Viessmann MPA51 Operating And Service Instructions page 16

Diagnosis
Diagnosis
(cont.)
Fault Display
*1
code
F A7 F A7
F A7 F A7
F A7 F A7
F A7 F A7
All fault codes are saved to the fault memory and the last 10 can be called up.
*1
16
System charac-
teristics
No flame signal
during safety time;
ionisation flame
monitor reports no
flame signal
No flame signal
during safety time;
ionisation flame
monitor reports no
flame signal
No flame signal
during safety time;
ionisation flame
monitor reports no
flame signal
I Danger
Plug-in termi-
nals on the
burner con-
trol unit are
'live'.
Check con-
nections
"L 1", "N" and
earth con-
ductor.
No flame signal
during safety time;
ionisation flame
monitor reports no
flame signal
Cause
Incorrect gas type
selected
Gas train does not
open
Connections "L1"
and "N" inter-
changed at the
power supply ter-
minal of the con-
trol unit or burner
control unit
Combustion char-
acteristics not ide-
al
Measures
Set correct gas
type (see
Vitocrossal service
instructions)
Check gas train
and replace if re-
quired
Check core alloca-
tions and alter if re-
quired
Adjust burner (see
Vitocrossal service
instructions)