In general, the concept of “coaxial” is used not only for chimneys. This is the designation for all structures that consist of objects located along a single axis. There are, for example, coaxial cables that have a shield and a center conductor that are aligned, but separated by an air gap or insulation..
In the case of a chimney, a coaxial channel is a channel that consists of several pipes of different cross-sections. A coaxial chimney is a duct for exhausting gases inside an external circuit. These two channels are separated by a heat-shielding layer. At the same time, thanks to special jumpers, the distance between the two pipes of the coaxial chimney will be the same along the entire length. Such a scheme can be simply called “a pipe in a pipe”.
Thanks to this layered structure, the coaxial chimney performs two functions at once:
- Fresh air is supplied through the outer pipe, which is necessary to maintain combustion.
- Combustion products are discharged through the inner pipe.
Important! Coaxial chimneys are used for gas boilers, convectors and radiators, during which combustion air is supplied from the street, and not from the room. For heating systems using solid fuel, this type of chimney is not used..
The advantages of a coaxial chimney include:
- Minimizing heat loss. Cold air from the street enters through a pipe in which there are combustion products with a high temperature. Passing through the canal, the air from the street has time to heat up, becomes warm, which reduces heat loss in the main.
- There will be enough air in the room where the boiler is installed, there will be no discomfort – the chimney will act as a fan.
- The coaxial pipe can be mounted both vertically and horizontally, installed in a supporting wall, led out through the roof.
Important! Vertical coaxial chimneys are much more expensive, they have a long channel length. Therefore, horizontal is more popular.
- It is possible to choose the optimal chimney size and power.
- Heating cold air from the street not only reduces heat loss, but also increases the efficiency of the boiler. And the higher the efficiency, the better the fuel burns, the less harmful substances entering the atmosphere. In addition, fuel consumption itself is reduced – direct savings for owners.
- As the hot combustion products pass through the inner tube, the entire system becomes much safer. The outer layer is cold air from the street, so there is much less risk of fire due to overheating of the chimney.
- It is not difficult to assemble a coaxial chimney with your own hands.
Coaxial chimneys also have disadvantages:
- Narrow field of application – only in boilers with a closed combustion chamber, gas.
- The chimney pipe stands out on the facade of the building, it may not look very aesthetically pleasing.
- At temperatures below -10 …- 15 ° C, the chimney may freeze up. Hot gases have time to cool down thanks to the air from the street even inside the chimney, so condensation, icicles, icing on the chimney head quickly appear in the cold. You can fight this phenomenon with additional thermal insulation..
The most durable coaxial flues are made from high alloy steel. There are models made of stainless steel, plastic and aluminum, combined, as well as galvanized steel. A simple coaxial chimney with a diameter of 60/100 millimeters costs about 2000-3500 rubles. However, additional elbows, extension cords may be needed – it all depends on how and where you will mount your smoke exhaust duct, on the required length, diameter and the presence of bends.
When choosing a pipe for your boiler with a closed combustion chamber, be sure to pay attention to coaxial chimneys. This is a suitable option for such a heating system, which has found wide application not only in private houses, but also in apartments with individual heating in multi-storey buildings..