106
Dis-
played
fault
code
Const.
Weath.-
comp.
System char-
acteristics
Cause
Measures
A9
X
The burner
operates at its
lower output if a
heating circuit
with mixer is
connected.
The burner is
blocked if only
one heating cir-
cuit without
mixer is con-
nected.
Internal circu-
lation pump
blocked
Check the circula-
tion pump
b0
X
X
Burner blocked Short circuit,
flue gas tem-
perature sen-
sor
Check the flue gas
temperature sen-
sor
b1
X
X
Control mode
as per deliv-
ered condition
Communica-
tion error,
programming
unit
Check connections
and replace the
programming unit if
required
b5
X
X
Control mode
as per deliv-
ered condition
Internal fault
Replace the control
unit
b7
X
X
Burner blocked Boiler coding
card faulty
Plug in boiler cod-
ing card or replace,
if faulty
b8
X
X
Burner blocked Lead break,
flue gas tem-
perature sen-
sor
Check the flue gas
temperature sen-
sor
bA
X
Mixer regulates
to a flow tem-
perature
of 20 °C
Communica-
tion error,
extension kit
for heating
circuit 2 (with
mixer)
Check extension
kit connections and
code
Troubleshooting
Fault codes
(cont.)
5457 552 GB