EF 349
FAULT CODE
Worcester Bosch
Central Heating Boil Detected
High Severity
Engineer Required
The boiler is operating at minimum burner load but the temperature difference between flow and return exceeds 18°C, indicating the system water is 'boiling' locally. Usually caused by very poor circulation past the heat exchanger.
Step-by-Step Fix Guide
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Step 1
Check system pressure and bleed all radiators
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Step 2
Ensure all radiator valves and isolation valves are fully open
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Step 3 Engineer only
If fault persists, call a Gas Safe engineer — a powerflush may be required if the system is sludged
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.