Printed in Germany / M-MT-BOS
• Edition11.99 • # 231 763
15 … 112
Servomotor air plugged in.
Coding plug gas plugged in instead of servomotor.
The internal self-tests are performed when the regulator issues a heating
request.
The servomotor air locates its reference point and then the servomotor air
moves to pre-purge position P9.
The idle position of the air pressure switch is checked and the flame monitoring
device is checked for flame simulation. If these checks are passed, the blower
is energised.
When the air pressure switch is closed, the preset pre-purge period elapses
and the remaining pre-purge period is displayed. Pre-purging is monitored by
LGW.
If a valve test has still not been performed after a power failure or fault shut-
down and the valve proving function is selected, a valve test and restart are
performed after the pre-purge period has expired.
Otherwise, the external valve Y1 (liquid gas) opens and the servomotor air
moves to ignition point P0 after the pre-purge period has expired. After the
servomotor air has reached the ignition point P0, the ignition is turned on for the
preset pre-purge period (with pre-ignition period = 2 s).
Valve Y2 is opened one second before the startup safety period commences
(the ignition is also turned on if pre-ignition period = 1s). The gas pressure
switch GW_min must indicate the presence of gas pressure within this period
of time. Otherwise, a safety shut-down will be triggered and the gas fail-safe
program executed.
If gas pressure is present after 1 second, the ignition is turned on (if pre-ignition
period = 0) and valve Y3 is opened. The ignition is turned off at the end of the
safety period and, provided that a flame is present, the servomotor remains in
the ignition position for the preset stabilising time. After the stabilising time has
expired, the servomotor runs to position P1 and dwells there for 8 s.
The automatic burner control is now in the service position.
If the MPA22 has already been in service for 24 hours, a controlled shut-down
is executed automatically.
If the heating request is cancelled, a controlled shut-down takes place. If the
leakage check is not activated, valves Y2, Y3 and the external valve close and
the blower runs on for the preset postventilation period. If the leakage check
function is activated, a leakage check is performed on gas valves Y2 and Y3
by means of GW_VPS which is fitted in between valves Y2 and Y3. The
postventilation period elapses in parallel with the leakage check. After the
blower has been switched off, the servomotor air moves to the preset standby
position. A restart lockout time (the time is displayed) now elapses (if set) or the
automatic burner control enters standby mode (readout on display = OFF).
If no flame is present after the startup safety period has elapsed, a safety shut-
down takes place and 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 while the burner is operating, the burner is restarted (if
set in the EEPROM). 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 will be triggered. 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
Operating mode
Gas firing, pneumatic
modulation
■ Configuration
Gas firing, pneumatic modulation
■ Functional sequence
Gas firing, pneumatic modulation
■ Response to faults
Gas firing, pneumatic modulation
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