Making a deflector on a chimney pipe with your own hands

A deflector or reflector is a specially shaped pipe structure mounted on the top of the chimney in order to protect the head. Its main purpose is to increase the draft created in the channels of heating systems and to ensure safe smoke extraction. If a deflector is not installed on the chimney, air will begin to penetrate into it, preventing the formation of a pressure difference inside and outside the chimney.

Brief information and principle of operation

In addition to its general purpose, which is to remove gases, the chimney deflector performs a number of auxiliary functions:

• equalizes the thrust (increases the supply of oxygen), which leads to the saving of fuel, which completely burns in a heat generator or furnace;
• prevents the formation of sparks, which often lead to the ignition of combustible materials;
• protects pipe cavities from precipitation and strong gusts of wind;

The use of a deflector guarantees uninterrupted operation of any heating device, even in bad weather conditions.

Its principle of operation is based on the laws of aerodynamics. In simple words, it can be represented as follows:

• Moving air masses flow around the walls of the outer cylinder of the reflector, creating a vacuum in this place.
• Part of the air flow forms vortices that rise along the body.
• They are mixed with the residues of combustion products discharged from the chimney.

The resulting mixture creates additional vacuum and increases the draft in the chimney.

Gaps are provided on the upper cylinder through which smoke is sucked into the pipe. Because of them, the air turbulences formed under the hood sometimes impede the extraction of smoke, which is attributed to the disadvantages of reflectors. To eliminate them, in some models, an inverted cone nozzle is installed under the umbrella, designed for reflection, dissection and subsequent removal of air masses.

Smoke reasons

The fuming of the stove is most often explained by the so-called "overturning of the draft", which occurs due to the long downtime of the heating system. 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 manifest itself in hot weather and frost. To eliminate the effect of back draft in the chimney, it will be necessary to increase the temperature in the chimney. One of the ways that this can be achieved is by installing a high-quality chimney deflector.

Types of nozzles

The modern chimney deflector has many designs, the most famous of which are:

• Grigorovich's nozzle;
• products manufactured in TsAGI laboratories;
• Round Volper;
• "Vane";
• H-shaped device.
• open type products Astato.

Each of the listed types of chimney nozzles needs separate consideration.

Products of Grigorovich and TsAGI

The Grigorovich deflector is the most affordable option that the user can easily make from scrap materials and pre-purchased blanks. The design includes two cylinders (upper and lower), as well as a tubing system, a cone and mounting brackets. Devices of this type have one significant drawback, which is the high position of the umbrella in relation to the diffuser. This often leads to blowing clouds of smoke into its side niches. In general, the effectiveness of this device is not very high. However, the samples of these deflectors do a good job with another task - to prevent the penetration of rain and snow into the chimney.

The universal version of the deflector devices, developed at TsAGI, is made in the form of a special shaped branch pipe fixed to the smoke exhaust pipe. In addition, it includes a diffuser, a ring and an umbrella head. The advantages of this design include a special device of the nozzle, which allows exhaust gases to be removed through the ventilation duct. Thanks to this, it is possible to increase the draft not only in the smoke channels, but in the existing exhaust and ventilation systems.

The design of TsAGI allows you to effectively cut the air flow, which contributes to the rapid removal of smoke from the exhaust duct. The umbrella located inside provides reliable protection against climatic influences. A significant drawback of this design is the complexity of making it at home.

Round wolper and H-shaped deflectors

The device called "Round Volper" has a design similar to the TsAGI model. Differences are noticeable only in the features of the upper part of the deflector body. A nozzle cap, which protects the inside of the pipe from debris and precipitation, is placed here on top of the diffuser, which eliminates some of the shortcomings of the TsAGI model.

The H-shaped model is simple enough to make your own. The assembly will require several pipe sections designed for strong gusts of wind. Elements of this design are assembled in the form of a horizontally located letter H, which excludes the possibility of atmospheric precipitation and debris getting into the pipe channel. The vertically positioned sidewalls allow to increase the draft in the chimney and distribute the outgoing flows in different directions.

Vane

The device consists of several interconnected visors, rotating on a needle base. In order for the structure to rotate under the influence of the wind, a special weather vane assembly is provided in its upper part. Some models are equipped with a small arrow pin to indicate the direction of the air flow.

The presence of visors that cut through the air when rotating, allows you to increase the draft in the chimney. In addition, with their help, it is possible to protect the boiler or furnace structure from contamination, possibly due to small particles entering from the outside. The disadvantages of this design include the unreliability of the bearing used in the vane rotation mechanism.

Deflector ASTATO

Under this designation, another model of a rotating ventilation-class deflector is presented, using not only mechanical, but also wind draft for this. Its design provides for the following mandatory units and elements:

• built-in electric motor;
• pressure meter;
• electronic time relay.

The latter is used to set the shutter speed, after which the operating mode is changed. When the wind reaches a certain force, the built-in motor is automatically turned off and the device operates according to the exhaust ventilation principle. With the weakening of the wind thrust, the electric motor starts up again, which does not impair the aerodynamic characteristics of the system, but allows to obtain the required vacuum (up to 35 Pa).

The electric motor of the deflector is quite economical, since it works only after it is turned on by a signal from a sensor that controls the pressure at the outlet of the chimney. The overwhelming majority of the operating period is a wind-driven deflector. If desired, the user can manually switch the device from one mode to another.

Self-made deflector

Since the Grigorovich deflector is one of the simplest and most easily reproducible types of protective turbo devices with a simple design, it is most suitable for self-assembly. To make a deflector for an exhaust pipe with your own hands, you will need blanks of tin or galvanized steel with a sheet thickness of at least 0.5 mm. To assemble the deflector, you also need to prepare the following set of tools:

• scissors for cutting sheet metal;
• hammer, electric drill and a set of drills;
• welding machine of any type;
• marking kit;
• cardboard sheet;
• self-tapping screws and other hardware (nuts and bolts).

Galvanized sheet 0.8 mm thick was selected as a starting material. In addition to them, you will need to prepare a set of steel strips of a given width. The homemade device is assembled in the following sequence:

1. The dimensions of the designed device are calculated, for which ready-made formulas given on the Internet are used.
2. On a cardboard sheet, a markup is applied to each of the working elements of the future structure.
3. Templates are cut out, which are then applied to one another to make sure that the contours match.
4. The templates are placed on the surface of the prepared steel sheets and outlined.
5. According to the resulting markings, workpieces are cut out with the help of scissors.
6. On the basis of the central part, a shape for the diffuser is cut out, along the edges of which holes are made for self-tapping screws.
7. In the same way, a blank for the outer cylinder of the deflector is formed.
8. At the penultimate stage of assembly, a cone-shaped cap is assembled from 2 obtained blanks.

Finally, six cuts are made along the edges of the upper cone, which serve to fasten the support posts. The latter are cut from steel strips 21 cm long and 5 cm wide. With their help, two conical blanks are fastened together with their edges.

The finished deflector hood is combined with the assembled diffuser, after which the entire structure is installed in the outer cylinder.

Mounting the device

In order for the chimney to be reliably protected in its upper part, it is important to correctly install the finished deflector on its head. To carry out this operation, you will need to prepare the following tools and fasteners:

• electric drill with a set of drills;
• full set of spanner wrenches;
• fastening threaded rods and nuts to them;
• special connecting clamps.

You also need to stock up on a ladder of suitable length, allowing you to climb to the roof of the house and move along it. In addition, it will be necessary to prepare a pipe section with a diameter exceeding the same standard size of the pipe channel.

The installation of a turbo deflector for the chimney is performed in the following order:

1. On the upper section of the chimney with an indent of approximately 8 cm from the edge, the holes for the fastening screws are marked.
2. Exactly the same marks are made on the wide part of the body.
3. Holes are drilled at the marked points.
4. Screws are inserted into them, and nuts are carefully screwed on the back side.
5. The finished reflector is pushed onto the chimney and attached to the head with clamps.

If, for example, a deflector that is too large in size has to be installed on the pipe of a brick house, it is recommended to use wire braces of the required length to strengthen its fastening.