356 High

Worcester Bosch 356 Fault Code

The Worcester Bosch 356 fault code means: your boiler has detected that the electricity supply coming from your home's mains is inconsistent or too low to operate the internal electronics safely.. It appears on 8 Worcester Bosch models in our database.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: Low mains voltage
Typical repair cost £120-250 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Worcester Bosch models that show the 356 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Worcester Bosch 356 fault code information on this page is sourced and cross-checked against the official Worcester Bosch service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026