We remind you hereafter of the prior recommendations
to be respected, these will have to be added to the
strict application of the whole DTU 24-2-2.
4.1 – Definition of components included in the
smoke evacuation system(Fig. 3)
4.2 – Characteristics and size of the smoke flue to
which the appliance must be connected
4.2.1 - Type of Smoke Flue
4.2.1.1 - New Smoke Flue
Use of the following materials:
Fireclay flue blocks compilant with French
Standard NF EN 1806.
Concrete flue blocks compliant with NF EN
1858.
Composite metal pipes compliant with NF EN
1856-1 and NF EN 1856-2 or which have
received "Avis Technique" approval (*) for this
use.
Fireclay bricks compliant with NF P 51-301.
Refractory bricks compliant with NF P 51-302.
The use of certified insulating materials means that
on-the-spot
insulating work can be avoided,
particularly where the chimney stack is concerned
(minimum thermal resistance 0.43 m
4.2.1.2 - Existing Smoke Flue
The installer is responsible for existing parts. He
should check the condition of the flue and carry out
any work required in order to ensure that it is in
proper working order and compliant with the
regulations in force.
He should sweep the flue and then check the
following very thoroughly :
Compatibility of the flue with the intended use ;
Stability
That the flue is empty and smoke-tight (DTU
24-1, Appendix II).
If the flue is not compatible, make a casing using
an approved method "Avis Technique" certificats (*)
or install a new flue.
(*) French assessment and certification system
4.2.2 – Minimum flue section
Sizing according to standard EN13384-1. In all cases
the cross section of the connecting flue must be at
least equal to the cross section of the nozzle of the
appliance.
4.2.3 - General Recommendations
A good flue will be built of materials with low heat
conducting properties so that it stays hot.
2
k/W).
12
Flue casing should be such as to limit the external
surface temperature to the following :
- 50°C in living areas
- 80°C in non-living or inaccessible areas
lt should be completely smoke-tight, stable and
have no rough spots.
There should be no sudden changes in section
(slope in relation to the vertical less than 45°).
It should extend at least 0,4 m above the ridge of
the roof and of adjacent roofs.
Two appliances should not be connected to the
same flue.
It should come out into the room containing the
appliance at a height of at least 50 mm.
Flue blocks should be placed with the male part
towards the bottom so as to avoid any leaks to the
outside.
The flue should include no more than two changes
of direction, i.e. no more than one non-vertical
section.
- If the flue is in masonry :
The bend angle should not exceed 45° over a
total flue height limited to 5 m. For any greater
height, this angle should not exceed 20°.
- If it is an insulated metal flue :
The bend angle should not exceed 45° with the
height limited to 5 m between the top and bottom
of the bend. There is no limitation as to total flue
height.
Smoke-tightness, insolation, openings in walls or
floors and sale fire distances should all strictly
comply with the provisions of DTU 24-2-2 and
DTU 24-1.
The safety distance between the connecting flue
and all vertical or horizontal parts in combustible
materials must be greater than or equal to 3 times
the rated diameter of the flue.
The safety distance between the smoke extraction
flue and all combustible materials is determined
depending on the heat resistance of the flue (Ru
expressed in m² K/W) :
Composite metal smoke flues
Ru ≤ 0.4
T°C class of the flue
T450
interdit
Single or multiple concrete and fireclay smoke flues
0.05 < Ru ≤
T°C class of the flue
0.38
T450
10 cm
0.4 < Ru ≤
Ru > 0.6
0.6
8 cm
5 cm
0.38 < Ru ≤
Ru > 0.65
0.65
5 cm
2 cm