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4.5
Air/flue gas system (LAS)
4.5.1
General instructions for the flue gas
system
DANGER: RISK OF POISONING
Flue gas escaping within enclosed rooms that are inad-
equately ventilated causes a danger of toxic poisoning.
▪ Install approved flue gas systems only.
▪ Depending on the installation variant, the stipulated
ventilation and rear ventilation must be ensured.
▪ Coverings over the flue gas mouth are not permissible
Minimum requirements
Observe country-specific regulations and EN 15287 for the design
and measurement of the flue gas system.
Basically, any flue gas pipe in accordance with EN 14471 with CE
mark can be used for the flue gas system (device type C
able) that meets the following minimum requirements:
▪ Suitable for gas.
▪ Suitable for flue gas temperatures of at least 120 °C (temperature
class T120 or higher).
▪ Suitable for at least 200 Pa overpressure (pressure class P1 or
H1).
▪ Humidity-resistant (condensation resistance class W).
▪ Sufficiently corrosion-resistant (corrosion resistance class 1 or 2).
The properties of the flue gas system must be identifiable on the in-
stalled system (type plate in the installation room).
The associated assembly instructions must be observed for installing
the flue gas and supply air guiding system components or their
means of attachment.
▪ Each flue gas line must be installed with a suitable test ad-
apter for checking and setting the combustion values. The
LAS construction sets shown contain one test adapter each
(D8PA)
▪ Depending on the local building regulations, inspection compon-
ents must be installed in the required locations.
Types of connection
▪ Directly at the back
(Fig.
4-1: SET H)
▪ On the side at the back
(Fig.
4-2: SET K)
▪ Direct roof lead-through
(Fig.
For further details of the three variants of the flue gas pipe, see
Chap.
4.5.3.
Installation position and piping height
▪ The maximum permitted flue gas counterpressure is 200 Pa. The
pressure loss in the supply line must not exceed 50 Pa.
▪ Angle of entry of the flue gas pipe into the chimney or installation
shaft: at least 3°.
▪ Avoid horizontal sections in the connection line or keep them as
short as possible.
▪ Slope for horizontal sections of the flue gas line: at least 3°.
Counter-slopes are not permissible at any point in the flue gas
line so that condensate can drain off without restriction.
▪ If more than 3 deflections >45° are needed for the flue gas line,
the maximum height for the flue gas line reduces by at least 1 m
per deflection (flue gas calculations may be needed).
(6)
Design for natural gas (G20), a horizontal connecting line with a length of 2 m and a deflection of 87° are taken into account
(7)
Shaft cross-section for DN 60: 115 mm × 115 mm, for DN 80: 135 mm × 135 mm
(8)
Concentric flue gas/supply line: DN 60/100
(9)
Concentric flue gas/supply line: DN 80/125
Gas Combi Unit
Floor-standing gas condensing boiler with integrated heat storage
008.1543899_02 – 04/2019 – EN
if applic-
63
4-7, Variants 2 and 3: SET L)
4
▪ If the horizontal connecting piece is extended to more than 2 m,
the maximum permitted height of the flue gas duct is reduced by
exactly that length.
▪ Flexible flue gas lines may not be used in horizontal connection
sections.
▪ Straight pipe sections must be fastened at intervals of < 2 m using
suitable wall brackets. Suitable spacers must be used within ver-
tical shafts.
Flue gas system resistance
A minimum resistance in the flue gas line is necessary, especially for
liquid gas devices, to ensure a safe burner start and stable flue gas
values in the lower output range.
After the initial burner start, the GCU compact first switches to stor-
age tank charging mode. In this mode, the burner blower runs at
maximum speed.
1
Switch on the burner (see Emissions measurement).
2
Measure the resistance with a differential pressure gauge on the
flue gas measurement section between the flue gas and supply
air measurement openings (differential pressure for all
GCU compact at least 0.2 mbar).
è A silencer must be installed (DN 80: E8 MSD or DN 110:
E11 MSD) if the differential pressure is not reached when the
burner blower is at maximum speed
Tab. 4-2
shows the maximum permissible height of the flue gas line
to ensure that the GCU compact can be operated in the nominal out-
put range.
Installation variant
Maximum height of the flue gas line
(according to
Fig.
4-7)
315 / 515
(7)
(8)
(9)
1
, 2, 3, 4
10
, 7
(7)
(7)
(8), (9)
5
, 6
25
Tab. 4-2
Maximum height of the flue gas line in m
The characteristics for the flue gas calculation can be obtained from
Fig. 4-15
and the
Chap.
14.1.
Fig. 4-15
Flue gas mass flow in relation to the burner load
GCU compact (all types)
A
Natural gas E/H (G20)
B
Natural gas LL/L (G25)
C
Liquid gas (G31)
m
Flue gas mass flow
AG
P
Burner loading
The flue gas mass flow of the system depends on the burner output
of the GCU compact.
Set-up and installation
(6)
GCU compact
320 / 520
524
528
(8)
(9)
(8), (9)
(8)
15
, 11
14
10
, 15
(8), (9)
(8), (9)
(8), (9)
25
25
25
Installation and operating instructions
(9)
23
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