Webasto Air Top 3500 ST Installation Instructions Manual - page 22
Combustion air inlet and exhaust lines
Air Top 3500 ST / Air Top 5000 ST
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Combustion air inlet and exhaust lines
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.
The lines must not point to the front of the vehicle.
The lines must be located so that they cannot become clogged with dirt.
IMPORTANT
If the exhaust pipe ends is other than as shown in the Figure 23 it will
pose a fire risk.
Length of the combustion air inlet and exhaust lines in total:
With exhaust silencer:
max. 2.0 m
Without exhaust silencer:
max. 5.0 m
NOTE:
If the exhaust line is over 2 m in length the lines must be insulated (to
prevent falling below the dewpoint)
Internal diameter of the lines:
Combustion air line:
25 mm
Exhaust line (metal):
24 mm
Minimum bending radius: 50 mm
Total bends:
Combustion air line:
max. 270°
Exhaust line:
max. 270°
Fig. 20: Prevent the formation of condensate
Fig. 21: The lines must not end pointing towards the front of the
vehicle
Fig. 22: Avoid the lines becoming clogged with dirt