Combustion Air Supply - Webasto Air Top Evo 3900 Workshop Manual

8 Servicing work

8.6.5 Combustion air supply

Under no circumstances may the combustion air be taken
from areas occupied by people. The combustion air intake
opening must not point in the direction of travel. It must be
located so that it cannot become clogged with dirt.
The combustion air must be extracted using a combustion
air line from a position that is as cool as possible and
protected from splashing water for petrol heaters.If the
heater is in a sealed installation box, the combustion air
must be drawn in from the outside and the emissions fed
to the outside.Pipe passage holes must be made in such
a way as to ensure that the ingress of exhaust fumes into
the interior of the vehicle should not occur.
If dirty combustion air is expected, a combustion air filter
may be fitted.
(Air Top Evo 3900/5500 D only). An intake silencer must
be used for an intake hose length of < 0.6 m.
8.6.6 Exhaust pipe
Rigid pipes of unalloyed or alloyed steel with a minimum
wall thickness of 1.0 mm or flexible piping of alloyed steel
only must be used as exhaust line.
The exhaust pipe must be secured to the heater and
exhaust silencer with a pipe clip, Part No. 20 965A.
The exhaust silencer (fig. 808) should ideally be installed
near the heater.
The flow direction is arbitrary.
The heater may also be operated without a silencer.
ø 6,5
Fig. 808 Exhaust silencer
8.6.7 Combustion air inlet and exhaust lines
To prevent damaging the metering pump cable, exhaust
line must not be used to extend the combustion air supply
line.
Length of the combustion air intake and exhaust lines:
with silencer:
without silencer:
806
NOTE
NOTE
max. 2.0 m
max. 5.0 m
Air Top Evo 3900/5500
Both lines are to be installed falling away from the heater.
If this is not possible, a condensate drain hole with a
diameter of 4 mm must be made at its lowest point or a
connection element with a condensate drain used.
Internal diameter of the lines:
Combustion air line:
Exhaust line:
If the exhaust line is 2 m or more, insulated exhaust lines
must be used (to prevent the temperature falling below the
dew point).
Minimum bending radius:
Total bends:
Combustion air line:
Exhaust line:
An attachment is required no further than 150 mm from
the end of the exhaust pipe to ensure that the angle of 90°
± 10° is achieved.
Fig. 809 Exhaust pipe mouth, installation position
WARNING
If the exhaust pipe ends is other than as shown in the fig.
809 it will pose a fire risk.
25 mm
24 mm
NOTE
50 mm
max. 270°
max. 270°
Discharge direction
almost vertical 90° ± 10°