High
347 on Worcester Bosch 1000

Your boiler has detected that hot water is flowing the wrong way or the pipes are incorrectly connected, causing it to shut down to prevent damage.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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

Return temp exceeds flow temp for over 20 sec

What causes this fault?

Temperature inversion fault

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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