F1
FAULT CODE
Saunier Duval
Ignition Failure / Lockout
Medium Severity
DIY Check Possible
The boiler has failed to ignite. The most common Saunier Duval fault code across all their ranges (Isotwin, Thema, Xeon).
Cold Weather Note
F1 in cold weather is commonly caused by a frozen condensate pipe on Saunier Duval boilers.
Step-by-Step Fix Guide
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Step 1
Check gas supply — try other gas appliances
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Step 2
In cold weather, check for a frozen condensate pipe and thaw with warm water
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Step 3
Press the reset button
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Step 4
If fault persists, call a Gas Safe engineer to inspect ignition electrodes and gas valve
Gas Safe Reminder
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.