Buderus LOGANO PLUS GB312 Installation Instructions Manual page 55

Display
1)
Type code Fault code
V 4A 520
V 4U 521
V 4U 522
V 4Y 523
V 4U 524
Table 22 Fault messages
1) V = locking; B = inhibiting; BC = operating code
Logano plus GB312 – 6 720 647 367 (2012/11)
Cause Description
Boiler safety temperature The flow temperature
limiter (STB). has reached 200 °F
(93 °C) (cut-out
temperature of boiler
temperature limiter).
Temperature difference at Temperature difference
twin boiler sensor too great. between flow
temperature sensors 1
and 2 too great
(divergence of > 9 °F/2s;
5 K/2s).
Short circuit between boiler A fault has been
sensors 1 and 2. detected in temperature
sensor test mode.
Circuit break on flow Temperature at flow
temperature sensor. temperature sensor.
< 23 °F (< -5 °C)
Flow temperature sensor Current supply
short circuit. temperature
> 266 °F (> 130 °C)
Troubleshooting
Testing sequence/
Cause Measure
Fault can only occur as a Check system
result of faults in system configuration.
configuration (e.g. only Check non-return valve
with 2-boiler systems). direction of flow.
Check connectors on Clean contacts/replace
boiler sensor and SAFe connecting lead if
for dirt/damage. necessary.
Check boiler sensor If there are
resistance against sensor discrepancies in
characteristic/visually the sensor readings or
check temperature the connector
sensor. is defective, the
temperature sensor
Check boiler sensor
must be replaced.
voltage levels against
table (SAFe Replace SAFe
documentation). if there are
discrepancies.
Check sensor lead. Replace if damaged.
Check connector. If dirty, clean
or replace as necessary.
Check sensor readings
against sensor If connector is loose,
characteristic. reconnect properly.
Check temperature Replace temperature
sensor voltage levels sensor if there are
against table (SAFe discrepancies.
documentation).
Replace SAFe
if there are
discrepancies.
Check sensor lead. Replace if damaged.
Check connector. If dirty, clean
or replace as necessary.
Check sensor readings
against sensor If connector is loose,
characteristic. reconnect properly.
Check temperature Replace temperature
sensor voltage levels sensor if there are
against table (SAFe discrepancies.
documentation).
Replace SAFe if there
are discrepancies.
Check sensor lead. Replace if damaged.
Check connector. If dirty, clean or replace
Check sensor readings as necessary.
against sensor If connector is loose,
characteristic. reconnect properly.
Check temperature Replace temperature
sensor voltage levels sensor if there are
against table (SAFe discrepancies.
documentation).
Replace SAFe
if there are
discrepancies.
10
55