Start Heater Operation

Start Heater Operation, Function

Shown On Models 215, 220:

Operating procedure
1 Heater operation has been triggered:
- The green or red indicator lamp in the STH switch (N72s12 or S46) illuminates.
- Coolant temperature < 30 degrees C.

2 The combustion air blower (A6m2) and the circulation pump (A6m1) start up. The combustion air blower (A6m2) delivers almost at top speed. The coolant flows through the heat exchanger (2) and the heating and cooling circuit.

3 An inquiry to the flame monitor is started for 1 s, the flame monitor heater element unit (A6r4) reports in its function as flame monitor:
"cold" = no flame --> the start is continued.
"hot" = flame --> the start Is interrupted because the glow pin is faulty (interference shut down)..

4 The heater element of the flame monitor heater element unit (A6r4) is switched on. The preheating time of approx. 30 s starts.

5 The preheating time is terminated, the combustion air blower (A6m2) is switched off for 3 s and the STH or heater booster fuel metering pump (Y23) begins to deliver fuel.

6 The combustion air blower (A6m2) starts up again.Within the next 60 seconds, the combustion air blower (A6m2) and the STH or heater booster fuel metering pump (Y23) increase their rotational speed and output to full load. In the burner housing (1), the fuel and the combustion air form the fuel-air mixture.

7 Once the increase in the flow of combustion air and fuel delivery have been completed, the heater element of the flame monitor heater element unit (A6r4) is switched off, and the safety period begins for approx. 45 sec. to check the flame.

8 The safety period is terminated, the flame monitor heater element unit (A6r4) reports in its function as flame monitor:
"hot" = sufficient combustion --> heater operation continues.
"cold" = none or insufficient flame formation --> the STH or heater booster fuel metering pump (Y23) is switched off and a once only start repeat is initiated.

9 Combustion has stabilized. The combustion air blower (A6m2) and the STH or heater booster fuel metering pump (Y23) continue to operate at their maximum rotational speed and output. Heat exchange in the heat exchanger (2) commences.

10 Coolant temperature > 30 degrees C:
- The STH or heater booster control module (A6n1) transmits the signal "Fan on" to the operating and control module (N18, N22 or N22/7) via the CAN Class B (CAN-B).
- The flow of hot air into the interior commences.