BoilerFaultCodesTechnical description
With flue gas cascade
What causes this fault?
This fault occurs when multiple boilers share a single chimney system and are failing to talk to each other correctly. It is usually caused by a poor wiring connection between the units or a conflict in the internal settings that tell each boiler which part it plays in the group. In some cases, a faulty electronic module or a blocked sensor in the exhaust pipe can also trigger this communication breakdown.
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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