Vaillant boiler showing F28
F28 means the boiler tried to light and could not. Sometimes it is your gas supply, not the boiler.
What it actually means
F28 is Vaillant's ignition failure fault: the boiler attempted to start, no flame was detected, and it locked itself out.
Before assuming the worst, rule out the supply side. If your gas hob or fire is also dead, the problem is the supply, not the boiler.
Try this first, before you spend a penny
- 1
Check other gas appliances
If the hob will not light either, check your meter: a prepayment meter out of credit or an emergency control valve turned off will stop everything.
- 2
In a cold snap, check the condensate pipe
A white plastic pipe running outside can freeze and shut the boiler down. Thaw it with warm (never boiling) water poured along the pipe, then reset.
- 3
Reset once
Press reset and let it try again. One reset is fine. Repeated resetting against a hard fault is not, it just masks the problem.
Safety line, not small print
Never open the boiler case yourself. If you can smell gas, stop and call 0800 111 999 first.
When it is a pro job
If gas is flowing to other appliances and a single reset does not clear it, an engineer needs to look at the ignition side: electrode, gas valve or the flue. That is strictly Gas Safe territory.
Gas Safe registered heating engineer
Typical UK range for an ignition fault diagnosis and common part replacement. Complex gas valve work can cost more; get an itemised quote.
£120 to £350
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