need to learn how to mark the patterns of the deflector parts using the external dimensions. For those who prefer to learn visually, we provide a selection of video tutorials on making parts for smoke deflectors:

Round umbrella:

Pyramidal (tent) umbrella with the top in the center:

Elongated faceted umbrella:

Transition from a square to a circle (a square inside a circle):

Very important for closed baffles for low-power furnaces and boilers, see below.

Moving from circle to circle:

All these patterns can be constructed using only a ruler and a goat’s leg compass (into which a pencil is inserted. Well, for those who are inclined to study the basics in depth, before getting down to business, we provide a selection of projections and formulas for accurately constructing part developments. Pay attention to elongated umbrellas: they are placed on 2-3 way chimneys. Smoke channels, each of the minimum cross-section allowed for a given heating device, are placed in a row. The probability of blowing out 2 channels at once is extremely small, and all 3 are practically absent.

Here in Fig. - data for constructing a truncated cone, of which there are more than enough in deflectors. The initial data is the height of the cone H, the radii of the apex and base R1, R2. Also pay attention to the inset marked in red: this is a development of the same Grigorovich cone. The forming angle (in this case 30 degrees) is found as φ = arcsin(H/r), where H is the height of the cone, and r is the radius of the base. The radius R is determined similarly to L for a truncated cone, but H and r are squared. However, for those who have not forgotten the Pythagorean theorem, this is already clear.

Construction of a development (pattern) of a tent (pyramid) with the vertex in the center

After the cones, it will not be difficult to figure out the development of a single-center tent, see fig. There is only one “but”: the allowance in the example of the pattern (on the right in the figure) is given based on a single riveting (for strength) solder seam.

How to construct a development of a truncated cone and Grigorovich cone

To connect metal up to 0.6 mm thick into a single fold, an allowance of 20 mm must be taken on one side, and 21+2+20 mm on the other. If the metal is 0.6-1.5 mm, then 30 and 31.5+3+30 mm respectively. But, generally speaking, a seam soldered and riveted at the edge is easier to make, it looks neater and resists corrosion better than a folded one. If the roof is covered with iron, then, of course, riveting and soldering the sheets is simply technically impossible. But the deflector umbrella is a different matter. It is assembled by soldering and riveting like this:

Mark and cut out the development;
Drill holes for the rivet;
Bend the sides (wings) of the allowance inward at 90 degrees;
Rivet the edge;
The sides are compressed through wooden backing bars with clamps;
Solder the seam.

In a similar way, a sweep is built and the hip tent (umbrella) of the chimney is assembled, see fig.

Construction of the development of the hip tent (umbrella) of the chimney

And finally, the most complex detail: the diffuser of an aerodynamically perfect closed deflector, also known as an adapter-skirt from a square to a circle (circle inside) for installing a smoke umbrella on a brick pipe. The construction rules are not complicated (see figure), but they require precision and accuracy in work.

Construction of a development (pattern) of the transition from a square to a circle (circle inside) for the diffuser (skirt) of the chimney deflector

Note: you can additionally equalize the draft of the open and imperfect deflectors on a round pipe, and also reduce the probability of blowing into the latter to negligible if the diffuser/skirt generatrix is bent inward, see fig. But the work is so complicated - after assembling the adapter from circle to circle, it needs to be knocked out on a block of hard wood.

Chimney deflectors with a diffuser with a curved generatrix

Causes of smoke

The principle of operation of the deflector as a gas exhaust structure
Smoking in a furnace is most often explained by the so-called “overturning of draft”, which occurs due to a long period of inactivity of the heating installation. This leads to cooling of the internal spaces and a decrease in the pressure gradient. As a result, the air flow in the pipe changes its direction and rushes not outward, but towards the heat source.

This phenomenon has nothing to do with the outside temperature and can occur in hot weather and cold weather. To eliminate the effect of backdraft in the chimney, you will need to increase the temperature in the outlet pipe. One of the ways this can be achieved is by installing a high-quality chimney deflector.

Constructions

Now let's see what is possible and how to make a deflector for a chimney yourself. It's easiest to start with an imperfect umbrella deflector; its capabilities are much wider than it might seem, and few materials and not very complicated work are required.

What can an umbrella do?

In the climatic conditions of the Russian Federation, a deflector-umbrella on a chimney is most often sufficient, especially since there is no evidence of waste caused by it either. But - if the smoke umbrella is made correctly. The most common mistake is that the cap is raised too high on the racks. This will not help return 100% of the original draft, but the likelihood of blowing into the pipe increases sharply.

The correct dimensions of the deflector-umbrella for the chimney are given on the left in Fig. For pipes with a clearance of 100-200 mm in diameter, they decrease proportionally, and then the value of H1 increases by 1.3 times for pipes of 150-200 mm and 1.6 times for pipes of 100-150 mm.

Dimensions of deflectors-umbrellas for chimneys and ventilation.

On the right in Fig. The dimensions of a non-blown deflector-umbrella are given, but in the conditions of the Russian Federation it is better to install it on a ventilation pipe for natural ventilation, because the mesh quickly becomes overgrown with soot or flue gas condensate, and then dust sticks to it very well.

It also does not blow out, retains the original draft and even slightly increases it with a two-story deflector-umbrella. The diagram of its action is given in pos. 1 next rice.:

Modifications of the deflector-umbrella for the chimney and ventilation pipe

For chimneys of low-power household stoves/boilers (up to approximately 40 kW), it can be simplified by making the floors the same, pos. 2. Each floor is a Grigorovich cone cut in half in height (see above); the distance between floors is equal to the height of the floor. The upper floor is gabled, i.e. the cut off top of the cone is closed with a blind lid. A 3-story umbrella for a ventilation pipe (item 3) freezes less often and clogs less than an umbrella with a mesh. For pipes 130-200 mm, the dimensions change proportionally. And finally, the Kiryushkin deflector (item 3; all cones are Grigorovich) is used primarily as an active-passive one - a low-power smoke exhauster at 12 V 100-200 mA is placed under the small cone.

TsAGI

Before we take on the aerodynamically open deflector, let’s see how the most advanced TsAGI deflector is modified for a private home. Its original design was designed primarily for industrial facilities and then for apartment buildings.

Drawings of 3 versions of the TsAGI deflector are shown in Fig. The dimensions of the original industrial version are shown at the top right. Not completely, because It is designed for a durable pipe and certainly not for a sandwich chimney. For a chimney of a private household, a Khanzhenkov deflector operating according to the same scheme (on the left in the figure) is more suitable. It produces less horizontal wind load and can be inserted into a pipe as described below.

Modifications of the TsAGI deflector for chimneys and ventilation pipes

And on the right in Fig. – dimensions of the TsAGI ventilation deflector. It can be converted from passive to passive-active by painting the shell with blacksmith's putty or other paint that well absorbs thermal radiation from the earth and objects surrounding the house. Of course, you should leave the fans in the vents of your home ventilation system, but you will have to turn them on occasionally. How to make a TsAGI deflector with your own hands, see video

Video: do-it-yourself TsAGI deflector made of metal tiles

Note: a ventilation deflector is not as luxurious as it may seem. When the wind blows through the vents, the bathroom is cold, and kitchen fumes and toilet odors are carried throughout the house. Fire valves do not solve the problem - if they slam shut, the bathroom and kitchen are stuffy.

What comes out of cones

Of the open type deflectors, the Volpert-Grigorovich deflector is the most accessible and, based on the entire range of technical indicators, is optimal for private households. Although, only they themselves knew how much of both there actually was in it.

The canonical (based on TsAGI studies) proportions of the Volpert-Grigorovich deflector are given in pos. 1 pic:

Proportions and dimensions of the Volpert-Grigorovich deflector for the chimney

On the left is a modification for an asbestos-cement pipe, which holds longitudinal loads well, but is fragile across it. The doubled height of the upper cone forming the body of rotation gives a greater lifting force, tending to tear the deflector off the pipe, but a tight clamp will hold it in any wind. For pipes 130-180 mm inside, the dimensions change proportionally.

Note: for another version of the homemade Volpert-Grigorovich deflector, see next. video clip:

Video: Volpert Grigorovich deflector to increase draft in the furnace

Reconstruction of the chimney is one of the solutions to the problem

The first sign of a permanently dying flame is an improperly designed chimney. There is no point in looking for other reasons why a gas floor-standing boiler blows out in the wind with such equipment. The gas supply is carried out under constant pressure; there are almost no significant differences. Any equipment malfunctions are unlikely, since modern boilers are reliable and simple in design. For example, the Conord boiler is known for its reliability and performance.

As for the chimney, the answer to the question of why a boiler blows out in a private house is the following:

The ventilation duct of the heating device becomes covered with an ice crust. As a result, the air circulation inside the chimney is disrupted and the gas boiler does not receive enough oxygen. In addition, water vapor enters the chimney channel, which is cooled by the ice layer and forms condensation. In turn, water droplets freeze on the walls of the chimney and the ice crust grows. Insulating the chimney duct helps solve the problem of what to do to prevent the gas boiler from blowing out. In this case, the resulting condensate will flow down the walls. The occurrence of reverse draft due to insufficient chimney height. An intensifying or changing direction wind creates a strong air flow, which enters the chimney duct and reaches the fuel combustion chamber. As a result, the flame in the burner goes out

This situation is considered more dangerous, so it is important to know what to do when the boiler blows out in a strong wind. The reverse movement of warm air simultaneously captures combustion products, therefore, they enter the boiler and pollute the combustion chamber

It is possible that harmful gases may enter the living space.

Weather vanes

Pipe deflectors - weather vanes are also called weather vanes. Sometimes all chimneys in general are called this, but this is incorrect, because... A weather vane is, by definition, a rotating device.

The deflector on the pipe - weather vane can be made rotary, self-orienting and rotating. The latter are also called turbo deflectors, and self-orienting smoke teeth, which is also incorrect. The smoke tooth is part of the chimney of an English fireplace. The weak point of all weather vane deflectors is the bearing. It becomes very easily clogged and covered with soot, and the seals are subject to increased wear. Therefore, you need to inspect the weather vane deflector at least once every 2 months. But the weather vane deflector itself almost never becomes overgrown with the main enemy of all fixed deflectors - icicles.

Pipe deflectors - weather vanes

A multi-bladed weather vane deflector (items 1 and 2 in the figure) provides stable draft in winds of up to 9-10 points with minor loads on the pipe, so it can be installed on sandwich, ceramic and glass chimneys. A single-blade weather vane deflector puts a lot of stress on the pipe in a strong wind, so it must be strong and the house must be located in a place where the storm wind will not blow up. But a single-bladed weather vane deflector can easily be designed in the shape of a bird (items 3 and 4).

Turbo deflector (item 5) – remember and don’t trust anyone – not smoke! It is ventilated or for gas boilers with electric ignition. The turbine rotates both by the wind and by the air current in the pipe, and a correctly made turbine, as in some types of wind engines, is self-spinning: the weakest initial thrust or a light breath of breeze is enough for the turbine to spin and draw air, and it will stop only when the thrust , and the wind will stop completely. In a house ventilation system with turbo deflectors, you have to turn on the fans in the vents, as they say, once a year, not every year. Unfortunately, the turbo deflector is easily filled with dust and debris from the air, so it also needs to be checked at least once every 2 months.

The technical properties of the turbo deflector are the same as those of a multi-bladed self-orienting one, but it loads the pipe even less. It is quite possible to make a turbo deflector with your own hands, see the video below.

Video: DIY turbo deflector

Deflector-vane

The weather vane deflector is assembled from such parts as:

a half-cylinder that serves as a barrier to strong winds;
a cover that blocks the entry of various debris into the chimney;
a canvas that rotates in accordance with the direction of the wind;
a central axis communicating with each element of the device;
a thrust bearing that performs the task of additionally securing the device on the smoke duct.

Compared to other draft leveling devices, the weather vane deflector is an improved device. It functions on the principle of a ship's sail. The weather vane deflector features a rotating body that moves under the influence of the wind.

The weather vane deflector is constantly in motion, so it easily improves traction

The manufacture of a weather vane deflector is the following process:

The lower and upper cylinders are cut and formed from metal sheets. To what will be below, racks are attached to the nuts and bolts. After this, the upper cylinder is attached to the structure, to secure which a clamp is taken. At the edges of the posts, using rivets, a reverse cone is fixed, thereby obtaining a base for the weather vane.
A fragment 12.5 cm long is cut from a pipe with a diameter of 1.3 cm - a support for the weather vane. One edge of the pipe is supplemented with the thread necessary for fastening. A bearing is inserted inside the product, and two steel strips are welded on the sides, tilted in the same way as a dome. It is important that the plates do not become obstacles to the movement of the structure in a circle.

To install the bearing, a thread must be made on the pipe

Using a compass, they install a compass rose - steel rods on which the letters are attached. The rotating structure is covered with a cap in order to block moisture from entering the housing.
A cap made of steel and shaped like an arrow is put on the pipe thread. A flag with a counterweight is attached to it.

In fact, a weather vane deflector is an improved version of a conventional device

Why are deflectors needed?

Every person may wonder: what are deflectors for? You can answer this question by familiarizing yourself with the design and main functions that this device performs. The main feature of the chimney, due to which smoke is removed from the system, is draft. Creating the necessary draft through a pressure difference contributes to the complete removal of combustion products outside the house. In order for the draft to be sufficient, the following parameters are calculated: the diameter of the pipes in the structure, the type of their cross-section, the material of manufacture, the height of the pipe above the roof, etc. The general shape of the structure is also an important factor.

In strong winds, air can enter the pipe lumen, thereby creating an obstacle to the normal removal of smoke from the system. In some cases, this can lead to the formation of backdraft and smoke in the heated room. The deflector not only protects the chimney from wind, but also uses its force to increase draft.

Manufacturing of deflectors

A chimney deflector is a device consisting of three main parts: a lower cylinder, an upper glass (diffuser) and a cone-shaped cap (umbrella).

The lower cylinder is made from a pipe, the material for which can be asbestos, metal or ceramics. An upper glass is attached to this element, fixed on three or four posts and increasing towards the bottom. A cone-shaped cap, sometimes called an umbrella, is installed above it.

In the upper section of both the lower and upper glasses, annular rebounds are created. They prevent the wind from taking a vertical direction.

The deflector consists of: 1 - umbrella-cap, 2 - legs, 3 - conical shield, 4 - diffuser, 5 - pipe, 6 - body

The weather vane is installed in a special way so that the wind blowing in any direction does not create barriers to the removal of gases. Air flows should facilitate the release of combustion products attracted by the upper and lower rings.

Diffuser and umbrella are products most often made of zinc coated steel. The best raw material for creating these deflector parts is high-quality boiler steel, because they operate in conditions of variable humidity, unexpected temperature changes and a high risk of rust formation.

According to their design, weather vanes are divided into types:

Grigorovich deflector;
weather vane deflector;
H-shaped deflector;
TsAGI deflector;
spark arrestor

Principle of operation

Regardless of the size, number of parts and shape of the reflectors, all deflectors operate on the same principle. The aerodynamic device is installed at the top of the chimney. This creates an obstacle to air flow. When hitting the cylinder walls, the wind loses its directional force, breaking up into many small and weaker air currents.

The remaining flows, rising through the body, partially capture the smoke coming out of the chimney. The draft in the chimney channel increases. Since there are no turbulences, carbon monoxide and smoke cannot get back into the pipe and are completely released out.

In addition to their main purpose, deflectors often perform a decorative role. However, the reflector itself will do nothing if it is installed incorrectly. Its effectiveness is influenced by the correctly selected cross-section of the connecting pipe, the chimney installed at a sufficient height and the location of the pipe on the roof.

Features of installation of a rotary deflector

Turbo deflector, rotary deflector, rotary turbine, Turbovent - all these names refer to one type of mechanical device for increasing traction. It consists of a static part connected to the chimney and an active head with ball-shaped blades.

The rotary deflector is the only device that is not recommended for installation on chimneys of stoves heated with solid fuel and wood-burning fireplaces. Turbovent has a characteristic feature - it removes air from the pipe even during periods when the heating is not working.

The direction of rotation of this nozzle does not depend on the strength or direction of the wind. It occurs in only one constant direction, creating the effect of an incomplete vacuum. As a result, the traction power increases in rarefied air conditions, and the risk of the traction capsizing is practically equal to 0.

On chimneys of gas boilers, Turbovent copes with its functions perfectly and can serve as a decoration for any facade. If we compare it with other types of deflectors, it is twice as effective as them.

The base of the rotary deflector can be round, square, or flat square. Head sizes range from 100 – 680 mm. Its service life is up to 15 years.

Despite all the advantages of a rotary turbine, there is one significant drawback - the device stops when there is no wind. If at this time there is precipitation at a temperature below 0, the head may freeze and measures will have to be taken to start it.

Despite the relative complexity of the design, installing a rotary deflector is not difficult. The device is lightweight, so installation requires only one person and takes about 2 hours. A suitable place is the highest point of the roof. This arrangement will prevent snow from getting into the pipe if precipitation accumulates around it.

The movement of the rotary turbine head is carried out using bearings. The device operates autonomously and copes very effectively with the task of removing gases, but in calm weather it is useless

For different models of rotary turbines, there is one requirement: the temperature of the combustion products above the chimney should not exceed 150-250⁰. The dimensions of the base must be precisely adjusted to the chimney. The turbocharged deflector must match the characteristics of the boiler, and this point must be taken into account when choosing a device.

There are turbo deflectors from different brands on the market. Among the most reputable are Turbovent, Turbomax, Rotowent. The first manufacturer produces products with bases of various geometries.

They can be identified by the markings TA-315, TA-355, TA-500. The number in it indicates the diameter in the case of a round cross-section or the dimensions of a rectangular base.

The Turbomax deflector is produced by a Belarusian company. The devices are made from high-quality material - stainless steel from a European supplier. Rotowent is also made of stainless steel supplied from Poland. Looks harmonious on any type of roof. Suitable for both chimney and ventilation pipes. Withstands high operating temperatures - about 500⁰.

Deflector design

The deflector prevents direct air flow from entering the chimney.

In the standard version it consists of 3 parts:

The upper cylinder (diffuser), expanded at the bottom. It is attached to the bottom using special racks.
The lower glass is made of metal, ceramics or asbestos cement.
A cap in the form of a cone-shaped umbrella.

The upper part and the lower cylinder are equipped with annular bumpers that deflect the air flow. Some models do not have a top element. Then the lower cylinder is installed on the pipe, followed by a diffuser and caps - forward and reverse.

The device works on a simple principle:

the walls of the cylinder located at the top absorb the wind blow and direct the air flow around;
Due to the sliding of individual air jets over the surface and their rise upward, gases coming from the chimney are sucked in.

The thrust increases in any wind direction except horizontal. In the latter case, air turbulences form inside the device, cutting off the smoke exit paths. This significant drawback is eliminated by adding an additional element - a reverse cone.

Structurally, the deflector consists of a diffuser (2) with a frame (3) installed on a pipe (1). These elements are located in the shell (4). Above the diffuser there is an umbrella (5) with thermal insulation (6) and a screen (7). Replaceable filter (10) is installed on supports (9) and secured with bolts (11)

The reverse cone is installed below the cap. The purpose of the deflector is to ensure that air flows are removed to the outside by crushing them.

How to install a deflector

It is optimal to install the deflector on the pipe before it is installed on the chimney or air duct on the roof. This will facilitate a rather labor-intensive process and make the work safer.

To install the deflector you will need the following tools and materials:

electric drill;
self-tapping screws;
threaded rods;
nuts;
open-end wrenches;
metal clamp.

An example of installation using a ready-made TsAGI deflector made of galvanized steel.

Marks for fasteners are placed on the outside of the chimney pipe at a distance of about 8 cm from the edge.
In a similar way, marks are applied to the wide part of the diffuser.
Using a drill, holes are drilled in place of the marks, which then need to be checked for symmetry.
Threaded rods are inserted into the finished holes, which are secured with nuts on the side of the diffuser and the chimney pipe.
The pipe, together with the installed deflector, is placed on the chimney duct and secured with a metal clamp.

Important! When installed on a cylindrical smoke duct or roof ventilation unit, installation of the TsAGI or Grigorovich deflector occurs quite quickly. But if we are dealing with a rectangular brick chimney, you will have to buy an additional adapter.

Self-assembly of the device

First, the patterns are prepared, then they are laid out on a sheet of metal and the parts are cut out using special scissors. The body is rolled up and the edges are secured with rivets. Next, the upper and lower cones are attached to each other, using the edge of the first one. it is larger and you can cut special fastening cuts about 1.5 cm wide in several places and then bend them.

Assembling a simple deflector is not difficult, but if a rotary-type device is to be installed, you will have to deal with many parts

Before assembly, 3 racks are installed in the lower cone, evenly distributing them around the perimeter and using threaded studs for this. To connect the umbrella with the diffuser, loops made of metal strips are rivet-fastened to the latter. The posts are screwed into the hinges and secured with nuts for greater reliability.

Next, they carry out the installation of a self-made deflector onto the chimney of a gas or other type of boiler. The assembled device is placed on the pipe and secured using clamps, avoiding gaps. Sometimes the joint is treated with a heat-resistant sealant.

Types of smoke deflectors

Today, the range of these devices is represented by several products that differ in design. Let's look at the most popular models:

ventilation TsAGI;
disc-shaped;
spherical "Wolper";
Grigorovich's device;
H-shaped.

Any of the above chimney deflectors has excellent performance. Different models may differ in size and sensitivity to wind currents.

Note! Such products also have one significant drawback - during periods of calm, they all resist the natural draft of the structure.

There are other devices that differ from classic models in design:

rotating deflector;
weather vane deflector.

The operating principle of such models is no different from classic ones. Their work is based on the same laws of physics.

These devices are made from different metals. The most common materials:

Cink Steel;
stainless steel;
copper.

Deflectors are most often made of materials that are resistant to corrosion. e.g. stainless or galvanized steel

All of the above materials have one common property - resistance to the destructive effects of corrosion. This is a very important quality, because the device is mounted outside the house, so it is exposed to various destructive environmental factors.

In addition, there are devices that are mounted in ventilation structures (plastic ventilation deflector). Plastic deflectors in ventilation structures perform essentially the same functions.

How to calculate a static deflector?

When making a deflector yourself, you need to perform calculations and sketch a sketch of the future product. You need to proceed from the internal diameter of the chimney pipe.

The photo shows the dependence of the size of the deflector on the diameter of the chimney. To determine the lower diameter of the diffuser, the basic parameter is multiplied by 2, the upper one - by 1.5, the height of the diffuser - also by 1.5, the height of the cone, including the reverse one, the height of the umbrella itself - by 0.25, the entry of the pipe into the diffuser - by 0.15

For a standard device, parameters can be selected according to the table:

Pipe inner diameter (cm)	Deflector height (cm)	Diffuser diameter (cm)
12	14,4	24
14	16,8	28
20	24	40
40	48	80
50	60	100

The table will allow you to select the dimensions of the deflector without performing calculations. But if there are no suitable sizes in it, you will still have to arm yourself with a calculator or find the appropriate program on the Internet.

When manufacturing a deflector with individual parameters, these special formulas are used to determine the dimensions: • D diffuser = 1.2 x din. pipes; • H = 1.6 x din. pipes; • Cover width = 1.7 x din. pipes.

Once you know all the dimensions, you can calculate the development of the umbrella cone. If the diameter and height are known, then the diameter of a round workpiece can be easily calculated using the Pythagorean theorem:

R = √(D/2)² + H²

Now we need to determine the parameters of the sector, which will subsequently be cut from the workpiece.

The length of a complete circle of 360⁰ L is equal to 2π R. The length of the circle underlying the finished cone Lm will be less than L. From the difference of these lengths, the arc length of the segment (X) is determined. To do this, make up the proportion:

L/360⁰ = Lm/X

The required size is calculated from it: X = 360 x Lm/ L. The resulting X value is subtracted from 360⁰ - this will be the size of the cut sector.

So, if the height of the deflector should be 168 mm and the diameter 280 mm, then the radius of the workpiece is 219 mm, and its circumferential length Lm = 218.7 x 2 x 3.14 = 1373 mm. The required cone will have a circumference of 280 x 3.14 = 879 mm. Hence 879/1373 x 360⁰ = 230⁰. The cut sector must have an angle of 360 – 230 = 130⁰.

When you need to cut a workpiece in the form of a truncated cone, you have to solve a more difficult problem, because... the known value will be the height of the truncated part, and not the entire cone. Regardless of this, the calculation is performed on the basis of the same Pythagorean theorem. The total height is found from the proportion:

(D – Dm)/ 2H = D/2Hp

This implies that Hp = D x H / (D-Dm). Having found out this value, calculate the parameters of the workpiece for the full cone and subtract the upper part from it.

With known parameters: the height of the cone - full or truncated and the radius of the base, using simple calculations, simply determine the outer and inner radius (in the case of a truncated cone) and then the initial angle and the length of the generatrix of the curve

Let's say you need a truncated cone with H = 240 mm, a diameter at the base of 400 mm, and the upper circle should have a diameter of 300 mm.

Total height Hp = 400 x 240/ (400 – 300) = 960 mm.
External radius of the workpiece Rz = √(400/2)² + 960² = 980.6 mm.
Radius of the smaller hole Rm = √(960 – 240)² + (300|2)² = 239 mm.
Sector angle: 360/2 x 400/980.6 = 73.4⁰.

It remains to draw one arc with a radius of 980.6 mm and a second with a radius of 239 mm from the same point and draw the radii at an angle of 73.4⁰. If you plan to overlap the edges, add allowances.

Read on to learn more about how to build a chimney deflector yourself.

Assembling a simple dish model

The easiest project to implement is making a dish-shaped deflector model. You can easily make such a chimney cap yourself. Its geometric parameters depend on the diameter of the pipe:

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Deflector design for round pipe

Diameter of the clamp for mounting the deflector

Chimney cap size

Distance between umbrella and mounting clamp

In order not to make mistakes in manufacturing and to accurately adjust the parts to the required size, it is advisable to first make a model of the deflector from cardboard. At this stage it is simpler and easier to make adjustments to the design. Cardboard blanks will also serve as a kind of patterns when cutting out the elements of the future deflector:

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Making a pattern for a chimney deflector

Assembling a metal chimney umbrella

Device of remote racks

Attaching the deflector fixing clamp

What is a deflector?

Strong winds can disrupt the stable operation of a gas boiler. In such conditions, the automation often works and the boiler turns off. Combustion products from a gas boiler, when removed ineffectively, pose a threat not only to health, but also to people’s lives.

To enhance traction by optimizing air flow, draft stabilizers or deflectors are used. Translated, its name sounds like a reflector, a deflecting device. His work uses the Bernoulli effect, which is based on a decrease in pressure during an air flow around an obstacle. It deflects air masses, increasing the strength of the main flow of the chimney.

The chimney of a gas boiler, equipped with a deflector, will not go out during strong gusts of wind. The design becomes more efficient because traction force increases up to 20%

The traction amplifier operates effectively in any wind force and even during strong gusts, if there is wind, the traction will not topple. But in complete calm, this aerodynamic device acts as an umbrella and is practically inactive, and sometimes reduces thrust. For this reason, many experts do not recommend installing deflectors on gas chimneys.

Despite the increased requirements for a deflector installed on the chimney of a gas boiler, in some cases this is the only solution to the problem. If this device is not included in the project, it is necessary to coordinate its installation with the gas workers. Only after fulfilling this condition can you begin installing the deflector.

According to the specifics of the device and the operating principle associated with this, deflectors are divided into the following types:

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Traditional umbrella-shaped deflector

H-shaped deflector devices

Deflector-weather vane with sail effect

Model with spark arrester