Deflector for the chimney of a gas boiler: installation requirements and installation rules

Regardless of the type of fuel, the chimney is an essential part of the heating system. How warm the house will be depends on its proper design.

Gas is a special type of fuel, since it is unsafe, so many people are concerned about the question: is a deflector needed for the chimney of a gas boiler and will such a solution to the problem be correct? Let's try to figure out this difficult issue in our material.

Popular types of traction enhancers

In modern designs, there are different types of deflectors, so you can choose a model for a house made in any architectural style.

Structurally, these devices differ:

• flat top;
• two slopes;
• semicircular lid;
• folding top.

Each of them has certain advantages: the opening lid on the deflector allows you to control the process of removing combustion products.

A flat top is perfect as a decorative element for a roof made in the Art Nouveau style; the best protection from weather conditions is a gable mini-roof. The material used for their manufacture is mainly galvanized metal, but sometimes it is coated with a layer of plastic or enameled.

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 flows, use traction stabilizers or deflectors. 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 gas boiler chimney, 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:

Deflector design

The deflector prevents direct air flow from entering the chimney.

In the standard version it consists of 3 parts:

1. Top cylinder (diffuser), expanded at the bottom. It is attached to the bottom using special racks.
2. Bottom glass made of metal, ceramics or asbestos cement.
3. 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.

Characteristics of popular models

Deflector models differ in both size and sensitivity to wind. The most popular models are TsAGI, Khanzhenkov, Volpert-Grigorovich, “Smoke Tooth”, “Hood” aka “Net”, “Shenard”. The first of these models was developed at the Aerodynamic Institute named after. Zhukovsky.

TsAGI is most often used in ventilation systems due to the difficulties that arise when soot removal. The second model is essentially the same TsAGI, but slightly improved by the inventor. Essentially, this is an additional cylinder around a pipe with an umbrella cover immersed inside the cylinder at a certain distance.

Homeowners choose the TsAGI deflector most often. It has a cylindrical shape. The device is made of galvanized or stainless steel

The Volpert-Grigorovich deflector has proven itself well as a draft amplifier on chimneys. It works effectively in areas with prevailing low winds. The design includes 2 cylinders - the lower one with two outlet pipes and the upper one with a cover.

The “smoke tooth” is mounted in a door specially provided in the chimney.Due to the fact that the design includes 2 handles, you can regulate the air flow.

Covers for chimneys are made in a variety of shapes. Sometimes they are coated with heat-resistant enamel. Some specimens look very decorative

The “Hood” deflector has a rotating design. It consists of a semicircular trough-shaped air trap mounted on a rotating rod mounted inside the pipe. An increase in traction power by installing a weather vane deflector occurs due to turbulence that occurs under wind load.

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:

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 more about how to build a chimney deflector yourself Further.

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.

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:

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:

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 enhancing 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.

Deflector Turbomax produced by a Belarusian company. The devices are made from high-quality material - stainless steel from a European supplier. Rotovent 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.

Deflectors-vanes for chimneys

Structurally, the chimney weather vane is designed so that gases, escaping freely from the leeward side, increase the draft force in the chimney pipe. The device is made of heat-resistant steel, which has proven itself in conditions of high temperatures and condensation formation.

Under the curved visor of the weather vane there is a bearing assembly that protects against problems with rotation. The bearing assembly is bolted to the chimney. A vacuum zone is created when the air flow passes through the space under the visors.

During installation, the base of the device is placed on the round chimney until it stops, and then secured with 3 bolts. The bolts should be tightened with great care because... the pipe may be damaged. Installation is completed by checking the verticality and rotation of the housing

The disadvantage of chimney weather vanes is that in strong winds they work unstably. The moving part must be periodically cleaned and lubricated. Moisture often accumulates inside the device, and flue gases leave a trace in the form of deposits.

Manufacturers themselves advise using their devices if the chimney is located in an unfavorable location. It, in fact, does not increase draft, but only protects the chimney.

Conclusions and useful video on the topic

Is it worth installing a traction amplifier at all if you have a gas boiler? You will find out by watching this video:

Making a turbo deflector with your own hands is not easy, but some craftsmen still do it and successfully operate it. Watch this video:

There are a lot of deflector designs, but we must not forget that gas is used for heating. Not all models can be used. Some of them are not suitable in principle because...intended for ventilation. In order not to block the smoke removal system, you must consult with a specialist and obtain permission to install the deflector.

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