F.27 — Safety switch-off: Flame simulation

What does F.27 mean?

The boiler has detected a 'flame simulation', meaning it registers a flame even when the burner is not supposed to be active. This is a safety shutdown.

• Moisture present on the electronic components.
• Electronics (specifically the flame monitor circuit) are defective.
• Gas solenoid valve is leaking, causing gas to pass when it shouldn't.

Click steps to track your progress.

1. 1

   Ensure the boiler's casing is securely closed to prevent moisture ingress.

2. 2

   Press the fault clearance key on the boiler to reset it.

3. 3

   If the fault persists, contact Vaillant Service Solutions immediately, as this indicates a potentially dangerous gas issue.