Smell gas? Leave the property and call the National Gas Emergency line on 0800 111 999
BoilerCodes
F.28
Vaillant fault code

Vaillant F.28: no flame detected when the boiler tried to light

Check these first, then call an engineer

The boiler tried to light but didn't detect a flame, so it locked out. In winter a common cause is a frozen condensate pipe. Vaillant also lists gas supply problems (such as low gas pressure or a gas meter fault) and ignition or electrical faults.

What you can safely do

  1. Check your gas supply: does your hob work? If you have a prepayment meter, check it has credit.
  2. In freezing weather, find the white plastic condensate pipe outside. If it is frozen, pour warm (not boiling) water along it until it thaws.
  3. Press the reset key for one second. Vaillant says to try this no more than three times.

Call a Gas Safe engineer if

  • The boiler still shows F.28 after three resets.
  • Your gas supply is fine and the condensate pipe isn't frozen.
  • 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.28 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 start-up: ignition unsuccessfulGas supply problems such as a defective gas meter, air in the gas or low gas pressure; ignition parts or electronics defective

Common questions about Vaillant F.28

Is F.28 dangerous?

The code itself means the boiler has shut down safely. If you smell gas, leave the property and call the National Gas Emergency line on 0800 111 999.

How many times can I reset a Vaillant boiler on F.28?

Vaillant's operating instructions say to press the reset key and, if the fault isn't cleared after three attempts, to contact a competent person.

Why does F.28 happen in cold weather?

Vaillant explains that the condensate pipe can freeze in very cold weather, which stops the boiler running. Thawing it with warm water often clears the fault.

Nearby Vaillant codes

F.22F.75F.29F.83F.23F.72F.20

See all 36 Vaillant codes

Sources