Viessmann FB2B Installation And Service Instructions Manual page 112

Troubleshooting
Fault codes
(cont.)
Displayed System characteris-
fault code tics
F0 Burner blocked
F1 Burner in a fault
state
F2 Burner in a fault
state
F3 Burner in a fault
state
F7 Burner blocked
F8 Burner in a fault
state
F9 Burner in a fault
state
FA Burner in a fault
state
FC Burner in a fault
state
112
Cause Measures
Internal fault Replace the control unit.
Flue gas tempera- Check the heating system
ture limiter has fill level. Vent the system.
responded.
Press reset button R after
the flue system has
cooled down.
The temperature Check the heating system
limiter has respon- fill level. Check the circu-
ded. lation pump. Vent the sys-
tem. Check the tempera-
ture limiter and connect-
ing cables.
Press reset button R.
Flame signal is Check the ionisation elec-
already present at trode and connecting
burner start. cable.
Press reset button R.
Short circuit or lead Check the water pressure
break, water pres- sensor and the connect-
sure sensor ing cable.
The fuel valve Check the gas train.
closes too late. Check both control paths.
Press reset button R.
Fan speed too low Check the fan, the fan
during burner start connecting cables and
power supply; check the
fan control.
Press reset button R.
Fan not at stand- Check the fan, fan con-
still necting cables and fan
control.
Press reset button R.
Gas train faulty or Check the gas train.
faulty modulation Check the flue gas sys-
valve control or flue tem.
gas path blocked Press reset button R.