Printed in Germany / M-MT-BOS
• Edition 11.99 • # 231 763
18 … 112
Operating mode
Oil firing, three stage
Servomotor air plugged in
Coding plug oil plugged in instead of servomotor gas.
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 preventilation position P9. Once the servomotor reaches this position,
a 5-second delay commences.
The air pressure switch is checked for idle state and the flame monitoring
device is checked for flame simulation. If these checks are passed, the blower
and the ignition are turned on.
The preset pre-purge period elapses and the remaining pre-purge period is
displayed. If the switch function has been activated, the preventilation cycle is
monitored 3 s after switching on the blower. To ensure that the preventilation
cycle is executed at the max. possible flow rate, the desired time should be
increased by 3 s in the EEPROM. Once the pre-purge period elapses, the
servomotor air moves to ignition point P0 and dwells there for 2 seconds, opens
valve Y1 and (if exist) an additional pre-valve connected in parallel with Y1.
The ignition cuts out at the end of the preset safety period and, provided that
a flame is present, the servomotor air dwells in the ignition position for the preset
stabilizing time. When the watchdog function is activated, oil pressure switch
input (GW_min) is monitored after the valve opens. If you want to monitor the
air pressure but not the gas pressure, a bridge can be attached to inlet GW_min
as a substitute.
After the stabilising time elapses, the servomotor air moves to position P1
(stage 1) and remains in this position for approx. 8 seconds. The automatic
burner control is now in the service position and accepts the signals applied
to the capacity control inputs for the second and third stages (Stage 2 and
Stage 3).
Changeover to the high load setting takes place within 6 seconds after the
signal is applied.
Changeover from the first stage to the second stage takes place within 6 s after
the contact of the second stage closes. The servomotor air moves to the
second stage P3 via changeover point P2 within t < 3 s, and valve Y2 (second
stage) is connected when the servomotor passes the changeover point.
Changeover from the second stage to the third stage takes place within 6 s after
the contact of the third stage closes. The servomotor air moves to the third stage
P9 via changeover point P4 within t < 3 s, and valve Y3 (third stage) is
connected when the servomotor passes the changeover point.
Changeover to the next lower stage is implemented in the reverse order.
Once a changeover has been initiated it is completed.
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. Valves
Y1, Y2 and Y3 close and the blower runs on for the preset postventilation period.
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 (display = OFF).
■ Configuration
Oil firing, three stage
■ Functional sequence
Oil firing, three stage
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