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Building Technologies Basic documentation LMV37.4... CC1P7546en
12 Fan control 17.12.2018
Plausibility check for range limitation
A plausibility check can be activated to show if the LMV37.4 remains on a range limit of
the trim function for a defined time (time setting = 0 deactivates the check / warning /
shutdown).
This can be used to identify an incorrect setting in the trim function.
In the default setting, no shutdown takes place and only a warning is generated.
This means that the LMV37.4 remains in operation.
Deactivation of the trim function and a shutdown can also be triggered in response to
the system remaining on a range limit for too long.
If error code C:156 is only output as a warning message, it can only be seen for the
period the error is active, as warning messages are not saved permanently in the error
history.
The PLC must therefore read out the current error memory of the LMV37.4 cyclically via
Modbus (e.g. every 2...30 s) and save a corresponding warning message permanently.
Error-
code
Diagnostic code Meaning for the LMV37.4
156 # Trim function: Maximum time for range limit exceeded
0 Trim function at lower limit
1 Trim function at upper limit
10 Fuel 1: Trim function at lower limit
11 Fuel 1: Trim function at upper limit
Analogue input test during burner startup
A test sequence with 2 current thresholds can be used to identify errors in the analog
input during burner startup.
To this end, the PLC must deliver a current of 10 mA (0%) during standby and a current
of 4 mA (-15%) during traveling to prepurging or the first 2 seconds in prepurging.
The LMV37.4 uses these test values to check for fault-free function of the analog value
recording and can therefore detect component faults and drift.
The expected values are also used for indirect supervision of the Modbus
communication and the external control (PLC).
In the event of an error, the burner startup is prevented (test in standby) or canceled
(test in prepurging).
The test can only be carried out during burner startup, a cyclical test during operation is
not possible.
For this reason, the forced intermittent operation may not be switched off when the
analog input test is activated.
This ensures that the analog input test is carried out at least once every 24 hours.
The supervision is carried out by LMV37.4.
The PLC or the external control can read out the LMV37.4 phase information required
for the test via Modbus.
Error-
code
Diagnostic code Meaning for the LMV37.4
157 # Trim function: Analog input test
0 Analog value standby
1 Analog value prepurging
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