Viessmann Vitodens 100-W fault 799
No DHW heating, no central heating, central heating circuit pump electrical fault
Gas boilerWhat it means
No DHW heating and no central heating because the central heating circuit pump reports an electrical fault and there is no flow rate.
Likely causes
- Central heating circuit pump reports an electrical fault
- No flow rate
Where to start
- Perform a power reset
- Check configured set room temperature per heating circuit
- Verify heating circuit pump ON/OFF points against the Heating limit outside temperature setting
The full answer, free
- 8 more checks in order
- The readings and component tests from the manual
- How to put it right, step by step
- The manual page for this fault (page 87), right under the answer
Safety: Isolate gas and power before you open the case. If you have been into the gas side, do a tightness test, and a combustion and flue check before you hand back. Gas Safe (UK) or RGI (Ireland) work only.
From the Viessmann manual for the Vitodens 100-W. Check the model on the data plate before you order parts.
Other Viessmann Vitodens 100-W fault codes
- 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