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6.11
Description of O
A special feature of the LMV52... is control of the residual O
content to increase the boiler's efficiency. The LMV52... uses a
QGO20..., an external PLL52..., and the standard components
of the LMV51... The PLL52... is a detached measuring module
for the O
sensor and for 2 temperature sensors (Pt1000 / LG-
2
Ni1000). The module communicates with the LMV52... via CAN
bus.
Sensor of
Combustion air
Temperature
LMV52...
6.11.1 Operating principle of O
The residual O
control system reduces the amount of combus-
2
tion air depending on the control deviation (O
tual of O
). The amount of combustion air is normally influenced
2
by several actuators and, if used, by a VSD. Reduction of the
amount of air is reached by reducing the «air rate» of the air-
regulating actuators.
For that purpose, the damper positions of these actuators are cal-
culated from some other load point on the ratio control curves.
Hence, due to the parameterized ratio control curves, the air-reg-
ulating actuators are in a fixed relation to one another.
O
trim control is supported by precontrol. Precontrol calcu-
2
lates the air rate reduction such that changes in burner load
do not require the O
trim controller to interfere.
2
Consideration is given to a number of measured values that are
ascertained when the burner is set. This means that the controller
only becomes active when environmental conditions (tempera-
ture, pressure) change, and not when the burner load changes.
For a correct system operation, it may be necessary to install an
additional transformer (AGG5 ..), depending on the number of ac-
tuators / modules or cables length. Consult the documentation /
wiring diagram of the burner.
Start-up, calibration and operation of the burner
trim control (optional)
2
trim control
2
setpoint minus ac-
2
The following generic diagram shows the system (Fig. 35).
2
CAN
The installation and setting of the system must be
carried out by qualified personnel, as indicated in
the specific documentation of the device.
WARNING
35
GB
QGO20...
Flue gas
temperature
sensor
O
module PLL...
2
S9903
Fig. 35
20156417
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