Printed in Germany / M-MT-BOS
• Edition 11.99 • # 231 763
16 … 112
Gas pressure switch GW_min is fitted upstream of the two gas valves of the
Ratio control.
If a pressure sufficient to actuate gas pressure switch GW_min does not build
up one second before the startup safety period commences, 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 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.
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).
■ Gas pressure switching
Gas fail-safe program for gas
burners with pneumatic modula-
tion
Operating mode
Gas firing, pneumatic
modulation
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