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Viessmann Vitodens 100-W fault codes

70 codes from the Viessmann manual for the Vitodens 100-W gas boiler. Pick one for what it means, the likely causes and where to start.

CodeWhat it means
100PlusBus voltage error
12Short circuit, collector temperature sensor
161HBMU heat management unit data memory access fault
162Processor low voltage
163Checksum error, data memory access, HBMU heat management unit
176Condensate backup in the heat cell
346Ionisation current calibration error
347Flue gas recirculation
348Gas modulation valve
349Air mass rate flow not detected correctly in fan unit
350Ionisation current lies outside the permissible range
351Ionisation current lies outside the permissible range
352Combustion CO limit exceeded
355Analogue signal reference check: flame signal already present at burner start
359No ignition spark, burner in fault state
361Flame signal not present or insufficient at burner start
364Internal fault, burner in fault state
368Gas pressure switch fault, burner locked out
369Flame lost immediately after flame formation (during safety time)
371Fan speed too low
372Repeated flame loss during calibration
373Heat transfer too low during calibration, temperature limiter shut down
374Burner restarts, stabilisation conditions for pre-calibration not met
375Ionisation current calibration not performed
376Ionisation current differential not plausible
377Post-calibration stabilisation conditions not met
379Flame signal not present or insufficient
383Possible contamination of gas line
384Possible contamination of gas line
385Short circuit, signal 1, ionisation current
386HBMU heat management unit faulty
387Earth fault, ionisation current
388HBMU heat management unit faulty
393Short circuit, second flue gas temperature sensor
394Lead break, second flue gas temperature sensor
395Burner in a fault state
396Burner in a fault state
399Burner in a fault state
400Burner in a fault state
401Burner in a fault state
402Burner in a fault state
403Burner in a fault state
404Burner in a fault state
405Burner in a fault state
406Burner in a fault state
408Burner in a fault state
410Burner in a fault state
416Flue gas temperature sensor placement fault during commissioning
417Burner in a fault state
418Burner in a fault state
447Burner in a fault state
448Burner in a fault state
449Burner in a fault state
451Burner in a fault state
452Burner in a fault state
453Burner in a fault state
454Burner in a fault state
455Burner in a fault state
456Burner in a fault state
457Burner in a fault state
458Burner in a fault state
461Burner in a fault state
463Burner in a fault state
464Burner in a fault state
468Burner in a fault state, ionisation current too high during calibration
471No heat demand, system pressure sensor not available
474Burner in a fault state, error in scheduled program run monitoring
517Normal operation, remote control not functioning
527Burner in a fault state, incorrect HBMU heat management unit parameter set
528Burner in a fault state, incorrect HBMU heat management unit parameter set