O2 Trim Control (Only With Lmv52; General - Siemens LMV51 Series Basic Documentation

O trim control
2
(only with LMV52...
system)

General

200/301
Siemens Building Technologies
HVAC Products
The O trim control system of the LMV52... offers a number of operating modes. In op-
2
erating mode «CtrlAutodeact», O
LMV52... if the O limit switch responds or if a fault in connection with actual value ac-
2
quisition of O occurs (O
2
trol can be deactivated manually, «mandeact». For this reason, the fuel / air ratio
curves with the LMV52... must always be set such that there are sufficient amounts of
excess air irrespective of environmental conditions (e.g. combustion chamber and fuel
pressure, and temperature and pressure of the combustion air) across the whole load
range – same as with a system without O
tio curves must be proven. The actual O2 value should not fall below the O2 setpoint of
O2 trim control.
A sufficient number of curvepoints (for actuator positions, O2 setpoints, etc.) should be
stored to ensure that there is a linear progression of the O2 value across the entire load
range. The second curvepoint must correspond to the low-fire position (or be set to a
lower value). The first curvepoint must lie sufficiently below curvepoint 2 (at about 50 %
load) so that the curves are defined for reducing the air rate by O2 trim control below
the low-fire position also.
The O2 min. value represents the switch-off threshold of the O2 monitoring function
and must be set and proven such that – across the entire load range and while taking
into account the combustion chamber and fuel pressure as well as the temperature and
pressure of the combustion air – there will be no dangerous increase of the CO and/or
soot values.
On the other hand, the safety distance from the dangerous area should be selected as
small as possible in order to prevent inadvertent or undesired shutdowns (guide values:
CO < 2000 ppm Vol % or soot number < 3 according to Bacharach).
The O setpoint must have an adequate distance from the above mentioned O
2
value (guide value: O setpoint = O
2
It must be made certain that all safety notes and the notes on mounting., electrical in-
stallation and service according to the above mentioned chapter and Data Sheets are
complied with.
Basic Documentation LMV5...
13 Duties of the authorized inspector
trim control is automatically deactivated by the
2
sensor, O module, O
2 2
trim control (LMV5...). Also, the fuel / air ra-
2
+ 1 % O
2 min. value
sensor test, etc.). Also, O
2
).
2
trim con-
2
min.
2
CC1P7550en
13.08.2004