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Building Technologies
Basic Documentation LMV5...
CC1P7550en
19 O2 trim control with LMV52 and PLL52
22.05.2018
19.6 Self-test
During the startup phase and during operation, the system performs a number of self-
tests to ensure that the QGO20 is working correctly.
19.6.1 O2 Sensor test
To detect aging QGO20, an O2 sensor test is made. An aged measuring cell can be
identified by its increased internal resistance. The cell is considered too old when the
internal resistance measured is Ri <5
ς
or Ri >150
ς
.
The display Ri = XXXX in the AZL52 signals that a sensor test has still not been
performed (e.g. after switching the mains voltage off and then on again up to the end of
prepurging).
The test is made at 23-hour intervals. To perform the test, a constant O2 value is
essential. This requirement is satisfied after prepurging or when a stationary load point
is reached. The system performs the test after 23 hours as soon as such stationary
values are available. If this is not the case after 24 hours, the load is «frozen» in
operation so that the test can be made. If the system is in standby mode, the test is
performed during the next startup phase (maximum 3 repetitions).
If the test is negative, the system’s response will be one of the following, depending on
the parameterization of
O2Contr/Alarm
:
man deact
(auto deact):
O2 trim controller and O2 alarm are deactivated. No O2 sensor test is
made
O2 Alarm / O2
Control:
O2 trim controller / O2 alarm is / are activated. If the test is negative,
safety shutdown is initiated, followed by a repetition, if possible,
otherwise lockout
conAutoDeac
:
Both the O2 trim controller and the O2 alarm are activated. If the test
is negative, O2 trim control is deactivated and the burner started up
without O2 trim control
Parameter
Gas:
OptgMode (auto deact / man deact / O2 Alarm / O2 Control /
conAutoDeac)
Oil:
OptgMode (auto deact / man deact / O2 Alarm / O2 Control /
conAutoDeac)
