Heating mode, coolant temperature in partial load mode ≥ 72 °C and outdoor air temperature ≤ 5 °C

P83.70-0337-09

1 Burner housing

2 Heat exchanger

A6m2 Combustion air blower

S25/17 ECT switch

S25/18 Air temperature switch

Y23 Stationary heater fuel metering pump

A6n1 Stationary heater/heater booster control module

G2 Generator

M13 Coolant circulation pump

Operation

1 Coolant temperature > 61 °C and < 72 °C
Outdoor temperature  5 °C
The switching contacts in the engine coolant temperature switch (S25/17) and air temperature switch (S25/18) are closed. A positive signal from the generator (G2), circuit 61 (charge indicator) is present at the control module (A6n1).

2 The heater operates at partial load. The combustion air blower (A6m2) and fuel metering pump (Y23) operate at partial load speed and output. The coolant circulation pump (M13) pumps coolant through the heat exchanger (2).

3 The coolant temperature increases in spite of the fact that the heater is operating at partial load due to the low heat requirement.

4 The coolant temperature reaches 72 °C.

5 The control module (A6n1) discontinues operation of the heater booster.

6 The fuel metering pump is switched off interrupting the combustion in the burner housing (1).

7 The heater shut-off delay of approx. 110 s starts to cool down the heater and purge the combustion chamber.

8 After completion of the heater shut-off delay the combustion air blower is switched off.

9 Operation of the heater booster is completed.

10 The coolant circulation pump (M13) continues to pump the coolant through the heat exchanger (2) even though the heater is switched off.

 The heater booster is started up again when the temperature of the coolant drops below 60 °C resulting from a decrease in the outdoor air temperature and /or the engine being shut off frequently, etc.