Buderus Logano plus GB312 Installation Manual page 76

10
Troubleshooting
Type Display
1)
code Fault code Cause
V 4U 521
V 4U 522
V 4Y 523
Tab. 17 Fault messages
1) V = locking; B = inhibiting; BC = operating code
76
Description
Temperature differ- Temperature differ-
ence at twin boiler ence between flow
sensor too great. temperature sen-
sors 1 and 2 too
great (divergence
of > 9 °F/2s; 5 K/
2s).
Short circuit between A fault has been
boiler sensors 1 and detected in temper-
2. ature sensor test
mode.
Circuit break on flow Temperature at flow
temperature sensor. temperature sen-
sor.
< 23 °F (< -5 °C)
Logano plus GB312 - Technical specifications are subject to change without prior notice
Testing
sequence/Cause Action
Check connectors Clean contacts/
on boiler sensor and replace connecting
SAFe for dirt/dam- lead if necessary.
age.
If there are discrep-
Check boiler sensor ancies in the sensor
resistance against readings or the
sensor characteris- connector is defec-
tic/visually check tive, the tempera-
temperature sensor. ture sensor must be
replaced.
Check boiler sensor
voltage levels Replace SAFe if
against table (SAFe there are discrep-
documentation). ancies.
Check sensor lead. Replace if dam-
aged.
Check connector.
If dirty, clean or
Check sensor read-
replace as neces-
ings against sensor
sary.
characteristic.
If connector is
Check temperature
loose, reconnect
sensor voltage levels
properly.
against table (SAFe
documentation). Replace tempera-
ture sensor if there
are discrepancies.
Replace SAFe if
there are discrep-
ancies.
Check sensor lead. Replace if dam-
aged.
Check connector.
If dirty, clean or
Check sensor read-
replace as neces-
ings against sensor
sary.
characteristic.
If connector is
Check temperature
loose, reconnect
sensor voltage levels
properly.
against table (SAFe
documentation). Replace tempera-
ture sensor if there
are discrepancies.
Replace SAFe if
there are discrep-
ancies.