403
Thermo G
4 Heater functions
After a safety period of 5 seconds the purge cycle 2 starts.
The flame monitoring is evaluated.
The purge cycle ends approx. after 115 seconds. The
combustion air fan is switched off.
The heater is in a controlled break.
The operation indication, the flame guard and the circula-
ting pump continue their operation.
NOTE:
If during the purge cycle 2 a “flame“ is recognized, the
combustion air motor is switched off and an appropriate
error message is given.
The operation indication, the flame guard and the circula-
ting pump continue to run until the purge cycle 2 is
terminated (after 115 seconds).
Once the temperature falls short of the lower switching
threshold, the heater restarts burner operation. It runs
through the same sequence as the switching-on
sequence.
4.2.2.1 Gradient evaluation
In case of low coolant flow or poor coolant circuit venting
the temperature quickly increases in heating operation.
The control unit recognises the quick temperature
increase and automatically sets the upper switching thres-
hold to a lower value.
The quicker the temperature increases, the lower the swit-
ching threshold for starting the controlled break is set.
In addition, the burner is also switched back on again after
the controlled break at a lower switching threshold.
This prevents residual heat triggering the overheating
protection.
If the temperature rise (temperature gradient) is again
within permissible limits, the thresholds are reset to
normal values immediately (lower threshold 72°C, upper
threshold 82°C).
4.2.3 Switching off
Switching the heater off ends the combustion process.
The operation indication goes off and the purge cycle is
initiated.
The purge cycle cools down the components. This
prevents that the residual heat in the heat exchanger,
which is still present, overheats the components.
The solenoid valves 1 and 2 at the gas pressure regulator
are closed, the flame extinguishes, combustion air fan and
the circulating pump continue running.
After a safety period of 5 seconds the purge cycle 2 starts.
The flame monitoring is evaluated.
The purge cycle ends approx. after 115 seconds. The
combustion air fan, the flame guard and the circulating
pump are switched off.
