Modern gas boilers are reliable equipment that can provide us not only with heat in the house, but also with hot water supply. But for their proper operation and high performance it is necessary to install a special chimney. It must carry out two main functions at once: oxygen supply to the burner and removal of combustion products outside the premises. For this, a coaxial pipe is used. Let's talk about what it is and what are its features.
General information
We will not talk now about any design features of heat generators. It is enough to understand that a chimney is necessary for their effective operation. Here the situation is the same as with the most ordinary wood-burning stove. Of course, the coaxial pipe for the boiler has a completely different design, and its installation is carried out with its own nuances, which will be discussed below. So, the key feature of such a chimney is that it works on the principle of “pipe in pipe”. It turns out that we have two pipes: one smaller, and the second larger diameter (outer and inner). On one of them oxygen enters the combustion chamber, and on the other combustion products are discharged into the environment. A very effective solution, especially if you take into account the fact that such a pipe takes up very little space and is installed in one day.
About the advantages of the system
A coaxial gas pipe has a number of significant advantages, thanks to which it has earned such popularity. Firstly, it is the localization of the combustion process, which is carried out by an isolated supply and exhaust of air and, accordingly, combustion products. As a result, there is no mixing of oxygen and gas mixtures. Consequently, the productivity of the equipment increases.
Another plus - in the process of entering the boiler, the air heats up. This is achieved due to the fact that the pipe through which it enters is subjected to heating by the waste products of combustion. In general, it is very effective, especially in the cold season. Of course, one cannot fail to take into account the fact that the “pipe in pipe” chimney design itself has smaller dimensions than a separate installation. At the same time, the number of fasteners is reduced, and the complexity of installation is significantly reduced.
A little bit about the minuses of the system
Of course, there is no ideal system that would not have flaws. In our case, although there are cons, you can simply ignore some of them , since they are insignificant, and you will have to put up with others.
The main disadvantage of such designs is that their cost is ultimately 20-40% higher than installing separate systems. Another problem is the concentric arrangement of pipes with hot and cold air. You must have noticed icing on such pipes more than once. It is formed due to the accumulation of condensate and its freezing at minus temperature. You can deal with this by installing additional drainage and insulation. But all this will further increase the price.
Well, the last drawback is the limited length of the coaxial pipe. It is approximately 4-5 meters. Therefore, if your boiler is not installed near a window or there is no way to output a coaxial pipe for any reason, this option is not suitable for you.
About the regulatory framework
It must be understood that it is impossible just to take and carry out installation of such a chimney, since the installation of a coaxial pipe is carried out taking into account existing requirements and norms. For example, there is a clear rule that says that you can install chimneys only through the roof. But this does not apply to individual heating, where it is possible to mount horizontal coaxial flues. In general, horizontal systems for the removal of combustion products and air supply can be installed only in private houses, and for multi-story buildings, vertical structures are provided that should rise 1.5 meters above the roof of the building.
System classification
All modern coaxial chimneys are divided into internal and external. The first in residential buildings are practically not used. Such structures are mounted in special mines or old chimneys. But they must comply with fire safety requirements. In addition, the installation of such systems is often very difficult, as well as maintenance.
Such shortcomings are deprived of external coaxial flues. By the way, it is customary to classify them also by warming. So, there are insulated and non-insulated. In regions where the air temperature does not fall below -10 degrees Celsius, chimneys can optionally not be insulated. In other cases, there is a risk of partial or complete freezing of pipes. In addition, there are individual and collective chimneys. The former are intended for servicing one gas boiler, and the latter for an entire multi-story building.
Structural composition and material of the chimney
The coaxial system is modular and consists of a large number of typesetting elements. This includes a gas boiler adapter, straight pipe sections, connecting elements such as couplings and tees, and much more. True, such components as a coaxial pipe extension, decorative pads may not be supplied in the kit - they need to be bought on their own if necessary. But the mounting hardware and gaskets, ensuring the strength and tightness of the system, must be present in the kit. When installing such a system, it is desirable to use jumpers. They are necessary for fixing the inner pipe relative to the outer.
As for the materials from which the coaxial pipe is made, most often it is galvanized and stainless steel, which can withstand high temperatures with ease and does not corrode for a long time. In some cases, it is advisable to use heat-resistant plastic or aluminum. Often, for the consumer, there is no difference what material the pipe will be made of, the main thing is to carry out the correct installation.
Features of the selection of the chimney
In most cases, the coaxial pipe is supplied with heating equipment, that is, with a gas boiler. That is why almost all manufacturers of heat generators produce chimneys of this type. In the installation instructions for equipment there is an item that indicates the maximum permissible length of the chimney. Under no circumstances should this value be exceeded. Otherwise, the efficiency of the equipment is significantly reduced. If the chimney runs on natural draft, that is, a fan is not provided in the boiler, a parameter such as the minimum pipe length is entered. If you install a chimney shorter in length, then there will be no draft and combustion products will remain in your apartment or house. The diameter of the pipeline in the passport data is recorded as 100/140, where the first value is the diameter of the inner pipe, and the second, respectively, is the outer one.
DIY coaxial pipe installation
The first thing you should remember is the presence of no more than 2 folds in your chimney. When installing the horizontal system, place a pipe with an inclination of at least 3 degrees. This is necessary in order for the condensate to drain on its own. If the coaxial pipe ultimately connects to a common chimney, then the angle must be changed in the opposite direction with a slope to the boiler.
The most critical stage of work is drilling a hole in the wall. This must be done using diamond equipment. But it is advisable to carry out such work if the house is being renovated, as there will be a lot of noise and dirt. After the hole is ready, it is necessary to lay the pipe, insulate it, seal. In general, there is nothing complicated. The main thing is that the chimney on the bends is well sealed. Also, do not forget about the minimum slope, which is necessary for the outflow of condensate.
System Installation Rules
A vertical coaxial pipe is mounted an order of magnitude simpler than a horizontal system. But to bring the chimney to the roof is not always possible. So, if you want the coaxial pipe to be installed correctly, you need to follow a few simple requirements.
So, you can not install the system below ground level. If the distance from the outlet to the ground is less than 1.8 meters, a deflector grill is installed to protect the pipe from dirt. If there are strong winds in your region, then it is quite possible that the boiler will go out and not work at full capacity. By installing a tin barrier, you can completely and completely solve this problem. Of course, it is advisable to entrust such work to specialists who installed heating equipment, but if this is not possible, then, observing these requirements, you can cope on your own.
Conclusion
We talked about what a coaxial pipe is. As you can see, this is a very efficient and appropriate chimney in terms of productivity and space saving. It is quickly assembled and maintained, which, without a doubt, is an important point. If necessary, you can install a coaxial pipe extension, which will slightly increase the total length of the chimney. Pay special attention to warming, as often such systems are completely freezing. There is nothing good about it. Moreover, this happens in the most severe frosts. Although the problem is solved quickly, it’s better to not have it. Now you can decide for yourself whether to use such a system or not. All the best!