10
Troubleshooting
Logano plus GB312 - Technical specifications are subject to change without prior notice
77
V
4U
524
Flow temperature sen-
sor short circuit.
Temperature at flow
temperature sensor
> 266 °F
(> 130 °C)
Check sensor lead.
Check connector.
Check sensor read-
ings against sensor
characteristic.
Check temperature
sensor voltage levels
against table (SAFe
documentation).
Replace if dam-
aged.
If dirty, clean or
replace as neces-
sary.
If connector is
loose, reconnect
properly.
Replace tempera-
ture sensor if there
are discrepancies.
Replace SAFe if
there are discrep-
ancies.
V
4A
575
ISTB response.
The boiler flow tem-
perature has
reached the maxi-
mum limit.
High temperature
safety cut-out has
tripped.
Check gas valve.
B
5L
542
Incomplete communi-
cation with SAFe.
The MC10 regis-
ters this fault if not
all required data is
supplied by the
SAFe.
Check wiring con-
nections between
SAFe and MC10.
If connections OK,
replace SAFe
Type
1)
Display
code
Fault code Cause
Description
Testing
sequence/Cause
Action
Tab. 17 Fault messages
1) V = locking; B = inhibiting; BC = operating code