Boiler shows E19, hot water temperature is unstable or excessively hot at taps.
Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
Possible Causes
How to Fix / Troubleshooting
Safety first: Risk of scalding from overheated water. Warn occupants and avoid using hot water until the fault is resolved.
User-level checks:
- Open the hot tap fully and mix with cold to reduce scald risk.
- Reset the boiler and test again; if the problem persists, switch off the DHW function if possible and call a technician.
Technical checks (qualified personnel):
- Check DHW NTC sensor readings and replace if inaccurate.
- Inspect and descale the plate heat exchanger to restore proper heat transfer.
- Verify gas valve modulation control from the PCB and adjust minimum and maximum burner pressures as per Chaffoteaux instructions.
- Confirm correct flow rate through the DHW circuit; clean filters and flow restrictors if necessary.
After repair, set DHW temperature to a safe level (typically 50–55°C) and verify stable outlet temperature.