Rules for installing a coaxial chimney for a gas boiler

When installing any heating boiler (with the exception of the electric one), it is necessary to take care of the smoke exhaust system and the oxygen flow that is needed to maintain the fuel combustion process. Boilers with a closed combustion chamber can be installed in any room. At the same time, the classical scheme for extracting combustion products is completely useless. A coaxial chimney is enough. In this article we will consider all the rules for installing a coaxial chimney for a gas boiler.

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The meaning of the word “coaxial” means “coaxial”. These are two tubes inserted one into the other and brought out. From the inside, the pipes do not contact each other due to the jumper system.

The reason for this is the different purpose of the tubes:

  • Small - designed to divert products formed during the combustion of fuel.
  • A large one is needed to supply air, and therefore oxygen, to the combustion chamber.

It turns out that fresh air and combustion products do not mix with each other. Such a system is reliably insulated, and the air from the room does not mix with the gases in the chimney.

Important! The most common coaxial structures are horizontal, although, in principle, a vertical chimney can also be equipped.

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The main advantage of this design is its versatility. It can be used for all varieties of heating boilers. The most efficient operation is the installation of coaxial chimneys for gas boilers with a closed combustion chamber and forced draft. The boiler itself can be wall or floor type.

Here are a few more benefits:

  • The location is horizontal. There is no need to punch a hole in the roof. It is enough to bring the pipe out of the window or make a hole in the wall closest to the boiler.
  • The flue system is insulated and not connected to the air in the room. There is no risk of carbon monoxide entering the room.
  • The air that enters from the street approaches the combustion chamber already warmed up due to the fact that it comes into contact with a hot chimney. This helps to increase the efficiency of the boiler.
  • Easy installation of a coaxial chimney. Work on its arrangement does not require special skill and special knowledge.
  • Security. The coaxial duct is reliably protected from the risk of fire, since the system is cooled by relatively cold air from the street.
  • No need to equip a separate boiler room. Any place convenient for you - a kitchen, an entrance, an extension or a basement, are suitable for installing a boiler.
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Rules for installing a coaxial chimney for a gas boiler

If it is planned to equip the coaxial smoke exhaust system, it is necessary to adhere to the installation and safety rules. This will avoid even the smallest risks associated with the ingress of exhaust gases into the room:

  • The maximum length of the outlet vertical pipe in the coaxial chimney is 3 m. Sometimes chimneys of a larger (up to 5 m) length can be found. For example, this concerns the installation of a coaxial pipe of a double-circuit gas boiler Ferroli floor type.
  • The pipe is discharged to the street horizontally. Moreover, the maximum length of the horizontal section is 1 m.
  • When installing forced fan traction, there is no need to equip a vertical section.
  • The height of the outlet of the gas duct above the surface of the earth is from 2 m, and relative to the boiler unit, the excess is from 1.5 m.
  • The minimum distance for the outlet of the chimney pipe from any window or doorway, as well as ventilation grilles, is 0.5 m.
  • It is undesirable to equip the outlet of the coaxial gas duct pipe under the window. But if you can not do without it, the minimum distance between the outlet of the chimney and the window is 1.0 m.
  • A slight slope of the pipe provides condensate drainage.


Chimney slope

There is no consensus on this issue:

  • The most common recommendation is to slope the pipes “away from the boiler”. In general, this is quite logical. Condensate formed during the operation of the boiler flows out, and does not enter the boiler. However, such a system works flawlessly before severe frosts. In winter cold, condensation running down simply freezes, sometimes even inside the pipe. All this worsens the air intake for the fuel chamber.
  • It is nevertheless necessary to make a decision to slope the pipe towards the boiler. To solve the problem of condensate entering the boiler, an additional condensate tank is installed.

Is the chimney insulated?

The fact is that the insulation of the flue pipes does not solve the problem. All the same, the condensate freezes. This problem can be solved more efficiently if the inner tube is slightly shortened. Naturally, this is true if the pipes are inclined from the boiler.

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Installation procedure

Unlike the usual vertical chimney, the coaxial system does not require any professional skills during installation. But at the same time, you must strictly follow the instructions. This is the only way to achieve complete security.

Installation of a coaxial chimney for a gas boiler is performed according to the following algorithm:

  • Determined with the location of the boiler. Wall-mounted models are located on the outer walls, floor-mounted on a small elevation.

Important! The excess of the outlet on the wall above the boiler, in accordance with the rules, is 1.5 m or more. The diameter of the hole in the wall should be slightly larger than the diameter of the outer pipe.

  • A special element is installed to connect the chimney to the boiler. All joints and turns are fastened with clamps. In this case, neither sealants nor adhesive tapes should be used.

Important! The number of swivel elbows for the entire system must not exceed 2.

  • The channel of the hole drilled in the wall is laid with insulation.
  • Fix the pipeline to the wall using brackets.
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Stock footage

The ratio of affordable price, ease of installation, long working life and efficiency made coaxial pipelines very popular. If you also decided to give preference to just such, be sure to follow the installation rules given in the article.

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