End heater operation, function

L83.70-0009-06

1 Water jacket

2 Coolant inlet

3 Coolant outlet

4 Heat exchanger

5 Combustor with downpipe

6 Main wiring harness connector to STH

7 STH connector in electric box

8 Connector to coolant circulation pump

A6 Stationary heater (STH)

A6m1 Combustion air blower

A6n1 Stationary heater control module

A6r1 Glow pin

A6r2 Overheating sensor for NTC resistor

A6r3 Temperature sensor for NTC resistor

A6r4 Flame sensor for PTC resistor

A8/3 STH radio remote control transmitter

M46/1 STH fuel metering pump

N34 Stationary heater timer

The normal end of heater operation, i.e. not triggered by a fault, can be triggered manually at the stationary heater timer (N34), with the radio remote control transmitter (A8/3) or automatically after the maximum heating time (2 hours) is over.

End heater operation manually or automatically

1 Combustion is stable. The fuel metering pump (M46/1) and the combustion air blower (A6m1) pump at their lowest capacity.

2 The end of heater operation is triggered manually or automatically.

3 The fuel metering pump (M46/1) is switched off and thus combustion is interrupted. The heater fan (M2) is switched off.

4 The run-on time for cooling the heater and for purging the combustion chamber starts (approx. 120 s).

Special case: If, by the time it is switched off, no fuel has been pumped or the unit is in the control pause, it is brought to a standstill without run-on.

5 The run-on time is over. The combustion air blower (A6m1) and the coolant circulation pump (M13/2) are switched off. Heater operation is over.

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The start of heater operation may be terminated by the following faults:

 defect in flame sensor (A6r4)

 no flame formation

During heater operation, the following procedures may cause heater operation to be terminated prematurely:

 overheating,

 under- or overvoltage

 flame-out

 defect in a heater component

 If the end of heater operation is triggered by a fault, there is a malfunction shut-off.

After eliminating the source of the fault, this can be canceled by switching the stationary heater off and on. After at the most 10 unsuccessful start attempts, a fault lock occurs. This fault lock is canceled by deleting the diagnostic trouble code memory in the STH control module (A6n1).

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No flame formation

1 After the safety time is over, an inquiry is made via the flame sensor (A6r4).

2 The flame sensor (A6r3) signals "cold".

3 The fuel metering pump (M46/1) and the heater fan (M2) are switched off.

4 The run-on time for purging the combustion chamber starts for approx. 120 s. During the run-on period, the combustion air blower (A6m1) runs in stage "SMALL".

5 The run-on time is over. The repeated start commences. The glow pin (A6r1) is switched on and the new starting procedure commences with approx. 50 s preheating time,
90 s safety time and the inquiry of the flame sensor (A6r4).

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6 The flame sensor (A6r4) again signals "cold". The stationary heater control module (A6n1) now initiates a malfunction shutoff .

7 The fuel metering pump (M46/1) and the heater fan (M2) are switched off.

8 The run-on time for purging the combustion chamber starts for approx. 120 s. The combustion air blower (A6m1) runs for approx. 35 s in partial load operation and for approx. 95 s in full load operation.

9 The run-on time is over. The combustion air blower (A6m1) and the coolant circulation pump (M13/2) are switched off.

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Heater overheating

1 The heater operates in stage "SMALL" or "LARGE".

2 The coolant temperature increases above 130 °C and thus reaches an inadmissible temperature value.

3 The stationary heater control module (A6n1) detects the overheating, interrupts the fuel metering pump circuit (M46/1) to protect the heater and triggers a malfunction shutoff.

4 The heater fan (M2) is switched off.

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5 The run-on time for cooling the heater and for purging the combustion chamber starts for approx. 120 s. The combustion air blower (A6m1) runs for approx. 35 s in stage "SMALL" and for approx. 95 s in stage "LARGE".

6 The run-on time is over. The combustion air blower (A6m1) and the coolant circulation pump (M13/2) are switched off.

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Under- or overvoltage during heater operation

1 The heater operates in stage "SMALL" or "LARGE".

2 The stationary heater control module (A6n1) detects a fault in the voltage supply.

2.1 If the voltage drops below approx. 10.2 V for at least 20 s:

 The control module initiates a malfunction shutoff to protect against battery discharge.

2.2 If the voltage increases above approx. 15.9 V for at least 20 s:

 The stationary heater control module (A6n1) initiates a malfunction shutoff to protect the electric and electronic heater components.

3 The fuel metering pump (M46/1) is switched off and thus combustion is interrupted.

4 The heater fan (M2) is switched off.

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5 The run-on time for cooling the heater and for purging the combustion chamber starts for approx. 120 s. The combustion air blower (A6m1) runs for approx. 35 s in stage "SMALL" and for approx. 95 s in stage "LARGE".

6 The run-on time is over. The combustion air blower (A6m1) and the coolant circulation pump (M13/2) are switched off.

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Flame-out or defect in flame sensor

1 The heater operates in stage "SMALL" or "LARGE".

2 The flame sensor (A6r4) signals "cold". This message may be caused by insufficient fuel or combustion air supply or by a defect in the flame monitor.

3 The stationary heater control module (A6n1) initiates a start attempt for approx. 90 s to repeat flame formation and thus to continue combustion.

4 The flame sensor (A6r4) monitors the start attempt.

4.1 The flame sensor (A6r4) within the start attempt lasting 90 s signals "hot" = repeated flame formation and thus continuation of combustion.

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4.2 The flame sensor (A6r4) at the end of the start attempt lasting 90 s signals: "cold" = no flame formation and thus no continuation of combustion process.

 The stationary heater control module (A6n1) initiates a malfunction shutoff .

 The glow pin (A6r1), the fuel metering pump (M46/1) and the heater fan (M2) are switched off immediately.

 The run-on time for cooling the heater and for purging the combustion chamber is started for approx. 120 s. The combustion air blower (A6m1) runs for approx. 35 s in stage "SMALL" and for approx. 95 s in stage "LARGE" during the run-on.

 The run-on time is over. The combustion air blower (A6m1) and the coolant circulation pump (M13/2) are switched off.

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Defect in coolant temperature detection

Coolant temperature detection is constantly monitored internally by the stationary heater control module (A6n1).

1 Heater operates in stage "SMALL" or "LARGE".

2 The control module (A6n1) detects a malfunction in coolant temperature detection. The temperature signal has exceeded the temperature detection range.

3 The control module (A6n1) triggers a malfunction shutoff to protect the heater.

4 The fuel metering pump (M46/2) is switched off and thus combustion is interrupted.

5 The heater fan (M2) is switched off.

6 The run-on time for cooling the heater and for purging the combustion chamber starts for approx. 120 s. The combustion air blower (A6m1) runs for approx. 35 s in partial load operation and for approx. 95 s in full load operation.

7 The run-on time is over. The combustion air blower (A6m1) and the coolant circulation pump (M13/2) are switched off.