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.