Fault
code
on the
display
Const.
weath.-
comp.
System char-
acteristics
Cause
Measures
A8
X
Burner
blocked. The
venting pro-
gram is started
automatically
(see page 36)
Air in the in-
ternal circu-
lation pump
Vent the system if
the fault message
continues to be
displayed
A9
X
The burner op-
erates at its
lower output if
a heating cir-
cuit with mixer
is connected.
The burner is
blocked if only
one heating
circuit without
mixer is con-
nected.
Internal cir-
culation
pump
blocked
Check the circula-
tion pump
b0
X
X
Burner
blocked
Flue gas
temperature
sensor
shorted out
Check the flue
gas temperature
sensor (see
page 85).
b1
X
X
Control mode
as per deliv-
ered condition
Communica-
tion fault;
program-
ming unit (in-
ternal)
Check connec-
tions and replace
the programming
unit, if necessary.
b4
X
X
Regulates as
if the outside
temperature
was 0 °C
Internal fault
Replace the con-
trol unit.
b5
X
X
Control mode
as per deliv-
ered condition
Internal fault
Replace the con-
trol unit.
Fault codes
(cont.)
75
Troubleshooting
5692
673
GB
Содержание VITODENS 300-W
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