F22
Viessmann
Low water content / dry firing protection
Dry fire / low water content detected, boiler shuts down quickly after start
Advertisements
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.
Advertisements
Possible Causes
Insufficient system pressure, Air lock in heat exchanger, Blocked system isolation valves, Faulty flow sensor or temperature rise detection
How to Fix / Troubleshooting
Safety: Running the boiler without water can damage the heat exchanger. Do not repeatedly reset.
- Check pressure: Confirm system pressure is within the recommended range (typically 1.0–1.5 bar cold). Top up via the filling loop if low.
- Open valves: Ensure all isolation valves under the boiler and on the system are fully open.
- Bleed air: Bleed radiators and any automatic air vents near the boiler to remove trapped air.
- Reset and observe: Reset the boiler and watch the temperature rise. If it spikes rapidly and F22 returns, stop and call a technician.
- Professional check: A technician may need to flush the system, check the internal bypass, and verify the flow sensor operation.
Advertisements
Repair Difficulty
Hard
4/5
Required Part
Primary Heat Exchanger
Check Price on Amazon
We may earn a commission from links on this page.
Advertisements