BoilerFaultCodesWhat the manual says
Manufacturer manualMMI software incompatible with IRIS software
From this model's manual
Verified against the Vaillant Ecomax Pro 28e installation & service manual, page 26.
What causes this fault?
This fault occurs when the boiler's internal control boards are running different versions of software that cannot speak to each other. It most commonly happens after a repair where a new part has been installed that is not programmed to match the existing chips, or if a power surge has corrupted the board's memory. Because the different components cannot coordinate safely, the boiler shuts down as a precaution.
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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