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5.11
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.
The following generic diagram shows the system (Fig. 38).
S9903
Sensor of
Combustion air
Temperature
LMV52...
5.11.1 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. It calculates the air
2
rate reduction such that changes in burner load do not re-
quire the O
trim controller to interfere. Consideration is given
2
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 (temperature, pressure) change,
and not when the burner load changes.
The installation and setting of the system must be
carried out by qualified personnel, as indicated in
the specific documentation of the device.
WARNING
20205796
Start-up, calibration and operation of the burner
trim control (optional)
2
trim control
2
setpoint minus ac-
2
2
CAN
40
GB
QGO20...
Flue gas
temperature
sensor
O
module PLL...
2
Fig. 38
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