"End heater operation upon exceeding cut-off threshold in partial load operation", function

W83.70-0017-09

1 Timer
2 Control module
3 Glow pin
4 Temperature sensor
5 Burner
6 Heat exchanger
7 Overheating sensor

V Combustion air
A Exhaust
KE Coolant inlet
KA Coolant outlet
KS Fuel

8 Coolant circulation pump
9 Burner housing
10 Flame sensor
11 Combustion air blower
12 Exhaust line with muffler
13 Combustion air line
14 Fuel metering pump
15 Automatic heater control panel

Function sequence

 Heater switched on with timer (1) for auxiliary heater.

 Heater operating in partial load range.

 The heater is switched off by the control module (2) upon exceeding the maximum temperature for the coolant. The heater then switches to the cooling phase with shut-off delay:

- The fuel supply is interrupted immediately by switching off the fuel metering pump (14).

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- The combustion air blower (11) continues to run for
210 seconds cooling the combustion chamber and flushing out any combustion gases.

 After completion of the cooling phase with shut-off delay the heater goes to the controlled shut-off phase:

- The blower for the vehicle heater continues to run.

- The coolant circulation pump (8) continues to run.

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Operating state upon exceeding maximum temperature

After the heater is switched off by the control module upon exceeding the maximum temperature the following components remain in operation:

 Cooling phase with shut-off delay

Combustion air blower, low stage = 1850 rpm

Fuel metering pump = off

Coolant circulation pump = running

Blower for vehicle heater = running

Operating state upon completion of cooling phase with shut-off delay

After completing the cooling phase with shut-off delay the following heater components remain in operation:

 Controlled shut-off phase

Combustion air blower = off

Fuel metering pump = off

Coolant circulation pump = running

Blower for vehicle heater = running