Ignition Failure / No Flame Detected
The boiler has failed to light after multiple ignition attempts. One of the most common faults, with several possible causes from frozen condensate to gas supply issues.
In temperatures below 0°C, the condensate pipe is the most common cause of F.28 on Vaillant boilers. Thaw it with warm water and reset.
Step-by-Step Fix Guide
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Step 1
Check that other gas appliances work (hob, gas meter) to confirm gas supply is on
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Step 2
Check your gas meter has credit if it is a prepayment meter
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Step 3
Locate the condensate pipe (usually a white plastic pipe on an outside wall) and check if it is frozen
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Step 4
If frozen, pour warm (NOT boiling) water along the pipe and wait for gurgling sounds
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Step 5
Press the reset button once
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Step 6
If the fault returns, call a Gas Safe engineer
Work on gas appliances must be carried out by a Gas Safe registered engineer. The steps above cover safe checks a homeowner can perform - any internal component replacement requires a qualified professional. If in doubt, always call an engineer.