To organize the output of combustion products and the supply of fresh air in a single pipe, a coaxial chimney is used. The design of the channel includes two contours of different sections, located one in the other, while the distance between the walls will be the same along the entire length. A complete tightness and gas tightness of the heating system is achieved when using such a discharge channel.
Definition of a coaxial chimney
The device works on the principle of combining in one product the functions of a chimney and a supply ventilation system. The combination of channels increases the productivity of the boiler and its efficiency. The temperature in the chimney is equalized, condensation drops are eliminated due to the mutual redistribution of heat between internal and external flows.
The coaxial type is suitable for gas boilers with a closed system and natural or organized forced traction. A small fan is installed inside the pipe. The condensate collector and inspection holes for cleaning are included in the design of the line.
Heat losses are minimized, because cold air is supplied in an external pipe heated from an internal channel with hot gases. Warm air enters the room and reduces heat loss. The boiler room will have clean air, because the coaxial channel simultaneously works as a supply ventilation.
The pipe can be placed in a vertical or horizontal position, installed in a wall form under the ceiling, brought out through the roof, wall or window construction. Pipe dimensions and power are selected in accordance with the calculation. Fuel burns out completely and less hazardous substances enter the atmosphere, gas is saved. The combustion products are discharged through the internal channel, and the external side maintains an average temperature, therefore, the risk of fire is reduced.
The principle of operation of the device
The inner surfaces of the pipes in the coaxial channel are not in contact with each other due to the reinforcing partitions located along the entire length. Such devices operate in a system of gas units, radiators and convectors, which use oxygen from the street, and not from the utility room, for combustion. The method of joint removal and ventilation cannot be used for units operating on solid fuels.
Features of the functioning of the coaxial chimney:
- fresh air is supplied through the outer shell from the street to support combustion;
- the internal passage serves to remove smoke from the premises.
The coaxial pipe line is composed of separate standard modules, as a result the chimney can be of different lengths or heights. With the help of straight sections of pipes, adapters, angles, tees, a pipeline of various configurations is carried out, which takes into account the architectural features of the structure.
Unified elements are selected for pipes of various sections in accordance with standards and technical requirements. Air in heating systems with a single chimney is taken from the boiler room, so the room becomes stuffy, breathing is difficult. Another option for oxygen supply involves a fence from the street, but requires the connection of an additional duct pipe.
Varieties of coaxial chimney
The pipe material is aluminum, stainless steel, plastic, or combinations are used. A plastic chimney is connected to the condensing gas units, but its disadvantage is a short service life. A heat-resistant polymer is used, which does not deteriorate when the smoke is heated to a maximum of + 205 ° C, so plastic can only be installed on boilers with a temperature regulator for the exhaust gases. Plastic lines are lightweight, do not require a frame device. Installation of inexpensive pipes is quick and easy.
According to the standards, stainless steel is the most resistant material, because it resists acids contained in the condensate and can withstand gases up to + 550 ° C. Manufacturers have developed several design types of separate inside pipelines. Products are used for a long time without loss of quality, used in mansions, multi-apartment buildings and industrial buildings. Coaxial stainless pipes are available in an insulated and simple version.
Insulated products are used for a two-channel chimney and serve more than three decades. The design uses a combination of materials, such as polymer and high alloy steel, stainless steel and aluminum.
External and internal systems
The chimney can pass inside the building or be located outside the wall. Structures on the outside worsen the appearance of the facade, so they are placed in the space of the room. Checks compliance with the installation rules that are prescribed in SNiP-91, p3.70 and 3.71.
Before installation, the internal smoke removal systems are checked for compliance with the dimensions of the connecting outlet of the boiler and the pipe. The diameter of the outer hole in the enclosing structure or roof is made according to the size of the pipe section. An internal chimney is installed from the stove or fireplace, attached to the walls with clamps, crimped with bolts. Decorative pipes, wooden or plastic, are placed on top of the pipes. They do not represent a fire hazard, because the outer layer is cooled by passing air from the street.
Installation of an external chimney also starts from the boiler. When passing the wall, the correct insulation of the hole is made. To set the required length, the coaxial chimney can be extended and extended, but this cannot be done in the thickness of the wall. The outer parts are attached to the fence with clamps. Assembly is carried out until the required height has been set; at the end of the pipe, a deflector is placed to enhance traction.
Insulated and non-insulated systems
Insulated from the cold, stainless coaxial pipes are ideal for outdoor flue. The aerodynamic characteristics of the channel are improved due to the insulation layer. Boilers with forced or free traction are connected, but the first option works more efficiently.
Insulation from the cold is needed because the external air supply chamber freezes at sub-zero temperatures, which reduces the amount of oxygen supplied. Gas burns unevenly, boiler efficiency worsens. The difference between the temperature of the inner pipe and the outer compartment increases, which leads to condensation and accelerates the destruction of the coaxial chimney for a gas boiler.
Used materials:
- mineral wool;
- basalt masses;
- glass wool;
- polyurethane foam, foam.
The insulated version of the pipe is a structure containing three pipes of various sections embedded inside. One cavity (external) is filled with insulating material from the cold.
Horizontal and vertical output
Coaxial chimneys were originally planned as horizontal highways, but such placement is not always convenient in the house. The number of turns of the chimney must not exceed three.A turn of 90 ° indicates an extension of the pipeline by 1 meter, a bend angle of 45 ° - by 0.5 meters, the total length of the pipeline should not be more than three meters.
To install a horizontal pipe can cause problems:
- small boiler room;
- a large number of windows (for the front part);
- the presence of foreign structures in the gap between the boiler and the wall with a hole;
- the inability to provide a standard slope of 3 ° for condensate drainage.
The output of smoke is organized vertically and in a mixed form. A vertical conclusion is resorted to if the roof structure allows this. In this embodiment, high-quality isolation of the passageway is required. Brackets are used for fastening to ensure the distance from the roof elements, since attention is paid to the prevention of fire. The protective cover closes the connection.
Collective and individual designs
The chimney division is introduced depending on the scheme and the number of users served. A collective chimney represents a mine system, to which separate pipelines from each heating unit are connected. Individual branches are thermally insulated, which increases their traction characteristics.
In multi-storey buildings, separate passages to the general vertical output are provided at the stage of building construction or are added during the reconstruction process. External wiring is used less frequently, while the gas units of the apartment building are connected, and the main vertical channel is located on the street side.
Separate pipes are connected using a tee adapter with gaskets, inside which there should be no obstacles and protrusions. They increase the length of the elements of the adapters, ensuring the tightness of the joint with the help of tightening clamps.
Individual chimneys are used for domestic purposes, they service one heating boiler and do not have branches. To collect condensate droplets in the line, collectors are provided in the form of standard pipeline inserts.
Advantages and disadvantages
Coaxial pipes are considered the most suitable for the installation of the chimney, because they increase the efficiency of the equipment. Productivity is increased by heating the outdoor air supplied to the hearth from the street.
Advantages of using coaxial pipes:
- the isolation of the system prevents carbon monoxide from entering the house;
- reduced risk of fire eliminates fires;
- universality of installation allows you to install pipes horizontally and vertically, to use in an apartment or private house;
- space saving due to combining two functions in one channel;
- installation does not require professional skills or special tools;
- reduction of emissions into the air due to increased productivity and complete combustion of fuel.
The disadvantage is that the coaxial chimney serves gas units with a closed firebox, but is not used for other boilers. The outer pipes are installed three-chamber, with factory insulation, and if additional insulation of the two-chamber pipe is carried out, the element needs to be decorated on the facade in accordance with the exterior of the building.
Size Selection Features
The technical data sheet of the heating unit contains information on the diameter of the connected pipe and the length of the coaxial channel. Increasing the parameters leads to a decrease in performance. The diameter is recorded in the article after the letter designation and contains 4 digits. The former speak of the internal cross-section of the pipe, while the latter two indicate the outer dimension of the flue manifold.
The length of the line cannot be more than three meters, according to the installation order, but individual manufacturers change this characteristic based on their technical indicators of their products.
Pay attention to the diameter of the outlet pipe of the unit, which must match the size of the pipe. Do not mount a chimney with a diameter less than the same size of the pipe. In the technical documentation, a selection table is attached, which takes into account the nuances of choosing the diameter, length, slope and number of turns of the channel.
Installation Rules
Installation of a chimney from coaxial pipes is not difficult. The axis of the pipe with forced exhaust can be shifted to the unit to the right or left.
Mounting Features:
- from the boiler to the outlet through the wall should be at least 0.5 m;
- height above the horizontal pipe inside the room - from 0.2 m;
- the external outlet of the pipe is more than 0.3 m;
- the height of the horizontal outer pipe from the ground - 2 - 2.5 m;
- the distance from the tip of the vertical pipe to the nearest wall is 0.6 - 1.5 m;
- neighboring windows or ventilation openings - no closer than 0.6 m from the chimney outlet.
The chimney is attached to the unit using an angular element (elbow), tightening clamps are used. An inlet is marked on the wall, the width of which exceeds the diameter of the pipeline by 5-10 cm.
Do not use adhesive tape, adhesive tape and sealants when connecting the elements of the line. Special gaskets or rubber are used. The passageway is isolated from the entry of cold by a non-combustible insulation. Vertical pipes are climbed to the required height, which is always higher than the ridge of the roof and the openings of the neighboring house. After installation, the system is checked.
