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Flue for pellet or wood stoves

Flue for pellet or wood stoves

Flue for pellet or wood stoves: regulations for installation and when it can be done without. Ventless stoves. Rules for the perfect insulation of the flue.

Flue, reference standard

What is the flue used for?

The answer is simple: this duct serves to convey all the fumes produced by combustion to the outside. The chimney expels the fumes by means of the so-calleddraft natural: the hot vapor (smoke) spontaneously fluctuates upwards following the path of the duct.

How is the chimney made?

Thereflueit consists of two elements, a smoke channel or flue connection and a proper flue. The flue gas connection or smoke channel generally has a perpendicular trend to the combustion chamber but, in the most careful designs, it can also have an irregular trend. The smoke channel is the duct that connects the fireplace or stove (whether it is wood or pellet) with the flue itself. There flue real is that insulated pipe that comes out of the roof and reaches the "chimney pot". In common parlance, we tend to call "flue"Both components but in technical terms, the whole of the flue and the smoke fitting is defined"smoke system“.

Certification of compliance with the Uni 10683 standard

Therelawrequires that each hearth (fireplaces, stoves, thermo-fireplaces, thermo-stoves…) must be connected to a duct for its exclusive use. The installation of the flue can never be done by doing it yourself because for the design it is necessary to issue the certification of compliance withlegislationof reference. Therelegislationcurrent is Uni 10683.

Flue for fireplaces and wood stoves

The trend of the flue gas connection of afireplaceor other wood-burning firebox, must be as vertical as possible. The maximum inclination can reach 45 °. The reference legislation also provides for the presence of more than one curve. The rules to respect:

  • The smoke system must be at least 4 meters in total
  • There is no maximum length limit, a draft between 8 and 12 Pa must be guaranteed when hot. The measurements must be carried out by a smoker technician.
  • The section of thefluemay vary depending on the product chosen or the overall height of the smoke system.
  • The section of theflueit must never be smaller than the diameter of the smoke outlet collar of the equipment, this diameter is generally 15 cm.

Flue pipe for pellet stoves and ventless stoves

We often hear aboutflue-free pellet stovesbut this term does not exactly correspond to reality. The definition offlue-less stovescan be misleading because the fumes produced by combustion must be expelled in any case!

We talk aboutflue-free pellet stovesbecause the aforementioned regulation (UNI 10863) specifies that pellet fires can expel fumes using a simple 8 cm duct. This pipe (very compact in size) can be installed on the roof and surmounted by a simple mushroom-shaped element or a chimney pot which facilitates its natural draft in the event of a power failure. What does electricity have to do with it? In pellet stoves and boilers, the draft is not "natural" but forced by an electric fan.

Before 2012, when the UNI 10863 standard had not yet entered into force, the pipe could also come out on the wall. In this context, the "ventless pellet stoves" could be easily installed even in an apartment building. Today, the legislation provides for the installation of a flue which, even if small in size, cannot expel the fumes from the wall.

For the construction of a flue for a pellet stove there are three options:

  • The flue reaches the roof directly through the attic.
  • The pipe comes out of the wall and from here conveys the fumes to a flue made outside.
  • A smoke connection is created to reach a pre-existing flue already present outside the building.


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