Dungs MPA22 User Manual

Printed in Germany / M-MT-BOS
• Edition 11.99 • # 231 763
12 … 112
Servomotor air plugged in
Servomotor gas plugged in
The internal self-tests are performed when the regulator issues a heating
request. First, the servomotor air locates its reference point, then the servomo-
tor gas.
The servomotor air then moves to pre-ventilation 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 successful, 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
the air pressure switch.
During the pre-purge period, the servomotor gas runs to position 109° to check
whether the servomotors for gas and air have been interchanged.
After the servomotor has reached the 109° position it returns to ignition point P0
during the pre-purge period.
If a valve test has still not been performed after a power failure or fault shut-
down and the valve proving function has been selected, a valve test and restart
are performed once the pre-purge period has expired.
Otherwise, external valve Y1 (liquid gas) of the servomotor air opens and the
servomotor air moves to ignition point P0 after the pre-purge period has
expired. After the servomotor air has reached 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 cuts out at the end of the safety period and, provided that a flame
is present, the two servomotors remain in the ignition position for the preset
stabilising time. After the stabilising time has expired, the servomotors alter-
nately move to position P1 in stepping mode. When the servomotors reach
position P1, the automatic burner control is in the service position.
If the “Lower limit” bu > 0, the automatic burner control operates according to
the characteristic curve defined by points P1 to P9, consecutively activating the
servomotors until it reaches the predefined minimum capacity point in the
closed-loop control mode.
The MPA22 is now in closed-loop control mode, i.e. it accepts the control
signals applied to the inputs capacity + and capacity - and thus regulates the
capacity over the predefined characteristic curve in the range between bu and
bo.
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
valve proving system is not activated, valves Y2 and Y3 and the external valve
Y1 close and the blower runs on for the preset postventilation period.
If the valve proving system is activated, a leakage check is performed on gas
valves Y2 and Y3. The post-ventilation period elapses in parallel with the
leakage check.
When the blower is switched off, the servomotor air runs to the set standby
position and then the servomotor gas runs to position 0°.
A restart lock-out period (if set) now elapses (the time is indicated on the
display), or the automatic burner control enters standby mode (readout on
display = OFF).
Operating mode
Gas firing, electronic
modulation
■ Configuration
Gas firing, electronic modulation
■ Functional sequence
Gas firing, electronic modulation

Dungs MPA22 Specifications

General

Brand	Dungs
Model	MPA22
Category	Controller
Language	English