Webasto Air Top 3500 ST D Workshop Manual - page 15
3 Function description
Air Top 3500/5000 ST
302
3.5
Control pause
After the temperature set on the control element has been
reached the heat output is reduced. The speed of the
heating and combustion air blower and the delivery rate of
the metering pump are reduced.
If, at minimum heat output, the intake temperature set on
the control element is exceeded, the metering pump is
shut down and the combustion process ended. To burn off
the flame properly the blower speed falls after 20 seconds
to low-fire rate speed and then returns to the initial speed
after 15 seconds, after which it falls to the control pause
speed in 3 minutes, where it remains for the entire control
pause.
The control pause speed on boat heaters is 0.
If the temperature set on the control element is exceeded
at the temperature sensor, the heater will restart.
NOTE
Changes to the setting on the control element are
implemented by the control unit and heater after a delay.
3.6
Switch off
When the heater is switched off the ON control LED on the
control element goes out. If no fuel has been transported
or if the heater is in the control pause, the heater is
switched off immediately without a slow down time.
If the fuel transport has been started it is ended when the
heater is switched off. The heater is switched off using the
same method as the transition from control mode to
control pause. The heater is then switched off
automatically.
NOTE
The heater may be switched on again during the slow
down time. In this case the slow down time is completed
and the heater is then restarted.
3.7
Heater functions
when installed in ADR vehicles
NOTE
Only for Air Top 3500/5000 ST D heaters that are
installed in vehicles for transporting hazardous
substances (ADR).
If the heater is switched off using the control element the
slow down time remains unchanged.
A brief slow down time (max. 40 seconds) is started
automatically if
•
the vehicle’s engine is switched off
•
a transport device is started.
After an ADR shut down process the control unit is in the
“Fault lock-out” position. Before it can be restarted the
control element must be set to “OFF”.
3.8
Fault lock-out
Errors on the various heater components and faults in the
starting process and in heating mode are identified in the
control unit. The heater is switched off and goes into fault
lock-out if the following conditions occur:
•
No or incorrect start
•
Temperature sensor defective
•
Overheating sensor interrupt or short circuit
•
Overheating sensor installed incorrectly
•
Glow plug/Flame monitor interrupt or short circuit
•
Blower motor overload or blocked or short circuit or
break
•
Error in metering pump circuit
•
Undervoltage below 10.5 V / 21 V for longer than
20 seconds
•
Overvoltage above 16 V / 32 V for longer than 6
seconds
•
Control unit defective
•
Overheating
The fuel supply is stopped if the heater overheats.
The heater continues to run in the same way as if it is
switched off manually.
After it stops the control unit will be set to fault lock-out.
The overheating is indicated by the indicator flashing
10 times.
Rectify the cause of the fault.
To reset the fault, switch the heater off briefly (at least
22 seconds) and then on again.
3.8.1 Error monitor
The overheat, incorrect start and flame failure errors are
counted and cause the heater to suffer a fault lock-out
after an error has occurred the maximum number of times.
The incorrect start counter FSZ is incremented by 1 each
time the heater fails to start and decremented by 1 each
time it starts correctly, but does not fall below 0. If the
incorrect start counter reaches its maximum value of 9 the
heater will go into the heater lock-out status HGV.