GF83.70-P-4060-01Q STH Heater Unit, Function

GF83.70-P-4060-01Q STH heater unit, function
- with CODE (228) Stationary heater [models 209.3 as of 1.6.04]


Heater operation starts
The combustion air blower (A6m2) and the circulation pump (A6m1) are initialized. The combustion air blower (A6m2) runs approximately at its highest speed.
The heater element of the flame monitor heater element unit (A6r4) is switched on. The preheating time of approx. 30 s starts. After the preheating time, the combustion air blower (A6m2) is switched off for 3 s and the STH fuel metering pump (Y23) begins to deliver fuel.
The combustion air blower (A6m2) starts up again. Within the next approx. 60 seconds the combustion air blower (A6m2) and STH fuel metering pump increase their speed and output to full load. The fuel and the combustion air form the fuel/air mixture in the combustor housing.
Once the increase in the flow of combustion air and fuel delivery have been completed, the heater element of the glow pin unit flame monitor (A6r4) is switched off, and the safety period begins for approx. 45 s to check the flame.

After the safety period is terminated, the glow pin unit flame monitor (A6r4) reports in its function as flame monitor:
^ "hot" sufficient combustion heater operation continues.
^ "cold" no, or insufficient, flame formation, the STH fuel metering pump (Y23) is switched off and a non-recurring second start is initialized.
If there is still no flame formation, the fuel supply is terminated by switching the STH fuel metering pump (Y23) off and the combustion air blower (A6m2) is shut off and powered-down.

Heating mode
The heater operation is controlled automatically in dependency on the coolant temperature. Possible statuses:
^ Full load operation
^ Partial load operation
^ control interval
The flame formation is monitored during the heater operation by the glow pin unit flame monitor (A6r4).
If there is no flame formation or if there is a flame-out, a non recurring second start is initialized. If there is still no flame formation, the fuel supply is terminated by switching the STH fuel metering pump (Y23) off and the combustion air blower (A6m2) is shut off and powered-down.

Overheating protection
The internal temperature sensing of the STH control unit (A6n1) recognizes the overheating and activates for approx. 120 s the heater interrupt after-run with subsequent interrupt blocking.

Heater operation is terminated
The combustion is terminated by switching the STH fuel metering pump (Y23) off.
The run-on time of the combustion air blower (A6m2) and the noncirculation pump (A6m1) starts.
The run-on time and the speed of the combustion air blower (A6m2) are dependent on from which operating condition the heater (A6) was switched off.