Stationary heater operation with heat requirement of 50 to 100% of heating capacity

P83.70-0391-09

1 Burner housing

2 Heat exchanger

3 Heater circuit thermostat

Y23 Stationary heater fuel metering pump

B Thermostat position with auxiliary circuit open

A6m1 Circulation pump

A6m2 Combustion air blower

A6n1 Stationary heater/heater booster control module

Operation

1 Coolant temperature > 59 °C :
The thermostat (3) is switched to heater operation, the auxiliary circuit for the stationary heater is connected to the vehicle cooling and heating circuit.

2 Start-up of the stationary heater is completed. The combustion air blower (A6m2) and fuel metering pump (Y23) operate at their lowest speed and output in the partial load mode.

Heat requirement > heater output available momentarily

3 The heater output is too low, the coolant temperature drops to below 68 °C. The heater output must be increased.

4 The stationary heater control module (A6n1) recognizes from the coolant temperature that the heater output is too low and switches over from partial load to full load.

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5 The fuel metering pump (Y23) and combustion air blower (A6m2) are switched over to full load within 50 s by infinitely increasing the power until they operate at maximum output and speed. The coolant temperature remains constant or increases depending on the heat requirement.

Heat requirement < heater output available momentarily

6 The heater output is too high, the coolant temperature increases to above 77 °C.
The heater output must be reduced to protect against overheating.

7 The stationary heater control module (A6n1) recognizes from the coolant temperature that the heater output is too high and switches over from full load to partial load.

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8 The fuel metering pump and combustion air blower are switched to partial load within 50 s by reducing the power infinitely until they again reach their lowest output and speed. The coolant temperature remains constant or decreases depending on the heat requirement.

Heat requirement > heater output available momentarily

9 The heater output is too low, the coolant temperature drops to below 68 °C.
The heater output must be increased.

10 The stationary heater control module (A6n1) recognizes from the coolant temperature that the heater output is too low and switches over from partial load to full load.

 Alternation between partial load and full load continues over the entire period the heater is in operation as long as the heat requirement does not change.