Buderus Logano plus GB402 Installation And Maintenance Instructions For Contractors page 49

1)
Type Display code Fault Code
V 4U 521
V 4U 522
V 4Y 523
V 4U 524
V 4A 575
Table 23 Fault displays
1) V = locking; B = blocking
Logano plus GB402 – 6 720 820 700 (2018/01)
Reason Description:
Excessive sensor Temperature
differential at the differential between
boiler sensor temperature sensors 1
between and 2 is too
temperature high(deviation > 5 K/
sensors 1 and 2. 2s).
Boiler sensor A temperature sensor
short circuit fault was detected in
between test mode.
temperature
sensors 1 and 2.
Interruption in the Temperature too low at
boiler the boiler temperature
temperature sensor
sensor. (< -5 °C)
Boiler sensor The boiler sensor
short circuit. detected an
excessively high
temperature (> 130
°C).
Intelligent high The boiler flow
limit safety temperature has
cut-out responds. reached its maximum
permitted level.
Test procedure/cause
Check that the "Reset" button
illuminates on the SAFe.
Check that the check valve on the
cylinder primary pump is closed.
Check whether the flow and
return have been connected
correctly.
Check whether the plug-in
connection on the boiler sensor
and on the SAFe are
contaminated or damaged.
Check the resistances at the
boiler sensor according to table or
visually inspect the plug at the
temperature sensor.
Check the voltage values on the
boiler sensor according to table.
Check the sensor lead.
Check the plug-in connector.
Check the sensor values against
the table.
Check the voltage at the
temperature sensor according to
table.
Check the sensor lead.
Check the plug-in connector.
Check the sensor values against
the table.
Check the voltage at the
temperature sensor according to
table (SAFe documentation).
Check the sensor lead.
Check the plug-in connector.
Check the sensor values against
the table.
Check the voltage at the
temperature sensor according to
table (SAFe documentation).
High-limit safety cut-out has
triggered.
Troubleshooting 11
Corrective measure
Press "Reset" on the SAFe.
Close the check valve if it is still
open.
If flow and return have been
swapped, connect flow and
return correctly.
If required, clean or replace the
plug-in connections.
Replace the boiler sensor if the
sensor values deviate from the
stated values, or if the plug is
faulty.
Replace the SAFe if there are
deviations.
Replace if damaged.
Clean if dirty or replace if
necessary.
Refit plug it is found to be
loose.
Replace the temperature
sensor, if there are any
deviations from the table.
Replace the SAFe in case of
deviations.
Replace if damaged.
Clean if dirty or replace if
necessary.
Replace if damaged.
Refit plug it is found to be
loose.
Replace the temperature
sensor, if there are any
deviations from the table.
Replace the SAFe in case of
deviations.
Replace if damaged.
Clean if dirty or replace if
necessary.
Replace if damaged.
Refit plug it is found to be
loose.
Replace the temperature
sensor, if there are any
deviations from the table.
Replace the SAFe in case of
deviations.
Check the gas valve.
(Does the flame extinguish
after a controlled shutdown?)
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