High Lockout
E00-722 on Worcester Bosch 24/28CDi II RSF

Your boiler's main control computer has developed an internal electrical fault and can no longer safely operate the system.

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

Circuit Board Bosch, Type Heatronic II282

What causes this fault?

This fault occurs when the boiler's internal computer experiences a critical communication failure or a short circuit on the main control board. The most common reason is age-related wear to the electrical components, though occasional power surges or water leaks onto the wiring can also trigger this total system failure.

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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