Smell gas? Leave the property and call the National Gas Emergency line on 0800 111 999
BoilerCodes
F.29
Vaillant fault code

Vaillant F.29: the flame went out during use and the boiler could not relight

Check these first, then call an engineer

The boiler was running, lost its flame, and failed to relight. Vaillant's current ecoTEC plus fault table lists a temporary break in the gas supply and a blocked condensate duct among the causes, along with earthing and ignition faults.

What you can safely do

  1. Check your gas supply: does your hob work, and does your prepayment meter have credit?
  2. In freezing weather, check the condensate pipe outside. If it is frozen, pour warm (not boiling) water along it, as Vaillant advises.
  3. Reset only if your user manual tells you to for this code.

Call a Gas Safe engineer if

  • Your gas supply is fine and the code comes back.
  • You smell gas at any point. Leave the property and call 0800 111 999.
Find a Gas Safe engineer near you Opens the official Gas Safe Register search.

Applies to: ecoTEC plus. Codes can differ between models, so check your manual.

What F.29 means on each Vaillant model

From Vaillant's own fault tables. Your model name is usually on the front of the boiler or in the user manual.

ModelMeaningCauses listed for engineers
ecoTEC plusFailure during operation: re-ignition unsuccessfulGas supply temporarily stopped, flue gas recirculation, condensate duct blocked, defective earthing, ignition transformer spark failure

Common questions about Vaillant F.29

What is the difference between F.28 and F.29?

F.28 means the boiler couldn't light when starting up. F.29 means it was already running, lost the flame, and couldn't relight.

Can a frozen condensate pipe cause F.29?

Vaillant's current ecoTEC plus fault table lists a blocked condensate duct as one possible cause of F.29.

Nearby Vaillant codes

F.22F.28F.75F.83F.23F.72F.20F.25F.27

See all 36 Vaillant codes

Sources