Printed in Germany / M-MT-BOS
• Edition11.99 • # 231 763
13 … 112
Operating mode
Gas firing, electronic
modulation
If no flame is present after the startup safety period has elapsed, a safety shut-
down takes place and the system executes a restart (if permitted). A fault
lockout is triggered otherwise.
If the presence of a flame is not indicated after a restart attempt, a fault shut-
down takes place and the burner enters the non-variable fault state.
If flame failure occurs when the burner is in operation, the burner is restarted
(if permitted). Otherwise, a fault shut-down takes place and the burner enters
the non-variable fault state.
In the event of a fault shut-down, all valves are closed and the blower and
ignition are turned off.
If the presence of a flame is signalled before the gas is enabled, the automatic
burner control enters the non-variable fault state.
If a malfunction occurs during the start-up phase or operating phase, a safety
shut-down is activated. Depending upon the nature of the fault, the burner
either enters the non-variable fault state or the start-up attempt is repeated.
After 5 failed attempts, the automatic burner control enters the non-variable
fault state.
The type of fault or disturbance is displayed.
The gas pressure switch GW_min is fitted in between gas valves Y2 and Y3.
At burner start-up, valve Y2 is activated 1 second before the startup safety
period commences and also 1 s before valve Y3 is opened.
If a pressure sufficient to actuate gas pressure switch GW_min does not build
up inside the space between valve Y2 and valve Y3, burner start-up is
interrupted. The valves are closed and the blower is switched off. The
automatic burner control waits for 2 minutes before repeating the start-up
attempt.
If there is a still a shortage of gas after this 2-minute wait, the start-up attempt
is repeated a third time after waiting another 2 minutes.
After the third failed start-up attempt, the burner waits for an hour before
attempting another restart.
This function makes possible leakage checks and gas pressure monitoring
with only one pressure switch. It does not give rise to a fault lockout in the event
of a gas shortage and reduces the frequency of start-up attempts if a gas
shortage exists over a lengthy period of time.
The gas pressure switch must be set to at least the flow pressure necessary in
between the two valves at full load.
Examples of a display during the wait period: 18 1-23 (= 1 minute 23 s
remaining waiting time)
The waiting time can only be reset by disconnecting the voltage supply to the
device (turn main switch OFF or disconnect the 7-pole connector).
■ Response to faults
Gas firing, electronic modulation
■ Gas pressure switching
Gas fail-safe program for gas
burners with electronic modula-
tion
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