BoilerFaultCodesWhat the manual says
Manufacturer manualInternal error.
From this model's manual
Verified against the Worcester Bosch/Worcester Bosch Greenstar 25i Zwb 7 25 installation & service manual.
What causes this fault?
This fault occurs when the boiler's internal computer suffers a communication failure or data error between its electronic components. The most common reason is a temporary electrical surge or a physical degradation of the circuits on the main control board, which prevents the boiler from safely managing the ignition and heating process.
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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Related fault codes
All 26 fault codes on the ZWB 7-25
Seeing a different code? Every code this model can display, in one place.