BoilerFaultCodesYour boiler thinks a flame is present even when the gas is turned off, which prevents it from starting up safely.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Flame simulation
What causes this fault?
This fault occurs when the boiler's control system detects an electrical signal suggesting a flame is present even though the gas valve is closed. The most common reason is a faulty sensing electrode that is sending a 'ghost' signal, or moisture and debris on the ignition lead causing a short circuit. Because the boiler believes it is unsafe to ignite while it thinks a flame already exists, it shuts down as a safety precaution.
This fault can be more frequent during periods of high humidity or heavy rain, as moisture entering the casing can interfere with the sensitive electrical components that monitor the flame.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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A boiler cover plan would cover faults like F.27 — no call-out fees, no surprises.
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