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Technical information
Existing flue gas systems may require upgrading
or adjustment of the flue duct cross-section as
indicated by a chimney engineer.
The correct functioning of the flue duct, i.e. the generation
of the required delivery pressure depends on:
a) the type (nature) of the chimney (thermal insulation,
interior surface roughness, sealing etc.)
b) the connection of the boiler to the chimney
according to specification
c) establishing the correct flue duct cross-section
dimension.
ref. a)
Chimneys according to EN 13384, part 2, execution
types I and II are appropriate for modern firing systems
(advice from the chimney specialist is necessary).
to b)
The flue gas pipe connecting the boiler to the flue gas
system must be as short as possible and placed at
an angle of 30-45°.
The entry location of the flue gas pipe must be
carefully sealed.
The introduction of the flue gas pipe into the chimney (a)
must be executed so that no condensate water can
flow from the chimney into the flue gas pipe and the
boiler. (Fig. 10)
Where possible, avoid 90° bends in the flue gas system!
Flue gas pipes longer than 1 m are to be insulated.
4. Installation
4.1 Boiler room requirements
Regarding the building specifications for boiler rooms
and their supply and extract air handling, the current
building supervisory office regulations specific to the
state or country are to be observed. In Germany the
firing regulations for the individual Bundesländer are
to be complied with.
Make sure there is an adequate supply of fresh
air to the boiler room,
to ensure that the combustion air supply necessary
for all the firing systems operated there can flow in
without hindrance and that no oxygen deficiency
occurs for the operating personnel.
Binding values for the size of supply air openings are
not generally specified in the relevant regulations; it is
merely required that no partial vacuum in excess of 3 N/
m
2
occurs. An opening or line leading into the open air
of at least 150 cm
2
. For every kW in excess of 50 kW,
a further 2 cm
2
must be calculated. In rectangular
openings, the ratio of the sides should not exceed
1.5:1; if a grid is fitted, an appropriate allowance must
be added so that the free cross-section area reaches
the amount given above.
In Austria ÖNorm H 5171 additionally stipulates a
flue air aperture. This must have a minimum cross
section of 180 cm
2
up to a rated heat output of
100 kW. For every further kW, the cross-section must
be increased by 1 cm
2
.
The flue gas system must be watertight, acid-
proof and approved for the corresponding
flue gas temperatures.
As a general rule, only one heat generator should
be connected to the chimney! When using two
heat generators, the corresponding regulations
must be observed.
4.2 Connection of the flue gas system
and flue duct dimensions
To guarantee economic and fault-free operation, boiler
and chimney must be mutually adapted to create
a functional unit.
Moisture-resistant and acid-proof flue gas
systems must be used in new installations.
a
Figure 10
