Vaillant · Current Vaillant F-code boilers
F.28Flame not detected during ignition
This code applies to ecoTEC plus, ecoTEC plus remastered, ecoTEC pro, ecoTEC exclusive, ecoFIT pure. Fault codes narrow down the likely problem, but they do not replace a model-specific diagnosis.
What you can safely check
- Check whether another gas appliance works and whether a prepayment meter has credit.
- In freezing weather, visually check an accessible external condensate pipe for ice and follow the manufacturer's thawing guidance if applicable.
- Reset once only if the user manual permits it. If the code returns, arrange an engineer.
How an engineer may fix it
Test the gas supply and inlet pressure, ignition and ionisation components, condensate route, flue, gas valve and combustion settings; repair or replace the failed component.
Vaillant states that meanings can vary by appliance. Confirm the exact model manual before acting.
Manufacturer source: Vaillant UK — Boiler fault codes list. Checked 15 August 2026. The appliance manual and an engineer’s on-site diagnosis take precedence. Never remove the boiler case yourself.