Coaxial flue for gas boiler - design and installation

Autonomous heating has recently become not only a necessary condition for living in a private house, but also a way of hanging comfort and saving money for the owners of the living space in apartment buildings. The increased demand for heating devices was the reason for the development of more powerful and productive models. Modern equipment imposes increased requirements for the safety of the connection and removal of combustion waste through the chimney channels. For this reason, a coaxial chimney for a gas boiler, whose device is fundamentally different from the ordinary, has come into use.

Device and functions

A coaxial chimney is a smoke removal channel, the design of which consists of two pipes of different diameters inserted into one another. The inner surfaces of the pipes do not touch each other, there is an air gap between the contours. The coaxial chimney is assembled from additional elements: straight pipes, outlets, tees, condensate collectors. It performs two main functions:

1. Removing smoke from the firebox. Smoke is called the mixture of gases resulting from the combustion of fuel. This task is performed by the inner pipe of the coaxial smoke removal system.
2. Air supply to the furnace. In order to maintain combustion in the gas boiler, it is necessary to ensure unhindered access to the oxygen furnace. In heaters with a conventional smoke exhaust duct, air is drawn from the room, which makes it stuffy and difficult to breathe inside. A coaxial chimney supplies air to the furnace through the external contour of the pipe.

Important! Such a device is designed according to the principle of dividing the chimney function. This allows you to increase productivity and efficiency. Combustion products, the temperature of which is quite high, heat the external circuit. And the external pipe through which atmospheric air passes, in turn, cools the internal one. Thanks to this design, the temperature in the chimney is equalized, which prevents the occurrence of condensate and reduces the risk of fire.

Benefits

Coaxial chimney is considered a more sophisticated and effective way to remove combustion products from the heater of the heater. Elements for assembly are often supplied complete with equipment. Most manufacturers recommend installing their products with chimneys of this type, as they have the following advantages:

• High performance. Due to the heating of atmospheric air entering the furnace from the street, the efficiency of the gas boiler is increased, and fuel consumption and costs are reduced.
• Isolation Due to the external air intake, the smoke removal system for heating partings with a closed firebox and a coaxial chimney is insulated. This means that carbon monoxide does not penetrate into the living quarters.
• Fireproof. Since the outer contour of the pipe through which atmospheric air moves has a lower temperature, the risk of fire due to the fault of the chimney is reduced to almost zero.
• Универсальность. Installation коаксиального дымохода выполняют через перекрытия и крышу или горизонтально, то есть через стену. Это позволяет использовать такой тип дымоудаления для частных домов и даже квартир.
• Compactness. The combination of two functions in one device saves space, since a high-performance coaxial type chimney of a smaller diameter can cope with any volume of gases.
• Easy installation. To bring the chimney of a gas boiler of a coaxial view to the street through the wall does not require special knowledge, experience or an expensive tool. Its design allows you to easily install and commission a wall or floor boiler.
• Environmental friendliness. Due to the high efficiency of the boilers using coaxial type smoke exhaust ducts, the gas is completely burned in the furnace. Such a device reduces gas emissions into the atmosphere, which is more environmentally friendly.

Important! The coaxial chimney is suitable exclusively for gas boilers with a closed firebox and a forced draft, operated by a small fan built inside the pipe. A draft of the smoke removal system of this type must include a condensate collector and an audit through which the pipe is cleaned.

Safety requirements for installation

According to statistics of the Ministry of Emergency Situations and manufacturers, coaxial smoke removal channels are considered safer and more efficient. However, when installing them, you must comply with certain requirements:

1. The maximum allowed for most models, the length of the pipe, which removes combustion products into the atmosphere, is 3 m. For individual devices, pipes up to 4–5 m long can be used.
2. The smoke pipe is brought outside the building through the wall adjacent to the wall of the heating boiler. The length of the horizontal section in the place of withdrawal should not exceed 100 cm.
3. The opening for taking the pipe to the street is placed at a height of at least 150 cm from the heating boiler and 200-250 cm from ground level.
4. The distance from the point of withdrawal of the pipe to adjacent structures should exceed 300 cm.
5. Coaxial chimney for gas boiler is not recommended to have under the windows. The minimum allowable distance from the output point to the window is 100 cm.
6. For forced-draft chimneys, a vertical pipe section is optional, it is enough to horizontally pull it through the wall.

Note! Professional builders argue about the effectiveness of the use of coaxial chimneys in the territory of central Russia and more northern regions, claiming that they developed them for use at temperatures as low as -15 degrees. Where in winter most of the time the temperature falls below this mark, they freeze. Manufacturers explain the problem of incorrect calculation of the diameter of the outer and inner pipes and the length of the chimney.

Installation

Unlike traditional smoke removal methods, a coaxial type chimney is simply mounted. To complete the installation, you must strictly follow the instructions of the manufacturer of gas equipment and fire safety requirements. Experienced masters advise to pay attention to the following points:

• The installation of the chimney produced in conjunction with the installation of heating equipment.
• Devices with a closed firebox do not require the equipment of a separate room for a boiler room, however the installation site should be sheathed from the bottom on the sides and from above with refractory material.
• On the wall, determine the point of the pipe through the wall to the street. It is located at a height of 1.5 m from the discharge pipe of the boiler. Cut a hole in the partition, the size of which is a couple of centimeters larger than the diameter of the chimney.
• A special connecting element is attached to the boiler nozzle and a chimney is assembled from individual segments. The joints are fixed with clamps. Important! For sealing the coaxial smoke exhaust system connections, you cannot use sealants or adhesive tapes, seals.
• The passage of the pipe through an obstacle in the form of a wall is insulated with a refractory material, for example, basalt fiber.
• The horizontal segment, which brings the tube to the street, is turned upward with the help of a diverging knee and put up to the required length. The vertical section is fixed on the brackets to the wall. A protective baffle is put on the tip.

Video instruction