Elements to expel combustion fumes
All materials fuels during combustion, they release smoke harmful, which are dispersed into the surrounding environment, through elements better known as cane flues.
These elements, over the centuries, have been made with a lot of materials different among them: stones, bricks, pipes of clay and different metals, often characterizing the urban landscape with their terminal configurations, better known as chimneys.
From source of heat in which the fumes and noxious fumes are produced, departs there cane chimney real, which starts from the top of the chimney where the combustion takes place and continues up above the coverage of the building, ending with the chimney.
A flue efficient it allows the combustion fumes to escape outside without coming missing inside heated rooms.
This efficiency depends on several factors; these, if neglected, can compromise its proper functioning.
The importance of recirculation for a good draft
The reason that allows the flue to perform its task is due to the fact that thehot air tends to to go up. But this is not enough, as, to complete the expulsion of the fumes, new cold air must enter, which, once heated, will trigger the phenomenon known as draft.
Let’s see, therefore, what are the elements that influence the draft of a flue in condition natural, that is, without the aid of other artificial suction mechanisms.
A first element to consider is the length of the flue, which increasing favors smoke evacuation.
Another important element to consider is the section of the flue.
This element is closely linked to the mentioned length, as the draft can be improved by their correct sizing.
This should not suggest that increasing beyond certain limits it is possible to obtain the best functioning of the flue. In fact, by stretching a excess the flue and reducing the section, there would be phenomena of friction internal and of dispersion excessive thermal.
Correct sizing at the base of good draft
This problem obviously recurs in the case of inversion in size, i.e. huge section and minimum length.
So what should you do when you need to install a flue?
What measures should be considered?
What materials should be used?
Are there unique rods for all types of outbreaks?
What is the best section?
What laws must be respected in order not to have problems?
I questions mentioned above, are those that normally arise when faced with the installation of a flue. Therefore, I will try to report in that sense, for the purpose of eliminate doubts and common mistakes, often due to malfunctions with serious consequences.
Pay the right attention to every detail
About the question of the sizing, I can immediately say that when you buy a fireplace, a stove or a simple oven, in the instructions supplied with the appliance, the size of the flue to be used, as well as other useful tips to facilitate draft and improve the heat output of the chimney.
The trouble arises when a particular project, in which the entire structure of the outbreak is made on site. In this circumstance, I recommend not to go by trial and error or similar projects already made, as the construction characteristics and the materials used could be different.
In this circumstance, it is necessary to request the intervention of a specialized technician, which will design the fumes expulsion system, following the precise specifications standards, as the UNI EN 13384-1.
Replace or repair ratings in this regard
Circa i materials to be used, it is necessary to evaluate if you need to replace an old existing flue, renovate it with the same material, or create it from scratch.
It is generally more practical to use modern insulated rods, made with efficient and safe materials. With them it is possible both the insertion in the existing ones and a new realization.
Regarding the shape of the section, it is necessary to keep in mind how irregular shapes made on site with sharp edges and inadequate dimensions, are the cause of turbulence phenomena, with consequent expulsion of smoke even in inhabited rooms, in certain atmospheric conditions.
Therefore, they are preferable circular or polygonal shapes, whose internal corners have suitable connections and in any case with curves having a radius of no less than 3 cm.
I remember that flues made of materials with the presence of roughness superficial, due to poorly executed joints or very rough materials, contribute to reduce the draft of the chimney, as well as imprisoning soot and pigments produced by combustion, with consequent reduction of the free section.
Local rules and regulations to install smoothly
Also remember how also shape and position of the chimney they are essential for a good draft, so it must be carefully designed and placed in the right position.
As regards the read to be respected in the municipal authorization, for the purposes of the new construction it is necessary to bear in mind that the flue is considered a technical volume and therefore there is no need to apply for a permit to build, except in cases where by size notable of the entire support structure, this installation constitutes one substantial modification of elevations and distances.
Just the distances, represent one more topic complex as they bring up the rules of the civil code to protect the rights of third parties.
In this regard, it is necessary to distinguish two situations, ie installation in common provided of building regulations, in which the distance is specifically indicated minima to be respected by other neighboring properties, which is generally 1.5 m.
Not just rules and regulations but case-by-case evaluations
I point out as in the case of regulated indications non it is possible to invoke exceptions, by virtue of different reasons, such as the non-harmfulness of the fumes, or the fact that frequent wind conditions reduce the phenomenon of harmful emissions.
For those situations in which no specific legislation exists, the jurisprudence indicates the figure of the competent magistrate, as the person to whom the evaluation of theadmissibility of the intervention.
In light of the above, it is understood how in absence of specific regulations in force in the area, in which the installation of a flue is required, will be the court to decide the minimum distance case by case, evaluating the possible concrete danger of the flue.
At the conclusion of what has been illustrated, I add some tips about the maintenance of the flue in order to keep it in perfect condition efficiency.
Flue maintenance: foundation for efficiency and safety
I start by remembering that the maintenance and cleaning of the flues of stoves and fireplaces are disciplined by legislation UNI 1068.
This legislation establishes that the cleaning of all flues must take place Once a year employing qualified personnel.
For the flues serving wood-burning fireplaces or similar, cleaning must be carried out every 40 quintals of wood burned; for pellet stoves and fireplaces the law requires cleaning when 20 quintals of pellets are burned.
The cleaning operation must be certified by a qualified operator, equipped with a regular license. Certification is important not only to certify the proper functioning of the fumes expulsion apparatus, but also protects the owner from accidents that can cause damage to himself or to third parties.
I happened to have to appraise damages deriving from‘fire of a flue caused by poor maintenance. I can guarantee that thecompensation burden who was in charge of the exercise in which the fire occurred was not light.
In addition to the obligation to do this, cleaning is also a lot convenient for the purpose of optimizing the thermal yield of the system served, extending its duration and efficiency, as well as involving a savings on the expense of fuel.
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