Heating mode, coolant temperature < 61 °C and outdoor air temperature ≤ 5 °C

P83.70-0339-09

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
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 full load. The combustion air blower (A6m2) and fuel metering pump (Y23) operate at maximum speed and output. The coolant circulation pump (M13) pumps coolant through the heat exchanger (2). The temperature of the coolant increases.

3 The coolant temperature reaches 61 °C, the maximum heating output can be reduced because the heat requirement has decreased.

4 The control module (A6n1) infinitely reduces the combustion air blower and fuel metering pump to partial load within
55 s.

5 The coolant temperature drops and the heat requirement increases again.

6 The coolant temperature reaches 56 °C, the heat requirement makes it necessary to increase the heating output.

7 The control module increases the combustion air blower and fuel metering pump infinitely to full load within 55 s.

8 The coolant temperature increases again.

 Alternation between full load and partial load continues until the coolant reaches a temperature of 73 °C or the outdoor temperature increases to a temperature of above 5 °C. In both cases operation of the heater booster is terminated and the heater shut-off delay started.