Buderus Logano plus GB402 Installation And Maintenance Instructions Manual page 59

Display Fault
1)
Type code code
V 4U 521
V 4U 522
Tab. 21 Fault displays
1) V = interlocking; B = blocking
Logano plus GB402 - Subject to technical modifications!
Cause Description
Excessive Excessive
sensor temperature
differential at differential
the boiler between
sensor temperature
between sensors 1 and 2
temperature (deviation
sensors 1 > 5 K/2s).
and 2.
Boiler sensor A temperature
short circuit sensor fault was
between detected in test
temperature mode.
sensors 1
and 2.
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
connection.
Check sensor values
according to table.
Check the voltage at the
temperature sensor
according to table.
10
Troubleshooting
Action
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 in case of
damage.
Clean or replace if
contaminated.
Refit plug it is found to
be loose.
Replace the
temperature sensor in
case of deviations.
Replace the SAFe in
case of deviations.
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